A First-principle Study On The Hydrogen Storage Performance Of Metal Atom Modified Boronene

Recently,environmental problems caused by the use of fossil fuels have becorne more and more serious.Hydrogen is expected to be a major power source in the future because of its abundance and environmental friendliness and has attracted great attention recent years.One of the biggest difficulties that hinder the widespread application of hydrogen is the safe and effective storage of this kind of energy.Finding suitable hydrogen storage materials becomes an interesting and urgent subject.Two-dimensional materials,such as graphene,are good candidate of hydrogen storage materials with great potential due to their light weight and large specific surface area.Pristine graphene cannot storage hydrogen because it has very weak interaction with hydrogen molecules via Van de Waals' force.However,recent studies have shown that the adsorption of hydrogen molecules on metal atoms modified graphene surface can be substantially enhanced.However,a related impeding issue is that metal adatoms dispersed on the graphene have a tendency to form clusters,which will significantly reduce the gravimetric capacities of the hydrogen storage.Borophene,a new type two-dimensional material,has been synthesized under ultrahigh-vacuum conditions recently.In this work,density functional theory is carried out to study the adsorption of metal atoms and hydrogen molecules on the surface of borophene.It is found that hydrogen molecules can only be physisorbed on the pristine borophene with a tiny binding energy.However,Li and Ca atoms can be chemisorbed on the borophene without clustering,and the adsorption of hydrogen molecules on Li/Ca doped borophene is greatly enhanced.The hydrogen storage gravimetric capacities on Li/Ca doped borophene can reach up to 10 wt.%.The adsorption binding energy for each hydrogen molecule on Li/Ca doped borophene is about-0.20 eV,which guarantees hydrogen molecule can be fully adsorbed/desorbed reversibly with operations at room temperature,representing that Li/Ca decorated borophene could be a promising candidate with low-cost,large capacity and light-weight as the hydrogen storage material.Furthermore,the mechanism of hydrogen molecule adsorption on the Li/Ca doped borophene is analyzed and the feasible methods to improve the hydrogen adsorption capacities are poposed.