Tungsten materials as durable catalyst supports for fuel cell electrodes

Durable platinum catalyst support materials, e.g. tungsten carbide (WC), tungsten oxide (W05) and selfsynthesized tungsten oxide (W05,) 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 HCI04, 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 inhouse 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,, or W05, supported catalysts showed much lower degradation rates compared to High Surface Area Carbons. The formation of WO, 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 5 is formed from WC as starting material under oxidizing conditions. Finally a 1000 h durability test with WO 5 as catalyst support material on the anode was done in a HT-PEM fuel cell with reformed methanol on the anode. (C) 2013 Elsevier B.V. All rights reserved.