Influence of metal oxides on Pt catalysts for methanol electrooxidation using electrochemical impedance spectroscopy

Carbon nanotubes used as supports for platinum catalysts deposited with metal oxides (CeO2, TiO2, and SnO2) were prepared for their application as anode catalysts in a direct methanol fuel cell. Cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy measurements were carried out in a solution of 0.5 M CH3OH and 0.5 M H2SO4. Catalysts with the addition of CeO2, TiO2, and SnO2 presented higher catalytic activity than pure platinum catalysts, and the catalysts with CeO2 were the best among them. Electrochemical impedance spectra indicated that methanol electrooxidation on these catalysts had different impedance behaviors at different potential regions. The mechanism of methanol electrooxidation changed with increases of the potential. The promotion effect of the metal oxides lies in the oxidation of intermediate COads on Pt at low potential regions. (C) 2009 Published by Elsevier B.V.