Adsorption Of H₂ And CO Molecules On Doped Graphene:A First-principles Study

Graphene is a two-dimensional material with a honeycomb planar structure.Its excellent electrical characteristics,good mechanical properties and light transmission have attracted extensive interest in the scientific community.Pristine graphene is a zero-bandgap semiconductor,which belongs to be semi-metallic.The band gap of graphene can be opened by physical and chemical means to make it widely used,especially in the field of gas sensors.In recent years,the improvement of the gas-sensitive properties has played a key role in the development of sensors.Based on the first principle of the density functional theory,the adsorption of hydrogen and carbon monoxide on doped graphene is studied.The main work is as follows:First of all,the main characteristics,classification and development trends of gas sensors are briefly introduced.The characteristic properties of two-dimensional graphene material are highlighted.Secondly,the theoretical basis of the first principle is introduced.Based on the mechanical modeling of graphene,four graphene structures doped with B,P,Pd,and Pt respectively are constructed on the basis of pristine graphene.The most stable structures of the four doping systems were obtained through optimization,and the comparisons were made from the results of formation energy,band structure,charge density and density of states:The formation energies of the four doping systems are all negative so that they are all stable.The band gap opened by doped with noble metal Pd/Pt is larger than that of B/P,and shows that the effect of dopant Pd/Pt is better than that of B/P.Then,a model of H₂ and CO molecules is established,and the adsorption of H₂and CO on pristine graphene is studied.The calculation results show that pristine graphene has weak adsorption of H₂ and CO,which is a physical adsorption.Additionally,the adsorption states of H₂ and CO on the four doped structures are compared.Based on the first-principles calculation,it is concluded that the doped graphene has a stronger adsorption on H₂ and CO.From the change of the adsorption structure,the graphene doped with B/Pt is more stable when adsorbing gas molecules.From the results of adsorption energy,charge density,band structure and density of states,Pd/Pt has a better adsorption effect on H₂ and CO.Finally,two co-doped graphene models are constructed based on the previous research.The adsorption states of H₂ and CO on the two co-doped graphene are studied.By calculating the electronic properties and comparing with the previous results,it is concluded that:the graphene doped with Pt and B and the graphene single-doped with Pt have the better adsorption effects on H₂;the double-doped Pt graphene and the graphene doped with Pt and B have better adsorption effects on CO.The first-principle method is used to study the adsorption characteristics of doped graphene on H₂ and CO,which can provide the theory support for improving the sensitivity of H₂ and CO adsorption on graphene,and lay a good foundation for subsequent research on the adsorption states of other gas molecules on graphene.