Tungsten-based Carbides as Anode for Intermediate-Temperature Fuel Cells

Abstract

Tungsten carbides were prepared from ammonium paratungstate via temperature-programmed carburization under flowing a gaseous mixture of CH4/H2 to employ as anode catalysts in fuel cells consisting of CsH2PO4/SiP2O7-based composite electrolyte operative at 200°C. The resulting materials were characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The heat-treatment at high temperatures promoted the reduction and carburization of tungsten component. The single phase of WC was observed for the samples subjected to the carburization at and above 800°C. The single cell employing the catalyst prepared at 850°C attained the best performance. The anode material containing the metallic W exhibited low stability under the power generation condition. With nickel or cobalt additives, the carburization of tungsten species was initiated at low temperatures. The samples with the additives heat-treated at high temperatures were composed of several tungsten carbides including WC. When these samples were applied as anode catalysts, the additive species lowered the cell performance. These results indicated that the WC phase was the most effective electrocatalyst for the hydrogen oxidation.