New synthesis of tungsten carbide particles and the synergistic effect with Pt metal as a hydrogen oxidation catalyst for fuel cell applications

Abstract

Some new tungsten carbides (WCs) were synthesized by the carburizing of tungsten nitrides (W2N) and tungsten sulfides (WS2) as precursors, which were prepared from different starting materials. The carbides were characterized by BET surface area measurements, XRD, SEM and TEM. WCs synthesized by these procedures afforded higher surface areas than those obtained from a conventional direct carburization of WO3. WC containing a small amount of Pt metal was prepared by a wet impregnation method and evaluated as an anode catalyst for the electrochemical hydrogen oxidation reaction. The property of WC which is associated with its synthetic pathway exerted a significant influence on the catalyst performance. The activity of a binary Pt-WC catalyst was greatly improved by choosing a suitable WC and modifying the preparative method. As a result, it turned out that the mass activity of the Pt-WC catalyst system was superior to the current commercial Pt catalyst although only one-tenth the amount of Pt metal was used. It is thought that there is a synergistic effect between Pt and WC in terms of activity, leading to a drastic reduction in the use of Pt metal. A Pt-WC catalyst system may be regarded as one of the candidates for cost-effective catalysts for the future fuel cell devices.