Abstract:

The efficient reduction of CO₂ through photocatalysis to produce value-added chemicals faces considerable difficulties, particularly in relation to the charge separation and transfer kinetics of photocatalysts, along with the thermodynamics of the CO₂ reduction process. Herein, we present a rational design of oxygen vacancy-mediated 2D/2D Bi₂MoO₆/Bi₂O₂S S-scheme heterojunctions via an in situ hydrothermal sulfidation strategy, where partial S²⁻ substitution for [MoO₄]²⁻ forms a tightly bonded heterointerface and induces oxygen vacancies, as evidenced by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) tests. Density functional theory (DFT) calculations reveal that the oxygen vacancy-mediated Bi₂MoO₆/Bi₂O₂S S-scheme heterojunction significantly lowers the energy barrier of ^*COOH formation rate-determining step, which in turn enhances the thermodynamics of CO₂ photoreduction. Consequently, the Bi₂MoO₆/Bi₂O₂S heterojunctions, especially BMOS5, possessed the highest CO yield of 11.01 μmol g⁻¹ h⁻¹, corresponding to 2.82 and 3.40 times the yields of bare BMO and BOS. Based on in situ XPS, band edge determination, and DFT calculations, the S-scheme charge transfer pathway was verified. The findings provide a viable pathway toward developing high-performance S-scheme heterojunctions with tailored defects for solar-driven CO₂ reduction.

Key words: S-scheme heterojunctions, CO₂ photoreduction, Charge separation and transfer kinetics, Density functional theory