Modulating C ₂ Selectivity in CO ₂ Electroreduction through Molecular Surface Engineering of Copper Nanowires

Electrocatalytic reduction of CO₂ to multicarbon products represents 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. Surface engineering has emerged as a powerful strategy to steer the selectivity of CO₂ electroreduction toward ethylene. Here, we introduce 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 architecture 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 have a profound effect on ethylene selectivity. Notably, electrodes incorporating electron-withdrawing groups achieved nearly a tenfold increase in Faradaic efficiency for ethylene relative to pristine CuNWs, whereas hydrophilic functionalities favored hydrogen production and suppressed C₁ and C₂ products. DFT calculations reveal how the substituents alter local electric fields and interfacial water binding, providing a molecular-level rationale for the observed trends. Ex situ characterization of core-shell electrodes further reveals that the polymeric coating stabilizes the Cu surface against corrosion and provides valuable insights into the structural reconstruction of CuNWs during the electrocatalytic process. This work not only advances the fundamental understanding of hybrid interface effects by providing a powerful and scalable approach for decoupling catalyst selectivity from the intrinsic properties of the metal surface but also offers a promising route toward efficient and industrially relevant carbon conversion technologies.