Tunable Coordination Number in Non-Metal-Introduced Copper Catalysts Enables High-Performance Electrochemical CO₂ Reduction to C₂ Products

Copper-based catalysts occupy a central position in electrocatalytic CO₂ reduction systems due to their unparalleled capacity to drive multicarbon (C₂₊) product formation. Nevertheless, the realization of efficient C₂₊ generation remains impeded by convoluted reaction pathways and prohibitively high activation energies for C─C bond formation. Strategic modulation of copper's coordination environment emerges as an effective lever to tailor CO₂ adsorption energetics and reconfigure reaction trajectories. Here, magnetron sputtering is employed to engineer non-metallic heteroatom-introduced Cu catalysts with precisely tuned coordination numbers. This coordination engineering induces a marked enrichment in surface-bound ^*CO intermediate density and reduces the kinetic suppression of ^*CO hydrogenation to ^*CHO via elevated transition-state energies. Such electronic restructuring redirects the catalytic pathway toward ^*CHO-^*CHO coupling, thereby unlocking selective ethylene (C₂H₄) production. The optimized Si-doped Cu catalyst, featuring a coordination number of 5.5, achieves a C₂₊ Faradaic efficiency of 80% at −1.1 V vs. RHE, surpassing conventional Cu-based systems. These findings establish coordination number tuning through non-metallic introduction as a generalizable paradigm for the rational design of high-performance CO₂ reduction electrocatalysts.