Achieving pH-universal electrosynthesis of formate under industrial-grade current density by enriched selenium vacancies

Electrosynthesis of formate via CO₂ reduction (CO₂ER) is of great significance for completing carbon cycle, however, low CO₂ utilization efficiency caused by slow reaction kinetics greatly hinder its large-scale application. Herein, we reported a ~50 nm-thick SnSe₂ nanosheets with enriched Se vacancies, which exhibits an excellent catalytic activity for pH-universal formate electrosynthesis. In alkaline, neutral, and acidic electrolytes, this catalyst reached up to the maximum formate Faradaic efficiencies of 94.1%, 81.7%, and 78.1%, respectively. Under corresponding pH conditions, the maximum formate partial current densities achieved 800, 568, and 495 mA cm⁻², respectively. Kinetic experiments combined with in situ electrochemical spectroscopy unveiled that the abundant Se vacancies promoted the dissociation of water to produce more protons, thereby accelerating the formation rate of key *OOCH intermediate. Theoretical calculations validated that the formation of enriched Sn active sites lowered the energy barrier for the *OOCH formation, eventually facilitating the formate electrosynthesis process.