Editable Hydrogen Bond Network Within the Electric Double Layer for CO₂ Reduction

The hydrogen bond network (HBN) of water is dynamic and highly sensitive to electrified interfaces, where its rigidity can be significantly altered. Tuning this property is crucial, as it directly impacts electrocatalytic performance and is a key requirement for scaling these processes industrially. In this study, the rigidity of the HBN within the electrical double layer (EDL) during electrolysis was edited by introducing different quaternary ammonium cations to a 1 M KHCO₃ buffer solution. CO₂ electroreduction was conducted using the different electrolytes, and the results reveal that the performance is highly dependent on the rigidity of the HBN within the EDL. A HBN with high rigidity favors CO production, whereas a HBN with low rigidity increases the formation of formate and H₂. Notably, the production of C₂₊ is maximized in an electrolyte where the HBN has moderate rigidity. By tuning the rigidity of the HBN, a Faradaic efficiency of 90.9% for C₂₊ products is achieved with a current density of 0.81 A cm^-2 over a typical Cu electrode. In situ spectroscopic and electrochemical measurements reveal that the rigidity of the HBN governs the configuration of the reaction intermediates and the kinetics of water dissociation, thereby dictating the final product distribution.