Supported tetra-atom clusters on g-CN as catalysts for electrochemical reduction of carbon dioxide to formate: A computational study

Single-cluster catalysts (SCCs) have emerged as highly efficient catalysts for the CO2 reduction reaction (CO2RR), providing a promising avenue to solve the carbon dilemma. Based on density functional theory calculations, we systematically investigated the capability of 12 tetra-atom transitional-metal clusters anchored on g-CN (TM4@g-CN) for CO2RR and found that all clusters have good stability on the substrate. Notably, the charge variation of the top metal atom (TM4) of six SCCs is close to zero which makes them readily donate electrons to the adsorbate CO2 and subsequent reaction intermediates. Our results demonstrate that CO2 can be efficiently reduced to HCOOH on Ni4, Cu4, and Au4@g-CN with low limiting potentials of −0.21, −0.22, and −0.19 V, respectively, outperforming the corresponding single-atom counterparts. Both ΔG(∗CO2) and ΔG(∗OCHO/∗COOH) exhibit a volcano relationship with the reaction activity, and the TM4 serves as electron reservoirs throughout the entire reaction process. This work offers valuable insights for the advancement of cost-effective supported single cluster catalysts.