Constructing surface oxygen vacancy-rich ln2O3-x/tubular carbon nitride S-scheme heterojunction for selective biomass-derivative oxidation coupled with H2 production

Abstract

The integration of selective oxidation of renewable biomass and its derivatives with hydrogen (H₂) production holds significant potential for simultaneously yielding value-added chemicals and “green H₂”, contributing to addressing sustainability challenges. The S-scheme charge transfer mechanism enhances charge separation by maintaining strong redox potentials at both ends, facilitating both oxidation and reduction reactions. Herein, we synthesize a visible-light-responsive, oxygen vacancy-rich In₂O_3-x/tubular carbon nitride (IO_OV/TCN) S-scheme heterojunction photocatalyst via electrostatic adherence for selective 5-hydroxymethylfurfural (HMF) oxidation to 2,5-diformylfuran (DFF) and 2,5-furandicarboxylic acid (FDCA), alongside H₂ production. Under anaerobic conditions and visible-light irradiation, the optimal IO_OV/TCN-10 catalyst achieves an HMF conversion of 94.8% with a selectivity of 53.6% for DFF and FDCA, and a H₂ yield of 754.05 μmol g⁻¹ in 3 h. The significantly improved photocatalytic activity results from enhanced visible-light absorption, reduced carrier recombination, and abundant catalytic active sites due to the synergistic effect of surface oxygen vacancies, the hollow nanotube-based architecture, and the S-scheme charge transfer mechanism. This work highlights the great potentials of S-scheme heterojunctions in biomass conversion for sustainable energy use and chemical production.