Interfacial hydrogen-bond network regulation enables selective CO2 reduction to ethanol on copper-free electrocatalysts

Developing a Cu-free electrocatalytic system for CO 2 reduction toward a multi-carbon product remains challenging due to the limited understanding of C–C coupling. Herein, an Ag/Cr 2 O 3 heterostructure is reported to achieve selective ethanol electrosynthesis from CO 2 with anions to modulate the electrocatalytic interfaces. The performance of Ag/Cr 2 O 3 follows the trend of ClO 4 − > NO 3 − > NO 2 − > HCO 3 − /HPO 4 2− /SO 4 2− for different anions, which is similar to the tendency of Hofmeister anions to disrupt water’s structure. Notably, Ag/Cr 2 O 3 exhibits a faradaic efficiency (FE) ethanol of 51.8% with a stable response at ∼160 mA cm −2 in a flow cell containing ClO 4 − . In situ characterizations and theoretical calculations demonstrate that ClO 4 − reduces the number of interfacial hydrogen bonds, thus inhibiting hydrogen evolution. While the Ag-Cr asymmetric sites stabilize the C–C coupling intermediates and favor the ethanol pathway over ethylene, this enables selective ethanol generation. This work extends the approach for multi-carbon generation from CO 2 .