Light-metal functionalized boron monoxide monolayers as efficient hydrogen storage material: Insights from DFT simulations

Exceptionally high energy density by mass, natural abundance, widespread applications, and environmental friendliness make hydrogen (H₂) a front-runner among clean energy options. However, the transition towards clean and renewable energy applications and the actualization of H₂ economy require an efficient H₂ storage medium. Material-based H₂ storage is a viable option, as liquefaction and storage under pressure require ultra-low temperature (−253 °C) and tremendously high pressure (700 atm), respectively. In this work, we highlight the exceptional H₂ storage capabilities of recently synthesized boron monoxide (BO) monolayer functionalized with light metals (Li, Na, K, and Ca). Our computational approach, employing density functional theory (DFT), ab initio molecular dynamics (AIMD), and thermodynamic analysis, reveals promising results. We found that up to four metal dopants (Li, Na, K, and Ca) can be adsorbed onto BO monolayer with significantly strong binding energies (−2.02, −1.53, −1.52, and − 2.24 eV per dopant, respectively). Importantly, these bindings surpass the cohesive counterparts of the parental metal bulks, consequently stabilizing the crystal integrities, as confirmed by AIMD simulations. Each metal dopant on BO efficiently adsorbs multiple H₂ molecules through electrostatic and van der Waals interactions. Interestingly, the metal-functionalized BO monolayers exhibit exceptionally high H₂ gravimetric capacities of 11.75, 9.52, 9.80, and 11.43 wt% for 4Li, 4Na, 4K, and 4Ca@BO, respectively. These promising capacities exceed the 5.50 wt% target set by the US Department of Energy for 2025. Following the same guidelines, the average binding energy per H₂ molecule is within the range of −0.17 to −0.32 eV. The adsorption and desorption of H₂ under practical working conditions are investigated by Langmuir adsorption model based statistical thermodynamic analysis, further supporting the potential of metal-functionalized BO monolayers for material-based H₂ storage applications.