Atomically Dispersed Cu Catalysts on Sulfide-Derived Defective Ag Nanowires for Electrochemical CO₂ Reduction

Single-atom catalysts (SACs) have shown potential for achieving an efficient electrochemical CO₂ reduction reaction (CO2RR) despite challenges in their synthesis. Here, Ag₂S/Ag nanowires provide initial anchoring sites for Cu SACs (Cu/Ag₂S/Ag), then Cu/Ag(S) was synthesized by an electrochemical treatment resulting in complete sulfur removal, i.e., Cu SACs on a defective Ag surface. The CO2RR Faradaic efficiency (FE_CO2RR) of Cu/Ag(S) reaches 93.0% at a CO2RR partial current density (j_CO2RR) of 2.9 mA/cm² under -1.0 V vs RHE, which outperforms sulfur-removed Ag₂S/Ag without Cu SACs (Ag(S), 78.5% FE_CO2RR with 1.8 mA/cm²j_CO2RR). At -1.4 V vs RHE, both FE_CO2RR and j_CO2RR over Cu/Ag(S) reached 78.6% and 6.1 mA/cm², which tripled those over Ag(S), respectively. As revealed by in situ and ex situ characterizations together with theoretical calculations, the interacted Cu SACs and their neighboring defective Ag surface increase microstrain and downshift the d-band center of Cu/Ag(S), thus lowering the energy barrier by ∼0.5 eV for *CO formation, which accounts for the improved CO2RR activity and selectivity toward related products such as CO and C₂₊ products.