Z-scheme heterojunction in CdS-decorated 3D flower-like CdIn₂S₄ nanospheres for enhancing visible light-driven CO₂ reduction

Design of efficient Z-scheme heterojunction photocatalysts remains a pivotal challenge in photocatalytic CO₂ reduction. Herein, a three-dimensional (3D) flower-like CdIn₂S₄ nanosphere photocatalyst decorated with CdS nanoparticles (CdS/CdIn₂S₄) was successfully synthesized via a one-pot solvothermal method. The unique hierarchical architecture exposes enhanced light-harvesting interfaces and abundant reactive sites, while coupling CdS with CdIn₂S₄ constructs a direct Z-scheme heterojunction at the interface that promotes photogenerated electron migration and charge separation efficiency. The optimized CdS/CdIn₂S₄-10 catalyst achieves exceptional visible-light-driven CO₂ reduction performance with a CO production rate of 12.9 μmol·g⁻¹·h⁻¹ and 100% selectivity, representing 8-fold and 5-fold enhancements over pristine CdS and CdIn₂S₄, respectively. In-situ diffuse reflection infrared fourier transform spectra (DRIFTS) and density functional theory (DFT) calculations elucidate the mechanism for photocatalytic CO₂ reduction: the built-in electric field at the interface of the Z-scheme heterojunction drives directional electron transfer to enable spatial separation of high-redox-potential photogenerated charge carriers, with *COOH intermediate formation identified as the key step to realize the photocatalytic conversion of CO₂ to CO. This work provides fundamental insights for constructing high-efficiency Z-scheme photocatalytic systems.