Porous carbon sphere supported Sv-CuIn₅S₈: a triple-engineered platform for high-efficiency photocatalytic CO₂...

Guided by the principles of active site exposure and electron transport kinetics, we innovatively constructed a porous carbon sphere photocatalyst loaded with sulfur-deficient bimetallic sulfides C/Sv-CuIn₅S₈ through a high-temperature calcination-induced vacancy strategy. By constructing a triple platform that integrates a hollow carbon sphere substrate, a bimetallic synergistic effect, and controllable sulfur defect states, the catalyst maximizes the efficiency of the entire CO₂ adsorption-activation-conversion chain, thereby exhibiting exceptional photocatalytic activity. Compared with pure CuIn₅S₈, the CH₄ and C₂H₆ production in C/Sv-CuIn₅S₈ increased significantly from 17.2 ± 0.5 μmol g^-1 and 7.9 ± 0.5 μmol g^-1 to 74.7 ± 0.4 μmol g^-1 and 28.4 ± 0.6 μmol g^-1, with the increase rates reaching 4.4 times and 3.6 times respectively, while also possessing superior stability (activity retention >90 % after 6 cycles). In-situ infrared spectroscopy and density functional theory calculations have elucidated its reaction mechanism, revealing that sulfur vacancies alter the reaction pathway: On C/Sv-CuIn₅S₈, the formation of the key intermediate HCOO* is nearly spontaneous with an energy barrier of -0.63 eV, thereby effectively suppressing the generation of CO. it is further inferred that the formation of C₂H₆ originates from the CC coupling of two CH₃ intermediates, while some of the uncoupled *CH₃ are protonated, leading to the high yield of CH₄. This study provides a reference for the application of bimetallic sulfide carbon-based composite materials in the photocatalytic reduction of CO₂.