Adsorption Properties To H₂ And CO Of Metal Decorated Phosphorene

As a new type of two-dimensional material,phosphorene possesses a great deal of excellent mechanical properties,electronic properties and photoelectric properties.Since the successfully experimental preparation in 2014,it has been the research focus of various academic fields.Researchers have conducted extensive researches on the application of this two-dimensional black phosphorus material in semiconductor devices,optoelectronic devices,and lithium ion battery electrodes.In addition,as a two-dimensional material,phosphorene possesses high surface-area/volume ratio,hence has natural advantage in gas adsorption and sensing.In this work,the VASP(Vienna Ab-initio Software Package)software package based on density functional theory was used to study the adsorption characteristics of H2 and CO on the phosphorene-based materials.The effects of various metal atoms decoration on the adsorption properties of H2 and CO were studied.The main contents of this paper and the results obtained are as follows:(1)First of all,the adsorption of H2 molecule on pristine phosphorene was calculated.The interaction between H2 and pristine phosphorene is very weak,and the adsorption energy is only 0.06eV per H2 molecule,which is not able to ensure the adsorption stability under ambient conditions.Through decorating with lithium,the adsorption energy of H2 increases obviously to above 0.20 eV,and each Li atom can adsorb up to 3 H2 molecules.The binding energy of Li atom on phosphorene is 2.17 eV/atom which is much larger than its cohesive energy,hence can prevent the Li atoms on phosphorene from clustering together.By means of density of states and Barder charge analysis,the mechanisms of interaction between Li and H2 molecules was discussed in detail,the H2 a bond states is strongly hybridized with the 2s and 2p orbitals of Li.The suitable storage medium with a storage efficiency of 4.4 wt%for hydrogen was obtained by increasing the decoration density of the metal Li on the phosphorene to 25%.(2)In this work,the effects of all the other metal elements on the adsorption of H2 on phosphorene were also considered,among which La is a representative of all the lanthanides metals.Applying the widely accepted energy "window" 0.20?0,60 eV as the criterion for adsorption energy to H2,Li?Sc?Ti?Cu?Y?Zr?Rh?Pd and La are screened out for their suitable adsorption energies to H2 molecules.Besides the suitable adsorption energies,each Li,Sc,Ti,Y,Zr and La atom can adsorb up to 3,4,4,4,3,5 H2 molecules.Hence these 6 metal elements are proposed as the decorating metals for phosphorene to store hydrogen.The representative atoms for each metal class are selected to analyze the adsorption properties of the metal on phosphorene and the interaction mechanism between the metals and H2.(3)Considering the relatively strong interaction between CO and the metal adatoms,which will weaken the binding between the decorating metals on phosphorene and the substrate,the binding energies for metal adatoms are required to be larger than their cohesive energies when conducting the adsorption of CO.Among all the metals considered,only Li,Na,K,Rb,Cs,Ca,Sr,Ba,Pd,La satisfy this criterion and were employed to decorate on phosphorene for the investigation of CO adsorption.Except for Rb,Cs and Pd,all the other metals can adsorb CO strongly to satisfy the stability under ambient conditions and adsorb up to 3?6 CO molecules around each metal adatom,hence can be used to eliminate the toxic CO.Li,Na,K,Ca,Sr,Ba possess an average adsorption energy among 0.20?0.60 eV for CO,hence can be used to decorating phosphorene for the efficient storage of CO.