Tungsten materials as durable catalyst supports for fuel cell electrodes

Abstract Durable platinum catalyst support materials, e.g. tungsten carbide (WC), tungsten oxide (WO x ) and self-synthesized tungsten oxide (WO xs ) were evaluated for the use in High-Temperature Proton Exchange Fuel Cells (HT-PEM) based on phosphoric acid doped polybenzimidazole as electrolyte. The support materials and the catalyst loaded support materials were characterized ex- situ by cyclic voltammetry in HClO 4 , potential cycling, CO-stripping, electron microscopy and X-ray diffraction measurements. The tungsten oxide and tungsten carbide based supported catalysts were compared to High Surface Area Carbon (HSAC), each coated with platinum via the same in-house manufacturing procedures. The in-house manufacturing procedures resulted in catalyst particle sizes on HSAC of 3–4 nm with a uniform distribution. The in-situ Potential Cycling experiments of WO x or WO xs supported catalysts showed much lower degradation rates compared to High Surface Area Carbons. The formation of WO x species on WC was proven by ex- and in-situ cyclic voltammetric studies and thermogravimetric analyses. X-ray diffraction, ex-situ cyclic voltammetry and in-situ cyclic voltammetry showed that WO x is formed from WC as starting material under oxidizing conditions. Finally a 1000 h durability test with WO x as catalyst support material on the anode was done in a HT-PEM fuel cell with reformed methanol on the anode.