Temperature-dependence of direct methanol oxidation rates at various platinum alloy electrodes

The temperature dependence of the methanol oxidation reaction (MOR) rate at various Pt alloy electrodes was investigated by using a thin layer flow cell in a wide temperature range from 20 to 120 C in 1 M CH3OH+0.1 M HClO4 solution under pressurized operation. At 60 degrees C and 0.55 V vs. RHE, the MOR current densities at Pt-Sn and Pt-Ti were about 4 times higher than that at pure Pt, although it was still lower than Pt-Ru. Such enhanced MOR activities at Pt alloyed with non-precious metals were ascribed to the modified electronic structure of Pt skin layer formed on the alloy surface, facilitating the oxidation of weakly adsorbed CO. However, these alloys lost high MOR activities once heated at the high temperature (> 80 degrees C) in the acid electrolyte solution, probably due to the thickening of Pt skin layer by a considerable dissolution of non-precious metal components from the alloys.