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

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-CuIn 5 S 8 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 CO 2 adsorption-activation-conversion chain, thereby exhibiting exceptional photocatalytic activity. Compared with pure CuIn 5 S 8 , the CH 4 and C 2 H 6 production in C/Sv-CuIn 5 S 8 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-CuIn 5 S 8 , 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 C 2 H 6 originates from the C C coupling of two CH 3 intermediates, while some of the uncoupled *CH 3 are protonated, leading to the high yield of CH 4 . This study provides a reference for the application of bimetallic sulfide carbon-based composite materials in the photocatalytic reduction of CO 2 .