Functionalised two Dimensional Nanomaterials for Hydrogen Storage Applications

Abstract

Two dimensional nano materials like graphene, silicene, phosphene, newlinestanane, germanane have attracted keen interest because of their potential newlineapplications in electronics, photonics, hydrogen storage etc. Due to the light newlineweight, high surface area and unique pore structures, the nano materials are newlineidentified as the most suitable candidate for H2 storage applications. The newlineinteraction between pristine graphene and hydrogen molecule is weak due to newlinethe Van der Waals force and hence the binding energy is less than 0.1 eV. This newlinevery low binding energy unholds the adsorbed H2 molecule at room newlinetemperature and unsets for practical storage applications. However, the newlinebinding energy is very large and desorption occurs at very high temperatures in newlinethe process of chemisorption. This is due to the formation and breaking of newlinecovalent bond during adsorption and desorption of H2 molecules. The binding newlineenergy values in the range 0.2 0.6 eV/ H2 is the most desirable one for near newlineambient condition applications. Hence, an increased interaction through newlinephysisorption or modified chemisorptions where hydrogen is stored in newlinemolecular form is necessary to identify a suitable storage medium. Density newlineFunctional Theory is used to calculate the H2 storage capacity, H2 adsorption newlinebinding energy and the adsorption mechanisms in the host systems. The host newlinesystems taken for investigation are functionalized graphene with the inclusion newlineof line defect, point defects, fluorinated graphene and finally the functionalized newlinesilicene. newlineIn a 4x4 graphene the line defects are introduced and the defect newlinestructures are optimized. The favourable site of adsorption of Li is found out newlinefrom its binding energy. The interaction of Li with the octagraphene is newlinediscussed using partial density of states. Li metalized octagraphene adsorps a newlinemaximum of 4H2 molecules with the average adsorption energy of 0.35eV/H2. newline