A Tandem Strategy for Enhancing Electrochemical CO2 Reduction Activity of Single‐Atom Cu‐S1N3 Catalysts via Integration with Cu Nanoclusters

Abstract We developed a tandem electrocatalyst for CO 2 ‐to‐CO conversion comprising the single Cu site co‐coordinated with N and S anchored carbon matrix (Cu‐S 1 N 3 ) and atomically dispersed Cu clusters (Cu x ), denoted as Cu‐S 1 N 3 /Cu x . The as‐prepared Cu‐S 1 N 3 /Cu x composite presents a 100 % Faradaic efficiency towards CO generation (FE CO ) at −0.65 V vs. RHE and high FE CO over 90 % from −0.55 to −0.75 V, outperforming the analogues with Cu‐N 4 (FE CO only 54 % at −0.7 V) and Cu‐S 1 N 3 (FE CO 70 % at −0.7 V) configurations. The unsymmetrical Cu‐S 1 N 3 atomic interface in the carbon basal plane possesses an optimized binding energy for the key intermediate *COOH compared with Cu‐N 4 site. At the same time, the adjacent Cu x effectively promotes the protonation of *CO 2 − by accelerating water dissociation and offering *H to the Cu‐S 1 N 3 active sites. This work provides a tandem strategy for facilitating proton‐coupled electron transfer over the atomic‐level catalytic sites.