The electrooxidation of hydrogen on platinum and gold electrodes is comparatively described in this paper. The reaction is faster on platinum than on the gold surface, because the reactive diffuses inside of the gold metal. This process is complicated with the lift of surface reconstruction of the (100) plane, which allows the fast penetration of the H atoms through the more open surface.
The diffusion limiting current is then discontinued and the current falls. On platinum, the current fall occurs simultaneously with the metal oxide formation. It is assumed that the hydrogen helps the adsorbed OH group formation, which is the first step of metal oxidation, and it has been called “incipient hydrous oxide” (IHO). Current begins to fall slowly at the (IHO) potential. At higher potential the current falls abruptly.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

Almeida, Norma V.

Barzola, Mariela N.

Esquenoni, Sylvia M.

Sustersic, María G.

Von Mengershausen, Alicia E.

Zerbino, Jorge Omar

Green and Sustainable Chemistry

English

SEDICI - Repositorio de la UNLP

Green and Sustainable Chemistry, 2014, 4, 55-59 
Published Online May 2014 in SciRes. http://www.scirp.org/journal/gsc 
http://dx.doi.org/10.4236/gsc.2014.42009  
How to cite this paper: Von Mengershausen, A.E., et al. (2014) Comparative Study of Hydrogen Electrooxidation on Gold 
and Platinum in Solutions Containing Perchlorate Ion. Green and Sustainable Chemistry, 4, 55-59.  
http://dx.doi.org/10.4236/gsc.2014.42009 
 
 
Comparative Study of Hydrogen  
Electrooxidation on Gold and Platinum  
in Solutions Containing Perchlorate Ion 
Alicia E. Von Mengershausen1, Norma V. Almeida1, Mariela N. Barzola1, Jorge O. Zerbino2, 
Sylvia M. Esquenoni1, Maria G. Sustersic1 
1Facultad de Ingenieria y Ciencias Agropecuarias, Universidad Nacional de San Luis, San Luis, Argentina 
2Comision de Investigaciones Cientificas de la Provincia de Buenos Aires, La Plata, Argentina 
Email: sustersic@gmail.com 
 
Received 11 October 2013; revised 12 January 2014; accepted 21 March 2014 
 
Copyright © 2014 by authors and Scientific Research Publishing Inc. 
This work is licensed under the Creative Commons Attribution International License (CC BY). 
http://creativecommons.org/licenses/by/4.0/ 
  
 
 
 
Abstract 
The electrooxidation of hydrogen on platinum and gold electrodes is comparatively described in 
this paper. The reaction is faster on platinum than on the gold surface, because the reactive dif-
fuses inside of the gold metal. This process is complicated with the lift of surface reconstruction of 
the (100) plane, which allows the fast penetration of the H atoms through the more open surface. 
The diffusion limiting current is then discontinued and the current falls. On platinum, the current 
fall occurs simultaneously with the metal oxide formation. It is assumed that the hydrogen helps 
the adsorbed OH group formation, which is the first step of metal oxidation, and it has been called 
“incipient hydrous oxide” (IHO). Current begins to fall slowly at the (IHO) potential. At higher po-
tential the current falls abruptly. 
 
Keywords 
Hydrogen, Electrooxidation, Gold, Platinum, Perchlorate Ion 
 
 
1. Introduction 
Study of the electrooxidation of hydrogen is of great importance because of their application in oxygen/hydro- 
gen fuel cells. Oxygen electrochemical dissolution is much slower than that of the hydrogen. Therefore, it pro-
vides the highest overpotential on the cell operation [1]. It is known that platinum is the metal on which the hy-
drogen electrode has the highest exchange current density [2]-[5]. However, the kinetic of the hydrogen elec-
trode, because of its speed, suffers interference of material transport and kinetic parameters obtained in acid me-
A. E. Von Mengershausen et al. 
 
 56 
dium are not reproducible [6]-[8]. Moreover, it is necessary to know the mechanism of the reaction to elucidate 
the application site of the electrocatalyst in porous media, due to the high cost of the noble metal. On gold, 
atomic hydrogen diffuses into the metal and its surface concentration is very low [9]-[12]. On both metals po-
tential assisted reconstruction surface occurs [13]. The reappearance of the structure (1 × 1) affects the reaction 
kinetics. This influence is notably manifested in the case of gold. On the surfaces of both metals, the diffusion of 
the reagent controls the reaction in conditions of low hydrogen partial pressure [12] [14]. 
2. Experimental 
A Pyrex glass cell with two compartments is used. In the main compartment the working electrode and the aux-
iliary electrode are placed. They are constructed with spectroscopic gold or platinum sheets of 5N purity. Ap-
parent area ratio between the auxiliary and working electrode (RHE) is approximately 40/1. A reversible hydro-
gen electrode, which is used as reference electrode, is placed in the lateral compartment connected to the central 
compartment by a Luggin capillary. The potentials shown in the figures are referred to the RHE. The electrolyte 
is a solution of 1M perchloric acid prepared with analytical reagent and degassed with nitrogen of high quality. 
To study the influence of pH on the reaction, solutions are prepared by mixing perchloric acid and lithium per-
chlorate, maintaining constant the ionic strength. Rectified hydrogen is used as a reactive. Partial pressure is 
controlled by mixing the reactive with nitrogen and controlling the flow of each gas by a Matheson flowmeter. 
The experiments were performed using a LYP potentiostat connected with a ramp function generator of the 
same brand. The voltammograms were recorded with an Allen XY recorder. 
3. Results and Discussion 
To study the electrooxidation of hydrogen (H), sweeps between 0.075 and 1.5 V on platinum and between 0.1 to 
1.7 V on gold in the absence of the reagent are performed. Then, hydrogen is bubbled at a given partial pressure 
during the necessary time to obtain a constant H concentration in the electrolyte (30 min). The Scan is then re-
peated with different potential limits for each metal. The variables studied are the gas partial pressure and the 
potential sweep rate, V. For both types of surface a linear relationship between the maximum current and the 
partial pressure approximately fits. The linearity between peak current and square root of the potential sweep 
rate is found only at low partial pressures, manifesting a diffusion control for those conditions, as shown in 
Figure 1. For partial pressures greater than 0.1 atm a mixed control probably occurs [12]. On gold, the current 
drops to zero when the surface reconstruction of (100) plane lifts. On platinum, hydrogen collaborates with the 
formation of OH groups on the surface, decreasing the current smoothly at potential greater than 0.7 V and 
dropping sharply at 0.8 V, potential at which the metal oxide appears. The current is anodic in the forward and 
in the reverse scans for both metals, indicating a strong reaction shift to the right. In the case of Pt, the interme-
diary is the adsorbed atomic H. For gold, it has been postulated a diatomic cation with a positive charge [12]. 
With platinum, sweeping between 0.075 and 1.5 V at 0.1 V/sec, the classic profile of Pt/HClO4 system is ob-
tained. The hydrogen and oxygen monolayer’s formation current can be observed. For studying the oxidation 
reaction of H2, the sweep between 0.075 and 0.8 V has been done. At first, the scanning in the absence of the 
reagent is performed. Then, H2 is bubbled at a given partial pressure for a time enough to obtain constant H2 
concentration in the solution. Then, the scan to 0.8 V is repeated. It is observed the same voltammogram profile, 
but moved up as if he had added a constant current. The current difference between the two records was plotted 
against partial pressure, obtaining a relation that can be approximately fitted to a straight line as shown in Figure 2. 
The great mass transport contribution on the reaction speed is then evident. 
Figure 3 shows voltammetric records obtained with platinum in perchloric acid saturated with hydrogen gas. 
Blank has been included (no reagent), for comparison purposes. The current is anodic in direct and inverse cycles. 
Up to 0.75 V, the current is constant and presents typical fluctuations due to convection interference with the me-
dia, as it held the gas bubbling through the experience. At potentials higher than 0.75 V, the current drops slowly 
and this is due to the presence of hydrogen which collaborates with the formation of incipient hydrated oxide [15], 
which takes place by the adsorption of OH groups. At higher potentials, the platinum oxide formed during direct 
cycle is not completely reduced and for this reason, the hydrogen oxidation current is lower in the reverse cycles 
than that in the direct cycles. For potential lower than 1.1 V, the reverse current cycle is the same as in direct 
cycles, indicating that the OH groups were removed from the surface at potentials lesser than 1.1 V in the reverse 
cycle. On the gold, (Figure 4), the metal oxide formation catalyzes the reaction and then the current is higher in  
A. E. Von Mengershausen et al. 
 
 57 
 
Figure 1. Plot of the maximum current of hydrogen oxidation in function of the square root of 
the potential sweep rate. Platinum electrode. H partial pressure: 0.1 atm, t = 25˚C.              
 
 
Figure 2. Representation of hydrogen limiting current as a function of its partial pressure. The 
straight line is the linear fit of the experimental points set. Platinum electrode.                 
 
 
Figure 3. Voltammetric records obtained with platinum electrode in perchloric acid saturated 
with hydrogen gas, sweepning between 0.075 and 1.5 V; v = 0.1 V/s, t = 25˚C.                  
 
 
Figure 4. Voltammetric records obtained with gold electrode in perchloric acid saturated with 
hydrogen gas, sweepning between 0.1 and 1.7 V, v = 0.1 V/s, t = 25˚C.                       
A. E. Von Mengershausen et al. 
 
 58 
 
Figure 5. Plot of the H limiting current vs. pH. Platinum elec- 
trode. T = 25˚C.                                         
 
the reverse cycle than that in the direct cycle. 
At higher pH, the reaction current is lower, as shown in the Figure 5. The lowering the current as pH is in-
creased has been observed also in previous works [2] and it shows the participation of hydrogen ions in the oxida-
tion reaction. 
4. Conclusions 
When the partial pressure is lower than 0.1 atm, the H reaction is diffusion controlled on both materials.  
In addition, the reaction is strongly shifted towards the right. The current drops abruptly when the surface re-
construction of plane (100) on gold lifts. On platinum, however, the current drop coincides with the formation of 
metal oxide at 0.8 V. Above this potential the contribution of both the reaction under study and the formation of 
the different metal oxides through the OH groups adsorbed is evident and the H oxidation is inhibited. On the 
other hand, sweeping the gold oxide potential region, the gold offers a more active surface for the H oxidation 
reaction. 
The presence of H promotes the formation of both the hydrous platinum oxide and other metals oxides at high-
er potentials. 
It is believed that under the experimental conditions the control of the hydrogen electrooxidation is diffusional. 
However, at higher potentials, the reactive contributes to the formation of different metal oxides through the ad-
sorbed OH groups on platinum and the reaction is passivated. 
Acknowledgements  
The Universidad Nacional de San Luis supports this research. M.G. Sustersic is member of Consejo Nacional de 
Investigaciones Científicas y Técnicas. Jorge Zerbino is member of Comisión de Investigaciones Científicas de 
la Provincia de Buenos Aires.  
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Comparative Study of Hydrogen Electrooxidation on Gold and Platinum in Solutions Containing Perchlorate Ion

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