Spatially isolated single-site VOx on activated carbon for efficient oxidation of carbohydrates to formic acid

Vanadium-based catalysts are widely used in the oxidation of carbohydrates to produce formic acid (FA), a promising liquid organic hydrogen carrier, but still suffers from low yield due to the formation of CO 2 . This study found that the spatially isolated VO x on active carbon (AC) can significantly increase FA yield from 43.5 to 72.9% in glucose oxidation compared with free VO x . Two specific roles of AC were revealed. Firstly, the oxygenated functional groups, high surface area and abundant microporous of AC, play a crucial role in the atomic dispersion of VO x , resulting in a heterogeneous, single-site VO x -AC catalyst. The isolated VO x site favors the oxidative C C bond cleavage in glucose via a stepwise α-cleavage pathway, thus improving FA selectivity. Secondly, the conductive AC acts as an electron buffer, which accelerates the catalytic redox cycle between V 5+ and V 4+ of the isolated VO x sites, thus increasing the reaction activity. The prepared single-site VO x -AC catalyst is reusable and can generate a concentrated FA solution (4.7 wt%) by simple filtration of the solid catalyst. This work presents a simple method for the production of H 2 energy carrier from biomass and provides a fundamental basis for designing efficient catalytic systems for aqueous-phase oxidation reactions.