Resolving non-covalent interactions between surface hydroxyl on Cu and interfacial water in alkaline CO electroreduction

Non-covalent interactions between the electrocatalyst surface and its electrolyte play a vital role in shaping the microenvironments of electrochemical interfaces. Yet, direct spectroscopic investigation of these interactions and their catalytic effects has remained elusive in electrocatalysis research. Here, using in situ Raman spectroscopy, we resolve a universal change of interfacial water structure at electrified Cu surfaces during alkaline CO reduction reaction. An intricate non-covalent interaction between interfacial water and surface hydroxyl (OH ad ) was recognized through a proposed OH ad ···M + (H 2 O) n complex, with M + representing electrolyte cations. On exposure to catalytic potentials, these non-covalent complexes evolve into local OH − ···M + (H 2 O) n species residing within the electrical double layer and favour CO reduction reaction into acetate over other C 2 products. These results demonstrate the crucial roles of non-covalent interactions in determining the activity of surface reactions, whose existence and rational design may offer opportunities for future fine control of electrocatalysis processes.