Corn-straw-derived, pyridine-nitrogen-rich NCQDs modified Cu0.05Zn2.95In2S6 promoted directional electrons transfer and boosted adsorption and activation of CO2 for efficient photocatalytic reduction of CO2 to CO

In this study, biomass-derived carbon quantum dots (CQDs) doped with different nitrogen sources were loaded on Cu0.05Zn2.95In2S6 (CZIS) to achieve efficient and highly selective CO2 photocatalytic reduction. Results of various characterizations demonstrated that CZIS@CQDs-T with the highest pyridine nitrogen content (30.4%) exhibited the best light utilization, the most efficient carriers’ separation. In-situ XPS demonstrated that NCQDs were conducive to promoting electron transferred directly from the Zn3In2S6 to NCQDs under light illumination. The CZIS@CQDs-T achieved a CO yield of 70.691 μmol·g−1·h−1 with selectivity of 100%, and the yield was 4.77 times higher than that of the CZIS. CO2-TPD showed that the CZIS@CQDs-T displayed the strongest adsorption capacity for CO2, and a weak adsorption capacity for CO. In-situ FTIR analysis showed COOH* was the key intermediates during CO2 photoreduction process. DFT calculation revealed that the limb-joined pyridine nitrogen of the CZIS had denser charge density when adsorbing CO2, and the adsorption energy of CO2 and desorption energy of CO were significantly enhanced compared with the CZIS. Based on the above analysis, possible pathways and mechanisms of CO2 reduction were inferred. This study provides inspiration for designing efficient photocatalysts for highly selective reduction of CO2.