Non-precious metal high-entropy alloys with d–d electron interactions for efficient and robust hydrogen oxidation reactions in alkaline media

Abstract

The imperative for cost-effective catalysts governing the hydrogen oxidation reaction (HOR) remains pivotal for advancing the commercial viability of alkaline H₂–O₂ fuel cells. High entropy alloys (HEAs) represent an exceptionally promising class of candidates due to their capacity to provide a multifaceted parameter space for optimizing electronic structures and catalytic sites. In this study, we employed the polymer-assisted pyrolysis method to synthesize FeCoNiMoW HEA nanoparticles (NPs) enveloped within a porous carbon skeleton. Such FeCoNiMoW NPs exhibit high entropy characteristics, subtle lattice distortions, and a modulated electronic structure, resulting in a discernibly enhanced HOR performance characterized by larger exchange/kinetics current densities and superior antioxidation ability compared to their pure Ni-based counterparts in alkaline media. Density functional theory (DFT) calculations elucidate the electronic structures of the FeCoNiMoW active sites, revealing robust d–d electron interactions within the constituent metals. The presence of multi-active sites with optimized adsorption energy for intermediates is also identified, thereby mitigating the Gibbs free energy barrier in the HOR process. This comprehensive investigation not only affords intricate insights into the complex structural attributes and catalytic mechanisms inherent in multielement HEA systems but also serves as a foundation for the informed design of highly efficient catalysts featuring d–d orbital interactions in hydrogen electrolysis, and beyond.