Double S-scheme junction of BiVO4/g-C3N4/Bi2O3 toward efficiently removal formaldehyde under simulated full-spectrum irradiation: Study of the catalytic mechanisms and reaction pathway

The double S-scheme BiVO₄/g-C₃N₄/Bi₂O₃ photocatalytic functional junction was designed and synthesized to oxidize and decompose formaldehyde into CO₂ and H₂O under simulated full-spectrum sunlight. BiVO₄/g-C₃N₄/Bi₂O₃-80 % has excellent photocatalytic activity and high CO₂ selectivity. After 3 hours, the HCHO (500 ppm) degradation rate reached 97.72 % and the CO₂ selectivity reached 99.56 %. The photocatalytic mechanism was proposed through the photoelectrochemical performance test and active free radical test and density functional theory (DFT) calculation, that the photogenerated electrons between BiVO₄-g-C₃N₄ and Bi₂O₃-g-C₃N₄ are transferred in a S-scheme path under the built-in electric field effect. This not only improves the separation and transfer efficiency of the photogenerated carriers, but also effectively inhibits its recombination; and a large number of photogenerated electrons gather on the conduction band of g-C₃N₄, and the holes remain in the valence bands of BiVO₄ and Bi₂O₃, respectively; and maintain the original strong redox ability of each unit catalyst. Therefore, a large amount of active free radicals •OH and •O₂^- are generated, which helps to improve the photocatalytic formaldehyde degradation activity. This work provides a new double S-scheme catalytic junction design idea for improving the activity of photocatalytic materials and BiVO₄/g-C₃N₄/Bi₂O₃ is expected to be popularized and applied in the field of environmental purification in the future.