(A) Schematic illustration of the synthesis procedure of hollow nitrogen-doped carbon tubes (h-NCTs). (B) SEM image of h-NCTs. (C) LSV curves of all h-NCTs samples and Pt/C. Adapted with permission from [113]. Copyright 2018, Royal Society of Chemistry. (D) TEM image of N,S-PGN-800. Adapted with permission from [178]. Copyright 2017, Royal Society of Chemistry. (E) SEM image of CoNC-800. (F) LSV curves of CoNC. Adapted with permission from [186]. Copyright 2017, American Chemical Society. (G) Fourier transformed EXAFS after phase-corrected spectra and (H) corresponding WT plots of Cu-K edge at R space of PPyCuPcTs. Adapted with permission from [189]. Copyright 2020, Elsevier.