Integrated Catalytic Sites for Highly Efficient Electrochemical Oxidation of the Aldehyde and Hydroxyl Groups in 5-Hydroxymethylfurfural

5-Hydroxymethylfurfural oxidation reaction (HMFOR) is regarded as a promising approach to attain biomass-derived high-value chemical products. As the HMFOR process is complicated, and the two-step oxidation of the aldehyde group andhydroxyl group in 5-hydroxymethylfurfural (HMF) is typically involved, it is fundamentally significant to understand the differentcatalytic processes for HMFOR. In this work, we identify direct and synergistic oxidation types for HMFOR on cobalt oxidecatalysts. For the direct HMFOR process, Co3O4was found to have a higher activity for the aldehyde group than for the hydroxylgroup due to the higher reaction barrier of hydration in the hydroxyl oxidation. By studying the hydroxyl oxidation behaviors intransition metal oxides, NiO exhibited optimal hydroxyl activity owing to the appropriate OH adsorption energy for alcoholdehydrogenation. Therefore, the optimal HMFOR performance was achieved by accurately introducing Ni into the tetrahedralcatalytic sites of cobalt spinel oxides to improve the hydroxyl activity. The integrated catalytic sites enhanced the overall activity ofHMFOR with 92.42% FDCA yield and 90.35% faradaic efficiency. This work provides a promising perspective for designing efficientelectrocatalysts for HMFOR.

Automated summary

This study investigates the different catalytic processes of HMFOR and identifies direct and synergistic oxidation types. The introduction of nickel into cobalt oxide catalysts improves the hydroxyl activity and achieves optimal HMFOR performance.