Defect-engineered N-doped carbon stabilizes Cu⁺ active sites for bifunctional CO₂ electroreduction to CO and formate

The development of bifunctional electrocatalysts capable of steering CO₂ reduction toward selective C₁ products under mild conditions remains central to advancing next-generation electrochemical technologies. Here, we demonstrate that stabilization of Cu⁺ species by N-doped carbon derived from tea leaves (TL9) enables highly selective and durable CO₂ electroreduction to CO and formate. Uniformly dispersed Cu₂O nanoparticles supported on TL9 exhibit strong metal-support interactions and form stable Cu-N _x coordination that preserves the active Cu⁺/Cu⁰ interface during operation. Structural, spectroscopic, and electrochemical analyses reveal that this tailored interface suppresses Cu agglomeration and hydrogen evolution, promoting efficient two-electron transfer pathways. The optimized TL9/Cu-40% catalyst achieves faradaic efficiencies approaching 90% for CO and formate at -0.6 V vs. RHE and maintains over 60% selectivity after 24 h of continuous operation. These findings highlight how defect-engineered carbon supports can precisely regulate Cu oxidation states to enhance efficiency, selectivity, and stability-offering a robust design principle for bifunctional catalysts that couple renewable electricity with CO₂ valorization.