In Situ Oxygen-Vacancy Engineering for Enhancing CO₂ Reduction Activity

Bulk metallic oxides with abundant surface oxygen vacancies are promising for the electrocatalytic carbon dioxide reduction reaction (CO 2 RR). However, the obscure quantification of oxygen-release behavior has hindered the development of highly active and robust electrocatalysts. Herein, based on theoretical guidance, graphene confined SnO x nanodots (rGO@SnO x ND) holding the capacity for in situ formation of reaction-induced oxygen vacancies were prepared and taken as the model catalyst. Operando X-ray absorption fine structure (XAFS) quantitatively analyzed the reversible oxygen-released behavior, promoting the SnO x lattice modulation of the adsorption of *OCHO intermediate. These structure changes further facilitate the exceptional performance, yielding a peak j formate of 567 mA cm –2, a selectivity of 92.5% and a 50 h long-term stability of rGO@SnO x ND. The findings significantly advance the comprehensive understanding of the quantitative relationship between controllable oxygen vacancies and reaction activity, highlighting the capabilities of operando spectroscopy toward much wider metallic oxide-based electrochemical systems.