S-scheme electron transfer promoted by novel indium oxide quantum dot-loaded carbon nitride heterojunctions promoted...

The graphitic carbon nitride (g-C₃N₄) photocatalysis has emerged as a clean method for cleaving lignin-linked bonds due to its mild and sunlight-driven reaction conditions. The fast electron-hole pair complex of g-C₃N₄ constrains its degradation efficiency, making the heterojunction construction a popular solution. The conventional methods of preparing g-C₃N₄ heterojunctions by physical mixing destroy π-conjugations in g-C₃N₄, reducing the adsorption of lignin containing benzene rings. In this study, a novel indium oxide (In₂O₃) quantum dot-g-C₃N₄ 0D/2D heterojunction was prepared through the high-temperature oxidation of pre-prepared indium-doped g-C₃N₄. The introduction of In₂O₃ at the quantum dot level minimizes the interference with lignin adsorption capacity. The strong combination of the two (In₂O₃ and g-C₃N₄) increases the intersection interface area, promoting the S-scheme transfer route of the photogenerated electrons. Consequently, this enhances the photoelectric conversion efficiency and carrier lifetime of the heterojunction, and inhibits the rapid recombination of photogenerated electron-hole pairs in g-C₃N₄. The proposed heterojunction was 3 times more efficient than g-C₃N₄ alone for selective cleavage of lignin β-O-4 bonds after 2 h of sunlight irradiation. Combined with inhibitor experiments and gas chromatography-mass spectrometry analysis, this paper defines the reactive oxides and proposes a cleavage pathway for the lignin β-O-4 bonds in In₂O₃-g-C₃N₄ heterojunction system.