Tuning Carbon Defect in Copper Single‐Atom Catalysts for Efficient Oxygen Reduction

Abstract Defect chemistry in carbon matrix shows great potential for promoting the oxygen reduction reaction (ORR) of metal single‐atom catalysts. Herein, a modified pyrolysis strategy is proposed to tune carbon defects in copper single‐atom catalysts (Cu‐SACs) to fully understand their positive effect on the ORR activity. The optimized Cu‐SACs with controllable carbon defect degree and enhanced active specific surface area can exhibit improved ORR activity with a half‐wave potential of 0.897 V RHE , ultrahigh limiting current density of 6.5 mA cm −2 , and superior turnover frequency of 2.23 e site −1 s −1 . The assembled Zn–air batteries based on Cu‐SACs can also show well‐retained reversibility and voltage platform over 1100 h charge/discharge period. Density functional theory calculations reveal that suitable carbon defects can redistribute charge density of Cu‐N4 active sites to weaken the O–O bond in adsorbed OOH* intermediate and thus reduce its dissociation energy. This discovery offers a universal strategy for fabricating superior single‐atom catalysts with high‐efficiency active sites toward energy‐directed applications.