Multifunctionality of vacancy-induced boron nitride monolayers for metal-ion battery and hydrogen-storage applications

Abstract

<p>Energy storage through metal-ion batteries (MIBs) and hydrogen (H₂) fuel presents significant opportunities for advancing clean energy technologies. This study comprehensively examined the structural, electronic, electrochemical, and energy storage properties of boron-vacancy induced porous boron nitride monolayers (BN:V_B) as multifunctional materials, anodes for MIBs and H₂ storage applications. Our computational approaches, density functional theory (DFT), ab initio molecular dynamics (AIMD), and thermodynamic analysis, revealed exceptionally high energy and gravimetric densities for MIBs and H₂ storage, respectively. We investigated the interactions of Li, Na, and K atoms on BN:V_B, which strongly bonded with binding energies stronger than their bulk cohesive energies, which ensured structural stability and the absence of metal clustering. Electronic properties, analyzed through spin-polarized partial density of states (PDOS), band structure, and Bader charge analysis, revealed significant charge transfers from the metal atoms to BN:V_B, enhancing the electronic conductivity of the latter. Theoretical specific capacities were calculated as 1821.53, 786.11, and 490.51 mA h/g for Li, Na, and K, respectively, which comfortably exceeded the conventional anodes, such as graphite. Average open-circuit voltages (OCVs) were found to be 0.15, 0.25, and 0.32 V, for Li, Na, and K, respectively, indicating strong electrochemical stability. Diffusion studies showed lower barriers of 0.47, 0.08, and 0.60 eV for Li, Na, and K, respectively, with increased metal loadings, suggesting enhanced mobilities and charge/discharge rates. On the other side, the metal-functionalized BN:V_B monolayers exhibited remarkably high H₂ gravimetric capacities of 10.64, 10.72, and 9.38 wt% for 4Li-,4Na-, and 4 K@BN:V_B, respectively, all surpassing the 5.50 wt% target set by the US Department of Energy for 2025. Average adsorption energies of H₂ on 4Li-, 4Na-, and 4K@BN:V_B, were found in perfect range for practical storage applications. The potential for practical H₂ storage were further supported by Langmuir adsorption model-based statistical thermodynamic analysis, which examined the adsorption and desorption behavior of H₂ under practical conditions. These findings position BN:V_B as a promising multifunctional candidate for high-performance MIBs anodes and H₂ storage material.</p>