Simple preparation of tungsten carbide supported on carbon for use as a catalyst support in a methanol electro-oxidation

Two types of supported tungsten carbides were prepared via the impregnation of tungsten precursors on carbon support followed by heat treatment. Depending on whether ammonium metatungstate (AMT) or tungsten chloride (WCl6) was used as the precursor, this process resulted in samples that are referred to as either WC-A or WC-W, respectively. Both WC-A and WC-W showed tungsten subcarbide (W2C) as the major crystalline phase, with tungsten monocarbide (WC) as a minor phase. More amount of tungsten carbide being formed when WCl6 was used as the precursor. This increased formation has occurred because the thermodynamically favorable proper-ties of WCl6 caused the contact area between the tungsten precursor and the carbon support to promote formation of tungsten carbide. The prepared tungsten carbides were used as a catalyst support of the Pt catalyst in a methanol electro-oxidation. The metal dispersion and the catalytic performance were increased as follows: Pt/C<Pt/WC-A<Pt/WC-W. It is believed that the tungsten carbides supported on the carbon support improved the dispersion of Pt and the activation of water for removal of intermediate CO, which enhanced the catalytic performance during the methanol electro-oxidation. (C) 2008 Elsevier B.V. All rights reserved.