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

Abstract

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 (<i>j</i>_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/cm²<i>j</i>_CO2RR). At -1.4 V vs RHE, both FE_CO2RR and <i>j</i>_CO2RR over Cu/Ag(S) reached 78.6% and 6.1 mA/cm², which tripled those over Ag(S), respectively. As revealed by <i>in situ</i> and <i>ex situ</i> 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.