Modulating Interfacial Hydrogen-Bond Environment by Electrolyte Engineering Promotes Acidic CO₂ Electrolysis

Abstract

Acidic CO2 electroreduction offers a promising strategy for achieving a high CO2 utilization efficiency. However, it is highly challenging to inhibit the competing hydrogen evolution reactions (HER) due to the high concentration of protons at the electrode–electrolyte interface. The interfacial hydrogen-bond environment greatly affects proton transfer and the kinetics of hydrogen-related reactions, e.g., HER and CO2 reduction. In this work, we demonstrate that sulfonate-based electrolyte additives, including sodium p-styrenesulfonate (SPS), sodium p-toluene sulfonate (STS), and sodium benzenesulfonate (SBS), enable reconstruction of the interfacial hydrogen-bond environment and enhance the CO2 electrolysis performance. Mechanistic studies uncover that the strong hydrogen-bond interactions of these sulfonate-based additives with H2O achieve the construction of a low proton-flux interface. This leads to the suppression of proton concentration-dependent HER. The SPS-assisted acidic CO2 electrolysis yields CO with a high selectivity of 97.8% and a high single-pass carbon efficiency of 66.3% at 250 mA cm–2 on commercial Ag catalysts in acid. This work provides a facile strategy to promote acidic CO2 electrolysis by modulating the interfacial hydrogen-bond environment through electrolyte design.