Investigation of methanol electrooxidation on Pt and Pt–Ru in H3PO4 using MEA with PBI–H3PO4 membrane

► CH3OH electrooxidation on Pt, Pt–Ru was studied in presence of H2O and CO in gas phase at 130–190°C. ► CH3OH oxidation orders in respect to H2O and CH3OH partial pressures were determined. ► On Pt–Ru oxidation proceeds primarily by indirect route via formation of intermediate COads. ► On Pt oxidation proceeds by direct route via formation of weakly adsorbed intermediates. Electrochemical oxidation of methanol on Pt/C and Pt–Ru/C electrocatalysts was studied by slow scan rate voltammetry at 130–190°C. The effects of partial pressures of water, methanol, and CO on the methanol electrooxidation rate were determined. It was found that methanol oxidation on Pt–Ru/C proceeds primarily via the “indirect” route through the formation of strongly adsorbed intermediate COads, while on Pt methanol electrooxidation occurs primarily via “direct” route through the formation of weakly adsorbed intermediates. At 140°C activity of Pt–Ru/C in methanol electrooxidation was found 2 orders of magnitude higher than that of Pt/C. Methanol oxidation reaction orders per water and methanol vapor pressures were determined. The main features of methanol electrooxidation both on Pt and Pt–Ru were accounted for assuming Langmuir–Hinshelwood mechanism of respective RDS.