Molybdenum and tungsten promoted carbons for use as catalyst supports in methanol electro-oxidation

Two types of the molybdenum and tungsten promoted carbons (MWCs) were prepared by the successive impregnation and co-impregnation of molybdenum and tungsten precursors on carbon black with a heat treatment. The resulting MWCs were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques and evaluated as a catalyst support for a Pt catalyst in methanol electro-oxidation. MWC-S, prepared by successive impregnation, showed a well developed carbidic phase with a large portion of tungsten carbide phase. In contrast, MWC-C, prepared by co-impregnation, had a lower amount of carbidic carbon and larger fraction of molybdenum carbide phase. MWCs-supported Pt catalysts showed higher catalytic activities than the Pt catalyst on pure carbon black in both CO oxidation and methanol electro-oxidation. In particular, Pt/MWC-S exhibited the highest performance among the Pt catalysts employed in this work. The high activity of Pt/MWC-S can be attributed to the positive effect of molybdenum-tungsten carbide phase, which promotes the activation of water and the removal of intermediate CO species.