The regulation of reaction processes and rate-limiting steps for efficient photocatalytic CO2 reduction into methane over the tailored facets of TiO2

Abstract

Photocatalytic CO₂ reduction into hydrocarbon fuels has attracted considerable attention as an effective solution to solve the problems of energy crisis and global warming; however, the elementary reactions are complicated and the reactive mechanism is still indistinct. Herein, anatase TiO₂ photocatalysts with tailored facets due to their generally excellent performance were chosen as model catalysts to investigate the underlying mechanism of CO₂ reduction using the density functional theory. It was found that the CO₂ reduction preferably occurred on the anatase {101} facet rather than on {010}. The rate-limiting step on the {101} facet was the final generation of CH₄, while it was the initial reduction of CO₂ on the {010} facet. Besides, the initial reduction of CO₂ was a pivotal step and the photocatalytic efficiency and selectivity were distinctly promoted due to the regulation of the reaction processes over different facets. Using these results, we put forward a new approach to understand the relationship between the reaction process and the reaction rate in photocatalysis, which indicates that tailoring the rate-limiting step is a key to achieve excellent efficiency and product yield in energy- and environment-related catalytic reactions.