Carbon-supported Pd-Fe electrocatalysts for oxygen reduction reaction (ORR) and their methanol tolerance

Carbon-supported palladium-iron bimetallic electrocatalysts of different Pd to Fe ratios (1:1, 2:1, 3:1) were prepared by a low temperature single step co-reduction method in alkaline media without any stabilizing agents. The physical characterizations of catalysts were done using XRD and TEM. The electrochemical characterizations were done using underpotential deposition (upd) of hydrogen and copper. Electrocatalytic activities for oxygen reduction reaction (ORR) were investigated and compared to that of standard Pt/C catalyst. The carbon-supported Pd-Fe bimetallic catalysts showed higher surface area than that of pure Pd/C. The half-wave potential of ORR on as-prepared palladium-iron bimetallic catalysts was shifted positively by similar to 75-100 mV from that of Pd/C in oxygen saturated 0.1 M HClO4 solution. The highest catalytic activity was obtained with Pd3Fe/C - catalyst and it was close to that of standard Pt/C. XRD analysis did not show any noticeable shift in peak position due to alloying. In presence of methanol, carbon-supported Pd and Pd-Fe bimetallic catalysts showed superior ORR selectivity and activity unlike Pt/C. The peroxide generation on Pd3Fe/C - the best of Pd based electrocatalyst - was comparable to that on Pt/C. These catalysts, prepared at low temperature and without any further heat-treatment, gave activities that were free from effects of crystallite size, segregation, and enrichment of precious metal content that might happen at high temperature. (C) 2011 Elsevier B.V. All rights reserved.