Abstract
A novel class of electrocatalyst for oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cell (PEMFC) was prepared by electrochemically dealloying Pt25Cu75 precursor alloys in a membrane electrode assembly (MEA) cathode. The precursor was prepared by a novel liquid impregnation-freeze drying route. The performance of the electrochemically de-alloyed catalyst was compared to 3 other catalysts, in particular (i) a chemically dealloyed Pt25Cu75, (ii) a precursor Pt-Cu with an atomic ratio of Pt:Cu identical to that of the acid dealloyed catalyst, and (iii) a commercial 30wt% Pt catalyst. The mass activity of the electrochemically dealloyed catalyst @ 0.9V-IR-free is superior to acid dealloyed or as prepared Pt-Cu catalysts and significantly better than reported values of state-of-the-art MEA activities (1). It is observed that electrochemical dealloying of Pt25Cu75 leads to Pt enriched surfaces, results in very Pt-like voltammetric behavior, however, shifts the water activation to more anodic electrode potentials suggesting delayed chemisorption hindering oxygenated species.