In Situ\nOxygen-Vacancy Engineering for Enhancing CO<sub>2</sub> Reduction\nActivity

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