Metal-decorated boron phosphide (BP) biphenylene and graphenylene networks for ultrahigh hydrogen storage

The synthesized carbon-based biphenylene materials have contributed to the recent increase in interest in inorganic biphenylene counterpart. It is expected that the inorganic biphenylene material will have suitable functionalities for different energy harvesting applications. In this study, we conducted first-principles density functional theory (DFT) calculations and thermodynamic analysis to explore the hydrogen (H 2 ) storage properties of pristine BP-biphenylene (b -BP) and BP-graphenylene (g -BP) monolayers and alkali metals (AM=Li, Na, K) decorated b -BP (labeled as b-BP(AM)) and g -BP (labeled as g-BP(AM)) systems. Both b -BP and gBP monolayers exhibit a weak affinity for (H 2 ) molecules. However, b-BP(AM) and g-BP(AM) overcome this limitation and exhibit the ability to adsorb multiple H 2 molecules. The positive charge generated by the AM adatoms is the cause of the neighboring H 2 molecules becoming polarized due to electron transfer to the b -BP and g -BP monolayers. This polarization facilitates their binding through van der Waals interactions, making the surrounding suitable to accommodate a significant amount of H 2 molecules. The storage capacities for b-BP(Li) and g-BP(Li) systems are 9.05 wt% and 6.99 wt% respectively, when operating under practical conditions. Notably, these values exceed the US Department of Energy's target of 5.50 wt% by 2025 and highlight the potential of b-BP(AM) and g-BP(AM) systems as promising materials for hydrogen storage applications.