DFT Study On The Effect Of Transition Metal Doping On The Electromagnetic Properties Of Gr Adsorbed H₂S

In recent years,with the increasing incidence of nervous system diseases,people pay more and more attention to the detection of harmful gases that harm the nervous system,so the gas sensor has been developed vigorously.Since graphene was mechanically stripped,two-dimensional materials（2D）have become ideal gas sensor adsorption materials due to their excellent electro-optical properties,mechanical properties and regulability,including the two-dimensional material graphene.Graphene,with its special Dirac cone bandgap structure and extremely high carrier mobility,has been extensively investigated in the field of optoelectronics,and it has great potential in the field of gas sensing itself.Therefore,this paper calculates the interaction at atomic scale based on density functional theory and studies the effects of various doping atoms on the adsorption properties of H₂S.The sensing mechanism was studied by comparing the optimized adsorption structure,adsorption energy,charge differential density,optical and magnetic properties.The main research contents are as follows:1.Based on the first-principles calculation of density functional theory,the effect of transition metal elements（Au,Ag,Cu,Fe,Ti）doped graphene surface on the adsorption performance of hydrogen sulfide gas was studied.The results show that hydrogen sulfide gas has very high sensitivity under the condition of Ag,12.5%Ag doping concentration and Ag-Fe-Ti co-doping.The adsorption energy and adsorption distance of Ag doped system are-15e V and 5.468（?）,respectively,the amount of transferred charge is 0.39e,and the energy band and state density change obviously.H₂S is adsorbed on the surface of Ag-doped graphene with strong chemical interaction.Compared with the graphene substrates doped with Au and Cu,the smaller adsorption energies of 5.10e V and 2.60e V and adsorption distances,as well as the very low charge transfer amount indicate that Au and Cu are not sensitive to H₂S gas.According to the band structure and state density diagram,impurity levels appear near the Fermi level in the adsorbing system of H₂S gas,and the doping type of the doping system also changes,from P-type doping to N-type doping,or from N-type doping to P-type doping.Therefore,the adsorption of H₂S gas changes the band gap of the system.After adsorption of H₂S gas,a new strengthening chemical interaction is formed between S atom and Ag atom of the base material.The orbital hybridization of some state density diagrams is strong,which proves once again that the doped Ag system has a strong chemical interaction with H₂S.Therefore,it is suitable to be used as the sensitive material substrate for detecting H₂S gas.Studies show that Ag-doped graphene is more suitable as a gas sensitive material for detecting H₂S gas than Au and Cu.2.The adsorption of H₂S by different concentrations of Ag atom doped graphene was studied.Through the study of the most stable structure and the analysis of adsorption energy and charge transfer,it is found that the performance of graphene under different doping concentrations is different.Compared with other doping concentrations,Ag has a larger adsorption energy and more stable adsorption structure when the doping concentration is 12.5%,with the lattice constants of-13.15e V and 9.84（?）,9.83（?）and 6.82（?）,respectively.Therefore,12.5%doping concentration is the best doping concentration.The adsorption capacity of 12.5%Ag doped graphene system to H₂S gas can be enhanced by co-doping.3.Fe and Ti atoms were introduced to be co-doped with Ag,and the optimal doping ratio was determined by studying the change of adsorption performance of H₂S gas adsorbed on the surface of the doped material.The doping of Fe and Ti atoms also changes the inherent properties of the whole system into metal or semiconductor.The charge distribution and spin of Fe,Ti and Fe-Ti co-doped system can all exist stably,but the excessive introduction of Fe atoms will cause serious distortion of the spatial structure of the system,and the excessive introduction of Fe atoms does not show excessive contribution in the spin spectrum.The calculated electronic structure and charge differential density show that 4:1:1 Ag,Fe and Ti have the strongest reaction effect when adsorbing hydrogen sulfide gas,and can be used as the best gas-sensitive materials for detecting hydrogen sulfide gas.