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

Acidic CO 2 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 CO 2 reduction reaction (CO 2 RR) performance. Modulating electrode structure plays a critical role in improving the local microenvironment of CO 2 RR 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/SiO 2 -3 catalyst has high formic acid (HCOOH) selectivity at high current density (∼90 % at −400 mA cm −2 ). Importantly, the Sn-C/SiO 2 -3 catalyst can operate stably for 45 h at −400 mA cm −2 . Combined in situ infrared analysis reveals that hydrophobic SiO 2 aerosol layer can engineer the local microenvironment over the Sn-C catalyst surface by increasing the coverage of *OCHO to improve the CO 2 RR, which ultimately promotes high-efficiency CO 2 conversion to HCOOH in strong acidic media. This surface coating strategy for adjusting the interface microenvironment can also be used for other electrocatalytic reactions.