Theoretical Prediction Of Small Molecule Gases Adsorption On Metal Decorated Phosphorene

As a new type of two-dimensional material after graphene,two-dimensional black phosphorus?also known as phosphonene?has excellent magnetic,optical,electrical,thermal and mechanical properties.Since it was successfully fabricated in 2014,domestic and foreign various studies on phosphorene have been carried out immediately.It has been found that phosphorene is a semiconductor with a direct band gap,and that the band gap varies with the number of layers and external conditions.In addition,it has a high carrier mobility and a high on/off ratio,which make phosphorene have great potential in field effect transistor applications.More importantly,as a two-dimensional material,the large surface/volume ratio makes phosphorene have a natural advantage in gas adsorption and detection.In this paper,the VASP?Vienna Ab-initio Software Package?based on density functional theory is used to study dichloromethane?CH₂Cl₂?,sulfur-based?H₂S,SO₂,SO₃?and nitrogen-based gas?NO,NO₂,NH₃?molecules adsorption on phosphorene.The CH₂Cl₂ molecule adsorption and dissociation on metal decorated phosphonene and the influence of various metal decoration on the adsorption characteristics of sulfur-based and nitrogen-based gas molecules were investigated.The main research contents of this paper and the research results obtained are as follows:?1?Firstly,the adsorption of CH₂Cl₂ on monolayer pristine phosphonene was studied.The study shows that the adsorption of CH₂Cl₂ did not change the electronic structure of phosphonene,and the adsorption energy of CH₂Cl₂ is 0.318 eV.Then,the phosphorene was decorated by metal atoms?Fe,Ni,Pd,Pt?,and the CH₂Cl₂ adsorption on all metal-decorated phosphorene was studied.The results show that metal decoration can effectively improve the adsorption strength of phosphorene to CH₂Cl₂ molecule.In particular,the adsorption energy of the CH₂Cl₂ molecule on Fe-decorated phosphorene can be up to 1.034eV.Based on the density of states and differential charge density,the internal mechanism of the interaction between the metal-decorated phosphorene and the CH₂Cl₂ molecule was analyzed.The electronic state of the CH₂Cl₂ molecule has a strong coupling with that of the metal atoms.Therefore,the decoration of metal can effectively improve the adsorption strength of phosphonene to CH₂Cl₂ molecules.Finally,based on the stable structures of CH₂Cl₂ molecule adsorption on metal-decorated phosphorene,the transition states of dissociation process?CH₂Cl₂?CH₂Cl+Cl?were searched by using the CI-NEB method,and calculated the reaction barrier.The study found that the dissociation process of CH₂Cl₂ on all metal-decorated phosphorene is exothermic.Especially on the Fe-decorated phosphorene,the dissociation barrier is only0.648 eV,which may occur rapidly at room temperature.Thus,the Fe-decorated phosphorene can be used as removal and and dissociation of CH₂Cl₂ gas molecule.?2?The sulfur-based gas?H₂S,SO₂,SO₃?molecules adsorption on metal-decorated phosphorene were studied.Considering the problem of the growth morphology of metal atoms on the surface of phosphorene,all decorated metal atoms are required to have stronger adsorption energy on phosphorene than their bulk cohesive energy.It is found that only 11 kinds of metal atoms satisfy this standard,namely alkali metal?Li,Na,K,Rb,Cs?,alkaline earth metal?Ca,Sr,Ba?,transition metal?Ni,La?and post-transition metal?Tl?.Except for H₂S adsorption on Tl-decorated phosphorene,the decoration of metal can improve the adsorption energy of H₂S,SO₂ and SO₃ on phosphorene.In particular,the adsorption energy of H₂S on Ni-decorated phosphorene is found to be 1.131 eV,and the adsorption energies of SO₂ and SO₃ molecules on La-decorated phosphorene can be up to 2.891 and 4.609 eV,respectively.In addition,by analyzing the band structure and density of states of the adsorption system,it is found that the adsorption of H₂S has little effect on the electronic structure of metal-decorated phosphorene.The electronic structure and magnetism of the metal-decorated phosphorene after SO₂ and SO₃ adsorption has some interesting effects.For example,the bP-Ca,bP-Sr and bP-La systems undergo semiconductor-to-metal transition after SO₂adsorption.For SO₃ adsorption cases,the bP-Li,bP-Na,bP-Ba and bP-Tl systems undergo metal-to-semiconductor transition,while bP-La undergoes semiconductor-to-metal transition.In addition,the disappearance of magnetism for bP-La systems after SO₂ and SO₃ adsorption.Thus,the bP-M systems are expected to be used for SO₂ and SO₃ sensing.?3?Based on the above 11 decorated metals,the nitrogen-based gas molecules?NO,NO₂,NH₃?adsorption on metal-decoreted phosphorene were studied.It is found that the decoration of metal can improve the adsorption energy of NO,NO₂ and NH₃ on phosphorene,except for NO adsorption on Tl-decorated phosphorene.In particular,the adsorption energy of NH₃ on Ni-decorated phosphorene is found to be 1.305 eV,and the adsorption energies of NO and NO₂ molecules on La-decorated phosphorene can be up to 2.475 and 3.734 eV,respectively.In addition,by analyzing the band structure and density of states of the adsorption system,it is found that the adsorption of NH₃ has little effect on the electronic structure of the metal-decorated phosphorene,while the electronic structure and magnetism of the metal-decorated phosphorene after NO and NO₂ adsorption has some interesting effects.For example,except for bP-La,the decorated substrates exhibit non-magnetism-to-magnetism transition after NO adsorption,and the bP-Ca,bP-Sr and bP-La undergo semiconductor-to-metal transition.Similarly,the disappearance of magnetism for bP-La systems after NO₂ adsorption.Furthermore,the bP-Li,bP-Na and bP-Tl experience metal-to-semiconductor transition,while bP-Ca and bP-Sr undergo semiconductor-to-metal transition.Thus,the bP-M systems are expected to be used for NO and NO₂sensing.