Oxygen Reduction by Sol-Derived Pt∕Co-Based Alloys for PEM Fuel Cells

A route toward the synthesis of several Pt/Co-based catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells is described here. The composition of these catalysts has been determined by X-ray diffraction studies, while their electrochemical activity was established using slow sweep cyclic voltammetry in 0.5 M H2SO4 at room temperature. We have found that by mixing a Co oxide sol precursor with Pt supported on carbon (Pt/C), followed by heat-treatment at 700 or 900DGC, the active PtCo alloy catalyst is formed. In contrast, when exactly the same procedure is followed but a Co oxide sol-derived Co/N/C catalytic material is employed, Pt3Co alloy catalysts, which are somewhat less active toward the ORR, are formed. Catalysts formed by heating at 900DGC are more active than those formed at 700DGC, and all of our Pt/Co catalysts are more active toward the ORR than pure Pt on carbon.