METHANOL OXIDATION ON SINGLE-PHASE PT-RU-OS TERNARY ALLOYS

Methanol oxidation was studied on are-melted Pt-Ru-Os alloys and on fu el cell catalysts prepared by the NaBH4 reduction of metal chloride sa lts. Both the are-melted alloys and the high surface area catalysts ha ve x-ray diffraction patterns indicative of single-phase face-centered cubic lattices. Hydrogen adsorption/desorption measurements on the po lished alloy electrodes, in the presence of adsorbed CO (25 degrees C) , show that selected ternary alloys have significant hydrogen gen adso rption/desorption integrals at adsorption potentials where Pt:Ru (1:1) was fully blocked and higher integrals at all adsorption potentials s tudied up to 400 mV vs. the reference hydrogen electrode. In situ diff use reflection Fourier transform infrared spectroscopy of the fuel cel l anodes showed that the alloy catalysts had reduced CO coverage relat ive to Pt, with the ternary catalyst showing the least coverage. Stead y-state voltammetry of the are-melted alloys at 25 degrees C confirmed that Pt-Ru-Os (65:25:10) is more active than Pt-Ru (1:1), particularl y above 0.6 V. Pt-Ru-Os (65:25:10) methanol consistently superior to t hose of Pt-Ru (1:1) (e.g., typically at 90 degrees C, 0.4 V; 340 mA/cm (2) with Pt-Ru-Os vs. 260 mA/cm(2) with Pt-Ru).