First Principle Study Of Gas Adsorption Based On Two-Dimensional Material Black Phosphorus Arsenic

In recent years,with the increasingly air pollution,people need to pay more attention to detect polluted gas.Gas sensors have developed rapidly.Since the stripping of graphene,two-dimensional（2D）materials have become ideal sensing materials for gas sensors due to their excellent electro-optic properties and mechanical ductility,including black phosphorus arsenic（As P）.As P has a wide direct band gap and ultra-high carrier mobility.Researchers have carried out extensive research in the field of Optics,and it also has great potential in the field of gas sensing.Therefore,based on the first principles calculation method,the adsorption characteristics of various gas molecules on As P are systematically studied on the atomic scale.The adsorption characteristics and sensing mechanism were studied by comparing the most stable adsorption configuration,adsorption energy,charge density,electrical and magnetic characteristics.The main research contents are as follows:1.Base on the first principles density function theory,the adsorption of several common gas molecules（CO,CO₂,NO,NO₂,NH₃,SO₂）on the surface of intrinsic As P was studied.The results show that As P is sensitive to NO,NO₂ and SO₂,but not to the other three gases.The adsorption energy and adsorption distance of CO,CO₂ and NH₃ are large,the transfer charge is small,and the change of energy band and density of states diagram is not obvious.NO₂ and SO₂ are adsorbed on the surface of As P with strong physical adsorption.Small adsorption energy and adsorption distance and appropriate amount of transferred charge show that single layer As P is sensitive to these two gases.From the energy band and density of states diagram,NO₂ has impurity level near the Fermi level,and SO₂ adsorption increases the As P band gap NO reacts most violently with the base material.After structural optimization,a new chemical bond is formed between the N atom of NO gas and the P atom of the base material.The energy band becomes smaller.The orbital hybridization of density of states diagram is obvious,and the desorption time is relatively short.So it is suitable to be the detection gas of As P.In addition,NO and NO₂ also induced 0.83μ_B and 0.78μ_B.The magnetic moment of material makes the whole adsorption system magnetic.The results show that single layer As P can be used as a gas sensing material for the detection of NO,NO₂ and SO₂gases.2.The adsorption of four organic gas macromolecules（CH₄,C₂H₆O,C₃H₆O and CH₂O）on As P surface was studied in this paper.Studies have shown that intrinsic As P is not sensitive to four organic gases.CH₂O gas has an order of magnitude greater adsorption energy than the others,and the adsorption capacity of single layer As P to CH₂O gas can be enhanced by doping.Li,Pt and Si atoms are introduced to study the changes of adsorption properties of CH₂O gas adsorbed on the surface of doped materials.It is determined that doping can improve the adsorption properties of the whole material.Moreover,the doping of atoms also changes the essential properties of the whole system into metal or semi gold properties.The formation energy and charge distribution after doping are calculated.The three kinds of doping can exist stably,and Li doping is bonded in the form of ionic bond.Subsequently,the calculated electronic structure,differential charge and desorption time show that Li-As P has a strong reaction when adsorbing formaldehyde gas,and can be used as a gas sensing material for detecting formaldehyde gas.