CO spillover and electronic coupling at CuO/Ni-N-C interfaces enable selective CO₂ reduction to ethylene

Tandem electrocatalysts that couple efficient CO-generating sites with Cu-based C–C coupling centers offer a promising route to high-rate CO₂ reduction to multicarbon products, yet the mechanistic role of atomically dispersed single-metal sites in such architectures remains poorly defined. Here, we develop a model tandem catalyst that integrates atomically dispersed Ni-N₄ sites (Ni-N-C) with CuO nanorods, enabling direct elucidation of how single-metal sites regulate local CO availability, electronic structure, and C–C coupling kinetics. The optimized CuO/Ni-N-C catalyst achieves a Faradaic efficiency of 45.7% for C₂H₄ in neutral electrolyte, a 7.8% enhancement over CuO alone. The catalyst delivers a partial current density of 218 mA cm⁻² with 27.3% C₂H₄ selectivity in a flow cell, demonstrating industrial-level performance. Operando Raman spectroscopy reveals earlier onset and higher coverage of *CO intermediates on CuO/Ni-N-C, while density functional theory shows that Ni-N₄ sites donate electrons to adjacent CuO domains and facilitate CO desorption, collectively lowering the free-energy barrier for C–C coupling. This work establishes a mechanistic blueprint for designing M-N-C-assisted tandem catalysts and highlights the critical role of atomically dispersed Ni sites in enabling high-rate, selective CO₂-to-C₂H₄ conversion.