S‐doped Ag–Sn Alloy Hollow Microbox for High‐Performance CO₂ Electroreduction to Formate

Abstract The dynamic catalyst's restructuring creates a new catalytic surface that is essential for boosting the efficiency of electrochemical carbon dioxide reduction reaction (CO 2 RR). In this work, we synthesize Ag‐decorated SnS 2 hollow microboxes using a coprecipitation method followed by a hydrothermal treatment. Based on a collection of in‐situ/ex‐situ characterizations including in‐situ Raman spectroscopy, rapid freeze‐quench (RFQ) 119 Sn Mössbauer spectroscopy, X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS), we discover that the Ag‐decorated SnS 2 (Ag@SnS 2 ) hollow microboxes undergo dynamic reduction and reconstruction during the electrochemical CO 2 RR, leading to the in‐situ formation of S‐doped Ag–Sn alloy (S‐Ag 3 Sn/Sn) hollow microboxes. This transformation results in a remarkable formate selectivity of 92.4% with a formate partial current density of 97.3 mA·cm −2 at −0.8 V versus RHE in an H‐cell. In‐situ attenuated total reflection surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS) measurements and density functional theory (DFT) calculations indicate that both S‐doping and Ag–Sn alloying enhance the CO 2 adsorption and improve the stability of *OCHO intermediate. This work offers a facile strategy for designing highly active and selective electrocatalyst for CO 2 RR.