Rational design of the first and second coordination spheres for copper single-atom catalyst to boost highly efficient oxygen reduction

Copper is an essential nutrient for all living things and as the component of more than 30 enzymes in the human body for the development of connective tissue, nerve coverings. However, carbon materials doped with nitrogen and transition metal singlet (M-N-C) with CuN4 site as reaction center usually exhibit unsatisfactory oxygen reduction reaction (ORR) activity, due to poor O2 adsorption and activation. In this work, density functional theory (DFT) was used to explore the effect of introducing heteroatoms such as B, N, P, and S into the first and second coordination spheres to improve the ORR catalytic activity for Cu-N-C. Through the study of 41 model systems, we predicted CuN3 (eta ORR = 0.32 V), CuN4P (II) (eta ORR = 0.49 V) and CuN4S2(II) (eta ORR = 0.37 V) fragments would have good ORR catalytic activity. This is due to the increased charge and tailored d-band fine structure, optimizing the reaction intermediate binding strength. These findings indicate the influence of the ligand field (formed by the anion in the first and second coordination spheres) on the catalytic activity and provide a new direction for the synthesis of high-efficiency electrocatalyst materials.