Cation vacancies creation propel pre-oxidation enhancing nickel hydroxide activity for highly efficient 5-hydroxymethylfurfural upgrading

The 5-hydroxymethylfurfural oxidation reaction (HMFOR) is an energy-saving alternative for H₂ production due to the low thermodynamic potential. However, the comprehensive investigation into the dehydrogenation pre-oxidation and substrates adsorption on catalyst with vacancy has not been carried out. Herein, we report a unique strategy to create cation vacancies by in situ molybdenum removal in pre-catalyst. The resulting vacancy-enriched V_Mo-NiO_xH_y catalyst enables a tripling promotion on current density than the pristine NiO_xH_y and delivers a much lower onset couple voltage than water splitting. The enhanced performance is attributed to the formation of Ni³⁺–O active substances induced by the vacancy manipulation pre-oxidation process, the optimized substrate adsorption, and the decorated Nickel electron coordination structure owing to the vacancy creation, which are evidenced by the operando spectroscopy measurements, density functional theory calculations, and X-ray absorption spectroscopy, respectively. This work shines new light on electro-catalysts design for value-added chemicals production via biomass upgrading.