Atomically dispersed Cu–N–C catalysts with carbon defects for efficient oxygen reduction reaction

• Cu–N–C single atom catalysts with adjustable carbon defects are fabricated. • Optimized Cu–N–C V -1000 shows superior ORR performance, outperforming Pt/C. • Cu–N–C V -1000-based ZAB has high peak power density and specific capacity. • High activity comes from synergistic effect between Cu–N x sites and carbon defects. • This work offers insights for designing efficient catalysts by defect engineering. Regulating the local microenvironment of metal centers represents an effective yet challenging approach to enhance the catalytic performance of atomically dispersed transition metal-nitrogen-carbon (M–N–C) catalysts towards the oxygen reduction reaction (ORR). Herein, atomically dispersed Cu–N–C catalysts featuring with adjustable carbon vacancies/defects concentrations (Cu–N–C V –X) are fabricated using a simple molten-salt-assisted pyrolysis strategy. The optimized catalyst (Cu–N–C V -1000) exhibits superior ORR catalytic performance with a half-wave potential ( E 1/2 ) of 0.89 V versus the reversible hydrogen electrode (RHE) and a turnover frequency ( TOF ) of 5.01 e site -1 s −1 at 0.85 V, surpassing Pt/C and most recently reported single-atom catalysts. Theoretical calculations confirm that defects adjacent to Cu–N 3 site downshift the d-band center of active sites, facilitating the desorption of *OH intermediate and thereby significantly enhancing the ORR kinetics. Consequently, the Cu–N–C V -1000-based zinc-air battery (ZAB) delivers a peak power density of 175.0 mW cm −2 along with a high discharge specific capacity of 819.4 mA g -1 Zn . This work confirms that the deliberate creation of suitable defects is an effective approach to optimize the intrinsic ORR activity of atomic M–N x sites, providing new insights into the rational design of high-performance catalysts for practical metal-air batteries.