Hydrogen storage on cation-decorated biphenylene carbon and nitrogenated holey graphene

Hydrogen storage on cation-decorated biphenylene carbon (BPC) and nitrogenated holey graphene (C₂N) layered materials are addressed by dispersion-corrected density functional theory calculations. Maximum storage capacity and adsorption energy of a gas-phase H₂ monolayer adsorbed on both sides of (Li⁺, Na⁺, Mg²⁺, Ca²⁺)-doped layers are investigated. We find that cations distribute homogeneously on BPC and C₂N with a maximum densities of 1.9 and 1.7 ion/nm², respectively. The H₂ adsorption on cation-decorated BPC shows binding energies that vary from ?0.14 to ?0.26 eV/H₂, depending on whether the cation is single or double charged, where the storage capacity are calculated to be around 10 wt%. Whereas, for cation-doped C₂N, the H₂ binding energies vary from ?0.11 to ?0.31 eV/H₂, with storage capacity between 7.3 and 8.8 wt%. Our results suggest that cation-doped C₂N is the most stable material, providing both reversibility and high capacity for hydrogen storage at operational conditions.