Optimizing high-coordination shell of Co-based single-atom catalysts for efficient ORR and zinc-air batteries

Atom-level modulation of the coordination environment for single-atom catalysts (SACs) is considered as an effective strategy for elevating the catalytic performance. For the MN x site, breaking the symmetrical geometry and charge distribution by introducing relatively weak electronegative atoms into the first/second shell is an efficient way, but it remains challenging for elucidating the underlying mechanism of interaction. Herein, a practical strategy was reported to rationally design single cobalt atoms coordinated with both phosphorus and nitrogen atoms in a hierarchically porous carbon derived from metal-organic frameworks. X-ray absorption spectrum reveals that atomically dispersed Co sites are coordinated with four N atoms in the first shell and varying numbers of P atoms in the second shell (denoted as Co-N/P-C). The prepared catalyst exhibits excellent oxygen reduction reaction (ORR) activity as well as zinc-air battery performance. The introduction of P atoms in the Co-SACs weakens the interaction between Co and N, significantly promoting the adsorption process of *OOH, resulting in the acceleration of reaction kinetics and reduction of thermodynamic barrier, responsible for the increased intrinsic activity. Our discovery provides insights into an ultimate design of single-atom catalysts with adjustable electrocatalytic activities for efficient electrochemical energy conversion.