Remarkable improvement in hydrogen storage capacities of two-dimensional carbon nitride (g-C3N4) nanosheets under selected transition metal doping

We have performed DFT simulations to quest for an optimal material for onboard hydrogen (H2) storage applications. Using first-principles calculations, we established that the selected transition metals (M: Sc, Ti, Ni, V) decorated two-dimensional (2D) g-C3N4 sheets as optimal materials with reversible and significantly high H2 gravimetric densities. By effectively avoiding metal-metal (M-M) clustering effect in case of mono doping, up to four molecules of H2 per dopant could be adsorbed with an average binding energy of around 0.30–0.6 eV/H2, which is ideal for practical applications. Decorating the g-C3N4 sheet with (M-M) dimers, the systems are found to be even more efficient for H2 binding than single dopant decoration. The stability of these M decorated g-C3N4 sheets have been confirmed with ab-initio molecular dynamics simulations. We have further calculated the H2 desorption temperatures of metal decorated g-C3N4 sheets, which confirms the practical application of these metal decorated sheets at ambient working conditions. •Graphite carbon nitride (g-C3N4) sheet has been investigated as H2 storage materials.•Selected transition metals (TMs) and their dimers were used for the first time to decorate the g-C3N4 sheet.•The stability of these TMs decorated g-C3N4 sheets have been confirmed with ab-initio molecular dynamics simulations.•Dimers doped g-C3N4 sheet are found to be more promising for H2 storage.•Binding energy per H2 molecule falls in the range of 0.3–0.7 eV/H2, which is ideal for practical applications.