Mesoporous Pd/W-doped SnO2 as CO-tolerant electrocatalyst for hydrogen oxidation reaction in acidic media: Influence of multivalent W and Sn ions and carbon modifiers

Hydrogen produced by hydrocarbon reforming typically contains trace amounts of CO, which severely poison anode catalysts in polymer electrolyte membrane fuel cells (PEMFCs). In this work, Pd was chemically deposited on a support consisting of mesoporous 10 mol% W-doped SnO 2 (Sn10W) and graphene nanoplatelets (GNP). Black Pearls 2000 carbon (BP) was subsequently introduced by mechanical mixing to obtain the final Pd/Sn10W-GNP-BP electrocatalyst for HOR in acidic media. The surface chemistry investigations by XPS highlighted the presence of Sn 2+ and W 4+ oxidation states, in addition to Sn 4+ and W 6+/5+ , after Pd deposition, as well as the oxygen bound in residual W=O groups and a highly hydroxylated Pd/Sn10W-GNP surface. SEM and TEM observations showed that Pd nanoparticles were preferentially located on the Sn10W oxide regions and at or near the edges of GNP flakes. Electrochemical half-cell measurements confirmed HOR activity in acidic media, while electroconductivity measurements demonstrated that BP improves the electronic connectivity of the composite and promotes Pd utilization. More importantly, Pd/Sn10W-GNP-BP showed remarkable CO tolerance, with CO oxidation starting at ~50 mV and the main oxidation peak at ~485 mV, both lower than that for commercial PtRu/C and Pt/C benchmark. The Sn10W-containing catalyst also exhibited substantially improved stability compared with the Pd/GNP control during the 500-cycle accelerated stress test. The combined results of structural, surface, and electrochemical analyses suggest a bifunctional mechanism in which the hydroxylated, defect-rich Sn10W surface promotes low-potential CO removal, while BP establishes the conductive network required for effective Pd utilization.