Step-scheme CsPbBr 3 /BiOBr photocatalyst with oxygen vacancies for efficient CO 2 photoreduction.

Metal halide perovskites with suitable energy band structures and excellent visible-light responses have emerged as promising photocatalysts for CO 2 reduction to valuable chemicals and fuels. However, the efficiency of CO 2 photocatalytic reduction often suffers from inefficient separation and sluggish transfer. Herein, a step-scheme (S-scheme) CsPbBr 3 /BiOBr photocatalyst with oxygen vacancies possessing intimate interfacial contact was fabricated by anchoring CsPbBr 3 QDs on BiOBr-Ov nanosheets using a mild anti-precipitation method. The results showed that CsPbBr 3 /BiOBr-Ov-2 with an internal electric field (IEF) heterojunction exhibited a boosted evolution rate of 27.4 μmol g -1 h -1 (CO: 23.8 μmol g -1 h -1 and CH 4 : 3.6 μmol g -1 h -1 ) with an electron consumption rate ( R electron ) of 76.4 μmol g -1 h -1 , which was 5.9 and 3.2 times that of single CsPbBr 3 and BiOBr-Ov, respectively. Density functional theory (DFT) calculations revealed that BiOBr with oxygen vacancies can effectively enhance the adsorption and activation of CO 2 molecules. More importantly, in situ infrared Fourier transform spectroscopy (DRIFTS) spectra show the transformation process of the surface species, while the femtosecond transient absorption spectrum (fs-TA) reveals the charge transfer kinetics of the CsPbBr 3 /BiOBr-Ov. Overall, this work provides some guidance for the rational design of S-scheme heterojunctions and vacancy-engineered photocatalysts, which are expected to have potential applications in the fields of photocatalysis and solar energy conversion.