Cu doping and Ti3C2OH quantum dots co-modifications of Zn3In2S6 boosted photocatalytic reduction of CO2 to CO via accelerating carriers transfer and enhancing CO2 adsorption and activation

In this study, the Zn3In2S6 was modified by Cu doping and loading of Ti3C2OH quantum dots (QDs) by hydrothermal method for efficient and highly selective photoreduction of CO2. Various characterizations and tests demonstrated that the Cu0.05Zn2.95In2S6@Ti3C2OH QDs exhibited desired morphology, superior light utilization ability, and the most efficient carriers’ separation and transfer. This optimized material exhibited a CO yield of 51.848 μmol g-1 h-1, with selectivity up to 99%. This high CO yield was 22.3 and 3.48 times of those of the Zn3In2S6 and Cu0.05Zn2.95In2S6, respectively; demonstrating that synergistic effect of Cu-doping and Ti3C2OH QDs modification existed for enhancing CO2 reduction to CO. Results of CO2-TPD and in-situ FTIR showed that the Cu0.05Zn2.95In2S6@Ti3C2OH QDs possessed the greatest CO2 adsorption and activation ability. DFT (density functional theory) calculation revealed that greatest CO2 adsorption energy, CO desorption energy and charge density distribution were key factors for the Cu0.05Zn2.95In2S6@Ti3C2OH QDs to achieve efficient reduction of CO2. Possible CO2 reduction pathways and mechanism were proposed. This study could advance the development of photocatalysts for highly selective CO2 reduction to CO and enrich related mechanism insights.