Controlled Formation of Defective Shell on TiO2 (001) Facets for Enhanced Photocatalytic CO2 Reduction

Abstract

AbstractDefective black TiO2 has attracted considerable attention as photocatalyst for highly efficient solar energy conversion. However, it still remains a challenge to understand the basic role of defective shell on the basis of crystal facet engineering, due to the difficulty in generating defects merely on a specific facet. Herein, we develop a novel strategy to precisely control the formation of defective shell only on {001} facets of TiO2 nanocrystals due to the anisotropic effect of the crystal facets, which enables the investigation of defective shell on a specific facet to be achieved. It is found that the defective shell, middle interface layer and crystalline core together constitute a homojunction (TiO2‐homojunction). The defective shell of TiO2‐homojunction realizes the effective spatial separation of photogenerated electrons and holes. Moreover, the presence of Ti3+ ion and oxygen vacancies in defective shell can induce high free electron concentration and serve as active sites to promote the adsorption and activation of CO2 molecules. As a result, the TiO2‐homojunction exhibits significant photocatalytic behavior for CO2 reduction in a gas‐solid system. More interestingly, the position of redox reaction is reversed due to the controlled formation of defective shell, where {001} facets act as reduction sites and {101} facets as oxidation sites during photocatalytic process.