Characterization and activity correlations of Pt bimetallic catalysts for low temperature fuel cells

Oxygen reduction tests using a half cell in phosphoric acid solution at 190 °C show monotonic decreases of electrode activity as time elapses for pure Pt, PtW, PtCu, PtZr and PtMn, whereas the rest show an initial increase that is followed by monotonic decrease over time. More pertinent increase at the initial stage was observed for PtCr, PtFe and PtAg catalysts due to the surface roughening effect. Among many parameters tested, a good correlation was found between the mass activity (A/g Pt) and the Pt surface area (SCV) obtained from the coulombic charge of the strongly adsorbed hydrogen. The specific activity (μA/cm2 Pt) based on SCV (m2/g Pt) was within the range of 2.12 ± 0.14 for all the tested PtM bimetallic catalysts.