Fig. 9

a Schematic of the synthesis of Fe–N₄ single site embedded graphene mimicking the heme cofactor structure of natural horseradish peroxidase (HRP). Reprinted from Ref. [90] with permission from Wiley–VCH. Copyright 2020. b OXD-like activity and TEM image of Fe–N₄ single-atom BMNZ. Reprinted from Ref. [91] with permission from Wiley–VCH. Copyright 2019. c Structure and TEM images of the ZIF-8 and ZIF-8 derived Zn–N₄ single-atom BMNZ. Reprinted from Ref. [96] with permission from Wiley–VCH. Copyright 2019. d Schematic and TEM images of Cu–N₄ single-atom BMNZ with SOD and CAT-like activities. Reprinted from Ref. [147] with permission from Wiley–VCH. Copyright 2023