Boosting CO 2 photoreduction by synergistic optimization of multiple processes through metal vacancy engineering

The photoreduction of greenhouse gas CO 2 using photocatalytic technologies not only benefits environmental remediation but also facilitates the production of raw materials for chemicals. However, the efficiency of CO 2 photoreduction remains generally low due to the challenging activation of CO 2 and the limited light absorption and separation of charge. Defect engineering of catalysts represents a pivotal strategy to enhance the photocatalytic activity for CO 2, with most research on metal oxide catalysts focusing on the creation of anionic vacancies. The exploration of metal vacancies and their effects, however, is still underexplored. In this study, we prepared an In 2 O 3 catalyst with indium vacancies (V In ) through defect engineering for CO 2 photoreduction. Experimental and theoretical calculations results demonstrate that V In not only facilitate light absorption and charge separation in the catalyst but also enhance CO 2 adsorption and reduce the energy barrier for the formation of the key intermediate *COOH during CO 2 reduction. Through metal vacancy engineering, the activity of the catalyst was 7.4 times, reaching an outstanding rate of 841.32 µmol g ‒1 h ‒1. This work unveils the mechanism of metal vacancies in CO 2 photoreduction and provides theoretical guidance for the development of novel CO 2 photoreduction catalysts.