New catalysts for oxygen reduction based on transition-metal sulfides

Novel catalysts, based on Mo, Ru and S or Se, for the electrochemical reduction of oxygen, have been prepared and characterised by a variety of analytical and structural probes. Such catalysts are attractive as cathodes both in direct methanol fuel cells and in solid-polymer electrolyte cells, and their structure appears to resemble that of commonly employed catalysts for hydrodesulfurisation (HDS). The electrocatalytic activity of these novel materials in Nafion-bound gas-diffusion electrodes in aqueous acid has been investigated. The polarisation of the MoRuS catalyst at 400 mA cm–2 was about 120 mV poorer than that of a conventional Pt-based electrode. However, the former was relatively unaffected by exposure to methanol, whereas the Pt-electrode performance declined by ca. 100 mV, becoming comparable to that of the MoRuS-based electrode.