Synergistic improvement in photocatalytic CO₂ reduction via oxygen vacancy engineering and S-scheme heterojunction construction in MnFe₂O₄/Bi₂WO₆ hybrids

The exploration of efficient photocatalytic materials for CO₂ conversion into hydrocarbon energy fuel is of paramount significance. However, problems, such as rapid charge recombination, low quantum efficiency, and poor product selectivity, still limit the efficiency of photocatalytic CO₂ reduction. Here, this study reports a S-scheme heterostructure of MnFe₂O₄/Bi₂WO₆, formed by loading MnFe₂O₄ nanoparticles onto Bi₂WO₆ microflowers with oxygen-rich vacancies, enabling photocatalytic CO₂ reduction. Notably, the developed MnFe₂O₄/Bi₂WO₆ heterostructure improved the photocatalytic CO₂ reduction ability, achieving a maximum CO generation rate of 32.7 μmol·h⁻¹·g⁻¹, which is 3.7 and 14.3 times higher than that of Bi₂WO₆ and MnFe₂O₄, respectively. Additionally, the CO production mechanism by CO₂ photocatalytic reduction was proposed based on detailed characterization and density functional theory (DFT) calculation. The findings of this study suggest that introducing oxygen vacancies and constructing heterojunctions can significantly improve the photocatalytic CO₂ reduction performance of Bi₂WO₆.