Decorating of 2D indium oxide onto 2D bismuth oxybromide to enhance internal electric field and stimulate artificial photosynthesis

CO₂ photocatalytic reduction is an excellent strategy for promoting solar-to-chemical energy conversion and alleviating the severe environmental crisis. In this study, 2D indium oxide (IO) is decorated on 2D bismuth oxybromide (BOB) nanosheets to gain BOB/IO (B_xI_y) heterojunction. The optimal B₃I₁ composite affords a CO production rate of 54.2 μmol⋅g^-1, about 2.2 times and 11.3 times higher than those of the pristine BOB and IO, respectively. The introduction of IO significantly enhances the internal electric field (IEF), leading to accelerated charge transfer and prolonged lifetime of the photogenerated carriers. In the B_xI_y composite, the BOB and IO serve as the electron acceptor and donor, respectively, facilitating the reduction of CO₂ and oxidation of H₂O. In-situ DRIFTs spectra are used to confirm the catalytic active sites and provide insights into the mechanism of CO₂ photoreduction. The results suggest *COOH and *CO₂^- species played a crucial role in the formation of CO. This work presents a valuable perspective on understanding the charge transfer route and developing highly efficient photocatalysts for CO₂ photoreduction.