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.