Construction of S-scheme Sb2O3/g-C3N4 heterojunctions for photocatalytic CO2 and Cr(VI) reduction.

Photocatalytic CO₂ reduction is a promising strategy to address excessive CO₂ emissions. g-C₃N₄ photocatalyst has attracted widespread attention due to its appropriate bandgap and low toxicity. However, the rapid recombination of electron-hole pairs and the limited number of active sites severely restrict its practical application. In this study, we reported S-scheme Sb₂O₃/g-C₃N₄ heterojunctions. Introducing Sb₂O₃ onto g-C₃N₄ enhances active sites and adsorption capacity, and improves photogenerated carriers separation efficiency via heterojunction formation. Under simulated solar light irradiation, the Sb₂O₃/g-C₃N₄ heterojunctions exhibits superior photocatalytic CO₂ reduction performance relative to the reference Sb₂O₃ and g-C₃N₄. In-situ X-ray photoelectron spectroscopy (In-situ XPS), surface photovoltage spectroscopy (SPS), electron paramagnetic resonance (EPR) and ultraviolet photoelectron spectroscopy (UPS) further reveal the electron transfer mechanism in heterojunctions. In-situ diffuse reflectance Fourier transform infrared (DRIFTS) spectroscopy provides insight into the dynamic behavior of CO₂ into CO and CH₄. This work offers a feasible strategy for developing high-performance g-C₃N₄ photocatalysts to address environmental challenges.