Light metal functionalized two-dimensional carbon nitride (C6N7) monolayers for efficient hydrogen storage

This study investigates light metal-decorated carbon nitride (C₆N₇) monolayers for hydrogen (H₂) storage using density functional theory (DFT). Compared with previously explored theoretical carbon nitride materials, this work focuses on experimentally synthesized C₆N₇, providing a realistic platform with verified chemical and thermal stability. Since pristine C₆N₇ exhibits weak H₂ adsorption, Na, K, and Ca are introduced as dopants to enhance storage performance. The stability of the metal-decorated systems is confirmed by ab initio molecular dynamics simulation, while binding energies are evaluated against the cohesive energies of the corresponding bulk metals. Charge transfer and projected density of states analyses reveal strong metal-C₆N₇ interactions and enhanced electronic polarization. The optimized systems achieve gravimetric storage capacities of 12.87, 11.67, and 11.61 wt% and volumetric capacities of 63.14, 59.76, and 69.14 g/L for Na-, K-, and Ca-functionalized C₆N₇, respectively. Moderate H₂ adsorption energies (−0.17 to −0.18 eV/H₂) indicate favourable reversibility for practical hydrogen storage.