Dynamic Reconstruction of Interfacial Hydrogen‐Bond Networks Enhances CO 2 Electroreduction Selectivity

ABSTRACT Electrochemical CO 2 RR to C 2 products is limited by sluggish C–C coupling and the hydrogen evolution reaction (HER). The interfacial microenvironment, particularly the hydrogen‐bond (HB) network, plays a crucial role in dictating reaction energetics by modulating H + availability, ion solvation, and intermediate stabilization, thereby governing the competition between CO 2 RR and HER. In this study, sodium perchlorate (NaClO 4 ) was employed to restructure the electrolyte HB network, enhancing C 2 selectivity by suppressing proton diffusion and stabilizing key intermediates. Infrared spectroscopy, 1 H NMR, and 23 Na NMR reveal that increasing NaClO 4 concentration disrupts the HB network by enhancing Na + –H 2 O coordination and ClO 4 − ‐induced disorder, reducing water mobility, modulating proton availability, and altering ion transport dynamics. Meanwhile, 1 H DOSY, 17 O NMR, and 13 C NMR reveal restricted proton diffusion, enhanced oxygen exchange between ClO 4 − and H 2 O, and altered bulk CO 2 dissolution and solution‐phase speciation. Complementary in situ infrared spectroscopy further reveals potential‐dependent changes in interfacial water and carbonate/bicarbonate‐related species under electrochemical conditions. Simulations show that Na + coordination lowers the C–C coupling barrier by 42%, promoting C 2 formation while restructuring the electric double layer (EDL) to suppress H + transport and HER. Dynamic regulation of the HB network boosts the faradaic efficiency (FE) of C 2 products from 0.69% to 83.30% and that of ethanol from 0% to 46.89% at a current density of 500 mA cm −2 .