Promoting CO ₂ -to-CO Photoconversion by Regulating Electron Transfer in Heterojunctions

In the present study, efficient photocatalytic reduction of CO₂ to low-carbon hydrocarbons (CO and CH₄) was achieved via the construction of a Bi₂O₃/Mn₃O₄ heterojunction composite photocatalyst. This catalyst exhibits outstanding catalytic performance under pure aqueous phase and sacrificial-agent-free conditions, achieving a CO yield of 10.164 μmol·g⁻¹·h⁻¹ with a CO selectivity of 76.04%. Notably, the total selectivity for C1 products (containing only CH₄ and CO, with no other carbonaceous products detected) achieves 94.3%. The characterization results show that the heterojunction structure effectively promotes the separation and transport of photogenerated carriers, while the bimetallic synergistic effect enhances the intrinsic activity of the active site. In situ infrared spectroscopy reveals that intermediate *COOH plays a critical role in conversion of CO₂ to CO. The emergence of peaks corresponding to intermediates such as *CHO and *CH₃O indicates the effectiveness of the catalyst in driving the conversion of CO₂ toward C1 products. A more intense *COOH peak in the Fourier transform infrared spectroscopy (FT-IR) of Bi₂O₃/Mn₃O₄-2 further demonstrates its superior capability to convert more CO₂ into CO. This study proposes a strategy to enhance photocatalytic activity by modulating the electron transfer capability of the material.