Unveiling the Synergistic Effect between Graphitic Carbon Nitride and Cu₂ O toward CO₂ Electroreduction to C₂ H₄

Electrochemically reducing carbon dioxide (CO₂ RR) to ethylene is one of the most promising strategies to reduce carbon dioxide emissions and simultaneously produce high value-added chemicals. However, the lack of catalysts with excellent activity and stability limits the large-scale application of this technology. In this work, a graphitic carbon nitride (g-C₃ N₄ )-supported Cu₂ O composite was fabricated, which exhibited a 32.2 % faradaic efficiency of C₂ H₄ with a partial current density of -4.3 mA cm^-2 at -1.1 V vs. reversible hydrogen electrode in 0.1 m KHCO₃ electrolyte. The introduction of g-C₃ N₄ support not only enhanced the uniform dispersion of Cu₂ O nanocubes, but also stabilized the important *CO intermediates. Moreover, the g-C₃ N₄ itself had a good activity of reducing CO₂ to form *CO, which enriched the key intermediates of C-C coupling around cuprous oxide. The findings highlight the importance of the g-C₃ N₄ support, a unique two-dimensional material, including not only the strong CO₂ adsorption and activation capacity but also its synergistic effect with the cuprous oxide in CO₂ RR selectivity.