Properties of the Hydrogen Oxidation Reaction on Pt/C catalysts at Optimised High Mass Transport Conditions and its Relevance to the Anode Reaction in PEFCs and Cathode Reactions in Electrolysers

Using a high mass transport floating electrode technique with an ultra-low catalyst loading (0.84–3.5 μgPt cm−2) of commonly used Pt/C catalyst (HiSPEC 9100, Johnson Matthey), features in the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) were resolved and defined, which have rarely been previously observed. These features include fine structure in the hydrogen adsorption region between 0.18 < V vs. RHE < 0.36 V vs. RHE consisting of two peaks, an asymptotic decrease at potentials greater than 0.36 V vs. RHE, and a hysteresis above 0.1 V vs. RHE which corresponded to a decrease in the cathodic scan current by up to 50% of the anodic scan. These features are examined as a function of hydrogen and proton concentration, anion type and concentration, potential scan limit, and temperature. We provide an analytical solution to the Heyrovsky–Volmer equation and use it to analyse our results. Using this model we are able to extract catalytic properties (without mass transport corrections; a possible source of error) by simultaneously fitting the model to HOR curves in a variety of conditions including temperature, hydrogen partial pressure and anion/H+ concentration. Using our model we are able to rationalise the pH and hydrogen concentration dependence of the hydrogen reaction. This model may be useful in application to fuel cell and electrolyser simulation studies.