Unravelling the effect of Ti3+/Ti4+ active sites dynamic on reaction pathways in direct gas-solid-phase CO2 photoreduction

Abstract

Converting CO2 to CH4 by solar-powered catalysis involves complex steps that produce a range of by-products. Therefore, designing efficient heterostructures for a particular chemical synthesis is challenging. The optimisation of photocatalyst surfaces can achieve the desired CO2 photoreduction pathway. Herein, we developed TiO2/CdSe nanocrystals with both amorphous and crystalline TiO2 surfaces. In situ EXAFS analysis revealed that the amorphous surface contains abundant active Ti3+ sites, while the crystalline surface is limited. Moreover, the amorphous surface of TiO2/CdSe exhibits self-regenerating Ti3+ active sites, which enable a novel CH4 cycle. Density functional theory calculation showed that an amorphous structure enhances electron transfer and localisation to Ti3+, favouring CO2 adsorption. In situ DRIFTS analysis showed different CO2 to CH4 pathways on both surfaces. These results show the potential for enhanced photocatalytic CO2 reduction through surface engineering, which has far-reaching implications for sustainable energy conversion. © 2024 Elsevier B.V.