Bulk-Palladium and Palladium-on-Gold Electrocatalysts for the Oxidation of Hydrogen in Alkaline Electrolyte

The commercial feasibility of alkaline-exchange membrane fuel cells and electrolyzers passes by the development of hydrogen oxidation and evolution reaction (HOR/HER) catalysts featuring an activity and/or cost advantage over platinum, which remains the most active metal for these processes. Among these alternatives, Pd appears as a promising candidate, since its price is typically 2-3 fold lower than that of Pt. With this motivation, the first section of this study displays our attempts at quantifying the kinetic parameters of the HOR/HER on bulk Pd in 0.1 M NaOH, which were prevented by the simultaneous absorption of hydrogen into bulk palladium. We succeeded at circumventing this issue by depositing Pd-adlayers on a polycrystalline Au-substrate by galvanic displacement of underpotentially-deposited Cu or by electrochemical plating of Pd2+. The resulting surfaces appear to consist of three-dimensional Pd-structures of an unknown thickness that we believe to scale with the palladium coverage, theta(Pd/Au). This last parameter is inversely proportional to the HOR/HER-activity of the Pd-on-Au surfaces, in agreement with numerous theoretical and experimental studies in acid media that correlate this effect to the tensile strain induced by the Au-substrate on the Pd-lattice. (C) The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.