(Invited) Hydrogen Oxidation Reaction (HOR) on Carbon-Capped Pd/C in Alkaline Media

Abstract

It is no secret alkaline fuel cells (AFC) using a liquid electrolyte (usually concentrated KOH) have assets over their proton-exchange membrane counterparts, in particular in niche applications where the latter are challenged by too harsh operating/environmental conditions [ 1 ]. AFC can also, in theory, use non-Pt catalysts at their electrodes without detrimental durability issues. However, recent studies from our group showed that Pt/C and Pd/C were very sensitive to the metal nanoparticles detachment from the carbon owing to their propensity to catalyze the carbon-support corrosion upon repeated alternation of the potential below/above their metal oxide potential (which is unavoidable at the anode upon start/stop of the fuel cell) [ 2-5 ]. In this presentation, it is highlighted that more robust hydrogen oxidation catalysts can be prepared by tailoring a carbon cap around the metal nanoparticles, in particular for palladium as the catalyst metal. Such “carbon-capped” Pd/C nanoparticles (ex. Pd G2 /C) exhibit a good compromise between their HOR activity and long-term stability (Figure 1), evaluated by identical location transmission electron microscopy upon accelerated stress tests (0.1 - 1.23 V vs . RHE stepped by 3 s – 3 s, 1000 times) (Figure 2). Their properties are very advantageous over non-capped (classical) Pd/C nanoparticles, demonstrating the interest of this strategy for the development of active and durable HOR catalysts for AFC anodes. References [1] G.F. McLean, T. Niet, S. Prince-Richard, N. Djilali, Int. J. Hydrogen Energy 27 (2002) 507-526. [2] A. Zadick, L. Dubau, N. Sergent, G. Berthomé, M. Chatenet, ACS Catal. 5 (2015) 4819-4824. [3] A. Zadick, L. Dubau, U.B. Demirci, M. Chatenet, J. Electrochem. Soc. 163 (2016) F781-F787. [4] C. Lafforgue, A. Zadick, L. Dubau, F. Maillard, M. Chatenet, Fuel Cells 18 (2018) 229-238. [5] C. Lafforgue, F. Maillard, V. Martin, L. Dubau, M. Chatenet, ACS Catal. 9 (2019) 5613−5622. Figure 1