1. A Comparison of Hydrogen Gas Production of
Copper and Gold Catalysts for the Water-Gas
Shift Reaction
By: Roman Hodson (rh28397)
Mullins Research Group

2. Abstract
This experiment used gas chromatography (GC) to determine the H2 production rate for
the Water-Gas Shift Reaction (WGSR) using HiFUEL W220 commercial copper, gold supported
on vanadium oxide (Au/V2O5), and gold supported on cerium oxide (Au/CeO2) catalysts. The
results show that the gold catalysts on a per gram metal basis produced more H2 than the
commercial copper catalyst, which gives credence to the notion that nanoparticle sized gold
displays good catalytic activity for the WGSR. Both the Au/V2O5 and Au/CeO2 display similar
WGSR catalytic behavior.
Introduction
Catalysts are an important aspect of chemical reactions as they increase the rate of reaction
and lower the amount of free energy needed to reach the transition state for a reaction.1 A catalyst
provides an alternate pathway for a reaction with a lowered activation energy, and therefore
increases the rate of reaction with respect to the uncatalyzed process. Figure 1 provides a
hypothetical energy diagram for non-catalyzed and catalyzed pathways.
Figure 1. Activation Energy Barrier1

3. Catalysts have made their way into industrial processes, as they allow for the creation of products
with the addition of less energy to overcome the activation energy barrier. For example, industry
implements the Haber-Bosch process which uses an iron catalyst treated with potassium hydroxide
as a promoting agent to produce ammonia, an important compound in fertilizer.2 The overall
reaction for ammonia production is shown in Scheme I, and the flow scheme for the Haber-Bosch
process is outlined in Figure 2.2
N2(g) + 3H2 ↔ 2NH3 (g) ΔH = -92 kJ mol-1 (I)
Figure 2. Outline of Haber-Bosch process3
The Haber-Bosch process combines nitrogen from the air and hydrogen gas, derived mainly from
methane, in a reversible exothermic reaction.3 In addition, the creation of ammonia is performed
at high temperatures even though the reaction is exothermic, in order to overcome kinetic
limitations, as at lower temperatures the reaction proceeds at a slower rate.3 Also, the reaction is

4. held at high pressures, around 200 atm, so that the nitrogen and hydrogen molecules have a greater
chance of interacting, which ultimately increases the production rate of ammonia.3
In 2007, scientist Gerhard Ertl elucidated the mechanism and reaction energy diagram for
the synthesis of ammonia.2 The reaction energy diagram for the synthesis of ammonia is provided
in Figure 3.
Figure 3. Reaction energy diagram for synthesis of ammonia2
Scientific findings like Ertl’s provide better insight into reaction kinetics, which help to provide
information as to how to maximize products for reactions by using the least amount of energy
needed.
An increased rate of reaction can imply a lowered activation energy. However, when
comparing two catalysts, an increase in the observed rate of reaction may also indicate a greater

5. number of active sites. An active site is a location on a catalyst where the reactant or reactant binds,
which facilitates the reaction by providing a more suitable chemical environment for the reaction
to occur.4 For example, in biological processes, a substrate binds to an enzyme (the catalyst), which
facilitates a reaction.4 This induced fit model is shown in Figure 4.
Figure 4. Induced fit model4
While the number of active sites and lowered activation energy cannot be totally distinguished
from one another, Equations 1 and 2 relate the rate of production to the activation energy
𝑟𝑎𝑡𝑒 = 𝑘[ 𝐴][ 𝐵] (1)
𝑘 = 𝐴𝑒
−𝐸 𝑎
𝑅𝑇 (2)
where k is the rate constant (M-1s-1), [A] and [B] are the concentration of reactants (M), Ea is the
activation energy (kJ mol-1), R is a constant (0.0083145 kJ K-1 mol-1), T is the temperature (K),

6. and the rate is given in M s-1. By using an Arrhenius plot, the ln(k) versus 1/T is plotted, which
provides a linear fit with a slope of –Ea/R, from which the activation energy can be calculated. A
generalized Arrhenius plot is provided in Figure 5.
Figure 5. Ideal Arrhenius Plot5
For many years, gold was believed to not have any catalytic properties, as it is normally an
inert material.5 However, in recent years, gold has shown catalytic properties when the particle
sizes are on the nano-scale.6 Gold catalysis is normally performed using gold nanoparticles
deposited on a support material.6 Normally, the support material is a metal oxide which can have
catalytic properties of its own. A study by Wu et. al states that a metal oxide support with a metal
deposited on it creates new catalytic activity, which can be engineered geometrically to facilitate
oxidation, hydrogenation, and coupling reactions.7
One of the techniques used to deposit the gold nanoparticles on the support material is
known as strong electrostatic adsorption, which is based on attraction due to differences in
electrostatic charge.8 Strong electrostatic adsorption is a wet laboratory technique performed at a
pH where the electrostatic interaction between the catalyst and support material is strongest.8

7. Figure 6 shows the adsorption of metals based on the pH of solution, as indicated by the Jiao et. al
study.
Figure 6. Strong electrostatic adsorption8
Strong electrostatic adsorption consists of suspending a support material, such as V2O5
(vanadia) on which the gold can deposit, in solution of dissolved gold precursor. Then, by adjusting
the pH, the metal precursor can adsorb to the support material due to electrostatic interactions.8
Vanadia in solution forms hydroxyls on its surface when dissolved in water. Therefore, at pH
values above the isoelectric point, these hydroxyls become deprotonated, and the vanadia surface
becomes negatively charged. However, vanadia has a low isoelectric point, and its hydroxyls
become deprotonated at pH values near 3. By using a positively charged gold precursor, the gold
can deposit successfully onto the support material. In the case of the strong electrostatic adsorption
performed in this report, the gold precursor employed was Au(en)2Cl3.
These findings have led to the testing of nanoparticle sized gold as a catalyst with processes
such as the Water-Gas Shift Reaction (WGSR). The WGSR is an industrial process which converts
carbon monoxide and water into carbon dioxide and hydrogen gas, as shown in Scheme II.9
CO + H2O → H2 + CO2 (II)

8. The WGSR is an important industrial process, as it is a component of fuel processing for fuel cell
applications.10 Industrially, this process is carried out in two steps, each using a different metal
catalyst. The first stage of the process is carried out at high temperatures, ranging from 573-673
K, using an iron catalyst.9 However, this stage is thermodynamically hindered as the WGSR is an
exothermic process (∆H = -41.4kJ mol-1).9 To increase the production, a second lower temperature
step, ranging from 473-523 K, is run using a copper catalyst.9 This second step is kinetically
limited. Because of these thermodynamic and kinetic obstacles, gold has been tested as a catalyst
for the WGSR at lower temperatures in this particular experiment, and has shown good catalytic
activity.
The goal of this particular experiment is to compare the rate of H2 production for the WGSR
for Au/V2O5, Au/CeO2, and copper catalysts, as well as to determine the WGSR activation energy
for each catalyst. By calculating H2 production on a per gram basis for each catalyst, the rate of
production can be determined. This rate of production can then be used to determine the WGSR
activation energy for each catalyst.
Experimental
The first part of this experimental procedure consisted of depositing gold on to the support
materials through strong electrostatic adsorption (SEA). For the Au/V2O5 catalyst, the first step in
the SEA procedure was dissolving 43 mg of a Au(en)2Cl3 precursor in 150 mL H2O, and placing
the resulting solution in a roundbottom flask. Then, the pH was adjusted to a pH of 6 by the
addition of 1 M Na2CO3. After adjusting the pH, 2 g of vanadia was added to the solution, and was
stirred for 2 hours while keeping the pH near a value of 6. After the two hours passed, the solution
was then centrifuged, and its supernatant was discarded. The resulting solid was then washed and

9. centrifuged with deionized water three times, and was then placed in a vacuum oven at room
temperature overnight. The SEA procedure for the Au/CeO2 catalyst was the same for the
Au/V2O5, except the gold precursor was 1.66 mg of HAuCl4 in 35 mL H2O, with 1 g of the CeO2
support material.
After the synthesis of the catalysts, the WGSR was analyzed using the gas chromatogram
(GC). For the Au/V2O5 catalyst WGSR, 100 mg of the catalyst was loaded into a quartz tube and
placed in the reactor system, with a water trap placed at the base to collect water vapor. After
loading the catalyst, it underwent a pretreatment step where the temperature of the system was
raised to 300 oC at a ramp rate of 5 oC/min in a flow rate of 60 standard cubic centimeters per
minute (sccm) of H2 and 16 sccm of H2O. The temperature was held at 300 oC for a total of 2
hours. After the two hours passed, the system was cooled to 100 oC in an Ar flow of 131 sccm.
After the pretreatment steps, the WGSR was run. First, the flow rates of the gases were changed
to 3 sccm CO, 16 sccm H2O, and 131 sccm Ar, with 11.8 μL/min H2O. The effluent was then
sampled every 10 minutes at temperatures of 100 oC, 200 oC, and 300 oC, with its H2 production
observed on the chromatogram. This process was repeated for both the Au/CeO2 and copper
catalysts. After the chromatograms for each catalyst were collected, they were analyzed using
Origin software. By integrating the chromatogram peaks corresponding to the different products,
the values were converted into H2 production in units of cc/(g-Au-hr) using a calibration curve.
Results and Discussion
In the WGSR run in this report, an indicator of a good catalytic activity is determined by
the rate of production of H2. The H2 rate of production of the catalysts on a per gram basis is shown
in Figures 1-3.

10. Figure 1. H2 rate of production of Cu commercial catalyst
Figure 2. H2 rate of production of Au/CeO2 catalyst
0
500
1000
1500
2000
2500
0 50 100 150 200 250 300 350
H2RateofProduction(cc/(g-Cu-hr))
Temperature (°C)
100 C
200 C
300 C
0
1000
2000
3000
4000
5000
6000
7000
0 50 100 150 200 250 300 350
H2RateofProduction(cc/(g-Au-hr))
Temperature (°C)
100 C
200 C
300 C

11. Figure 3. H2 rate of production of Au/V2O5 catalyst
Figures 1-3 show that the Au/V2O5 catalyst produces the most H2 on a per gram basis, and that the
commercial copper catalyst produces the least H2 on a per gram basis. Figures 4-6 provide the
Arrhenius plots used to find the activation energies of the reactions, shown in Table 1.
Figure 4. Copper catalyst Arrhenius plot
0
2000
4000
6000
8000
10000
12000
14000
0 50 100 150 200 250 300 350
H2RateofProduction(cc/(g-Au-hr))
Temperature (°C)
100 C
200 C
300 C
y = -4683.8x + 16.103
R² = 0.9024
2
3
4
5
6
7
8
9
10
0.0015 0.0017 0.0019 0.0021 0.0023 0.0025 0.0027 0.0029
ln(k)
1/T (Kelvin)

12. Figure 5. Au/CeO2 catalyst Arrhenius plot
Figure 6. Au/V2O5 catalyst Arrhenius plot
y = -3722.8x + 15.305
R² = 0.9938
2
3
4
5
6
7
8
9
10
0.0015 0.0017 0.0019 0.0021 0.0023 0.0025 0.0027 0.0029
ln(k)
1/T (Kelvin)
y = -4751.7x + 17.807
R² = 0.9922
2
3
4
5
6
7
8
9
10
0.0015 0.0017 0.0019 0.0021 0.0023 0.0025 0.0027 0.0029
ln(k)
1/T (Kelvin)

13. Table 1. Activation energies of catalysts
Catalyst Activation Energy (kJ mol-1)
Copper 38.94346
Au/CeO2 30.95322
Au/V2O5 39.51039
Table 1 shows that the activation energy of the Au/CeO2 catalyst is the lowest, and the activation
energy of Au/V2O5 is the highest. However, the R2 value for the copper catalyst is not close to 1,
which means that the activation energy calculated from the Arrhenius plot in Figure 4 is not
reliable. While the activation energy for Au/V2O5 is greater than the activation energy for
Au/CeO2, the H2 rate of production is greater for Au/V2O5 than that of Au/CeO2. A greater H2 rate
of production indicates a greater number of active sites. On another note, the activation energies
are similar to the activation energy found in literature, of 40 kJ mol-1.11 In essence, these results
are promising as they show that the gold catalysts are more productive than the commercial copper
catalyst on a per gram basis.
Conclusion
The data from this experiment provides good information concerning the WGSR. The
results show that on a per gram basis, the gold catalysts have a greater H2 production rate than the
commercial copper catalyst, which strengthens the argument that gold nanoparticles are a viable
option as catalysts. In addition, the greatest activation energy was found to be for the Au/V2O5,
and the smallest activation energy was found to be for the Au/CeO2 catalyst. However, the

14. Au/V2O5 catalyst may have more active sites, as the H2 production rate observed over Au/V2O5 is
higher than Au/CeO2.
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