2D/2D CsPbBr/BiOCl Heterojunction with an S-Scheme Charge Transfer for Boosting the Photocatalytic Conversion of CO.

The rational design of a two-dimensional (2D)/2D "face-to-face" heterojunction photocatalyst is crucial for the mediation of interfacial charge transfer/separation. Herein, a unique 2D/2D step-scheme (S-scheme) photocatalyst of CsPbBr/BiOCl is constructed by the self-assembly of CsPbBr and BiOCl nanosheets (NSs). Profiting from the effective interface contact and appropriate band structures between CsPbBr and BiOCl NSs, a valid S-scheme heterojunction of CsPbBr/BiOCl is established. Density functional theory (DFT) calculations and a series of characterization techniques including X-ray photoelectron spectra (XPS), photoassisted Kelvin probe force microscopy (KPFM), and electron spin resonance (ESR) systematically corroborate the S-scheme charge-transfer mechanism between CsPbBr and BiOCl. The formation of an S-scheme heterojunction endows the photocatalyst with boosted charge separation and retainment of the highest redox ability. As a result, the obtained 2D/2D CsPbBr/BiOCl S-scheme photocatalyst shows much superior CO-reduction performance to single CsPbBr and BiOCl. This investigation provides new insights into the construction of novel S-scheme heterojunctions based on 2D/2D photocatalytic systems.