Methanol Oxidation on Single‐Phase Pt‐Ru‐Os Ternary Alloys

Abstract

Methanol oxidation was studied on arc‐melted Pt‐Ru‐Os alloys and on fuel cell catalysts prepared by the reduction of metal chloride salts. Both the arc‐melted alloys and the high surface area catalysts have x‐ray diffraction patterns indicative of single‐phase face‐centered cubic lattices. Hydrogen adsorption/desorption measurements on the polished alloy electrodes, in the presence of adsorbed CO (25°C), show that selected ternary alloys have significant hydrogen adsorption/desorption integrals at adsorption potentials where Pt:Ru (1:1) was fully blocked and higher integrals at all adsorption potentials studied up to 400 mV vs. the reference hydrogen electrode. In situ diffuse reflection Fourier transform infrared spectroscopy of the fuel cell anodes showed that the alloy catalysts had reduced CO coverage relative to Pt, with the ternary catalyst showing the least coverage. Steady‐state voltammetry of the arc‐melted alloys at 25°C confirmed that Pt‐Ru‐Os (65:25:10) is more active than Pt‐Ru (1:1), particularly above 0.6 V. Pt‐Ru‐Os (65:25:10) methanol fuel cell performance curves were consistently superior to those of Pt‐Ru (1:1) (e.g., typically at 90°C, 0.4 V; 340 mA/cm2 with Pt‐Ru‐Os vs. 260 mA/cm2 with Pt‐Ru).