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

Abstract

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-N3 sites and ultrahigh specific surface area (1419 m2 g−1) via high-temperature full-gasification of graphitic C3N4, 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-N3 sites with a lower free energy barrier and a higher intrinsic activity compared to in-plane Mn-N4 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 kgZn-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.Wh