Regenerative energy replacing CO₂-releasing fossil fuels has drawn widespread attention in wind/solar energy storage and conversion. In particular, CO₂ reduction to valuable chemicals using renewable energy is attractive and alleviates global warming. Cu is prominent for CO₂ reduction to derive multi-carbon products, such as ethylene. However, the productivity, energy efficiency, and cost-effectiveness of Cu-based electrocatalysts remain unsatisfactory in meeting industrial requirements. Hence, ultrathin CuCo nanocrystals are exploited for CO₂ reduction to ethylene, delivering a high faradaic efficiency of 81.3% at a potential of −1.5 V vs. reversible hydrogen electrode (RHE). Tailoring the d-band states and synergistic cooperation between Cu and Co are significant to boost activity via controlling the intermediate binding energy and lowering the reaction energy barriers.