Synthetic tuning produces multi-junctions of copper for efficient electroreduction of carbon dioxide

Electrochemical carbon dioxide reduction (CO₂RR) to value-added multi-carbon products is crucial for decarbonization and efficiently utilizing renewable electricity for energy storage. However, achieving high selectivity for C₂₊ products remain a significant challenge during the CO₂RR. Herein, we design a highly active multi-copper junction catalyst that features a spikes metallic Cu shell and a Cu₃N-CuO composite junction core with a unique oval shape. The Cu⁰ spikes on the outer shell and the Cu₃N junctions could protect the CuO core from degradation during CO₂RR under high current density. The sharp spikes on the Cu@Cu₃N@CuO-1 catalyst surface enhance the adsorption of *CO and OH^- species. Meanwhile, nitrogen from the Cu₃N junction has a strong capability, along with a higher content of Cu²⁺ in CuO significantly boosts C-C coupling, thereby improving the selectivity for C₂₊ products. Moreover, the Cu₃N junction provides core support interaction between the CuO core and Cu⁰ spikes, promoting the high selectivity for ethylene (C₂H₄), ethanol (C₂H₆O), and Propanol (C₃H₈O) production through *CO dimerization in different pH medium. Density functional theory calculations identify the rate-determining steps, overpotential, and reaction intermediates in the CO₂RR process. In particular, the Cu@Cu₃N@CuO-1 catalyst achieved a Faradaic Efficiency for C₂₊ products (FE_C2+) of 82.58 + 2 % and a partial current density (J_C2+) of −64.28 mA cm⁻² at −1.1 V in a H-cell test. Moreover, this catalyst exhibited a promising FE_C2+of 59.89 %, including a prominent yield of C₂H₄ (50.48 ± 2 %) at a high current density of 400 mA cm⁻² under flow cell conditions.