High CO Tolerance ofN,N-Ethylenebis(salicylideneaminato)oxovanadium(IV) as a Cocatalyst to Pt for the Anode of Reformate Fuel Cells

Abstract

In reformate-type polymer electrolyte fuel cells (PEFCs), CO tolerance of the anode catalysts is a central issue because CO inevitably comes out of the reformer and poisons very seriously the platinum-based catalysts. In this work, long desired novel-type CO-tolerant electrocatalysts have been developed from Pt and organic metal complexes (N,N-ethylenebis(salicylideneaminato)oxovanadium(IV) [abbreviated as VO(salen)] that are potentially superior to Pt−Ru and practically usable as such anode catalysts. These anode catalysts were tested for their CO tolerance using a half and a single fuel cell, at a cell temperature of 70 °C in the presence of 10, 50, and 100 ppm CO. The original metal complexes were mixed with the platinum precursor, platinum tetra-ammine chloride, and supported on the carbon black supporting material and heat-treated at various temperatures. The mixed catalysts Pt−VO(salen)/C revealed only little deterioration for less than 100 ppm CO, which was never attained by the state of the art alloy catalysts. The function of organic metal complex may originate during the heat treatment of catalyst preparation, and this suggests that the valence states of vanadium in Pt−VO(salen)/C play a role in manipulating the oxidation states of platinum. The catalysts were characterized using XRD, TEM, XPS, and XAFS techniques.