fig4

Figure 4. (A) (a) TEM image of graphene layer; (b) LSV curves of ORR for the catalyst at different electrolytes; (c) Polarization and power density curves of ZABs^[21]. Copyright 2016, Wiley-VCH. (B) (a) SEM images of N-GDY-900; (b) ORR and OER performance of four catalysts compared with commercial Pt/C and IrO₂; (c) Charge and discharge polarization curves of N-doped GDY^[25]. Copyright 2021, Elsevier. (C) (a) SEM image of 2D-PPCN; (b) ORR activity of the prepared samples; (c) GCD polarization curves of 2D-PPCN and Pt/C+Ir/C based air electrode^[26]. Copyright 2018, American Chemical Society. (D) (a) TEM image of NSP-Gra; (b) ORR and OER performance of the catalysts; (c) Polarization and power density curves of the primary ZABs^[28]. Copyright 2021, Elsevier.