Descriptor‐Guided Stabilization of Reconstructed Active Phases for High‐Activity and Durable CO 2 ‐to‐Formate Conversion

ABSTRACT Sn oxides are promising CO 2 RR electrocatalysts for formate production, but their high activity is difficult to sustain because cathodic reconstruction can over‐reduce active oxide‐derived surfaces to metallic Sn. This dynamic evolution makes it challenging to identify and stabilize the true working‐state active phase. Here, we construct a descriptor‐guided framework that links dynamic Sn‐oxide reconstruction with electronic‐structure evolution and formate‐producing activity to identify and stabilize the favorable working‐state active phase. Electronic‐structure analysis shows that the optimal Sn x O y /Sn surface stabilizes the *OCHO intermediate through coupled charge‐polarization redistribution and Sn 5 s /5 p orbital modulation. To quantify this effect, we develop a TD descriptor integrating Bader charge, Sn 5 p coupling, and Sn 5 s lone‐pair activation, which exhibits a volcano‐type correlation with the limiting free energy, with the minimum at TD = 0.67 corresponding to the most favorable reconstructed Sn x O y /Sn surface. Guided by this descriptor, amorphous SnO 2 is designed to stabilize the favorable Sn x O y /Sn working state and suppress deep reduction, achieving an HCOO − partial current density of 438.0 mA cm −2 at −1.8 V vs. RHE, 1.8 times that of commercial SnO 2 . This work provides a descriptor‐guided strategy for stabilizing reconstructed active phases in CO 2 RR.