Highly accessible single Mn-N3 sites-enriched porous graphene structure via a confined thermal-erosion strategy for catalysis of oxygen reduction

Carbon-supported single Mn atoms catalysts are seen as one of the most promising substitutes for the conventional Pt-based catalysts owing to weaker Fenton reaction , higher stability and lower cost. We here report a confined thermal-erosion strategy for converting Mn-based MOF materials (Mn-ZIF-8) into a pore-rich graphene structure (4 ∼ 5 layers) with highly accessible defect-hosted Mn-N 3 sites and ultrahigh specific surface area (1419 m 2 g −1 ) via high-temperature full-gasification of graphitic C 3 N 4 , which can serve as an efficient single Mn atoms catalyst for oxygen reduction reaction (ORR). The catalyst shows superior ORR catalytic activity with a half-wave potential of 0.863 V ( vs. RHE), high cycling stability and four-electron selectivity for the ORR. Theoretical calculations indicate that the promoted ORR activity of the Mn-SAC catalyst may be mostly attributed to the defective Mn-N 3 sites with a lower free energy barrier and a higher intrinsic activity compared to in-plane Mn-N 4 sites. The Zn-air battery assembled with this catalyst represents a maximum power density (226 mW cm −2 ) and superior energy density of 857 Wh kg Zn -1 , far exceeding the air battery performance using the Pt/C catalyst. Our findings can provide new design methods and in-depth insights for defect-hosted active single-metal-atoms ORR catalysts. W h $\mathrm{W}\mathrm{h}$