A study of RhxSy/C and RuSex/C as methanol-tolerant oxygen reduction catalysts for mixed-reactant fuel cell applications

For efficient operation, mixed-reactant fuel cells utilise highly selective anode and cathode electrocatalysts. While platinum and its alloys are the most widely used ORR electrocatalysts in conventional DMFCs, they suffer from both their very high activity for methanol oxidation and their inherent cost. Platinum-free precious metal chalcogenides have been suggested as alternatives with comparable oxygen reduction activity in the presence of methanol. Of these, commercially available carbon supported rhodium sulphide and developmental ruthenium selenium were electrochemically tested and assessed for their potential as selective ORR cathode catalysts. Both materials exhibited oxygen reduction activity approaching that of platinum, albeit at potentials 150 and 80 mV more negative. The three materials’ ability to maintain their oxygen reduction activity in the presence of methanol ranks ruthenium selenium > rhodium sulphide ≫ platinum.