A simple approach is reported for utilizing phosphomolybdic acid, H3PMo12O40, (HPMo) to enhance the electrocatalytic activity and carbon monoxide (CO) tolerance of platinum electrocatalysts supported on multi-walled carbon nanotubes (MWCNTs) in acidic medium. Pt/MWCNTs catalyst is prepared by the ethylene glycol reduction method, and then physically mixed with HPMo for electrochemical characterizations in terms of alcohol and CO electro-oxidation using cyclic voltammetry (CV), chronoamperometry and electrochemical impendence spectra (EIS). The results show that HPMo can efficiently enhance the electrocatalytic activity and CO-tolerance of Pt/MWCNTs catalyst. The effect of HPMo wt.% on the electrocatalytic activity towards methanol electro-oxidation of Pt/MWCNTs is also investigated by CV. The best results appear at the HPMo wt.% = 30%. We further investigated the reason of Pt/MWCNTs + HPMo composite catalyst with good stability. (c) 2009 Published by Elsevier B.V.