Activation to Deactivation Dynamics of Cu-Embedded TiO2 for Solar CH4 Generation

Abstract

Photocatalytic CO2 reduction is known to accelerate on surfaces with defects such as oxygen vacancies (Vo), undercoordinatedmetal atoms, and hydroxyl groups (OH − ). This is further boosted while these defects, Vo-coupled undercoordinated metal atoms,and proximal OH − , act synergistically. However, it is challenging to make atomic-level patterns of such structural arrangementsand monitor their activation anddeactivation pathways. Herein, we report single-atom hydroxylated-Cu in the vicinity of Ti atomthat triggers Vo generation owing to specific structural arrangements. It finally activates CO 2 by coordinative activation andeventually transforms CO2 to CH 4 through Cu–*CHO intermediate. Alongside the activation, deactivation of photocatalyst alsoproceeds, accompanied by the change in the binding environment of the Cu, generation of the oxidizing hydroxyl radicals, andphotocatalytically inactive carbonaceous species. This work outlines the efficacious role of Cu in CO2 reduction to CH 4 andprovides valuable insights into the activation and deactivation mechanisms.