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 CO 2 reduction systems due to their unparalleled capacity to drive multicarbon (C 2+ ) product formation. Nevertheless, the realization of efficient C 2+ 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 CO 2 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 (C 2 H 4 ) production. The optimized Si‐doped Cu catalyst, featuring a coordination number of 5.5, achieves a C 2+ 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 CO 2 reduction electrocatalysts.