Facile one-step synthesis of Ir-Pd bimetallic alloy networks as efficient bifunctional catalysts for oxygen reduction and oxygen evolution reactions

This paper introduces a facile one-step process to synthesize highly interconnected nanoporous Ir-Pd alloys supported on carbon that exhibit excellent bifunctional electrocatalytic activities for both the oxygen reduction and oxygen evolution reactions with reasonable stability in alkaline electrolytes. Nanoporous Pd networks with crystalline {111} faces were shown experimentally to serve mainly as active sites for the oxygen reduction reaction, whereas the Ir nanoparticles incorporated in the Pd nanoframe networks, where the optimized Ir:Pd ratio was 0.23:0.77 (n = 10), were responsible for the oxygen evolution reaction. Such three-dimensional architectures provide a high density of active sites for the oxygen electrochemical reaction and facilitate electron transport. More importantly, the nanoporous Ir-Pd alloy nanocomposites exhibited similar stability for the oxygen reduction reaction but superior catalytic activity to the commercial Pd catalyst in alkaline solutions. In addition, the materials were also highly active for the oxygen evolution reaction, e.g., a small overpotential at 10 mA cm−2 (1.628 V vs. reversible hydrogen electrode), making it a high-performance bifunctional catalyst for both the oxygen electrochemical reaction. Rotating ring-disk electrode measurements showed that the oxygen reduction and oxygen evolution reactions on the Ir-Pd catalysts proceeded predominantly through the desired 4-electron pathway.