Electron-rich SnO promote CO activation for stable electrocatalytic CO reduction.

Electrocatalytic CO reduction reaction (CORR) to formate offers a promising route for carbon neutralization, but its reactivity is largely compromised due to the competitive hydrogen evolution reaction (HER) accompanying the activation of CO at high potentials. Herein, we modulated the charge density around Sn atoms by introducing LaSnO into SnO, with the rich grain boundaries and fast electron transport of the heterostructure promoting CO reduction. Combined theoretical calculations and in situ electrochemical attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) characterization revealed enhanced activation of CO and adsorption of *OCHO intermediates by the constructed electron-rich SnO. During the CORR process over 5 % LaSnO/SnO catalyst, the Sn oxidation state can be effectively stabilized by the oxygen vacancies and amorphous phases appearing around SnO, with a FE of 70.7 % for HCOOH at -0.9 V vs. RHE and stable electrolysis of 39 h. This work provides an ideal approach for the development of highly stable Sn-based electrocatalysts.