(280e) PdCu Alloy Nanoparticles As Highly Active Electrocatalysts for Hydrogen Oxidation in Alkaline Electrolyte
Alkaline membrane fuel cells hold promise to reduce cost by employing a non-precious metal cathode catalyst, however, exploring more efficient anode catalyst to improving hydrogen oxidation reaction, which becomes sluggish in alkaline electrolyte, remains a great challenge. Herein, we report that the bcc-phase PdCu alloy nanoparticles synthesized via a wet-chemical route followed by a thermal-treatment exhibit surprisingly higher HOR mass and specific activities than those of Pd/C and Pt/C in a liquid alkaline electrolyte. HRTEM, XPS, HAADF-STEM element mapping and EELS scanning results show that the particle size, surface composition, and chemical state of PdCu nanoparticles do not change during applied thermal treatment. In-situ HE-XRD characterization reveals that low annealing temperature favors formation of a PdCu fcc structure, but at higher annealing temperatures, the bcc structure dominates PdCu NPs. HOR activity of PdCu catalyst can be attributed to bcc phase dominance. Density functional theory (DFT) computations further unravel the enhanced HOR activity on the bcc structure PdCu NPs originates from contributions from both H and OH adsorption. With the incorporation of Cu, the PdCu catalyst exhibits much weaker hydrogen adsorption strength than that on Pd surface. The PdCu fcc and bcc surfaces possess very similar H binding strength, however, the PdCu bcc surface features much stronger OH binding as compared to that on PdCu fcc surface, which is closer to that on the most HOR active Pt model surfaces. Therefore, the PdCu-bcc phase exhibits much higher HOR activity than its fcc counterpart due to synergistic optimization of both H and OH binding strength.