Enhancing Electrochemical\nCO Reduction to Methane\nby Modulating the Interfacial Water Structure with Glycerol

Interfacial water serves as the proton source in both\nthe electrochemical\nCO reduction reaction (CORR) and the competing hydrogen evolution\nreaction (HER). Engineering the interfacial water structure to enhance\nthe CORR and suppress the HER is an effective strategy but remains\nunderexplored. In this study, we demonstrate that adding low amounts\nof glycerol to the electrolyte can effectively modulate the interfacial\nwater structure and influence the CORR product distribution. Glycerol\naddition suppressed the HER and promoted the CORR conversion to CH<sub>4</sub>, with its Faradaic efficiency increasing from 5.4 ±\n3.3 to 23.9 ± 2.7%. Electrochemical <i>in-situ</i> Raman\nspectroscopy combined with ab initio molecular dynamics (AIMD) simulations\nreveals that the glycerol additive reduces the interfacial water content\nand strengthens the interfacial hydrogen bonding network, thus inhibiting\nwater dissociation and promoting *CO protonation to produce CH<sub>4</sub>. These findings shed light on the significance of the interfacial\nwater structure in dictating CORR selectivity.