Surfactant-free polyol synthesis of effective Pd-Cu nanomaterials for H2/O2 solid polymer electrolyte fuel cells

Abstract

This study presents a facile synthesis of carbon-supported binary palladium-copper (Pd-Cu/C) nanomaterials designed to achieve competitive catalytic activity while reducing material costs in solid polymer electrolyte (SPE) fuel cells. A surfactant-free, microwave-heated polyol process is employed to synthesize Pd/C and Pd-Cu/C nanomaterials with mean particle size below 4.0 nm. The electrocatalytic activity toward the oxygen reduction reaction (ORR) and the corresponding kinetic parameters of Pd-Cu/C electrodes with varying compositions are systematically interrogated using rotating disk electrode (RDE) measurements. Notably, Tafel analysis reveals a slope of 60 ± 2 mV per decade at low current densities, indicating that the first electron transfer to molecular oxygen (O2) is the rate-determining step. At higher current densities, a slope of 144 ± 8 mV per decade suggests a transition to proton-coupled electron transfer as the dominant mechanism. Furthermore, electrochemical performance of membrane-electrode assemblies (MEAs) reveals a peak power density of 475 mW cm−2 with a Pd/C cathode under optimal operating conditions. However, increasing the Cu content in the Pd-Cu/C catalysts results in a marked decrease in current density, likely due to partial Cu dissolution. These findings highlight the potential of binary Pd-Cu nanomaterials as promising alternatives to platinum-based catalysts for Pt-free SPE fuel cell applications.