Modulating C₂ selectivity in CO₂ electroreduction through molecular surface engineering of copper nanowires

Electrocatalytic CO₂ reduction to multicarbon products represent a key target in the development of artificial (photo)synthetic systems. Copper-based electrodes are uniquely suited for this purpose yet achieving high selectivity toward C–C coupled products such as ethylene, over undesired byproducts like methane and hydrogen, remains a major challenge. For CO₂ reduction to ethylene, we introduce here a modular hybrid electrode architecture composed of copper nanowires (CuNWs) coated with a thin, functional organic shell formed via electroreduction of ethylene-bridged dipyridophenazine (dppz) dication derivatives. This core–shell system enables fine-tuning of the interfacial catalytic environment through rational molecular design. We demonstrate that subtle structural variations affecting the electronic distribution of the phenazine moiety, particularly electron-donating or hydrophilic substituents, have a profound impact on the ethylene selectivity. Notably, electrodes incorporating electron-donating groups achieved nearly a tenfold increase in Faradaic efficiency for ethylene relative to pristine CuNWs, while hydrophilic functionalities favored hydrogen production and suppressed C₁ and C₂ products. Ex-situ characterization of core-shell electrodes further reveals that that the polymeric coating stabilizes the Cu surface against corrosion and provides valuable insights into the structural reconstruction of CuNWs during the electrocatalytic process. Our findings highlight a powerful and scalable approach for decoupling catalyst selectivity from the intrinsic properties of the metal surface, offering a tunable platform for next-generation CO₂ electroreduction. This work not only advances fundamental understanding of hybrid interface effects but also provides a promising route toward efficient and industrially relevant carbon conversion technologies.