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 CO₂ -to-CO conversion comprising the single Cu site co-coordinated with N and S anchored carbon matrix (Cu-S₁ N₃ ) and atomically dispersed Cu clusters (Cu_x ), denoted as Cu-S₁ N₃ /Cu_x . The as-prepared Cu-S₁ N₃ /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-N₄ (FE_CO only 54 % at -0.7 V) and Cu-S₁ N₃ (FE_CO 70 % at -0.7 V) configurations. The unsymmetrical Cu-S₁ N₃ atomic interface in the carbon basal plane possesses an optimized binding energy for the key intermediate *COOH compared with Cu-N₄ site. At the same time, the adjacent Cu_x effectively promotes the protonation of *CO₂ ^- by accelerating water dissociation and offering *H to the Cu-S₁ N₃ active sites. This work provides a tandem strategy for facilitating proton-coupled electron transfer over the atomic-level catalytic sites.