Cobalt single atom catalysts for enhanced O2 evolution

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Supporting Information
High-density Cobalt Single Atom Catalysts for Enhanced Oxygen
Evolution Reaction
Pawan Kumar,1
* Karthick Kannimuthu,1†
Ali Shayesteh Zeraati,1†
Soumyabrata Roy,2
Xiao
Wang,3‡
Xiyang Wang,4
Subhajyoti Samanta,5#
Kristen A. Miller,2
Maria Molina,1,6
Dhwanil
Trivedi,1
Jehad Abed,7
M. Astrid Campos Mata,2
Hasan Al-Mahayni,3
Jonas Baltrusaitis,5
George
Shimizu,6
Yimin Wu,4
Ali Seifitokaldani,3
Edward H. Sargent,7
Pulickel M. Ajayan,2
Jinguang
Hu,1
* and Md Golam Kibria1
*
1
Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University
Drive, NW Calgary, Alberta, Canada
2
Department of Materials Science and NanoEngineering, Rice University, 6100 Main St.,
Houston, TX 77030, USA
3
Department of Chemical Engineering, McGill University, Montreal H3A 0C5, Canada
4
Department of Mechanical and Mechatronics Engineering, Waterloo Institute for
Nanotechnology, Materials Interface Foundry, University of Waterloo, Waterloo, Ontario N2L
3G1, Canada
5
Department of Chemical and Biomolecular Engineering, Lehigh University, B336 Iacocca Hall,
111 Research Drive, Bethlehem, Pennsylvania 18015, United States
6
Department of Chemistry, University of Calgary, 2500 University Drive NW, T2N 1N4 Calgary,
Canada
7
Department of Electrical and Computer Engineering, University of Toronto, 10 King's College
Road, Toronto, ON, M5S 3G4, Canada
*Email: Pawan Kumar (pawan.kumar@ucalgary.ca); Jinguang Hu (jinguang.hu@ucalgary.ca);
Md. Golam Kibria (md.kibria@ucalgary.ca)
†Contributed equally

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‡Current Address: Department of Chemical Engineering, Massachusetts Institute of Technology,
Cambridge, MA 02139, USA
#
Current Address: Department of Chemical Sciences (DCS), Tata Institute of Fundamental
Research (TIFR), Mumbai, 400005, India
Contents
1.0 Experimental details
1.1 Reagents and Materials………………………………………………………………... Page S4
1.2 Physicochemical characterization……………………………………………………... Page S4
2.0 Synthesis of materials
2.1 Synthesis of cobalt phthalocyanine tetramer (C120H24N32O24Co4)…………………………..…..Page S9
2.2 Synthesis of melem, (2,5,8-triamino-s-triazine)…………………………………………………..Page S10
2.3 Synthesis of single atom Co-N4(pyridinic)-MM (CoMM)…………………………………………... Page S10
2.4 Synthesis of single atom Co-N4(pyridinic)-ML (CoML)…………………………………………..…Page S11
2.5 Synthesis of single atom Co-N4(pyrrolic)-GML (CoGML)……….……………………………...... Page S12
2.6 Synthesis of Co entrapped in N-doped carbon nanotubes using melem (Co-CMM)……..… Page S12
2.7 Synthesis of Co entrapped in N doped carbon nanotubes using melamine (Co-CML)……. Page S13
2.8 Synthesis of carbon nitride (g-C3N4; CN)………………………………………………………....Page S13
3.0 Electrochemical Studies
3.1 Electrochemical characterizations…………………………………………………………..…… Page S13
3.2 Electrochemical OER………….…………………………………………….………………….…. Page S13
4.0 Additional Characterizations
4.1 XPS analysis of CoPc tetramer……………………………………………………….………Page S18
4.2 Surface area analysis………………………………………………………………….......…. Page S20
4.3 Electron energy loss spectroscopy (EELS)…………………………………………..….… Page S28
4.4 Electron Paramagnetic Resonance (EPR)……………………………………………...…. Page S32
4.5 Raman analysis…………………………………………………………………………...…… Page S33
4.6 Fourier transform infrared spectroscopy (FTIR)………………………………………… Page S34
4.7 X-ray diffraction (XRD)……………………………………………………………………… Page S35
4.8 Synchrotron-based Wide-angle X-ray scattering (WAXS)………………………………. Page S36
4.9 X-Ray Photoelectron Spectroscopy (XPS) and Auger electron spectroscopy (AES).... Page S38
4.10 XPS and Raman analysis of Co-Mel-600…………………………………………...… Page S42
4.11 NEXAFS for C K-edge and N K-edge……….…………………..………………….….Page S43
4.12 Synchrotron-based soft-X-ray NEXAFS analysis for Co L-edge…………….…….. Page S45
4.13 XANES analysis……………………………………………………………………….…. Page S46
4.14 Post OER ICP-OES analysis of electrolyte…………………………………………….Page S55
4.15 Post OER XPS analysis………………………………………………………………......Page S56
4.16 Post OER Raman analysis…………………………………………………………….....Page S57
Scheme S1. Synthetic protocol of -COOH and -CONH2 cobalt phthalocyanine tetramer…….….... Page S10
Scheme S2. Plausible condensation mechanism of CoPc and melamine/melem………….………...Page S12
Figures
Figure S1. FE-SEM, EDX mapping and spectra of CoCML……………………..…………..….… Page S14
Figure S2. FE-SEM images, EDX elemental mapping and spectra of CoCMM……...………….. Page S15
Figure S3. HR-TEM and SAED images of CoCMM……………………………………….……… Page S16
Figure S4. HR-TEM, FFT and SAED images of CoCML………………….……………………. Page S17
Figure S5. HR-TEM image of CoGML………………………………………………………....... Page S18
Figure S6. XPS spectra of CoPc and type of carbon and nitrogen in deconvoluted HR-XPS…........Page S19
Figure S7. N2-adsorption desorption isotherm, pore size distribution of samples……….….…...… Page S21
Figure S8. FE-SEM, EDX mapping and spectra of CoMM……………………………...…..…….. Page S22

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Figure S9. FE-SEM images, EDX mapping and EDX spectra of CoML……………….…...….… Page S23
Figure S10. HR-TEM, AC-HAADF STEM image and EELS analysis of CoMM………….……. Page S24
Figure S11. AC-HAADF STEM images of CoMM………………………………………………..Page S25
Figure S12. HR-TEM images, STEM elemental mapping of CoML………………...………….….Page S26
Figure S13. AC-HAADF STEM and EELS analysis of CoML………………………….……....… Page S27
Figure S14. AC-HAADF STEM and EELS of CoML after 1 and 15 min of beam exposure…...... Page S29
Figure S15. AC-HAADF STEM of CoMM, EELS spectra after 1- and 15-min beam exposure…...Page S30
Figure S16. EELS spectra and comparison of overlapped EELS spectra CoMM and CoML…..…. Page S31
Figure S17. Solid-state X-band EPR spectra of CoMM and CoML……………………………….. Page S33
Figure S18. Raman, XRD and FTIR spectra of control materials……………………….……..........Page S36
Figure S19. Synchrotron-based WAXS 2D images and Q-1
values……………………………......Page S38
Figure S20. High resolution XPS spectra of CN in (a) C1s (b) N1s region………………………...…Page S39
Figure S21. XPS and Auger spectra of CoMM, CoML, CoGML, CoCML and CoCMM……...... Page S41
Figure S22. XPS and Raman spectra of Co-Mel-600………………………………………...….… Page S43
Figure S23. EEMS map and NEXAFS spectra of CoCMM for C K-edge and N K-edge……....…. Page S45
Figure S24. XANES spectra of CoCML, CoCMM, CoGML, Co nitrate, Co3O4 and CoPc…..….... Page S47
Figure S25. DRIFT spectrum of the catalysts without CO probe………………….……………... Page S48
Figure S26. LSV and Tafel plot for CoGML and CoCML……………………………….……...….Page S49
Figure S27. EIS of CoML, CoMM, IrC and PtC at 393 mV……………………………………….PageS49
Figure S28. Overpotential vs current density of catalysts ……………………………….……...…..Page S50
Figure S29. Cdl plots of samples in a non-Faradaic region……………………………………….....Page S50
Figure S30. Specific activities of CoMM and CoML electrodes…………………………………....Page S51
Figure S31. Summary of conductive graphene/N-carbon based catalysts………………………….PageS52
Figure S32. EIS-Nyquist plot of CoMM, CoML, Ir/C and Pt/C catalysts in 1.0 M KOH………..…Page S53
Figure S33. Chronopotentiometric stability of CoMM and CoML at 10 mA cm-2
……………….....Page S54
Figure S34. Chronopotentiometric stability studies for CoML…………..……………..……...…..Page S54
Figure S35. Post-OER EIS-Nyquist plot of CoML and CoMM……………………………..….….Page S55
Figure S36. XPS spectra of CoMM after OER………………………………………………….….Page S57
Figure S37. Raman spectra of CoMM after OER………………………………………………….Page S58
Figure S38. GC chromatogram of gaseous reaction product displaying intense signals of O2….......Page S59
Figure S39. Photographs of electrochemical cell used for the in operando XAS measurement…...Page S59
Figure S40. The calculated Co-Co atomic distance…………………………………………………Page S60
Figure S41. Schematics of OER mechanism over pyridinic-nitrogen-cobalt single-atom model.……...Page S61
Figure S42. Schematics of OER mechanism over pyrrolic-nitrogen-cobalt single-atom model.…….....Page S61
Figure S43. Bader charge analysis for *OH and *O intermediates………………………………...…....Page S62
Figure S44. Electron density difference for *OH and *O intermediates on the pyrrolic model………...Page S63
Tables
Table S1. Elemental composition/types of C and N’s of CoPc using XPS……….………………... Page S20
Table S2. Elemental composition of Co-NC samples using XPS and ICP-OES………………...….Page S21
Table S3. The quantification of N and C present in Co-NC samples using XPS……………......…..Page S31
Table S4. Elemental composition of Co-based samples using EELS……………………………….Page S32
Table S5. Surface area, mean pore diameter and pore volume of the samples…………………...…Page S41
Table S6. The EXAFS fitting parameters show coordination number (C.N.) and bond length……Page S47
Table S7. Previously reported N-carbon/graphene-based electrocatalysts…………………………Page S52
Table S8. ICP-OES analysis results of pure KOH electrolyte and CoMM electrolyte after 16 h…….…..Page S55
Table S9. The calculation of average Co-Co distance………………………………………….…...Page S60
Table S10. The calculated electron energy from DFT (EDFT)……………………………………...…...Page S63

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1. Experimental details
1.1 Reagent and materials
Dicyandiamide, DCDA (99%), melamine (99%), cobalt chloride hexahydrate, CoCl2.6H2O (98%),
pyromellitic dianhydride, PMDA (97%), ammonium molybdate tetrahydrate, (NH4)2MoO4
(99.98%), urea (99%), glucose (99.5%), ammonia solution, NH4OH (25%), carbon black
(>99.95%), graphite flakes (>100 mesh), KOH (≥85%), H2SO4 (99.99%), Nafion (5 wt% in a
mixture of lower aliphatic alcohols and water, contains 45% water), HPLC grade water were used
throughout the experiments.
1.2 Physicochemical characterization
1.2.1 Field-emission scanning electron microscopy (FESEM)
The morphology and microstructural attributes of synthesized materials were analyzed using field-
emission scanning electron microscopy (FESEM) on a FEI Quanta 250 FEG field emission SEM,
operating at 10 keV with XFlash 5030 detector and armed with EDS analysis.
1.2.2 High-resolution transmission electron microscopy (HR-TEM)
The nanoscopic structural attributes of the materials were determined using a high-resolution
transmission electron microscopy (HR-TEM), recorded on an FEI Titan 80-300 LB operating at
an acceleration voltage of 300 KeV. The HR-TEM images of CoCML, CoGML and CoCMM
samples were collected on a JEOL JEM-ARM200CF S/TEM operating at an acceleration voltage
of 200 keV.
1.2.3 Aberration-corrected high-angle annular dark field-scanning transmission electron
microscopy (AC-HAADF-STEM)
Scanning transmission electron microscopy (STEM) elemental mapping of the samples was
recorded on Thermo Scientific Talos 200X operating at 200 keV equipped with an X-FEG source
and four in-column SDD Super-X detectors. The obtained .dm4 and .dm3 files were further

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processed with Gatan micrograph software to measure the d-spacing, FFT, iFFT, and live profile.
The aberration-corrected high-angle annular dark-field STEM (AC-HAADF-STEM) images of the
samples were collected on an FEI Titan 80-300 HB TEM/STEM operating at an accelerating
voltage of 200 keV from an XFEG source. The obtained .emi files were processed using TIA (TEM
Imaging & Analysis) software and converted into .dm4 files.
1.2.4 Electron energy loss spectroscopy (EELS)
The FEI Titan 80-300 HB TEM/STEM microscope possesses the feature of double aberration-
corrected TEM/STEM and is armed with EELS spectroscopic accessories. The EELS was used to
determine the inner shell ionization edge (core loss) of different elements present in the sample.
The EELS spectra were obtained by mapping the selected area and elemental composition was
calculated from an annular dark field (ADF) electron image to know the position of C K-edge, N
K-edge, O K-edge, and Co L-edge. Further, the processing of images was done in the Gatan
micrograph to calculate the elemental composition of the samples.
1.2.5 X-ray diffraction (XRD) pattern
The crystalline nature of the materials was determined using X-ray diffraction (XRD) recorded on
a Bruker D8 Discover instrument using Cu-Kα radiation (40 kV, λ = 0.15418 nm) equipped with
a LynxEYE 1-dimensional detector. The spectra were accumulated by using a scan size of 0.02°
within a 2θ range of 4–60°.
1.2.6 X-ray photoelectron spectroscopy (XPS)
The binding energies of various elements in the materials and surface/subsurface (~10 nm)
chemical composition were determined using X-ray photoelectron spectroscopy (XPS) on an Axis-
Ultra, Kratos Analytical instrument and a monochromatic Al-Kα source (photon energy ≈1486.7
eV, source voltage-15 kV, current-10 mA, power-50 W, Rowland circle monochromator) under
ultrahigh vacuum (∼10−9
Torr). The instrument’s work function was calibrated using binding
energy (BE) of metallic Au 4f7/2 line at 83.96 eV. The charge correction and binding energies of
all the elements were referenced with respect to C1s binding energy of adventitious carbons (BE
≈ 284.8 eV). The obtained data in .vms format were processed using CasaXPS (2.3.23PR1.0)
software. The XPS peak fitting and deconvolution were done by following previously reported
literature at a magic angle (~54.7º), using Shirley baseline and Lorentzian asymmetric (LA) and
Gaussian-Lorentzian (GL) function.1-4
The quantification of elements was done by considering
relative sensitivity factors (RSF) provided in CasaXPS software. For the XPS measurement, the
sample’s thin film was deposited on FTO to minimize the charging effect.
1.2.7 Fourier transform infrared (FT-IR) spectroscopy
The chemical functional groups on the materials and vibrational features of the materials were
determined using Fourier transform infrared (FT-IR) spectroscopy on a Perkin Elmer Frontier FT-
Infrared spectrophotometer equipped with a ZnSe ATR accessory. For the measurement, the

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powder samples were mounted on a ZnSe crystal in an ATR assembly and pressed with a torque
knob. The spectra were collected in the frequency range of 400–4000 cm-1
and the final spectra
were obtained by averaging 32 scans.
1.2.8 Raman spectroscopy
The Raman spectroscopy was carried out to investigate the change in the molecular polarization
and associated scattering frequencies of the materials using a Thermo Scientific DXR2 Raman
Microscope equipped with a 532 nm laser at an incident power density of 5 mW cm−2
.
1.2.9 CO-diffuse reflectance infrared Fourier transform spectroscopy (CO-DRIFTS)
CO-probed DRIFT studies were performed in a Thermo Nicolet iS50m (mercury-cadmium-
tellurium) MCT equipped infrared spectrometer cooled with liquid nitrogen with a Harrick Praying
Mantis diffuse reflection accessory and ZnSe windows for determination of the metal dispersion
and surrounding environments. A thermocouple was attached to the Harrick cell and connected to
the temperature control cell for the analysis. The collection of the initial IR gas-phase background
was performed by placing a reflective mirror in the laser path while using the Harrick Praying
Mantis attachment. The Harrick cell was modified with Kalrez O-rings. In each measurement, 20
mg powder catalyst was loaded into the Harrick environmental cell supported over quartz wool
(HVC-DR2). The spectra were taken in the absorbance mood with a spectral resolution of 4 cm-1
comprising 96 scans. The outlet gas exhaust was cleaned using a NaOH stripping solution.
Initially, the sample surface was cleaned at 120 °C by flowing pure N2 gas controlled by a mass
flow controller, MFC (ALICAT Scientific) with a 30 SCCM flow rate for one hour followed by
ramping it to room temperature. The samples were purged with 100% pure CO gas by an MFC,
and the exhaust gas was trapped in a bleach solution. Extreme precautions were taken when
performing the CO-DRIFT analysis due to the highly poisonous nature of CO gas.
1.2.10 Electron paramagnetic resonance (EPR)
The X-band continuous wave electron paramagnetic resonance (EPR) spectra of materials were
acquired on a Bruker EMX EPR spectrometer (Germany). The instrument was equipped with ER
073 10" Magnet, 2.7 kW power supply (100 G - 10 kG operating range), high sensitivity cavity
(ER 4119 HS) high-pressure dielectric resonator, operating at X band microwave frequency (~
9.87 GHz). A magnetic field modulation of 100 kHz with an amplitude of 0.2 mT was used for
lock-in amplification while center field 3519.80 G, cavity Q quality factor was kept above 4000.
The solid samples were charged in a Pyrex EPR tube and inserted inside the RF cavity to measure
the spectrum.
1.2.11 N2 adsorption-desorption isotherm
The surface-specific properties of like Brunauer–Emmett–Teller (BET), surface area (SBET), and
Barrett–Joyner–Halenda (BJH) porosity of materials were investigated by N2 adsorption-

S7
desorption isotherms at 77K on Autosorb Quantachrome 1MP instrument. Before the
measurement, the samples were degassed under vacuum at 200 ºC.
1.2.12 Inductively coupled plasma-optical emission spectroscopy (ICP-OES)
The cobalt content of the samples was determined using inductively coupled plasma-optical
emission spectroscopy (ICP-OES) on a Varian 725-ES ICP-OES. The samples for the ICP-OES
were prepared by leaching the samples in a concentrated 3/1 HCl/HNO3 solution at 70 ºC followed
by dilution with water. Five standard samples were also measured to prepare a calibration curve.
1.2.13 Soft X-ray absorption spectroscopy (sXAS):
To understand the electronic and bonding state of the materials, synchrotron-based soft X-ray
absorption spectroscopy (sXAS) was utilized. The soft X-ray-ultraviolet (SUV) beamline of the
Singapore synchrotron light source facility was used for the analysis of most of the samples except
CoCML and CoCMM. The beamline operating energy range was 3.5–1500 eV, monochromator-
VLS-PGM, deviation angle 140-176.3º, spectral resolution- 104
(E/ΔE) @100eV, 10 µm slit width
and spot size 2x 0.2 mm2
. The XAS analysis of CoCML and CoCMM samples was performed at
spherical grating monochromator (SGM) beamline 11ID-1 of the Canadian Light Source (CLS)
synchrotron operating in the energy range of 250 to 2000 eV. All measurements were performed
in an ultrahigh vacuum (~10-6
Torr), at room temperature. For the analysis, samples were deposited
on carbon tape that was mounted on a tin holder and secured in a vacuum chamber. The sample
holder was mounted at 45º w.r.t. to beam and detectors and irradiated with soft X-ray while keeping
the spot size 50 and 100 microns using the Kirkpatrick-Baez mirror system. An Amptek silicon
drift detector (SDD) with an energy resolution of ~100 eV was used for the measurement of partial
fluorescence yield (PFY). Additionally, total electron yield (TEY) was also determined and
compared signals with PFY. Before the measurement, Excitation-Emission Matrix Spectroscopy
(EEMS) was measured to know the energy edges of all the elements present in the materials in an
energy range of 250 to 2000 eV (energy resolution ~5 eV). EEMS maps were obtained on a
spherical grating monochromator by screening the incident X-ray beam on the sample while
collecting emitted X-ray fluorescence spectra. Ten scans were averaged with an exposure time of
1 min. To avoid beam damage and the possibility of false signals the sample was moved 0.1 mm
after each measurement.
1.2.14 X-ray absorption near edge structure (XANES) and Extended X-ray absorption fine
structure (EXAFS)
The valence state, local chemical environment, and coordination pattern of samples were
determined by X-ray absorption near edge structure (XANES) and Extended X-ray absorption fine
structure (EXAFS) on 06ID-1 Hard X-ray MicroAnalysis (HXMA) beamline of Canadian light
source. The energy range for the beamline was 5-40 KeV with a superconducting Wiggler source
and photon flux of 1012
@12 keV. The spot size was 0.8 x 1.5 mm while the spectral resolution
was 1x10-4
. For the measurement, samples were mounted on a hollow plastic holder by depositing
samples on a Kapton® tape. Before the measurement, the energies were calibrated with standard
samples with a -1 lower atomic number metal. The measurement was done in transmittance mode

S8
and the Co edge was measured in the energy range of 7510-8350 eV. Few samples were analyzed
in the BioXAS-Spectroscopy sector of the Canadian light source operating in an energy range of
5-32 keV using a 22-poles (11 periods), 2.1 Tesla, Flat-top Wiggler source. The photon flux of the
main beamline was 1 x 1012
@12 keV with a spot size of 3 x 0.5 mm and spectral resolution of 1 x
10-4
. The optics and detector for BioXAS beamlines were: M1 mirror: Toroidal, 1 m, Si, Rh-coated,
Sagittal radius: 33 mm. Water-cooled. Monochromator: LN2 cooled, Si(220), ϕ = 0o
and 90o
,
double-crystal, non-fixed exit slit (see mono gitch database) M2 mirror: Flat Bent, vertically
focusing, 1.1 m. Si, Rh-coated Detectors: Ionization chambers, PIPS, Canberra 2 x 32-element
HPGe solid-state (Main BL) and 32-element HPGe (Side BL). The acquired data were analyzed
using Athena software.
1.2.15 Operando X-ray absorption spectroscopy (XAS)
To discern the oxidation state and coordination structure change during the electrocatalytic
conditions operando XAS was performed at the Hard X-ray MicroAnalysis (HXMA) beamline of
the Canadian light source. For the measurement, a custom-made electrochemical cell was used
which contains a plastic window fixed at 45º with respect to the beam (Figure S39). The whole
assembly was made up of stainless-steel coated Teflon and an electrode connection was linked to
the window cell. The sample deposited on carbon paper was mounted on the plastic window using
Kapton® tape to make a connection with the electrode. The cell was filled with 1.0 M KOH and
closed with a lid that has a Pt counter and Ag/AgCl electrode. The cell was fixed in a holder while
keeping the window parallel to X-ray beams and ensuring that the beam is falling on the sample
surface. After that XANES spectra were collected in transmittance mode at an open-circuit voltage
(OCV) and 1.773 V vs RHE.
1.2.16 Synchrotron-based Wide Angle X-ray Scattering (WAXS)
The fine details of the sample's crystalline nature and validation of the absence of any nanoparticles
in single-atom catalysts (CoMM, CoGML and CoML) were done by synchrotron-based wide-
angle X-ray scattering (WAXS) measurement. The WAXS analysis was carried out at 04ID-1
BXDS-WLE Low Energy Wiggler Beamline of Canadian light source. The energy range for this
beamline was 7-22 keV, with a maximum photon flux of 1 x 1012
to 5 x 1012
photons/s in focus on
the sample at 250 mA ring current. The typical spot size was 150 μm vertical x 500 μm. Other
parameter were as follow: resolution: ΔE/E, Si (111): 2.8 × 10-4
at 7.1 keV to 6.4 × 10-4
at 15.9
keV. Si (311): 2.5 × 10-4
at 12.9 keV to 4.5 × 10-4
at 22.5 keV, photon energy: 15116 eV (λ =
0.8202 Å) using Si(111) and default detector: Dectris Mythen2 X series 1K. For the measurement,
a small amount of powder sample deposited on glass slides was mounted on multisamples holder.
The X-ray wavelength was 0.8202 nm (15116 keV) while the detector distance was 170 mm. For
the calibration, a standard LaB6 sample was measured and the obtained q-1
values were compared
with the reported value (also available on the CLS site:
https://brockhouse.lightsource.ca/about/low-energy-wiggler-beamline/).5
The acquired .xye files
were processed to calculate q-1
and d-spacing using GSAS-II software.
1.2.17 Density functional theory (DFT)

S9
DFT studies were carried out using the Gaussian and Plane Waves method (GPW) in the Quickstep
module of the CP2K software package.6
We employed Goedecker–Teter–Hutter (GTH)
pseudopotentials7-8
with an energy cutoff of 450 Ry in all simulations. The optimization of
different systems adopted the double-ζ shorter-range (DZVP-MOLOPT-SR-GTH) basis set
optimized in molecular calculations9
and the Perdew-Burke-Ernzerhof (PBE) exchange-
correlation functional within the generalized gradient approximation (GGA).10
. To capture Van
der Waals interactions, we harnessed Grimme et al.’s DFT-D3 dispersion correction method11-12
with the Becke-Johnson (BJ) damping function.13
Additionally, to cancel out the spurious
electrostatic interactions because of the asymmetry of the slabs14-15
, we applied dipole correction
in perpendicular to the catalyst surface.16
We created the pyridinic-nitogen-cobalt and pyrrolic-nitrogen-cobalt single-atom models from a
graphene structure with periodic boundary conditions. Each unit cell has a height of 30 Å to ensure
enough vacuum space for each system. For the geometry optimizations, the convergence criteria
for the maximum force acting on each atom were set to be 0.023 eV/Å, and the BFGS method was
used as the optimizers. Although many reaction mechanisms for OER have been investigated17-19
,
we adopted the conventional mechanism involving *OH, *O, and *OOH intermediates considering
that *O-O* coupling is unlikely to take place on single-atom catalysts.
The Gibbs free energy (G) of each system was calculated using the harmonic limit case of the
thermochemistry module in the Atomic Simulation Environment (ASE).20
More specifically, we
determined the Gibbs free energy of each system by considering the calculated electron energy
from DFT (EDFT), the zero-point energy (EZPE), the thermal energy (∫CVdT), the temperature (T
at 298.15 K), and the entropy (S). A detailed summary of these terms for each system is listed in
Table S10. The equation used to calculate G is shown below.21-22
G = EDFT + EZPE + ∫CVdT – TS (1)
The Bader charge analysis was performed using the Bader analysis program written by Henkelman
et al.23-25
The charge density difference plots were generated from the cube files containing the
electronic density.
2.0 Synthesis of materials
2.1 Synthesis of cobalt phthalocyanine tetramer (CoPc: C120H24N32O24Co4)26
Cobalt phthalocyanine hexadecacarboxylic acid tetramer, CoPc-(COOH)16 was prepared by
following the literature method with slight modification (Scheme 1). Cobalt chloride
hexahydrate, pyromellitic dianhydride (PMDA), ammonium chloride and urea were calculated
according to an appropriate molar ratio and ground together. The obtained mixture was
transferred to a beaker and heated in a household microwave at 700 W for 10 min (in 2-3 steps).
The resulting product was grounded and washed with methanol to remove soluble uncondensed
organics. The obtained powder was treated and digested in 200 mL of 2M HCl saturated with

S10
sodium chloride and filtered. The obtained solid was dispersed in 200 mL of 2M KOH
containing NaCl followed by heating at 90 ºC. The green-blue solution was filtered to remove
the insoluble part. The liquid solution was acidified with 200 mL of 2M HCl and the flocculated
solid was separated by centrifugation followed by redissolving in 0.1M KOH and filtration. The
obtained solution was again acidified to precipitate the phthalocyanine and centrifuged. This
process was repeated three times to remove unreacted organic and metallic impurities. The
obtained hexadecacarboxy-cobaltphthalocyaine tetramer (CoPc-(COOH)16: CoPc) was dried at
70 ºC.
Scheme S1. Synthetic protocol of cobalt phthalocyanine tetramer and amido cobalt phthalocyanine
tetramer.
2.2 Synthesis of melem, (2,5,8-triamino-s-triazine)27-28
Melem (2,5,8 -triamino-s-heptazine) was synthesized by thermal annealing of melamine (10 g) at
425 ºC for 12h in an alumina crucible covered with a lid. The obtained powder was grounded well
and refluxed in DI water to remove any unreacted melamine and soluble impurities. The obtained
suspension was centrifuged, and the resulting white powder was dried under a vacuum. The
resulting data were well-matched with the reported literature.29
2.3 Synthesis of single atom Co-N4 (pyridinic) porous graphenic network using melem Co-
N4(pyridinic)-MM (CoMM)
The single atom cobalt decorated graphenic catalysts (CoMM) with porous structure was prepared
by thermal annealing of melem and ammonia-treated cobaltphthalocyanine tetramer precursor. In
brief, 200 mg (0.0746 mmol) CoPc was dissolved in ammonia solution (NH4OH) to convert it to

S11
CoPc-CONH2 and mixed with melem powder (2 g) until a slurry was obtained. The resulting
mixture was stirred for 30 min to get a homogeneous mixture. The afforded mixture was dried at
70 ºC in a vacuum oven to remove water and ammonia. The resulting powder was grounded well
and annealed at 800 ºC under N2 flow (60 mL/min) with a heating rate of 5 ºC/min. After cooling,
the obtained black powder was directly used for the electrode fabrication.
2.4 Synthesis of single atom Co-N4 (pyridinic) graphene network using melamine Co-
N4(pyridinic)-ML (CoML)
The single atom cobalt decorated graphenic catalysts (CoML) with graphenic structure was
prepared using melamine and CoPc precursor by following a similar protocol used for the
synthesis of CoMM, except the amount of melamine was tripled (6 g) considering the theoretical
condensation degree.
The carboxyl groups present on the CoPc provide sites for the growth of carbon nitride
framework. At elevated temperature, cyclization of neighboring COOH groups on CoPc
produces CoPc anhydride which reacts with melamine/melem to form cyclic imides.30
The
reaction of CoPc cyclic imides with melamine and melem forms NH-linked polymeric
melamine and melem units respectively, which finally condensed to CoPc entrapped CN
framework above 550 ºC. The CoPc entrapped CN framework after further condensation and
carbonization yielded graphenic structures. Since stable melem units condense at a high
temperature via N bridging and do not cyclize like melamine, therefore relatively small domains
remain available for the fusion in case of melem condensation. Our studies reveal that upon
carbonization, C6N7 units fuse to form a C-N graphenic structure which is supported by the
existence of C6N7 stochiometric CNs reported theoretically.31-32
The random polymerization
and lack of cementing effect led to the growth of porous structure in CoMM.

S12
Scheme S2. Plausible condensation mechanism of CoPc and melamine/melem (1) structure of CoPc (2)
formation of CoPc anhydride30, 33
(3) reaction between CoPc anhydride and melamine/melem to produce
imide. It should be noted that CoPc and melamine react at 325 ºC while CoPc and melem react at 425 ºC to
form imide linkage. Melamine also self polymerize at <320 ºC to create a branched crosslinked network
while melem forms a sparse crosslinked network above 525 ºC.34-37
(4) melamine cross-linked network
after further condensation translates to graphenic structure. (5) melem’s spacious structure condenses into
a porous structure due to the less availability of molecules for self-condensation.
2.5 Synthesis of single atom Co-N4 (pyrrolic) graphene network using melamine and glucose
Co-N4(pyrrolic)-GML (CoGML)
For the synthesis of single atom Co-N4 (pyrrolic) graphenic structure, melamine, CoPc, and
urea were used as precursors. In brief, 200 mg (0.0746 mmol) CoPc was dissolved in an
ammonia solution followed by mixing with melamine (6 g) and glucose (2 g) powder to make
a slurry. The obtained slurry was dried at 70 ºC under vacuum and the resulting solid was
grounded well. The final CoGML catalysts were obtained by thermal annealing of the mixture
at 800 ºC under N2 flow (60 mL/min) with a heating rate of 5 ºC/min.
2.6 Synthesis of cobalt entrapped in N-doped carbon nanotubes using melem (CoCMM)
The cobalt metal entrapped in N-doped carbon nanotubes (CoCMM) was synthesized by using
cobalt nitrate instead of CoPc while following a similar protocol as discussed above. In brief,

S13
10 mg (0.084 mmol) of CoCl2.6H2O was dissolved in a minimum amount of water and mixed
with 2 g of melem powder to make a thick slurry and stirred for 30 min. The obtained slurry
was dried at 70 ºC, grounded, and annealed at 800 ºC under N2 flow (60 mL/min) with a heating
rate of 5 ºC/min. Previous literature using carbon nitride-impregnated cobalt chloride has also
reported the formation of Co entrapped CNTs (Co-CNTs).38
2.7 Synthesis of cobalt entrapped in N-doped carbon nanotubes using melamine (CoCML)
The cobalt metal entrapped in N-doped carbon nanotubes (CoCML) through melamine was
synthesized by following a similar protocol as CoCMM except using melamine (3 times)
instead of melem.
2.8 Synthesis of carbon nitride (g-C3N4; CN)39
A control sample of carbon nitride was also prepared by thermal annealing of melamine at 550
ºC in programmed heating of 8 °C min-1
up to 300 ºC and 2 °C min-1
up to 550 ºC and finally
holding the temperature 550 °C for 4 h. The resulting yellow solid was crushed in a mortar
pestle.
3.0 Electrochemical Studies
3.1 Electrochemical characterizations
The electrochemical studies of the built SACs were carried out using an Autolab workstation. For
the electrode fabrication, 3 mg of electrocatalyst, 0.8 mL ethanol and 200 μL isopropanol were
mixed and kept in ultrasonication for 1h to form a complete homogenous ink. 68.5 μL of the
obtained dispersion was drop-casted on a carbon paper (AvCarb MGL190, Fuel cell store) at (1×1)
cm2
which corresponds to the loading of 0.205 mg cm-2
. The electrode was dried at 70 ºC for 4h
and directly used as electrodes for the analysis. Finally, the developed electrodes were ready for
the OER and HER experiments.
3.2 Electrochemical OER studies
Electrocatalytic OER studies were carried out in a typical three-electrode electrochemical setup
using 1 M KOH as electrolytes respectively. A graphite sheet as a counter electrode, Ag/AgCl as
a reference electrode and the prepared Co electrodes acted as working electrodes. O2-saturated
fresh KOH electrolytes (50 mL) were used to study OER. After 10 CV scans at 100 mV s-1
, LSV
studies were carried out at a scan rate of 5 mV s-1
. The LSV curves are 50% iR-corrected from the
Rs values read in the EIS analysis. The EIS was tested at different applied potential biases with an
AC amplitude of 0.005 V in the frequency range of 100 kHz to 0.1 kHz. Electrochemical active
surface area (ECSA) was derived from the Cdl method in a non-Faradaic region (0.0-0.1 V vs
Ag/AgCl) and calculated from ja-jc vs . The obtained Cdl was converted into ECSA by the
following formula,
ECSA = Cdl/Cs
where Cs is the specific capacitance and for flat electrodes, the value is around 0.04 mF cm-2
. The
stability of the electrodes was measured via the galvanostatic method at a constant current density
of 5 mA cm-2
for 300 h in OER. TOF for OER was calculated using the following formula,
TOF = jS/4nF

S14
where, j – current density, S – geometrical surface area, n – active molar sites (from ICP-MS), and
F – Faraday constant. The mass activity was calculated as follows,
Mass activity = Current density (j)/loading (mg)
where the loading values were derived from the ICP-OES analysis and defined at various
overpotentials. The specific activity of the electrodes was measured by normalizing the current
with the calculated ECSA values. For the comparison, Ir/C and Pt/C electrodes were prepared in
the same way and tested for activity and stability.
4.0 Additional Characterizations
Figure S1. FE-SEM images of CoCML at (a) 20 μm (b) (c) 4 μm scale bar showing the cobalt entrapped carbon
nanotubes-like structure. EDS elemental mapping (d) composite of C and Co (e) Co map showing the presence
of Co NPs in nanotubes (f) EDX spectra of CoCML. Key points: SEM images of CoCML showing the presence
of a nanotube-like structure with cobalt embedded at the top of the tips. EDX elemental mapping demonstrates
the presence of Co NPs centered at the tip of nanotubes. EDX spectra confirm a significant concentration of Co
in the materials.

S15
Figure S2. FE-SEM images of CoCMM at (a) 100 μm scale bar showing bunches of Co-containing nanotubes.
(b) FE-SEM images at 500 nm scale bar showing the individual nanotubes with earthworm type structure and
Co at the tip of the nanotubes (c) FE-SEM image at 4 μm scale bar displaying bundles of Co entrapped carbon
nanotubes-like structure. EDS elemental mapping (d) composite of C and Co (e) Co map showing the presence
of Co NPs at the tip of nanotubes (f) EDX spectra of CoCMM. Key points: SEM images of CoCMM showing
the presence of a nanotube-like structure with cobalt embedded at the tip of tubes. EDX elemental mapping
demonstrates the presence of Co nanoparticles centered at the tip of nanotubes. EDX spectra confirm a
significant concentration of Co in the materials.

S16
Figure S3. HR-TEM image of CoCMM at (a-b) 200 nm (c) 100 nm (d) 50 nm scale bar showing Co entrapped
nanotubular structure. (e-g) HR-TEM image at 20 and 10 nm scale bar displaying cobalt core and carbon shell
along with lattice fringes of the carbon structure. (h) magnified region of g displaying lattice fringes and d-
spacing of 0.37 nm. Bottom inset showing d-spacing calculated from live profile. (i) SAED pattern of the image
showing diffraction ring due to the presence of monocrystalline Co. Key points: Low magnification images in
(a-d) show the presence of dark Co NPs in the carbonaceous matrix. High magnification TEM images in (e-g)
displayed lattice fringes of crystalline stacked carbon around Co NPs. SAED pattern exhibits rings
corresponding to crystalline carbon and Co.

S17
Figure S4. HR-TEM image of CoCML at (a) 50 nm (b) 20 nm scale bar showing Co entrapped nanotubular
structure. (c) HR-TEM image at 10 nm scale bar displaying lattice fringes of carbonaceous structure. Bottom
inset: displaying interplanar d-spacing of 0.36 nm. Top inset: showing d-spacing calculated from live profile.
(d) HR-TEM image at 10 nm scale bar showing crystalline Co core at the tip of nanotubes. (e) magnified part
of the image d showing lattice fringes of Co, Top inset: FFT of the selected region displaying the interplanar
distance of 0.224 nm, Bottom inset: d-spacing calculated from live profile. (f) SAED pattern of the image shows
a faint diffraction ring due to the presence of monocrystalline Co. Key points: Low magnification images
revealing the presence of dark Co NPs embedded in N-doped carbonaceous nanotubes. High-magnification
TEM images displayed lattice fringes and corresponded to stacked carbon. HR-TEM images in (d-e) show
metallic Co embedded in carbon with a lattice spacing of 0.225 nm. FFT exhibits the presence of a sharp dot
corresponding to monocrystalline cobalt. SAED reveals the crystalline nature of Co in the material.

S18
Figure S5. HR-TEM image of CoGML at (a) 200 nm (b) 100 nm scale bar showing nanosheets type structure
(c) 50 nm and (d) 20 nm scale bar displaying an absence of any nanoparticles and lattice fringes originating
from short-range stacking. Inset in d showing amorphous nature of CoGML. Key points: HR-TEM images and
corresponding FFT of CoGML show amorphous materials and no trace of Co NPs/clusters.
4.1 XPS analysis of CoPc tetramer
The chemical composition of CoPc and the oxidation state of Co were determined using XPS
analysis. The survey scan of CoPc for elemental analysis displayed all core level peaks (C1s, N1s,
O1s, and Co2p) and inner/sub-core-level peaks (OKLL, O2s, Co3s, Co3p) corroborating the
presence of all the constituting elements in the CoPc skeleton (Figure S6a). The C, N, O and Co
atomic percentage was close to the theoretically calculated ratio demonstrating a well-constituted
CoPc structure (Table S1). High-resolution XPS (HR-XPS) of CoPc in the C1s region can be
deconvoluted into three peak components centered at 284.2, 285.3 and 287.5 eV (Figure S6b).
The XPS peak component at the ≈BE 284.2 and 285.3 eV originated from the sp2
C of benzenic
(Cbenzene) and pyrrolic (Cpyrrole) rings of isoindole constituted phthalocyanine framework.40-41
It
should be noted that pyrrolic Cs are attached to two more electronegative carbons and thus

S19
appeared at a higher BE value. The calculated atomic ratio of Cbenzene/Cpyrrole was found to be
∼3.08/1.00 which matched well with the theoretically calculated ratio of 3.00/1.00 (Table S1).
The XPS peak at a higher BE value of 287.5 eV was assigned to carboxylic (COOH) carbons. The
Cbenzene+Cpyrrole/CCOOH ratio of CoPc was calculated to be 85.42/14.58 (5.86/1.00) which was in
close agreement with the theoretically calculated value of 86.66/13.33 (6.5/1.00). The slight
variation might be due to some isoindole units were not completely functionalized. The N1s XPS
spectra of CoPc demonstrate two peak components located at 398.2 and 399.0 eV originated from
the ring (Nring) and pyrrolic (Npyrrolic) nitrogens constituting the 18π cyclic conjugated system
(Figure S6c).42-44
The calculated atomic ratio of Nring/Npyrrolic was found to be 54.88/45.12
(1.21/1.00) close to the theoretically calculated 1/1 ratio (Table S1). Similarly, the O1s spectra of
CoPc were deconvoluted into two peak components centered at 530.4 and 531.8 eV attributed to
carbonyl C=O and hydroxyl (OH) groups of COOH. The ratio of C=O and OH peak components
was found to be 50.03/49.97 (1/1), slightly lower than the expected value (1/1) (Figure S6e). The
above-mentioned observations and calculated ratios of various carbons and nitrogens demonstrate
the presence of a well-constituted phthalocyanine network with carboxylic group
functionalization. The two intense XPS peak components at the BE value of 780.40 and 795.60
eV resulted from the Co2p3/2 and Co2p1/2 peak components of cobalt present in the +2 state (Figure
S5f).45
Figure S6. XPS spectra of CoPc (a) survey scan, HR-XPS in (b) C1s and (c) N1s region. (d) show the type of carbon and
nitrogen in deconvoluted HR-XPS (e) O1s and (f) Co2p region.

S20
Table S1. Theoretical and calculated elemental composition/types of carbon and nitrogen in CoPc using XPS
Survey C N O Co
Observed 41.29 16.12 36.65 5.93
Theoretical 49.38 15.36 26.34 8.08
HR-XPS Cbenzenic Cpyrrolic COOH Npyrrolic Nring
Observed 64.52 20.90 14.58 45.12 54.88
Theoretical 60.00 26.66 13.33 50.00 50.00
4.2 Surface area analysis
The surface properties of the materials such as Brunauer-Emmett-Teller (BET), surface area
(SBET), Barrett-Joyner-Halenda (BJH) pore diameter (rp) and pore volume (Vp) were determined
using N2 adsorption-desorption isotherm (Figure S7a). The N2 adsorption-desorption isotherm
of CoMM displayed type-IV isotherm with H3 hysteresis loop in the partial pressure (P/P0) range
of 0.6-1.0, demonstrating the mesoporous nature of the materials with ink bottle shaped pores.46-
48
The calculated mean pore diameter (rp) and pore volume (Vp) of CoMM were found to be
82.433 Å and 0.382724 cm³/g (Figure S7b). The shape of the adsorption-desorption isotherm and
mean pore diameter between 2-50 nm indicate the mesoporous nature of materials as per the
IUPAC recommendations.49-50
As expected CoMM displayed the highest surface area of 185.71
m2
g-1
among all the samples due to its porous structure which is also confirmed by TEM (Table
S2). In contrast, the CoML shows type-II adsorption-desorption isotherm with an H4 hysteresis
loop and a nonreversible desorption loop suggesting slit shape mesopores. The calculated SBET,
rp, and Vp of CoML were found to be 37.81 m2
g-1
, 75.031 Å and 0.071788 cm³ g-1
. The observed
slit-shaped mesopores and relatively low surface area and pore volume compared to CoMM
demonstrate that the graphenic structure in CoML possesses severe stacking thus blocking
accessible surface area and mesopores. The long-range graphenic structure in CoGML leads to a
type-I adsorption-desorption isotherm consisting of an H4 hysteresis loop with SBET, rp and Vp
values of 73.16 m2
g-1
, 20.026 Å and 0.036486 cm³ g-1
respectively. These observations
demonstrate the microporous nature of the materials.51-52
Since graphenic structure formation
using glucose as a precursor proceeds via cyclization with a significantly small loss of carbon and
gas evolution and therefore CoGML has a less porous structure. However, due to the presence of
large 2D graphenic sheets the surface area of the sample was relatively higher than the CoML.
Interestingly, CoCML and CoCMM displayed type IV adsorption-desorption isotherm with H2
hysteresis loop suggesting mesoporous structure evolves in Co embedded nanotube-like
structure.53
The SBET, rp and Vp value of CoCML were calculated to be 40.05 m2
g-1
, 55.033 Å
and 0.058193 cm³ g-1
while these values for CoCMM samples were found to be 43.40 m2
g-1
,
52.593 Å and 0.058193 cm³ g-1
, respectively.

S21
Figure S7. Bottom to top (a) N2 adsorption-desorption isotherm (b) pore size distribution of CoMM, CoML,
CoGML, CoCML and CoCMM.
Table S2. The calculated surface area, mean pore diameter and pore volume of the samples
Samples Surface area, SBET (m2
g-
1
)
Mean pore diameter rp (Å) Pore volume Vp (cm³ g-1
)
CoMM 185.71 82.433 0.382724
CoML 37.81 75.031 0.071788
CoGML 73.16 20.026 Å 0.036486
CoCML 40.05 55.033 Å 0.056834
CoCMM 43.40 52.593 0.058193

S22
Figure S8. FE-SEM images of CoMM at (a) 10 μm scale bar showing the porous structure (b) EDS elemental
mapping showing a composite of C, N and Co (c) only Co. FE-SEM images at (d) 4 μm (e) 1 μm scale bar
displaying magnified porous structure (f) image showing graphitic sheets structures. (g) elemental mapping for
Co (h) composite of C, N, O and Co. (i) EDX spectra of CoMM. Key points: SEM images of CoMM display
a porous structure composed of a graphenic sheets. Mapping demonstrates the uniform distribution of Co in the
carbonaceous scaffold.

S23
Figure S9. FE-SEM images of CoML at (a) 20 μm (b) 4 μm scale bar displaying graphinic structure. (c) EDS
elemental mapping showing the distribution of Co. EDS composites map of (d) C, N and Co (e) C, N, O and
Co. (f) EDX spectra of CoML. Key points: The FE-SEM images of CoML show graphene-type sheets and
exclude the possibility of bigger nanoparticles. Mapping images demonstrate that Co was homogeneously
distributed over the sheets. EDX spectra demonstrate a sharp peak for Co suggesting a higher concentration of
Co in the sheets.

S24
Figure S10. HR-TEM image of CoMM (a) at 100 nm scale bar showing porous structure (b) at 10 nm scale bar
displaying graphenic structure; bottom right inset: the enlarged image of the marked area showing localized
carbon stacking generated lattice fringes; bottom left inset: d-spacing calculated from live profile. Top right
inset: FFT of complete images showing the amorphous nature of the materials. (c) HR-TEM image and
corresponding FFT. (d) SAED pattern showing absence of any diffraction pattern for metallic Co NPs. (e) AC-
HAADF STEM images of CoMM at (e-h) 2 nm scale bar; white arrow displaying bright spots for single atom
cobalt. The inset in (h) is showing the line intensity profile for the bright Co center corroborating the presence
of a single atom. (i) annular dark field (ADF) electron image of the area mapped for the EELS spectrum. EELS
mapping for (j) N (k) Co (l) C (m) O. (n) corresponding EELS spectrum showing the peak for Co L-edge. Inset
is an RGB composite of C (red), N (green) and Co (blue). Key points: Low magnification HR-TEM images of
CoMM displaying the highly porous nature of the materials. High-magnification HR-TEM images show the
absence of any nanoclusters. FFT and SAED patterns show the amorphous nature of the material. AC-HAADF-
STEM shows the presence of single atoms while the line scan reveals an intense profile for single atoms. EELS
maps show uniformly distributed Co SA over the carbonaceous/nitrogenous scaffold. EELS spectra show the
presence of Co-L3 and Co-L2 energy loss peaks.

S25
Figure S11. AC-HAADF STEM images of CoMM at (a,b) 5 nm scale bar (c,d) 2 nm scale bar showing the
dense distribution of single Co atoms (bright spots).

S26
Figure S12. TEM images of CoML at (a) 0.5 μm (b-c) 100 nm scale bar showing nanosheet morphology (d)
SAED pattern of the selected area in image c showing absence of any crystalline features. (e-g) high-resolution
TEM images of CoML showing the absence of nanoparticles or nanoclusters. Inset in image (f) shows the FFT
with no diffraction pattern. (h) enlarged HR-TEM image of the area in figure g showing amorphous graphenic
structure and inset FFT further confirm the absence of any nanoparticle/nanocluster. (i) STEM electron image.
Elemental mapping of CoML for (j) C, (k) Co (l) N (m) O and (n) corresponding EDX mapping. Key points:
Low magnification HR-TEM images of CoML displays graphenic structure. The absence of any additional ring
in the SAED pattern excludes the possibility of any nanoparticles/nanoclusters. Images at high magnification
(10 nm scale bar) and their FFT show amorphous nature and the absence of any nanoclusters. STEM mapping
images confirm the uniform distribution of N and Co on the graphenic sheets. EDX further confirms the
presence of high concentration of Co.

S27
Figure S13. AC-HAADF STEM images of CoML at (a) 5 nm and (b) 1 nm scale bar; white arrow and circles
displaying bright spots for single atom cobalt. (c-e) at 5 nm and (f) expanded image at 1 nm scale bar; white
arrow and circles displaying bright spots for single atom cobalt. The inset in (f) is showing the size of the bright
spot is 0.65 Å corroborating the presence of a Co single atom. (g) at 5 nm showing single atoms of Co (h)
annular dark field (ADF) electron image of the area mapped for the EELS spectrum. EELS mapping for (i) C
(j) O (k) Co (l) N and RGB composite of (m) C (red), N (green) and Co (blue). (n) EELS spectrum of the
complete area in image h and (o) EELS spectrum of small spot marked in the image h. Key points: AC-
HAADF-STEM images show the presence of Co single atom structures. Line scan for intensity profile shows
intense regions for Co atoms. EELS mapping and composite images show the absence of any nanoclustering
and the presence of Co on graphenic sheets. EELS spectra of a small pixel in the ADF image show the presence
of Co with a populated concentration of isolated Co.

S28
4.3 Electron energy loss spectroscopy (EELS)
The chemical structure, electronic environment and bonding pattern of the materials were
deduced using electron energy loss spectroscopy (EELS). The elemental composition of the
CoML and CoMM was determined by processing the EELS spectra and the results are
summarized in Table S3. A certain area of the materials at high magnification was scanned for
the EELS data collection and used for the elemental mapping. To validate the ubiquitous
distribution of Co, small pixels were also used for EELS spectra determination which displayed
a sharp peak of Co suggesting Co was homogeneously distributed (Figure 2, S10 and S13). Since
high energy electron beam was utilized during EELS measurement, we observed that samples
tend to degrade after long beam time exposure (Figure S14-15). Previous reports also
demonstrate N rich carbonaceous materials lose N content under beam exposure.54-55
Thus, the
obtained quantification of the materials using EELS is not conclusive and just provides an
approximation of the elemental composition. We have determined the elemental composition of
the materials after 1 and 15 min beam exposure time. It can be seen from Table S3 that after 15
min beam exposure, the N content was gradually reduced while C and Co contents were increased
demonstrating some N-rich sites were degraded under high energy beam.
The full range EELS spectra of CoML and CoMM displayed all peaks associated with C K-edge,
N K-edge and Co L-edge energy losses verifying the well-constituted N-rich carbon scaffold
containing a significant amount of cobalt (Figure S16a). To understand the bonding pattern in
the materials, we carefully evaluated the C K-edge and N K-edge energy loss regions of CoML
and CoMM. The C K-edge signal of CoML and CoMM displays two peak components located at
284.8 and 294.7 eV assigned to 1s-π* and 1s-σ* electronic transition in sp2
hybridized carbons
present in N-rich hexagonal framework (Figure S16b).56-57
Similarly, N K-edge regions
displayed two peak components centered at 400.9 and 408.8 eV corroborated to 1s-π* and 1s-σ*
electronic transition in sp2
hybridized N doped in the carbonaceous network (Figure S16c).58
Interestingly, the relative intensity of π* C K-edge and N K-edge signal intensity of CoMM was
higher compared to CoML, suggesting the increased conjugation degree in the CoMM.29, 59
The
increased conjugation degree can be explained due to the use of fused three-membered triazine
containing heptazine precursor which can easily coordinate with phthalocyanine and conjugate
during the annealing step. On the other hand, the synthesis of CoML was executed using the
melamine precursor which polymerizes during the thermal annealing steps followed by
coordination with CoPc. Thus, the fusion of monomeric triazine ring to heptazine ring might
introduce many points and sp3
defects in the CoML structure resulting in a decreased conjugation
degree.

S29
Figure S14. AC-HAADF STEM images of CoML at 5 nm scale bar (a) after 1 min of beam exposure showing
the absence of any NPs/clusters (b) after 10 min of beam exposure showing the formation of nanoclusters. AC-
HAADF STEM images of CoML at 5 nm scale bar (c) after 1 min of beam exposure display the absence of any
nanoclusters. (d) ADF electron image of the same area after 10 min of beam exposure mapped for EELS
showing the beam damage and formation of cobalt clusters. EELS mapping of the selected area showing the
distribution of (e) N (f) C (g) O and (h) Co (i) EELS spectrum of image d showing Co L-edge (Inset showing
RGB map of C, N, and Co). Key points: EELS map collected in just 1 min do not show any clustering however
after 15 min beam exposure Co gets agglomerated and showed visible nanoclusters.

S30
Figure S15. AC-HAADF STEM images of CoMM at 5 nm scale bar (a) after 1 min of beam exposure showing
the absence of any NPs/clusters (b) after 10 min of beam exposure showing the formation of nanoclusters. AC-
HAADF STEM images of CoMM at 5 nm scale bar (c) after 1 min of beam exposure show the absence of any
nanoclusters. (d) ADF electron image of the same area after 10 min of beam exposure mapped for EELS
showing the beam damage and formation of cobalt clusters. EELS mapping of the selected area showing the
distribution of (e) Co (f) C (g) O and (h) N (i) EELS spectrum of image d showing Co L-edge (Inset showing
RGB map for C, N and Co). Key points: AC-HAADF-STEM and EELS ADF images show the absence of any
nanoclusters after 1 min of data collection, however, Co clusters were observed after 15 min of beam exposure.

S31
Figure S16. Electron energy loss spectroscopy of (a) Full range data showing C K-edge, N K-edge and Co L-
edge of CoMM (lower panel) and CoML (upper panel). Overlapped EELS spectra of CoMM and CoML in (b)
C K-edge region and (c) N K-edge region showing π* and σ* transition.
Table S3. Elemental composition of CoMM and CoML determined using EELS spectrum.
EELS
Element CoMM
after 1
min
(At%)
At.
ratio
CoMM
after 15
min
(At%)
At.
ratio
CoML
after 1 min
(At%)
At. ratio CoML
after 15
min (At%)
At. ratio
C 64±2 1.00 75±3 1.00 61±2 1.00 66±2 1.00
N 25.7±0.9 0.40 20.3±0.8 0.27 31.8±1.1 0.52 25.7± 0.9 0.39
O 4.1±0.14 0.064 1.5±0.06 0.021 3.56 ± 0.12 0.059 3.6± 0.13 0.056
Co 6.4±0.2 0.10 3.14±0.12 0.042 3.91 ± 0.13 0.064 4.60±0.16 0.07

S32
Table S4. Elemental composition of Co containing samples determined using XPS survey scan and ICP-OES
XPS (at%) ICP-OES
Sample C N Co O Co (wt%) Co
(μmol/mg)
CoMM 44.69 52.13 3.18 2.57 10.6 1.800
CoML 44.42 53.02 2.54 3.55 11.13 1.889
CoGML 81.63 17.4 0.97 6.28 - -
CoCML 91.64 3.94 4.42 3.06 8.90 1.511
CoCMM 92.42 2.63 4.95 3.12 18.13 3.114
4.4 Electron Paramagnetic Resonance (EPR)
Room temperature Electron Paramagnetic Resonance (EPR) of solid CoMM and CoML was
measured to deduce the paramagnetic nature and charge relaxation mechanism. Due to the
extreme ferromagnetic nature of Co NPs and clusters, they usually give an intense broad band at
the g value ≈ 2.870. Notably, we have not observed any metallic Co-related signals suggesting
the absence of any clustering in the materials. Despite the ferromagnetic nature of single atom
Co2+
sites, no detectable signal was observed due to their short relaxation time which was in
closed agreement with previous reports on Co-N-C SACs.60
Usually, graphenic materials with extended conjugation demonstrate EPR signals at g value ≈
2.000 due to the presence of free charge carriers in sp2
domains. In a defect-free extended π
network, the fast relaxation rate led to a diminution of the signals.61
Further, previous reports also
suggest that isolated metal centers such as Fe, decrease the relaxation time, therefore, reducing
the EPR signal intensity.62-63
As can be seen from Figure S17, the CoMM does not show any
trace of EPR signals at a g-value of ≈ 2.000 demonstrating the presence of an ordered long-range
π conjugated network. Since melem was used as a precursor for the synthesis of CoMM, it can
condense more efficiently with CoPc and with other melem units to form a long-range network.
The presence of a higher conjugation degree in CoMM was also obvious in the EELS spectra
which demonstrates relatively intense π* transition peaks in C K-edge and N K-edge spectra
(Figure S16b-c). It should be noted that even after extreme porous structure, the CoMM displayed
a higher conjugation degree suggesting planer CoPc and melem condense laterally to produce
ordered localized planer structure. In contrast to CoMM, CoML displayed a broad EPR signal at
a g-value of ≈2.000 which arises from the localized defects slowing the relaxation time (Figure
S17). Since melamine was used as a precursor for the synthesis, it requires additional
condensation steps to form melem units followed by the evolution of ammonia. The condensation
of melamine units to form heptazine units and conjugation with CoPc leaves plenty of room for
the introduction of defects in CoML compared to CoMM where melem units directly react with
CoPc.

S33
Figure S17. Solid-state X-band EPR spectra lower panel: CoML and upper panel: CoMM.
4.5 Raman analysis
To validate the successful synthesis and the nature of chemical functional groups, Raman spectra
of materials were collected and displayed in Figure 2a and Figure S18a. Raman spectra of
CoMM and CoML displayed a broad Raman signal extended in the frequency range of 1150-
1700 cm-1
due to cumulative D and G bands (Figure 2a).64
In general, the D band originates due
to the out-of-plane vibration of sp3
hybridized carbon and nitrogen while the G band is a feature
of in-plane vibration of sp3
hybridized C/Ns in the graphitic framework.65
However, in contrast
to graphenic materials which possess sp2
/sp3
carbons and show distinct well-separated D and G
bands, CoMM and CoML displayed a broad band. As materials were prepared by using melem
and melamine precursors and possess a significantly high N content, the carbon nitride (CN) type
structure might be dominating in the materials. Due to the presence of sp2
N bridged alternate C-
N structure, CN is not completely planer thus out-of-plane incoherent vibration of C-N's in
heptazine constituted structure gives rise to the D band.66-67
The intensity of the D band is highly
dependent on the N content.68
Since CN has high N content, the D band remains dominating, and
a broad peak is observed due to the high permutation of vibration modes. Indeed, the Raman
spectra of CoMM and CoML were closely matched to CN except for shifting of the D and G band
suggesting partial retainment of CN-type structure.69
To compare the chemical structure of
CoMM and CoML, we also measured Raman spectra of carbon black (CB), reduced graphene

S34
oxide (RGO) and nitrogen-doped reduced graphene oxide (NRGO) (Figure S18a). It can be seen
from Figure S18a, that CB displayed a sharp D and G band with an intense 2D band. The 2G
band represents intensive π-π stacking in the materials.70
Contrarily, RGO displayed a weak D
band suggesting the removal of oxygen functionalities and reversal of sp2
structure. Further, 2D
band intensity for RGO was also increased. Interestingly, after N doping, the 2D peak intensity
in NRGO was significantly decreased. These comparisons demonstrate that CoMM and CoML
have intensive N doping that leads to decreased 2D band intensity. However, graphenic/carbon
black type structure cannot be verified since the D and G bands were merged. Previous studies
suggest that high-temperature treatment of carbon nitride generates C6N7 (heptazine) units.71
In
our synthesis protocol, these units can fuse with growing melem-CoPc conjugate to form a
carbonaceous structure with a C6N7-type atomic arrangement. It is worthy to mention, that the
formation of melem or melamine to C6N7 units will proceed with the removal of terminal NH2
groups thus overall structure will be similar to graphene except N atoms are more periodically
arranged as in CN.72
Indeed, this structural model explains the exceptionally high N content,
pyridinic structure, and diminished 2D band. Furthermore, distinct from CN, the Raman band
positions for the CoMM and CoML were almost identical to CB and NRGO, which further
strengthens the presence of a fused planer structure with plenty of Ns arranged in a similar fashion
as in CN. Such periodic arrangement of N in graphenic structure is reported for 2D g-CN, C3N,
C5N C2N polymers.73-75
The C1s and N1s XPS spectra of CoMM and CoML also displayed peak
features similar to CN but with increased C-C intensity suggesting some N’s were lost during the
annealing step (Figure 2g-h and Figure S20).
In contrast, the Raman spectra of CoGML, CoCML and CoCMM display sharp D and G bands
with an almost negligible contribution of 2D band indicating the formation of NRGO-type
graphitic structure.76
Interestingly, the peak corresponding to Co metallic vibration at 672, 517,
462 and 186 cm-1
were quite evident in the Raman spectra of CoCML and CoCMM validating
the presence of metallic Co embedded in the carbon matrix. These peaks were absent in CoML
and CoMM despite their equal Co concentration which substantiates the presence of Co in a
highly dispersed state.
4.6 Fourier transform infrared spectroscopy (FTIR)
To investigate the chemical structure of the materials, infrared active vibrational features were
measured using FTIR (Figure S18b). The FTIR spectra of the melem exhibited a sharp peak at
791 cm-1
due to the bending vibration of the C3N3 (δC3N3) ring system suggesting the successful
formation of the melem.77
A broad band at the frequency of 3084 cm-1
appeared due to the
stretching vibration of –NH2 (νN–H) groups along with a small contribution in the range of 3283-
3459 cm-1
originated from the intercalated water molecules (νO–H). The bending vibration of
intercalated molecules (δO–H) also gives a sharp band at ~1600 cm-1
. The broad bands extended
from 1230-1520 cm-1
originated due to the combinational stretching vibration of the C6N7 unit.
CN also displayed similar vibrational features except for the intensity of νN–H and δO–H was
decreased due to the removal of NH2 groups and intercalated water present in the H-bonded

S35
structure.78
The synthesis of CoML and CoMM proceeds via the fusion of melem and melem-
cobaltphthalocyanine units thus specific C3N3 stretching vibrations feature of melem/CN at 791
cm-1
was lost suggesting the integration of C6N7 units in N-rich carbon scaffold. The presence of
trace C3N3 signals and a broad C-N stretching region substantiate the formation of an N-rich
carbonaceous scaffold that was arised via direct C6N7 fusion. However, compared to N-doped
reduced graphene oxide (NRGO) the C-N stretching features remain strong suggesting a
relatively higher concentration of N in CoMM and CoML. Indeed, the FTIR spectra of CoMM
and CoML were closer to CN except for free NH2 and C3N3 stretching features lost indicating the
formation of an N-doped graphene-type structure with an atomic arrangement of N’s close to CN.
4.7 X-ray diffraction (XRD)
XRD spectra of CoMM, CoML, and CoGML displayed a broad peak around ~26º due to (002)
reflection of amorphous carbon and a very faint peak around ~43º due to (100) plane (Figure
2b).79
The broad peak in all these materials demonstrates the amorphous nature of the materials.
It is interesting to note that CoCML displayed a sharp (002) peak demonstrating intensive π-π
stacking in the material.80
Additional peaks centered at 44.10, 51.57 and 75.75º were also
observed and assigned to (111), (200) and (220) planes of metallic α-Co with face-centered cubic
(fcc) structure.38, 81-82
Compared to CoCML, the (002) peak intensity for the CoCMM was
decreased suggesting a less stacked structure. To gain further insight, the XRD pattern of melem
and CN was also collected (Figure S18c). Melem exhibited sharp XRD peaks at 6.1, 12.3, 26.7,
and 30.9º that were closely matched with previously reported XRD features of H-bonded
melem.77, 83
The absence of any of these peaks in the CoML and CoMM displays that
melem/melamine was completely fused without a trace of melem/melamine. CN on the other
hand displayed characteristic signature peaks at 12.9 and 27.3º due to in-plane spacing and
stacked sheet structures.84
The (002) peak of CN was found to be slightly higher compared to
CoCML and CoMM suggesting better stacking in CN sheets which arise due to the populated
electronegative N atoms in the CN structure. Further information on the localized structural
attributes was derived from the synchrotron based WAXS analysis and is explained in the next
section.

S36
Figure S18. (a) Comparison of Raman spectra of CoML and CoMM with carbon black (CB), reduced graphene
oxide (RGO), and nitrogen-doped reduced graphene oxide (NRGO). (b) FTIR spectra of NRGO, melem, CN,
CoML and CoMM. (c) XRD spectra of melem, CN, CoCML and CoMM. Key points: The peaks corresponding
to the (100) plane of CN were absent while the (002) peak was shifted to a lower 2θ value in CoCML and
CoMM due to the graphitization of the carbon nitride framework. CoMM displayed decreased peak intensity
suggesting transformation to the carbonaceous structure. CoCML displayed peaks for the (111), (200) and (220)
due to the presence of metallic α-Co with a face-centered cubic (fcc) structure.
4.8 Synchrotron-based wide-angle X-ray scattering (WAXS)
To deduce the nanocrystalline attributes and localized crystalline features of the materials,
synchrotron-based wide-angle X-ray scattering (WAXS) was performed. Synchrotron-based
radiation allows better resolution and detection limits on a sub-nanometric scale due to the use of
a relatively high-energy monochromatic beam.85-86
The wavelength (λ) of CLS beamline radiation
was 0.8202 Å compared to CuKα radiation (1.5418 Å), a better spectral resolution can be
achieved.5
Due to the variation in wavelength parameters, the Q value (in Å-1
) which is
independent of incident beam wavelength is reported for comparison with existing data.87
Further,
corresponding d-spacing was also calculated. The WAXS 2D map of the CoMM does not display
any narrow diffraction ring corresponded to any Co species suggesting the absence of any
nanoscale clustering in the materials (Figure 2c).88-89
However, the presence of a few dimeric to

S37
oligomeric species cannot be neglected since EXAFS displayed a small contribution of Co-Co
interaction. It should be noted that AC-HAADF STEM and EELS at high magnification do not
show any clusters thus the Co-Co interaction might arise just because of the contribution of a few
dimeric to tetrameric Co species embedded in graphenic scaffold. An intense broad band at a Q
value of 1.846 Å-1
corresponding to 3.37 Å d-spacing originated due to (002) reflection of stacked
graphenic sheets (Figure 2e).90-91
Another minuscule band at 3.070 Å-1
(2.04 Å spacing) was
assigned to (110) plane of the conjugated 2D structure.92-93
In contrast, the CoCML prepared
using cobalt salt and melem displayed a sharp circular ring in the WAXS 2D map validating the
presence of crystalline Co NPs (Figure 2d). The calculated Q values and corresponding d-spacing
validates that the Co was present in the metallic α-Co state which was in close agreement with
the X-ray diffraction results (Figure 2f).94
Similarly, the CoML and CoGML do not display any
other peak except (002) and (110) diffractions suggesting the monomeric distribution of Co
(Figure S19a-b, d-e). CoCML also displayed all features that appeared in CoCMM for metallic
Co (Figure S19c and f). It is interesting to note that the d-spacing of CoGML synthesized using
glucose was found to be 3.64 Å which was relatively higher than other materials. Since d-spacing
demonstrates the distance between sheets and is sensitive to effective interaction between sheets
and the presence of defects, it can give an idea about the nature of the interaction. The replacement
of carbon with relatively more electronegative N in graphenic structure induces asymmetric
charge distribution resulting in increased attraction between the sheets thereby reducing d-
spacing. The institution of defects in planer graphenic structure introduce out-of-plane sp3
C and
N functional groups leading to enhanced d spacing. As CoGML synthesis was achieved using O-
rich glucose and carbonization proceeds via a complex carbonization process of ring formation
thus numerous defects and residual O groups remain in graphenic structure leading to increased
d spacing. The XPS quantification in Table S5 also demonstrates a high population of C=O/O-
C=O (10.41/5.07) compared to 2-3% in CoMM/CoML. Despite the low N content compared to
CoGML, the CoCML and CoCMM displayed smaller d-spacing which was due to better
graphitization and stacking of graphenic structure. The better stacking of CoCML and CoCMM
was clearly evident from the HR-TEM image showing long-range order lattice fringes. The
smallest d-spacing (3.37 Å) was observed for the CoMM which was close to CN suggesting
partial preservation of N-rich structure and better graphitization. CoML on the other hand has a
d-spacing of 3.47 Å demonstrating plenty of defects in the structure. The comparison of EELS
spectra in Figure S16 verifies that π* contribution in CoMM was higher compared to CoML due
to less abundant defects. The abundance of sp3
C/N in CoML was also strengthened by a relatively
intense D band in Raman spectra.92

S38
Figure S19. Synchrotron-based WAXS 2D map and obtained Q-1
values of (a and d) CoML (b and e) CoGML
and (c and f) CoCMM.
4.9 X-Ray Photoelectron Spectroscopy (XPS) and Auger electron spectroscopy (AES)
The surface/subsurface (~10 nm) chemical composition and elemental binding energies of the
materials were determined using X-Ray photoelectron spectroscopy (Figure 2g-h and Figure
S20-21). The XPS survey scan of CoMM, CoML, CoGML, CoCML, and CoCMM displayed
core-level and sub-core-level peaks associated with C and N. For the CoMM, CoML, and
CoCML, the Co high and low energy core-level transition peaks (Co2s, Co2p, and Co3s) were
quite obvious while CoGML does not display any detectable peak. The absence of Co peak for
the CoGML was due to significantly low concentration because of a high degree of graphitization
of glucose as confirmed earlier from ICP-OES. The detailed quantification of all the materials is
presented in Table S4. Interestingly, the N content of the CoMM and CoML was significantly
higher (52.13 and 53.02 at%) compared to CoGML (17.4 at%), CoCML (3.94 at%), and CoCMM
(2.63 at%). Despite CoCML and CoCMM being synthesized using the same melamine and melem
precursors, the N contents were astonishingly low compared to CoML and CoMM suggesting
CoPc promotes stabilization of N functionalities due to conjugate formation between CoPc and
melamine/melem. Since CoPc has a planer structure and plenty of available COOH groups, it can
react with -NH2 functionalities of melamine/melem and facilitates efficient fusion of rings
without elimination of ring Ns. Furthermore, conjugation also provides a long-range order
bonding enhancing the thermal stability excluding loss of N during the annealing step. The
observed value of N content for CoCML and CoCMM was in close agreement with the previously
reported protocols.38
The evidence that CoPc promotes stabilization of N-rich units due to

S39
conjugate formation was also provided by CoGML where CoPc, glucose, and melamine were
used as precursors and displayed a high N-content of 17.4 at%.
The core-level high-resolution (HR) XPS spectra of materials in the C1s region were
demonstrated in Figure 2g. The deconvoluted C1s HR-XPS spectra of CoMM and CoML exhibit
four different peak components assigned to C-C, N-(C)3, N=C-N/C-N, and O=C-O carbons. It is
worth mentioning that the N=C-N/C-N peak components intensity of CoMM and CoML was
significantly higher validating the presence of high N content. The peak features were quite
similar to XPS spectra of CN except C-C intensity was increased suggesting successful
carbonization of materials while N remains inside the conjugated ring system (Figure S20).
Additionally, the K2p3/2 and K2p1/2 peak components in CoMM and CoML originated from the
residual potassium in CoPc.95-96
In contrast, CoGML, CoCML and CoCMM displayed entirely
different XPS features matching closely with N-doped carbon with higher C content representing
different carbonization mechanisms similar to graphitization of carbonaceous precursors.
The HR-XPS spectra of CoMM and CoML in the N1s region displayed three peak components
(Figure 2h). The major intense peak components at relatively low BE originated from the C-
N=C/pyridinic Ns (Npyr.) while another relatively less intense peak component resulted due to the
combinational contribution of pyrrolic Ns (Npyrr.) and Co bonded Ns (Co-N).97-99
A significantly
small shoulder peak was also observed at a higher BE value for the graphitic Ns. Fascinatingly,
for CoGML, CoCML, and CoCMM, the contribution of pyrrolic peak components drastically
increased reaching the highest value for the glucose-assisted CoGML.100
The at% of Npyridinic in
CoMM and CoML was found to be 66.88 and 74.12 which was significantly higher compared to
CoGML (50.14), CoCML (55.06), and CoCMM (55.56).38, 101
Previous reports displayed that M-
N4-graphenic catalysts with pyridinic N-bonded metals (Co, Fe, etc) are relatively more stable
compared to pyrrolic N-coordinated metal centers. The pyridinic N configuration provides
stability to the CoMM catalysts.99
Figure S20. High-resolution XPS spectra of CN in (a) C1s (b) N1s region.

S40
The O1s spectra of all the materials displayed two peak components with a major contribution of
residual C=O/N=C-O and a minor peak contribution for the surface adsorbed -OH functionalities
(Figure S21b).102
The Co2p HR-XPS spectra of all materials displayed two major Co2p3/2 and
Co2p1/2 spin-orbit splitting.103
The BE value of the Co2p3/2 peak component for CoMM and
CoML was found to be 779.9 and 780.2 eV respectively demonstrating that Co was present in a
2+ state which was also in the agreement with XANES and soft X-ray analysis (Figure S21c).104
The HR-XPS of CoGML does not display any peak which was assumed due to extremely dilute
Co concentration arising from the large degree of graphitization in glucose-assisted synthesis. As
expected, the CoCML and CoCMM displayed the Co2p3/2 peak component at a relatively low BE
value due to the presence of Co in the (0) oxidation state.38, 105
It should be noted that due to the
encasing of Co metal in the carbon matrix, the CoCML and CoCMM do not show any trace of
oxidized Co2+
(Co oxides) species. Furthermore, Auger electron spectroscopy (AES) which is
very much sensitive toward the surface composition was used for determining the presence of Co.
All samples except CoGML displayed a CoLMM peak in the 710-718 eV energy range (Figure
S21d).106-107
Since Co in CoMM and CoML graphenic scaffold was present in a more exposed
state compared to CoCML and CoCMM, relatively high CoLLM peak intensity was observed for
the CoMM and CoML. As expected, no Auger peak for CoGML was observed due to a less
populated concentration of Co.

S41
Figure S21. (a) XPS survey scan (b) O1s (c) Co2p and (d) CoLMM Auger spectra of Bottom to top: CoMM,
CoML, CoGML, CoCML and CoCMM respectively.
Table S5. The quantification of different types of Ns and Cs present in Co-containing samples determined using
XPS.
Sample Npyridinic Npyrrolic Ngraphitic C-C/C=C C-N3/C-N N-C=N C=O O-C=O
CoMM 66.88 29.12 4.0 43.12 12.06 34.53 - 2.11
CoML 74.12 24.19 1.67 37.91 17.3 30.11 - 3.06
CoGML 50.14 41.36 8.23 57.97 26.55 - 10.41 5.07
CoCML 55.06 33.43 11.51 71.37 17.12 - 5.54 3.22
CoCMM 55.56 35.93 8.51 64.51 16.0 - 11.63 4.91

S42
4.10 XPS and Raman analysis of the material prepared via annealing of CoPc and melem
at 600 ºC (Co-Mel-600)
To understand the effect of annealing temperature on the structure of CoPc-melem conjugate and
graphitizational level, the CoPc and melem mixture was annealed at 600 ºC (denoted as Co-Mel-
600) and analyzed with XPS (Figure S22a-e). The XPS survey scan demonstrates all core/sub-
core-level peaks associated with C, N, O, and Co (Figure S22a). The HR-XPS spectra of Co-
Mel-600 in the C1s region were deconvoluted in three peak components centered at 284.8, 286.5,
and 288.1 eV assigned to C-C, C-(N)3 and N-C=N carbons (Figure S22b).108-109
It can be seen
that C1s spectra demonstrate a significant contribution of secondary N-C=N carbons suggesting
retainment of CN framework at 600 ºC. The similarity of C1s spectra with CN also suggests that
the N-rich framework was preserved during annealing and supplies N during the fusion of rings
in the graphitization step. The four peak components at BE values of 398.5, 399.4, 401.0, and
403.4 eV in N1s spectra were assigned to C-N=C, N-(C)3, primary/uncondensed C-NH2, and
aromatic skeleton’s π-π* transition (Figure S22c).110-111
A sharp XPS peak in O1s XPS spectra
of Co-Mel-600 demonstrated two peak components due to residual uncondensed N-C=O/C=O
(531.7 eV) functionalities and surface adsorbed -OH groups (Figure S22d).112
The incorporated
Co was still present in the 2+ state (BE≈781.0 eV) with a peak showing Co-N contribution (783.9
eV) (Figure S22e).113
These findings suggest that the CoPc unit was incorporated into the CN
framework at elevated temperature, however, the CN structure was not carbonized at 600 ºC and
requires >600 ºC to fuse the CN and CoPc ring system. Furthermore, Raman spectra of Co-Mel-
600 displayed an intense broad band extending from 970-1735 cm-1
originating from the
combinational vibration of the D and G bands (Figure S22f). The presence of a combinational
bands in Raman spectra again suggests the N Rich framework with plenty of out-of-plane
vibrations associated with C-N=C nitrogen.

S43
Figure S22. XPS spectra of Co-Mel-600 (a) survey scan. Core-level HR-XPS in (b) C1s (c) N1s (d) O1s (e)
Co2p regions (f) Raman spectra of Co-Mel-600.
4.11 Near Edge X-Ray Absorption Fine Structure (NEXAFS) for C K-edge and N K-edge
Synchrotron-based near-edge X-ray absorption fine structure (NEXAFS) spectroscopy using soft
X-ray was performed to determine the electronic state and coordination pattern of the materials
(Figure S23). The N K-edge NEXAFS spectra of materials are given in Figure 2i and Figure
S23d. The N K-edge NEXAFS spectra of CN displayed two characteristics π* resonance peaks
centered at 396.0 and 398.9 eV, assigned to the π*C–N=C transition of nitrogen in heptazine (C6N7)
units and π*N–C3 of bridging nitrogen (Figure 2i).114-115
Another broad region corresponding to
σ* resonance originated due to the contribution of σ*C–N and σ*C–N=C transitions. As expected,
CoPc exhibited two signature π* peaks at 394.6 and 396.7 eV assigned to π*C-N(ring) resonance of
ring nitrogen and π*C-N(pyrrolic) bonded to the cobalt center.116-117
Despite the identical nitrogen in
the ring and pyrrolic units, the peak intensity of π*C-N(pyrrolic) was lower which might be due to
partial charge transfer to the cobalt center. The N K-edge NEXAFS of CoGML displayed two
intense peaks for π*C-N and π*N(pyridinic) of nitrogen at 394.7 and 396.0 eV respectively. A very
small resonance band at 397.5 eV was assigned to π*N(pyrrolic) transition corroborating the presence
of a small fraction of pyrrolic Ns.118
Interestingly, the N K-edge NEXAFS spectra of CoML and
CoMM unveil two intense π* resonance peaks at 399.7 and 402.6 eV for π*N(pyridinic) and
π*N(graphitic) transitions.119-120
The peak positions and pattern of CoML and CoMM were closely
matched to π*C–N=C and π*N–C3 of CN due to identical coordination.121-122
However, the peak
intensity π*N–C3 (assigned as π*N(graphitic) for CoML and CoMM) was significantly decreased
suggesting the removal of bridging Ns during the thermal annealing step. Based on these findings,
it can be speculated that during thermal annealing heptazine units fuse with CoPc leaving the

S44
signature of the C6N7 unit’s coordination pattern in the materials. Additionally, the relative peak
intensity of π*N(graphitic) was higher in CoMM compared to CoML which was in close agreement
with the Ngraphitic concentration calculated using XPS (CoMM-4.0 at%, CoML-1.67 at%) (Table
S5). The N-edge excitation-emission matrix spectroscopy (EEMS) map of CoCMM displays a
sharp intense band around ~285 eV corresponding to C K-edge while another faint band around
~400 eV was assigned to N Kedge. The presence of a faint N K-edge band agreed with the low
N content observed in the XPS analysis (Table S4). The NEXAFS in the N K-edge region of
CoCMM displayed three peaks for π* N(pyridinic), π*N(pyrrolic), and π*N(graphitic).
The C K-edge NEXAFS spectra of CN exhibit two main peaks in the π* resonance region. A
weak signal at 284.8 eV was attributed to the π*C=C resonance of adventitious carbons while
another sharp peak at 287.7 eV originated due to π*N-C=N transition in C6N7 units (Figure 2j).123-
124
For the CoPc, an intense peak for π*C=C was observed due to the aromatic conjugated skeleton
while another peak was assigned to π*N-C=N constituting the 18π conjugated system. CoGML
demonstrated a broad band in C K-edge NEXAFS spectra due to the presence of various carbons.
Since CoGML was prepared using oxygen-rich glucose and melamine precursor that can lead to
the introduction of various oxygen-containing carbons thus giving a wide signal. The XPS
analysis also reveals the high oxygen content in CoGML. The C K-edge NEXAFS spectra of
CoML and CoMM reveal a sharp peak for π*N-C=N resonance demonstrating the presence of plenty
of nitrogen in the structure.125
Another weak peak at 284.8 eV originated from the π*C=C
contribution of adventitious carbons and C=C coordination in the N-doped graphenic structure. It
should be noted that the π*C=C peak intensity of CoML was higher suggesting more carbon
contribution in the conjugated ring system.126
Additionally, the broader σ* region was due to sp2
σ*N-C=N and sp3
σ*C-N contributions. The C K-edge EEMS spectra of CoCMM displayed a sharp
band around ~285 eV suggesting the presence of abundant carbons (Figure S23a).127
The
NEXAFS C K-edge spectra of CoCMM displayed a sharp peak at 284.4 eV due to π*C=C
resonance of aromatic carbon of graphenic structure (Figure S23b). The peak corresponding to
nitrogen’s π*N-C=N transition was very broad and relatively weak suggesting the low N content
and the presence of chemically different Ns (Figure S23b).

S45
Figure S23. Excitation-Emission Matrix Spectroscopy (EEMS) map of CoCMM showing (a) C K-edge (b)
NEXAFS spectra in C K-edge showing π* and σ* transition. (c) EEMS map showing faint signal of N K-edge
and (d) NEXAFS spectra in N K-edge showing π* and σ* transition of pyridinic, pyrrolic, graphitic, and C-
N/C-N=C nitrogen.
4.12 Synchrotron-based soft-X-ray NEXAFS analysis for Co L-edge
To understand the chemical nature and oxidation state of the Co sites, Co L2,3-edge NEXAFS
spectra were collected using soft X-rays. The Co L2,3-edge NEXAFS spectra of CoPc displayed
two main Co L3 and L2 edges at 780.4 and 794.7 eV with a 14.3 eV separation (Figure 3a). The
Co L3-edge originated from the 2p3/2→3d while Co L3-edge was due to the 2p1/2→3d electron
transitions. Interestingly, Co L3-edge was composed of two components with a small band at
777.8 eV and complied with previously reported spectra for Co2+
state of CoPc.128
For the cobalt
nitrate, two well-resolved Co L3 and Co L2 edges were observed at 778.5 and 793.7 eV. Compared
to cobalt nitrate, the Co L3 edge energy for CoPc was higher probably because of the agglomerated
form with O/-OH coordination. Previous reports also demonstrate phthalocyanines usually
present in μ-oxo dimeric form in the bulk state.129-130
The presence of two peaks compared to one
peak in Co L3-edge spectra also verifies O-ligation at the Co sites resulting in a decreased
electronic density and the appearance of Co L3-edge peak at a relatively higher position.131
The
NEXAFS spectra of CoGML, CoMM, and CoML also displayed Co L3 and Co L2 edges at 778.7
and 793.9 eV without any splitting.132
The absence of any splitting in NEXAFS spectra of Co-
Nx-C demonstrates that CoPc basic skeleton was destroyed during the annealing step.

S46
Additionally, the Co L2,3-edge energy of CoGML, CoMM, and CoML was slightly lower than the
CoPc suggesting Co ion in graphenic structure do not have any O coordination at the Co center.
Due to the presence of an extended conjugated system in N-rich carbon, Co ion has more electron
access (electron transfer) compared to the 18π ring system of phthalocyanine. Because graphenic
structure has extensive conjugation compared to CoPc, it can be inferred that the effective charge
transfer between N coordinated graphene and Co took place. The obtained results suggest the
successful incorporation of Co2+
ions in the N-doped graphenic system.
4.13 XANES analysis
Co K-edge X-ray absorption near-edge structure (XANES) spectra of materials were collected to
elucidate the local coordination structure and oxidation state (Figure 3b,c and Figure S24). The
XANES spectra of CoPc displayed a characteristics weaker pre-edge peak at ∼7707 eV due to
1s→3d transition. The pre-edge peak represents a non-centrosymmetric coordination
environment originating from the 3d+4p mixing in the non-centrosymmetric environment
(Figure S24).133
The intense rising edge at 7713 eV was attributed to 1s→4pz transition and a
white line transition at ∼7724 eV emerged from 1s→4px,y transition. The 1s–4p + shakedown
transitions demonstrate the square planer structure of CoPc and Co was present in a 2+ oxidation
state, which was in good agreement with previously reported literature.134-135
Cobalt acetate and
cobalt nitrate display Co K-edge peaks located at 7716 and 7717 eV demonstrating the 2+
oxidation state (Figure 3c and Figure S24). On the other hand, XANES spectra of metallic Co
displayed a transition edge at lower energy representing the metallic state. As expected, CoO
displayed a transition edge at relatively higher energy due to coordination with more
electronegative oxygen (Figure 3c). Distinct from CoO, the Co3O4 with mixed oxidation state
Co2+
and Co3+
centers displayed a shift toward higher energy. The 1s→4p transition edge for
CoMM was observed at a slightly lower energy range compared to CoO due to coordination with
less electronegative N atoms (Figure 3c).98, 136
The absence of any pre-edge feature and sharp
rising edge suggests a centrosymmetric square planer structure of the Co centers. Also, high white
line intensity and absence of CoPc features suggest the fusion of CoPc macrocyclic ring in
graphene structure followed by the formation of an N-coordinated square planer structure.48
In
contrast to CoMM, CoML displayed transition edges at relatively higher energy which might be
associated with a higher oxygen content of CoML compared to CoMM (Figure 3c and Table
S4). The XANES spectra of CoGML were in the intermediate energy of CoPc and CoMM which
complies with the soft X-ray data showing a broad peak due to the presence of variable oxidation
state of Co centers (Figure 3a and Figure S24). Also, N1s XPS spectra of CoGML displayed
higher pyrrolic N content thus the coordination environment will be an intermediate of CoPc and
pyridinic N containing structure. The presence of higher O content in CoGML must also be
leading to a different coordination environment than CoML and CoMM. Interestingly, the
CoCMM prepared using metal salt displayed Co K edge matched with metallic Co validating the
encasing of metallic Co in carbon scaffold (Figure S24).

S47
Figure S24. Normalized XANES spectra of CoCML (yellow), CoCMM (violet), CoGML (green), Co nitrate
(blue), CoPc (pink), and Co3O4 (purple).
Table S6. The EXAFS fitting parameters show coordination number (C.N.) and bond length
Sample bond C.N. Length
(Å)
δ2 (10-3
) ΔE R-factor
CoML Co-N 3.93 (±0.07) 2.14 7.8 (±1.2) 3.7 (±1.5) 0.006
Co-C 3.41 (±0.09) 3.03 9.4 (±0.7) 2.3 (±1.1)
CoMM Co-N 3.99 (±0.04) 2.01 9.1 (±0.8) 9.7 (±0.4) 0.001
Co-C 3.87 (±0.08) 2.62 7.2 (±1.3) 9.3 (±0.6)
CoAcetate Co-O 3.98 (±0.03) 2.15 4.6 (±1.0) 5.7 (±1.8) 0.020
Co foil Co-Co 12* 2.49 5.9 (±0.2) 7.2 (±0.4) 0.001

S48
Figure S25. (a) Bottom to top: DRIFT spectra of the catalysts without CO probe for CoMM, CoML, CoGML,
and CoCMM. Background subtracted CO-DRIFTS time profile spectra of (b) CoML (c) CoGML obtained
at room temperature.

S49
Figure S26. OER study in 1 M KOH. (a) Polarization curves (b) Corresponding Tafel plots for CoGML (green)
and CoCML (yellow) respectively.
Figure S27. EIS of CoML, CoMM, IrC and PtC at 393 mV

S50
Figure S28. Histogram demonstrating the change in the current density of catalysts versus applied
overpotentials for OER.
Figure S29. Double-layer capacitance (Cdl) in non-Faradaic region (0-0.1 V vs Ag/AgCl). (a-e) Rectangular
Cdl response with respect to scan rates (v) with increasing ja and jc for CoMM (red), CoML (blue), CoGML
(green), CoCML (yellow) and CoCMM (violet), respectively.

S51
Figure S30. OER specific activities of CoMM (blue) and CoML (red) after ECSA normalization. (a) ECSA
normalized LSV curves, (b) Mass activity versus potential (RHE), and (c) TOF versus potential (RHE).

S52
Figure 31. Summary of conductive graphene/N-carbon based catalysts with metal loading higher than 10%
and their synthesis route. Details are summarized in Table S7.
Table S7. Previously reported N-carbon/graphene-based electrocatalysts with higher than 10 wt% metal
loading, synthesis and applications.
S. No. SAC
(wt%)
Precursor/synthesis conditions Support Application Ref.
1 Co (15.3) Co-based ZIF-67+ 750 ºC N-doped 2D
carbon NSs
ORR 137
2 Co (20) Co-doped ZIF+1100 ºC nanocarbon (NC) ORR 138
3 Cu (20.9) CuBTC
MOF+dicyandiamide+800 ºC
Nitrogenated
carbon NSs
ORR 139
4 Ni (23) 2D-ZIF-8 derived NC+
NiCl2+two step annealing
N-Carbon eCO2RR 140
5 Fe (12.1) Glucose+O-rich carbon
support+melamine+heat
N-Carbon ORR 141
6 Ni (20.3) Ni(acac)2+DCDA 800 °C Ni-CNTs eCO2RR 142
7 Ni (20) 1. oxidized CNTs+NH3+800 ºC
2. Ni(II) acetylacetonate+o-
CNT+ 400 ºC
Ni-CNTs eCO2RR 143
8 Ni (15) GQDs-NH2 (1,3,6-trinitropyrene
+ NH3)+Ni
N-graphene eCO2RR 79
9 Ni (23) CVD nanoporous Ni+ H2/Ar+
pyridine+850 °C
Ni, N-graphene Zn–Air Batteries 144
10 Fe (16) Ferrocene+perfluorotetradecanoi
c acid (PFTA) +polypyrrole
(Ppy)
N, S, and F -
doped carbon
ORR 145
11 Co (10.6) CoPc tetramer+melem+800 ºC N-Carbon OER This
work

S53
Figure S32. EIS studies at various potentials vs Ag/AgCl in 1 M KOH electrolyte. Nyquist plots of (a) CoMM
(b) CoML (c) Ir/C (d) Pt/C catalysts in 1.0 M KOH at various applied potential bias (e) comparison of Nyquist
plots at 0.5 and 0.7 V vs Ag/AgCl for CoML, CoMM, Ir/C and Pt/C electrodes. (Note – inset of each figure
depicts the magnified images especially in high-frequency regions to analyze the difference in semi-circles (Rct)
in the prepared electrodes).

S54
Figure S33. Chronopotentiometric stability study of the best active electrodes (a) CoMM and (b) CoML
compared with IrC for OER at 10 mA cm-2
in 1 M KOH for 16 h.
Figure S34. Long run stability study of CoML as anode and cathode for 200 h at 5 mA cm-2
.

S55
Figure S35. Post OER EIS studies of (a) CoMM (b) CoML.
4.14 Post OER ICP-OES analysis of electrolyte
To probe the CoMM’s catalytic stability in a long-term reaction condition, the electrolyte was
analyzed after the OER using ICP-OES analysis. To trace any Co leaching, the following
electrocatalytic OER experiments were designed to discern the stability of CoMM after OER (1)
OER at 5 mA cm-2
current density for 16 h (2) OER at 10 mA cm-2
current density for 16 h (3) CV
cycling for 500 cycles at 100 mV sec-1
. No trace of Co was detected in both galvanostatic and
potentiodynamic conditions demonstrating the resilient performance of CoMM for long-term
usage (Table S8).
Table S8. ICP-OES analysis results of pure KOH electrolyte and CoMM electrolyte after 16 h reactions.
S. No Analyte Wavelength ppm Co Molar
Concentration
1 Pristine KOH 228.616 -0.75 ~nM (too low to detect)
2 KOH after 5 mA cm
-2
for 16 h 228.616 -0.741 ~nM (too low to detect)
3 KOH after 10 mA cm
-2
for 16 h 228.616 -0.717 ~nM (too low to detect)
4 KOH after 500 cycles at 100 mV
sec
-1
228.616 -0.741 ~nM (too low to detect)
5 Standard 50 ppm Co 228.616 49.617 ~170 M

S56
4.15 Post OER XPS analysis
To investigate the chemical structure and oxidation state of Co species in CoMM, XPS analysis of
catalysts were carried out after OER experiments (Figure S36). The OER was carried out at 5 and
10 mA cm-2
current density for 16 h using a CoMM electrode coated on carbon cloth (CC). Further,
the CoMM electrode after 500 CV cycles at 100 mV sec-1
was also analyzed. XPS survey scan of
CoMM as-deposited sample and catalysts after OER displayed all the characteristics of core-level
peaks associated with Co, C, N and O (Figure S36a). An additional peak for F1s/FKLL appeared
due to fluorine present from PTFE in the carbon cloth. Wide scan XPS of as-coated electrode and
electrodes after OER in the C1s region displayed signature peak of CoMM (C-C, N=C-N and C-
N3) without any significant changes (Figure S36b). Additional peaks at high BE values appeared
from the C-F carbon of CC and residual KOH (K2p3/2 and K2p1/2) from the electrolyte. The high-
resolution O1s XPS of as-deposited CoMM show two peak components for C=O and -OH which
remain almost unchanged after OER suggesting a stable carbon skeleton (Figure S36c). Three
characteristic peaks for pyridinic, pyrrolic and graphitic nitrogen in CoMM remain intact after
OER and demonstrate robust N-rich structure of Co SACs (Figure S36d). The XPS in F1s region
also follows a similar pattern and originated from the carbon cloth substrate (Figure S36e). The
Co2p XPS spectrum of CoMM as-coated sample on CC displayed a Co2+
peak with corresponding
satellite peaks (Figure S36f). However, after OER at 5 and 10 mA cm-2
, a new peak corresponding
to the Co3+
oxidation state was also observed which might be associated with the formation of Co-
-O species (CoOOH). The formation of undercoordinated (high oxidation) species was also proved
by operando XAS analysis. The XPS analysis of the CoMM sample after 500 CV cycles also
displayed the formation of CoOOH species. These findings suggest that undercoordinated Co
species were formed during the OER.

S57
Figure S36. XPS spectra (a) survey scan (b) in C1s (c) N1s (d) O1s (e) F1s (f) Co2p region of lower to the
upper panel: CC (carbon cloth), CoMM as coated on CC, CoMM after OER at 5 mA cm-2
for 16 h, CoMM
after OER at 10 mA cm-2 for 16 h, CoMM after 500 CV cycles at 100 mV sec-1.
4.16 Post OER Raman analysis
Raman analysis of CoMM after OER at 5 and 10 mA cm-2
for 16 h was also measured to find the
formation of any metal/metal oxide species and the change in the carbon skeleton (Figure S37).
Interestingly, no significant change was observed in the Raman spectra of CoMM after OER
depicting the catalyst was stable under electrocatalytic conditions. In contrast to XPS analysis,
Raman spectra do not show the presence of any CoOOH peak due to the atomic distribution of
CoOOH species. The absence of any Co metal/metal oxide-related peak also verifies the absence

S58
of any aggregation during OER condition and explains the long-term catalytic stability.
Furthermore, the D and G bands of CoMM remain almost identical to fresh catalysts and indicate
the negligible chemical change in the carbonaceous scaffold.
Figure S37. Raman spectra in the frequency range of (a) 100-800 cm-1
(b) 100-800 cm-1
lower to upper panel:
CoMM as coated on CC (green), CoMM after OER at 5 mA cm-2
for 16 h (pink), CoMM after OER at 10 mA
cm-2 for 16 h (blue), CoMM after 500 CV cycles at 100 mV sec-1 (red)

S59
Figure S38. GC chromatogram of gaseous reaction product displaying signals of O2 OER when CoMM was
studied in 1M KOH electrolytes.
Figure S39. Digital photographs of electrochemical cell used for the operando XAS measurement (a) complete
picture of the cell (b) image showing lid with mounted reference and counter electrode while working electrode
was attached to main cell (c) back view of a plastic window with the sample having a connection with the
working electrode (d) front view of the window showing sample exposed to X-ray beam (e) picture of cell
secured and aligned on beam for the measurement and attached to the electrochemical workstation.
Literature citations for Figure 4f
1. 0.50Ni/Co/NC 146
2. 0.7-Co@NG-750 147
3. Co SA-NC 148
4. CoCo LDH 149
5. CoPc-SO3H/CNT 150
6. Co-SA-HCS 151
7. Co-TAS2
152
8. Fe3C-Co-NC 153
9. α-Co(OH)2 nanosheets 154
10. CeO2/Co(OH)2
155
11. Co9S8@MoS2
156
12. CoS-Co(OH)2@aMoS2+x /NF157
13. Co@Co3O4/NC 158

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