Electra-oxidation of methanol was studied on carbon-supported Pt-Sri/// electrodes in silcotungstic acid (SiWA) at various concentrations. The Porous-carbon electrodes employing Pt-Sri/// catalyst have been characterized using chemical analyses, X-ray Powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) in conjunction with electrechemistry. The presence of Pt-Sn and Pt,Sn alloys along with Pt and SnO, phases in the catalyst were identified by XRD. XPS analysis showed a lower amount of PtO species in the Pt-Sn/C catalyst with respect to the corresponding Pt/C sample. From the steady-state galvanostatic polarization data on Pt-Sri/// electrodes in SiWA, it is inferred that a one-electron process is the rate determining step. The performance of the electrodes in 0.084 M SiWA was better than in 2.5 M H,SO, under similar conditions up to load currents of about 100mAcm-2 indicating the promoting behaviour of the electrolyte. At currents larger than 100mAcn-2, the performance of the electrodes in 0.084SiWA was poorer than that in 2.5 M H,SO, mainly due to the dominance of mass polarization in the former owing to the large size of Keggin units associated with the structure of SiWA. This aspect was supported by cyclic voltammetry and uc impedance studies on Pt-Sn/C electrodes. Simulation of the electrochemical impedance response for the oxidation of methanol in SiWA was carried out using the equivalent electrical circuit model.