Bimetallic Palladium-Base Metal Nanoparticle Oxygen Reduction Electrocatalysts

Abstract

Bimetallic palladium-base metal nanoparticle catalysts are being investigated as alternatives to platinum-based catalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells. We report here our results on the palladium-copper, palladium-nickel, and palladium-iron systems. We are studying the effect of synthetic procedure, palladium to base metal ratio, heat treatment temperature, and heat treatment atmosphere on the ORR activity as well as on the valence band structure of these systems. Palladium-copper nanoparticle catalysts synthesized by the colloidal technique with a composition of 75 mol% copper are the most active investigated thus far. This catalyst shows an ORR activity which is approximately 75% that of platinum (per gram of platinum-group metal). The corresponding valence band structure is strongly modified compared to that of Pd and Cu alone and resembles that of Pt, which is believed to be the reason for its superior performance among the other investigated platinum-free alternatives.