Efficient Electrochemical Reduction of CO₂ on g-C₃ N₄ Monolayer-supported Metal Trimer Catalysts: A DFT Study

The electrochemical reduction of CO₂ into valuable chemicals and fuels is a promising but challenging method to realize the carbon cycle. In this work, a series of transition metal trimer clusters supported on g-C₃ N₄ catalysts (M₃ @g-C₃ N₄ , M=Cr, Mn, Fe, Co, Ni, Cu, and Ru) for electrochemical CO₂ reduction (CO₂ RR) toward C₁ and C₂ products were systemically studied using density functional theory (DFT) calculations. Our results show that CO₂ could be adsorbed and activated effectively on M₃ @g-C₃ N₄ from adsorption configurations and electronic structures analyses. Cu₃ @g-C₃ N₄ is a promising electrocatalyst for CH₄ production with a limiting potential of -0.42 V. Cr₃ @g-C₃ N₄ , Fe₃ @g-C₃ N₄ , and Co₃ @g-C₃ N₄ produce a low limiting potential of -0.64 V, -0.45 V, and -0.64 V for C₂ H₄ production, respectively. Hydrogen evolution reaction is refrained on Cu₃ @g-C₃ N₄ , Cr₃ @g-C₃ N₄ , and Co₃ @ g-C₃ N₄ . This work provides useful insights into transition metal trimer cluster catalysts with enhanced activity and selectivity in CO₂ RR.