Theoretical Investigation Of Gas Sensing Properties Of Ni/ZnO-graphene Composite

In recent years,there are many types of gas sensors appeared.Most of the current industrialized gas sensors are not stable enough and greatly affected by the environment,so their application is limited.In order to overcome the existing shortcomings and further develop gas-sensitive materials,on the one hand,people further improve the performance of the developed gas-sensitive materials,on the other hand,they make full use of nano-materials,thin film and other new materials to find better sensing materials,such as the manufacture of graphene gas sensors.Based on actual needs,through density functional theory(DFT),this paper explores the gas adsorption properties of(1)Ni(111)-supported graphene and defect graphene composite systems(2)the surface and interface of Zn O(002)-supported Graphene composite systems.For nickel-based graphene(G/Ni),nickel-based mono-carbon vacancy graphene(VC-G/Ni),nickel-based di-carbon vacancy graphene(V2C-G/Ni),nickel-based Stone-Wales defect graphene(SW-G/Ni)system.Due to the defects and the composed with nickel of graphene,the problem of poor electron transport of pristine graphene is improved.Especially in VC-G/Ni and V2C-G/Ni system,the existence of dangling bonds improves the interaction between graphene and gas molecules.The density of states(DOS)shows that the material does have the ability of gas adsorption.According to the results,two CO molecules will bond to form C₂O₂molecules and chemically adsorb on G/Ni and VC-G/Ni.This experiment provides an excellent gas-sensitive material for the capture and sensing of CO molecules.When NO₂is adsorbed on V2C-G/Ni,it can be stably adsorbed on the surface of V2C-G/Ni in any orientation,which shows that V2C-G/Ni can be used as a good NO₂sensor.The existence of an external electric field can significantly change the adsorption energy of NO₂and improve the sensitivity of substrates.The conclusion shows that G/Ni and its related defect system can be used as a feasible gas sensor,and the external electric field can change the sensitivity of the material.For the adsorption condition of NO₂,NH₃and H₂S on Zn O,Zn O-based graphene(G/Zn O),Zn O-based single-carbon vacancy graphene(VC-G/Zn O)and Zn O-based graphene interface(Inter-G/Zn O),it can be seen from the results that the presence of dangling bonds will improve the adsorption of the substrates for NO₂gas molecules,indicating that VC-G/Ni is a good material for NO₂adsorption.When NO₂is adsorbed on Inter-G/Zn O,the strong interaction of the interface makes the adsorption energy increase significantly,which is more stable than that of NO₂adsorbed on the surface of Zn O.A transverse comparison of the three gas molecules shows that the substrate has a strong adsorption effect on NO₂.The Inter-G/Zn O adsorption system has a good performance on the adsorption of NH₃,which reflects superiority of the Inter-G/Zn O as an adsorption site.It can be seen intuitively from the charge density difference that the charge transfer not only occurs between Zn O and gas,but graphene also provides assistance.This shows that the presence of graphene facilitate gas adsorption on Zn O,especially in the Inter-G/Zn O system.The results of this paper confirm that the composites with graphene can improve the gas sensing ability of traditional sensors and enhance the sensitivity and selectivity of substrates.The results above provide theoretical guidance for the feasibility of new nano-material solid chemical gas sensors.