Regulating single-atom Mn sites by precisely axial pyridinic-nitrogen coordination to stabilize the oxygen reduction

Designing single-atom catalysts for oxygen reduction reaction (ORR) are fashionable but challenging to boost the zinc-air battery performance. Significantly enhanced ORR activity by manganese (Mn) single-atom catalysts can be achieved by accurately regulating the coordination number of isolated Mn atoms. Theoretical calculations indicate that the single Mn-N5 sites possess lower free energy barrier and higher oxygen adsorption performance than single Mn-N4 sites to accelerate the ORR kinetics. Target to it, here we synthesize an atomically dispersed Mn-N5 catalyst by precisely axial coordination of pyridinic-N doped into two-dimensional (2D) porous nanocarbon sheets (∼3.56 nm thickness), which reveals outstanding catalytic activity and ultrahigh stability for the ORR in zinc-air battery owing to the inhomogeneous charge distribution of Mn-N5 sites compared to the conventional single-site Mn-N4 catalyst and Pt/C. This work gives a new strategy for in situ regulating the electronic structure of metal single-atoms and further promoting the overall ORR performance in energy systems.