Electro-oxidation of Methanol on Fuel Cell Catalysts and Evaluation of their Catalytic Activities by Cyclic Voltammetry

The electro-oxidation of methanol on smooth Pt-strip and 10 % Pt supported on Vulcan XC-72 was studied in acidic medium using cyclic voltammetry. The electro-oxidation of methanol gave well-defined anodic peaks in both anodic and cathodic sweeps. Real surface area, roughness factor, exchange current density, peak current and the heterogeneous rate constant for electro-oxidation of methanol were found to be higher on 10 % Pt-catalyst as compared with smooth Pt-strip. The thermodynamic parameters, ΔH*, ΔS* and ΔG298* were evaluated. The value of ΔH* for electro-oxidation of methanol on smooth Pt-strip was higher and found 57 kJ mol-1, while the value of ΔH* on 10 % Pt-catalyst was 26 kJ mol-1. The more positive value of ΔH* obtained on smooth Pt-strip was attributed to its poor catalytic activity for electro-oxidation of methanol. The values of ΔG298* were also positive indicating that the electro-oxidation of methanol on fuel cell catalysts was an endothermic and non-spontaneous process and hence the higher temperature might be more favorable for increasing the catalytic activity of fuel cell catalysts.