Photocatalytic CO₂ reduction utilizing solar energy to convert CO₂ into value-added fuels and chemicals is regarded as a promising strategy for alleviating energy crises and achieving carbon cycling. However, this process remains limited by rapid recombination of photogenerated carriers and sluggish CO₂ activation kinetics. In this work, Bi₂MoO₆ (BMO)-based photocatalysts with Co doping and in-situ formation of Bi⁰ nanocrystals were developed through a facile one-step solvothermal method. X-ray absorption spectroscopy analysis reveals that Co species are atomically dispersed within the BMO lattice in a CoO₄ coordination configuration. The weak crystal-field environment of CoO₄ preserves unpaired 3d electrons and induces spin-polarized electronic states, thereby decreasing the photocarrier recombination. Meanwhile, the Co doping leads to in-situ formation of Bi⁰ nanocystals on the catalyst surface, which promotes photocarrier transfer between Bi⁰ and Co-BMO and facilitates the photocarrier separation. The Co doping increases the CO₂ adsorption energy on the Bi active sites and decreases the energy barrier for the formation of the key *COOH intermediate. Moreover, the Co doping generates extra Co and Bi⁰ active sites for CO₂ photoreduction reactions. The cascade synergistic mechanism significantly boosts the photocatalytic CO₂-to-CO conversion, where the optimal Co₂-BMO sample delivers a CO production rate of 158.47 μmol g⁻¹ h⁻¹ that is 3.8 times higher than that of pristine BMO. This work provides an intriguing strategy for designing efficient solar-driven CO₂ conversion photocatalysts from the perspectives of electronic spin manipulation and interfacial charge transfer.

How to tailor the interface charge transfer in heterostructured photocatalysts via energy band engineering has been an important research topic in boosting photocatalysis and promoting its application in hydrogen evolution. In this study, we have developed Bi₂S_3−x@Cd_0.7Zn_0.3S (BS-Sv@CZS, Bi₂S_3−x with S vacancies labeled as BS-Sv) heterostructured photocatalysts, where the energy band structures of BS-Sv were continuously regulated via creating S vacancies in the lattice to realize manipulation of the interface charge transfer and boost the photocatalysis for H₂ generation. The BS-Sv@CZS photocatalysts are constructed into double-shell hollow hexagonal nanocages with BS-Sv coating on the outer surface of CZS nanocages. It is demonstrated that with increasing the S vacancy concentration in BS-Sv (i.e., elevating the energy band positions of BS-Sv), the interface electric field of BS-Sv@CZS gradually increases; and more importantly, the photoelectron transfer behavior from CZS to BS-Sv is tailored from conduction band (CB)-to-CB transfer to CB-to-CB/valence band (VB) transfer, and then to CB-to-VB transfer. The BS-Sv@CZS heterostructured photocatalysts are endowed with much improved photocatalysis for H₂ evolution; particularly, the BS-Sv2@CZS with CB-to-CB/VB photoelectron transfer displays the highest photocatalytic activity (H₂ generation rate: 2.56 mmol·g⁻¹·h⁻¹) that is 4.1 (or 8.0) times larger than that of CZS (or BS-Sv2). The photocatalytic enhancement mechanism was deeply elucidated via combined experimental and theoretical studies. This study highlights an important strategy for boosting photocatalytic H₂ evolution of heterostructured photocatalysts.