Steering CO ₂ Electroreduction to Methane Production Over Copper via Polymer‐Regulated Hydrolysis

Carbon dioxide (CO₂) electroreduction in aqueous electrolytes is a complex electrochemical process that involves the transfer of multiple electrons and protons, resulting in various reaction pathways and products. A critical step in this process is the dissociation of water, which provides protons and significantly affects * CO hydrogenation pathways, as well as hydrogen evolution. In this study, copper‐based catalysts are modified through in situ polymerization of dopamine to create intimate polymer coatings that regulate the surface water dissociation process. This modification leads to a notable shift in the product distribution of CO₂ electroreduction, from predominantly multicarbon compounds to methane, accompanied with the ratio of CH 4 /C 2+ changing from 0.5 to 1.8. At high current densities, the polymer‐modified catalyst exhibited stable methane production with a Faradaic efficiency of up to 60%. Kinetic isotopic effects, in situ infrared spectroscopy, and theoretical calculations revealed that polydopamine plays a crucial role in altering product selectivity by regulating hydrolysis. This work signifies the importance of polymer‐regulated hydrolysis to steer the electrochemical CO 2 reduction pathways.