Fe-NC Single-Atom Catalyst with Hierarchical Porous Structure and P-O Bond Coordination for Oxygen Reduction

Developing hierarchical porous heteroatom-doped carbon materials as efficient and durable electrocatalysts for oxygen reduction reaction (ORR) is of great importance for realizing electrochemical energy conversion and storage devices. Herein, we report a strategy of introducing the P-O bond to tune the intrinsic activity of the single Fe atom catalyst in a porous carbon matrix for ORR. Experimental analysis associated with theoretical calculations revealed that the P-O bond dopant in traditional Fe-N-4 center-enriched porous carbon regulates the electronic structure of the Fe-N-4 center and lowers its energy barrier for ORR. In particular, the P-O bond in the third coordination shell of the Fe center accelerates the rate-determining step of hydrogenation of adsorbed oxygen on the Fe-N(4 )site. Besides, this material features additional structural benefits by providing an enviable arrangement of large internal reactive surface areas, abundant hierarchical porosity, and a fast charge transport path, eventually leading to good ORR electrochemical performance.