(A) Schematic illustration and SEM images of the G-NP. (B) DFT calculations of H adsorption free energy and electronic property of different N,P co-doped graphene. Adapted with permission from [172]. Copyright 2019, Royal Society of Chemistry. (C) The structure of CB[6]-Ir. Adapted with permission from [174]. Copyright 2021, Willy-VCH. (D) The DFT calculations and HER catalytic activity of Ni NP|Ni-N-C/EG towards HER. Adapted with permission from [175]. Copyright 2019, Royal Society of Chemistry.