Efficient acidic CO2 electroreduction to formic acid by modulating electrode structure at industrial-level current

Acidic CO2 electroreduction has the potential to synthesize low carbon footprint chemicals using renewable electricity. However, proton-rich environments can lead to strong hydrogen evolution reaction (HER) and severe degradation of electrochemical CO2 reduction reaction (CO2RR) performance. Modulating electrode structure plays a critical role in improving the local microenvironment of CO2RR electrolytes. Here, by covering the catalyst layer with a hydrophobic silica aerosol layer, the surface of the catalyst is protected from corrosion, thereby increasing the efficiency and stability of the system. In the flow cell, the Sn-C/SiO2-3 catalyst has high formic acid (HCOOH) selectivity at high current density (∼90 % at −400 mA cm−2). Importantly, the Sn-C/SiO2-3 catalyst can operate stably for 45 h at −400 mA cm−2. Combined in situ infrared analysis reveals that hydrophobic SiO2 aerosol layer can engineer the local microenvironment over the Sn-C catalyst surface by increasing the coverage of *OCHO to improve the CO2RR, which ultimately promotes high-efficiency CO2 conversion to HCOOH in strong acidic media. This surface coating strategy for adjusting the interface microenvironment can also be used for other electrocatalytic reactions.