High-Entropy Environments Enable Metal Surface-Catalyzed Nucleophilic Electrooxidation

Abstract

Electrochemical biomass conversion offers a sustainable route to diverse products, minimizing environmental impact. However, conventional 5-hydroxymethylfurfural electrooxidation (HMFOR) catalysts such as Ni(OH)₂ and NiS suffer from low conductivity, poor stability, and limited active sites. This work introduces a CoNiMnMoPd high entropy alloy (HEA) to address these limitations by simultaneously maintaining high conductivity, stability, and a high Ni oxidation state, enabling nucleophilic dehydrogenation. The HEA catalyst achieved a 92.5% 2,5-furandicarboxylic acid (FDCA) Faradaic efficiency, 89.5% HMF conversion, and 95.8% FDCA selectivity, maintaining performance for over 100 h. Experimental and theoretical investigations revealed that the multielement composition of the HEA enabled Ni sites to maintain a high-valence state, serving as the primary adsorption sites for HMF, and the dehydrogenation reaction occurs preferentially at non-Ni sites within the HEA. Compared to monometallic Ni, the d-band center shift and reduced antibonding filling contributed to a decrease in the energy barrier for the rate-determining step (RDS) in the HMF-to-FDCA conversion, from 0.770 to 0.567 eV. This work offers novel insights for the development of Ni-based HEA catalysts for biomass valorization.