Switching CO2 Electroreduction Pathways between Ethylene and Ethanol via Tuning Microenvironment of the Coating on Copper Nanofibers

Engineering the microenvironment of electrode surface is one of the effective means to tune the reaction pathways in CO2RR. In this work, we prepared copper nanofibers with conductive polypyrrole coating by polymerization of pyrrole using polyvinyl pyrrolidone (PVP) as template. As a result, the obtained copper nanofibers Cu/Cu2+1O/SHNC, exhibited a superhydrophobic surface, which demonstrated very high selectivity for ethanol with a Faraday efficiency (FE) of 66.5% at ‐1.1 V vs reversible hydrogen electrode (RHE) in flow cell. However, the catalyst Cu/Cu2+1O/NC, which was prepared under the same conditions but without PVP, possessed a hydrophobic surface and exhibited high selectivity towards ethylene at the given potentials. The mechanism for switch of reaction pathways from ethylene to ethanol in CO2RR was studied. Incorporating pyrrolidone groups into the polymer coating results in the formation of a superhydrophobic surface. This surface weakens the hydrogen bonding interaction between interfacial water molecules and facilitates the transfer of CO2, thereby enhancing the local CO2/H2O ratio. The high coverage of *CO promotes the coupling of *CO and *CHO to form C2 intermediates, and reduces the reaction energy for the formation of *CHCHOH (ethanol path) at the interface. This ensures that the reaction pathway is directed towards ethanol.