Defect Engineering Induces Phase Transformation to Promote the Electrochemical Reduction of CO2 to CO by N and In Codoped SnO2

In the electrocatalytic CO₂ reduction reaction (ECO₂RR), the adsorption of the intermediate *COOH is a critical factor influencing the ability of SnO₂-based catalysts to generate CO. In this study, SnO₂ nanomaterials rich in oxygen vacancies were prepared via plasma spraying, and In and N atoms were successfully incorporated into the SnO₂ crystal through a one-step method (N,In-SnO₂). This catalyst demonstrated excellent electrochemical performance, achieving a Faradaic efficiency (FE) for CO of over 70%. Analysis revealed that the doping of In atoms, due to charge imbalance, readily induces a further increase in the level of oxygen vacancies in SnO₂, while N atoms can reduce the binding strength of Sn-O bonds. Together, these effects promote a phase transition in SnO₂ and the formation of a SnO₂/Sn heterostructure. The formation of this structure, in conjunction with the electronic structure modulation by the heteroatoms (In and N), synergistically optimizes the *CO₂-*COOH reaction energy barrier and directs the catalytic reaction toward the favorable formation of CO.