The synergy of low S-vacancy and Cu sites in Cu-In4SnS8 promotes the favorable conversion of CO2 to ethanol with full selectivity

Direct photocatalytic CO 2 conversion to C 2 products holds notable potential, but this technology is still limited by the high thermodynamic energy and sluggish kinetics. By introducing Cu in In 4 SnS 8 catalyst, we here developed low S vacancies and chemical reactive sites photocatalysts Cu-In 4 SnS 8 , enabling photocatalytic CO 2 to ethanol with full selectivity. Minor electron paramagnetic resonance peak intensity and large formation energy for S-vacancy suggest Cu introduction suppresses S vacancies formation. Low S vacancies photocatalysts Cu-In 4 SnS 8 possess excellent carrier transfer and separation ability by the steady photoluminescence and transient fluorescence characteristic results. Furthermore, in situ, FTIR measurements confirmed ethanol formation via the presence of the intermediates *COOH, *CO, *OCCO(H), and *OCH 2 CH 3 . Also, theory calculations reveal that Cu efficiently reduces the energy barriers of the rate-limiting steps of *COOH and *COH, and promotes C-C coupling and multi-proton coupled electron transfer processes by co-adsorption and asymmetric charge distribution effects. As a result, the optimized sample achieves 0.73 μmol h −1 CH 3 CH 2 OH generation with full selectivity.