Highly-configured TiO2 hollow spheres adorned with N-doped carbon dots as a high-performance photocatalyst for solar-induced CO2 reduction to methane

Abstract Transforming CO2 into solar fuel using renewable solar energy and a catalyst is an effective approach that simultaneously addresses energy scarcity and climate deterioration. Therefore, it is necessary, albeit challenging, to design a catalyst that works effectively for this purpose. Herein, we have rationally developed a hybrid catalyst composed of highly-configured TiO2 hollow spheres (TOH) and N-doped carbon dots (CD), referred to as CD/TOH, and use this hybrid as a catalyst for photocatalytic CO2 reduction to produce CH4 under simulated sunlight. The electron microscopy results revealed that the CD/TOH hybrid possesses a porous hollow sphere structure uniformly adorned with N-doped carbon dots. Moreover, the CD/TOH hybrid demonstrates many beneficial properties for CO2 photoreduction reactions, including a large surface area, effective light-harvesting capability, high CO2 adsorption, and, most importantly, significantly enhanced separation of photoexcited charges. Consequently, the CD/TOH containing 2 wt% CD achieves an optimum CH4 formation rate of 26.8 μmol h−1 g−1, corresponding to 98% CH4 selectivity against competitive H2 production. Further, the hybrid also demonstrated stable CO2 reduction activity during consecutive test runs. Thus, the insights gained from this study may aid in the development of effective catalysts for CO2 photoreduction.