Fig. 20.

a Schematic illustration of the synthetic routes for the fabrication of N-FLG-T. b Rate capability of N–CNTs and N-FLG-T at various current densities. Reproduced with permission from Ref. [128]. c Cycling performance of C/g-C₃N₄ Na half cells at 0.4 A g⁻¹. Reproduced with permission from Ref. [53]. d Illustration of the mechanism of the sodium storage in g-C₃N₄ film activated Cu foil. Reproduced with permission from Ref. [129]. Copyright permission from Wiley–VCH. (Color figure online)