Fig. 5

a Structural and dynamics of Fe-N₅C₁₀ site in electrocatalytic ORR. b Schematic illustration of the operando synchrotron characterization (C.E., counter electrode; R.E., reference electrode; W.E., working electrode) and the dynamic evolution of Ni-N₄ site. c Schematic illustration of the dynamic evolution of Cu-N₄ site. a Reproduced with permission from Ref. [99]. Copyright 2020, Elsevier. b Reproduced with permission from Ref. [100]. Copyright 2020, American Chemical Society. c Reproduced with permission from Ref. [101]. Copyright 2021, American Chemical Society