Theoretical Study Of Metal Doping And Its Synergistic Effect With Defects On Adsorption Of HCHO By MoS₂

HCHO is the most common indoor air pollutant emitted by many decorative and building materials,and its reversible adsorption and desorption on detection materials remains an important technical challenge.In recent years,MoS₂ has attracted extensive attention due to its unique physical,chemical and electrical properties,which is a special gas storage material and gas sensing material because of its large specific surface area,surface activity and excellent adsorption properties.In this paper,the geometric and electronic structures of the transition metal（TM）doped MoS₂ surface（TM-MoS₂,TM=Zn,Zr,Nb,Tc,Ru,Rh,Pd,Ag,Cd and Au）and TM doped with defects co-exist on the surface of MoS₂（TM-v_s-MoS₂,TM=Zn,Zr,Nb,Tc,Ru,Rh,Pd,Ag,Cd and Au）were discussed with the level of density functional theory（DFT）by VASP calculation software.Meanwhile,the configurations,electronic structures and adsorption performance of HCHO adsorbed on two surfaces were studied comprehensively.The results show that in TM-MoS₂ system,TM atoms and adjacent Mo atoms form a new single-cluster catalyst（SCC）:small cluster of TM-Mo₃,which makes the surface highly selective.Compared with the intact MoS₂ surface,the surface binding energy of TM-MoS₂ was significantly increased（0.11-7.02 e V）,indicating that the system stably exists after introducing TM atoms into MoS₂ surface.Doping MoS₂ surface by TM,Zn,Zr,Nb,Tc,Ru,Ag and Cd atoms lose electrons（0.13-1.22 e）,Rh,Pd and Au atoms obtain electrons（0.06-0.16 e）.Through the calculation of density of states（DOS）,it is found that nd orbital of metal atom and 4d orbital of Mo atom are hybridized to different degrees near Fermi level（E_f）,and the magnetic moment is changed,which greatly affects the electronic structure of MoS₂ surface.After TM doping and defects synergistically affect the MoS₂ surface,different from TM doping,the magnetic moment of Cd doping changes from 2.00μ_B to 0.00μ_B,and the others magnetic moments are reduced.Furthermore,the adsorption of HCHO on TM-MoS₂（TM=Zn,Zr,Nb,Tc,Ru,Rh,Pd,Ag,Cd and Au）was discussed,showing that HCHO adsorption on the surface of Zn,Zr,Nb,Tc,Ru,Rh and Cd doped MoS₂ exhibits better adsorption performance and chemical activity than physical adsorption on the surface of intact MoS₂.When the doped atoms are Zr,Nb,Ru and Rh,HCHO was highly activated with extended C-O bond.Electronic structure shows that for Zn,Zr,Nb,Tc,Ru,Rh and Cd doped MoS₂ surface,the interaction between nd orbitals of TM atom and molecular orbitals of HCHO is strong near E_f,and the gas molecules are activated.For Pd,Ag and Au doped MoS₂ surface,the orbitals of HCHO molecules overlap with the nd orbitals of Pd,Ag and Au atoms to a lesser extent,indicating that the interaction between HCHO and doped surface is weak.Bader charge indicates that for Zn,Zr,Nb,Tc,Ru,Rh and Cd doped surfaces,HCHO obtains electrons（0.04-0.78 e）from TM-MoS₂ surface;for Pd,Ag and Au doped surfaces,HCHO lose electrons（0.01-0.03 e）.Finally,the configuration,electronic structure and adsorption performance of HCHO adsorbed on TM-v_s-MoS₂ were studied.Finding show that compared with TM-MoS₂,adsorption energy of TM-v_s-MoS₂ is significantly improved after HCHO is adsorbed,Except for Zr and Nb doping TM-v_s-MoS₂ surface adsorption energy decreased.In TM-v_s-MoS₂（TM=Zn,Tc,Pd and Cd）adsorption system,distance between TM and S-plane increases slightly,for TM-v_s-MoS₂（TM=Zr,Nb,Ru,Rh,Ag and Au）adsorption system,distance between TM and S-plane decreases.Bader charge indicates that for TM-v_s-MoS₂ surface adsorption systems,HCHO is used as an electron acceptor.Through DOS analysis,molecular orbital of HCHO and nd orbital of TM atom overlap near E_f.Magnetic moment calculations show that except for the Rh-v_s-MoS₂ has a magnetic moment of 0.05μ_B,the others almost no magnetic moment.