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

In the present study, efficient photocatalytic reduction of CO 2 to low-carbon hydrocarbons (CO and CH 4 ) was achieved via the construction of a Bi 2 O 3 /Mn 3 O 4 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 CH 4 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 CO 2 to CO. The emergence of peaks corresponding to intermediates such as *CHO and *CH 3 O indicates the effectiveness of the catalyst in driving the conversion of CO 2 toward C1 products. A more intense *COOH peak in the Fourier transform infrared spectroscopy (FT-IR) of Bi 2 O 3 /Mn 3 O 4 -2 further demonstrates its superior capability to convert more CO 2 into CO. This study proposes a strategy to enhance photocatalytic activity by modulating the electron transfer capability of the material.