Construction of a 0D/2D S-Scheme Heterojunction Based on Ni-Doped CsPbBr3 and ZnO for Enhanced Photocatalytic CO2 Reduction

Abstract Doping with transition metals and constructing S-scheme heterojunctions are well-recognized strategies for boosting photocatalytic CO2 reduction. Herein, we adopt a cascade design approach to fabricate a Ni-doped CsPbBr3/ZnO S-scheme heterojunction, aiming to further improve the material’s photocatalytic activity. First, Ni-doped CsPbBr3 nanocrystals were prepared by a hot-injection method. Subsequently, they were loaded onto ZnO nanosheets through a simple electrostatic self-assembly approach, successfully yielding a 0D/2D Ni-CsPbBr3/ZnO S-scheme heterojunction photocatalyst. In this system, the introduction of transition metal Ni, which possesses a relatively high d-band center position, into CsPbBr3 effectively extends the light response region and enhances the light-harvesting capacity. Meanwhile, the dimensional effects of the 0D/2D heterostructure shorten the transport path of photogenerated carriers, while the internal electric field formed at the Ni-CsPbBr3/ZnO heterojunction interface further promotes carrier separation and transport, resulting in an increased local electron density. Under UV-Vis illumination for 4 h, the CO and CH4 yields over 4CsPbBr3-3Ni/ZnO reached 155.06 and 125.87 μmol/g, respectively, which are 4.38-fold and 5.43-fold those of CsPbBr3-3Ni, 4.33-fold and 60.22-fold those of pure ZnO, and 1.40-fold and 4.32-fold those of 4CsPbBr3/ZnO. The excellent photocatalytic CO2 reduction performance is attributed to the synergistic interplay between d-band center engineering and S-scheme heterojunction formation. This synergy concurrently strengthens light harvesting, facilitates directional charge migration, maintains a high redox potential, and optimizes the CO2 adsorption and activation. This study offers meaningful guidance for the rational design of high-efficiency photocatalysts.