Abstract
The increasing global energy demand and pressure to lower greenhouse gases have propelled green hydrogen to emerge as a promising substitute for traditional petroleum and coal. Renewable energy sources generate green hydrogen, which provides an economically viable and secure energy solution. Molecular hydrogen requires storage in gases, liquids, or solids. The storage of hydrogen within a solid matrix offers possible benefits, improved safety, and higher energy density than standard storage methods such as liquid hydrogen or compressed gas. However, solid-state storage materials, which are both practical and viable, pose significant barriers; hence, further investigation is required. Complex metal hydride materials have attracted significant attention owing to their potential use in hydrogen storage applications. However, further research and development are required to overcome the existing challenges, improve their performance, and make them more competitive with other hydrogen storage methods. Borophene, a material possessing a planar structure, is a promising candidate for hydrogen storage in transitional applications, owing to its reduced binding energy and reversible characteristics.
The unique electronic characteristics of the material also allow it to demonstrate a greater capacity for hydrogen adsorption than complex metal-based hydrides, thereby surpassing the benchmarks set by the U.S. Department of Energy. Borophene has exhibited significant potential as a hydrogen storage medium; however, its suitability for extensive commercial utilization remains limited. Borophene nanoparticles exhibit prominent chemical and physical characteristics such as binding energies and the ability to store hydrogen. Current discourse revolves around the significance of borophene in the context of hydrogen storage, the obstacles it encounters, and its potential outlook. Extensive experimental investigations, such as ALD, can provide a complete analysis of the characteristics of borophene while enabling the discovery of its potential use in practical hydrogen storage. This study utilized density functional simulations to investigate the effects of Yttrium (Y) doping on the hydrogen storage capabilities of borophene monolayers. Theoretical analysis showed that the adsorption of hydrogen molecules on Y-doped borophene monolayers has a negative adsorption energy, indicating that the process is thermodynamically exothermic and stable. The adsorption energy results in this study demonstrate that the doped Y atoms exhibit a strong attachment to the borophene surface. In addition, borophene monolayers do not tend to form metal clusters. The results demonstrate that Y-borophene can form chemical bonds with up to six hydrogen molecules with an average adsorption energy of -0.141 eV /H2. The adsorption energies
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measured for the Y-borophene complex and hydrogen molecules ranged from -0.133 eV to -0.178 eV. The obtained results are acceptable for highly efficient hydrogen-storage materials. The potential of Y-borophene exceeded the hydrogen gravimetric density target of 5.5 wt%. This high hydrogen storage capacity demonstrates that borophene-based materials are promising materials for reversible hydrogen storage applications. Moreover, the electronic characteristics indicated charge transfer from the boron atom to the Y atom to the borophene and from the hydrogens to the Y atom. The confirmation of orbital hybridization between the Y-d, H-s, and B-p orbitals was revealed by projected density of states (PDOS) analysis. This result indicates the possibility of hydrogen adsorption. The transfer of electrons from H2 to Y was determined by Hirshfeld charge analysis, which showed that Y atoms functioned as electron acceptors. The desorption temperature range of Y-borophene was confirmed to be 186–334 K based on molecular dynamics simulations. This material exhibited high H2 desorption performance at ambient temperatures, making it suitable for car fuel cell operations. Hence, our theoretical investigation introduces Y-borophene as a highly promising material for hydrogen storage. To the best of our knowledge, no similar study has been conducted on Yttrium dope borophene; therefore, the current research is novel.
Keyword: Borophene, Hydrogen storage, Density functional theory, Yttrium, dopant, 2D materials, Molecular Dynamics Simulation, Atomic layer deposition