Computational studies on electronic structure of borophene and phosphorene and hydrogen storage capabilities of phosphorene

Abstract

Two-dimensional nanomaterials are developing as a promising class of newlinematerials, with a wide range of applications. There are no naturally occurring 2D newlinematerials. In some layered materials, the layers are held together by weak van der newlineWaals (vdW) forces and they can be easily exfoliated into thin, one-atom or few newlineatoms thick layers. Examples include graphite, MoS2, h-BN and black newlinephosphorus, of which graphite and black-phosphorus is mono-elemental. However newlinesuch examples of using mechanical exfoliation to obtain new 2D materials are newlinelimited. One then needs to fabricate 2D materials (those without an analogous newlinebulk form) using PVD and CVD processes in a bottom-up approach. Hydrogen, newlinethe smallest of all the existing elements is very abundant and an important clean newlinefuel. It is not readily available in its elemental form and has to be extracted from newlineits compounds like water, methane etc. However, safe storage and easy newlineavailability on demand are the most important problems faced while using it as a newlinefuel. The most viable method is to store hydrogen as adsorbed onto solid surfaces. newlineIt can be released (desorbed) and made available for the fuel cells, as and when newlinerequired. Hydrogen storage capabilities of blue phosphorene nanosheet, decorated newlinewith lithium and sodium atoms were systematically studied using ab-initio newlineDensity Functional (DFT) calculations. Hydrogen molecule adsorbs on pristine newlineblue phosphorene with an adsorption energy of 0.06eV, which is much lower than newlinethe threshold energy of ~0.10eV required for practical applications. When blue newlinephosphorene is decorated with lithium or sodium atoms on its surface, hydrogen newlineadsorption energies are drastically increased to 0.25eV and 0.18eV respectively. It newlineis found that a lithium atom adsorbs up to three and sodium atom up to four newlinehydrogen molecules. Analysis of density of states and difference charge density newlinecalculations confirm the hybridization of hydrogen and lithium states. newline