Tungsten Carbide as Alternative for Precious Metal Based Hydrogenation- and Electrocatalysts

Tungsten carbides (WC, W2C) possess catalytic properties comparable to platinum. However, the material costs are significantly lower. High surface area WxC catalysts are prepared in an isothermal synthesis with the addition of SiO2 as support. This synthesis method enables the phase pure preparation of the metastable W2C. The catalysts are tested in the hydrogenation of butyraldehyde to butanol. The optimum synthesis parameters for a high catalytic activity are determined in a design of experiments. A layer of carbon deposited on the air-sensitive catalyst provides short-term protection from oxidation. The catalyst can be reactivated by treating it with hydrogen at a high temperature. Ways to lower the reactivation temperature are critically evaluated. In combination with Ni, WxC catalyzes the hydrogenation of furfural. In the solvent isopropyl alcohol, the ring-opening of furfural to 1,2-pentanediol is possible. The selectivity to this high-value chemical is dependent on the ratio of Ni and W in the catalyst. Ni facilitates the WxC synthesis, fastening the reduction and increasing the carbon insertion. A WC electrode is prepared and tested on its electrocatalytic performance in the splitting of water at elevated temperatures. Molten CsH2PO4 contained under its water vapor pressure serves as the electrolyte. At 390 °C WC shows a better performance than Pt in the hydrogen evolution reaction. The WC electrode is stable under electrolysis conditions, according to first stability tests.