Graphenylene Monolayers Doped with Alkali or Alkaline Earth Metals: Promising Materials for Clean Energy Storage

Biphenylene carbon (BPC) functionalized with alkali and alkaline earth metals is considered for its potential as a high capacity hydrogen storage material. Using density functional theory calculations all dopants are found to bind with the BPC substrate strongly enough to avoid metal clustering. The strong binding between the membrane and the dopant has been confirmed by consideration of their partial density of states. The positive charge of the metal dopants resulting from donation of charges to the BPC sheet polarizes the nearby H₂ molecules and binds them through electrostatic and van der Waals interactions. Each dopant can adsorb multiple H₂ molecules leading to a moderately high storage capacity (6.14 wt %) with adsorption energies (ca. -0.30 eV/H₂) suitable for ambient condition applications.