Stepwise Ligand Tuning of Copper Clusters for CO2 Electroreduction Pathway Control

Abstract Copper-based materials with tailored surface modifications hold great potential for electrocatalytic CO2 reduction reactions (CO2RR), particularly in the selective formation of multicarbon (C2+) products. However, progress remains limited by an incomplete understanding of the atomic-level coordination environment and associated physicochemical properties. Here, we investigate ligand effects on CO2RR performance by a series of atomically precise Cu clusters–Cu6(X)6, where X represents the thiourea derivative. Notably, Cu6(N,N′-diphenylthiourea)6 achieves maximum Faradaic efficiency of 80.6% toward C2 products at 150 mA cm−2, demonstrating an optimized balance of multiple proton-coupled electron transfer pathways. In contrast, the incorporation of an electron-donating ligand (−NMe2) shifts approximately 30% of C2 products to CH4, while an electron-withdrawing ligand (−CF3) increases the proportion of C1 products driven by modified hydrophilicity and electron-donating capability. These findings provide critical insights into atomic-level surface engineering and offer valuable guidance for the rational design of CO2RR catalysts.