The Effect of Alloying of Transition Metals (M = Fe, Co and Ni) to Palladium Catalyst on Durability of Electrocatalytic Activity of Oxygen Reduction Reaction in Alkaline Media

Abstract

Polymer electrolyte membrane (PEMs) fuel cells have attracted a great deal of attention as next-generation electrical portable device due to the high energy efficiencies and carbon-free emission. However, the cost of electrocatalyts in PEMs is very high because platinum (Pt) is used as electrocatalyst for both the oxidation of hydrogen in the anode and oxygen reduction reaction (ORR) in the cathode. Palladium (Pd) is an attractive candidate as an alternative electrocatalyst towards the ORR in alkaline media because Pd is more abundant, much less expensive than Pt, and has a higher activity towards ORR than pure Pt in alkaline media [1]. Stable and long-term electrocatalytic performance towards the ORR was achieved by Pd-shell Pd3 M-core (M = Fe, Co, Ni and Cu) structures on carbon supports. Herein, we report on the synthesis of Pd-based bimetallic compounds using 3d transition metals, such as Fe, Co, and Ni, as secondary materials and demonstrate enhanced electrocatalytic activity towards the ORR in alkaline media as well as improved durability. The catalytic activity of these nanoparticles has been compared to that of pure Pd nanoparticles. We have also dealloyed the catalysts using electrochemical treatment by potential cycles in alkaline media and examined their activities towards the ORR. The various bimetallic Pd-M (M = Fe, Co and Ni) nanoparticles (NPs) were prepared by an impregnation method followed by an annealing treatment. In order to enhance the electrocatalytic activity towards the ORR, bimetallic Pd-M nanoparticles were electrochemically deallyoed. Dealloyed Pd-M NPs exhibit a core-shell structure, Pd3 M-Core and Pd-shell, and showed enhanced catalytic activity towards the ORR as well as better durability than pure Pd. [1] Sun, W.; Hsu, A.; Chen, R.; J. Power Sources, 2011, 196, 4491.