A Study On Graphene Adsorption Of HCN And CO Molecules Using First-principles

Graphene since its first discovery in 2004, with its superior performance, has become hot research field in physical, chemical, material and biological etc. Thanks to its light quality and the theory of specific surface area is 2630 m2/g, which makes it become the motivation of study adsorption material.This paper start from the adsorption performance of graphene, studying of graphene in intrinsic and doping state of adsorb HCN and CO moleculars. This paper involves four parts: one report on the discovery of graphene, preparation, properties. The second report introduces first-principles calculation method used in this paper. The third report introduces the adsorption of HCN under intrinsic graphene and doping with 3d, 4d, 5d element. In the case of pure graphene, the adsorption of HCN molecular can be only physisorbed, which indicated that PG is not sensitive for detecting the presence of HCN molecular. When we study 3d element Cr, Mn, Fe doped graphene, it is found that HCN molecule can be chemisorbed on Fe, Mn and Cr doped graphene. It is also observed from band structure that Cr doped graphene will change from half-metallic behavior to semiconductor. From the phonon density of states(PDOS) observed Cr doped graphene is stable, so Cr doped graphene is a suitable candidate for HCN sensor. When the graphene doped 4d element Y, Zr, Nb, Mo, Tc, Ru. Change of conductivity of Y, Zr, Nb and Tc doped graphene is smaller, while conductivity of Mo and Ru doped graphene can be affected significantly by adsorption HCN molecular. In the PDOS, found that Mo and Ru doped graphene is absence of imaginary frequency, shown that doping form stable structure, which is a suitable candidate for HCN sensor. When 5d element Hf, Ta, W, Re, Os, Ir, Pt, Au and Hg doped graphene. Because of Hg atom can form saturated structure with valence electron configurations of 5d106s2, so it need not share electron with C atom. Ta and W doped graphenes are semiconductors with band gap value of 0.307 e V and 0.235 eV. They change from semiconductor to metal behavior after adsorption HCN molecule, obvious changes have taken place in the band structure before and after adsorption. Therefore, we make a conclusion that Ta and W doped graphenes may be suitable candidate for HCN sensor. The fourth part mainly introduces the intrinsic graphene and 3d element Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn doped graphene adsorption CO molecule. When the graphene is pure, adsorption of CO molecule is physisorbed. Therefore, researching the case of doped. Under this situation, Co, Ni, Cu, Zn systems formed are physisorbed, Sc,Ti,V,Cr,Mn,Fe systems formed are chemisorbed. Cr and Fe doped graphenes after adsorption CO molecule, the band gap were changed 21%, 27% respectively. With PDOS to study the vibrational mode, the long-range order of graphene was destroyed by doping Sc, Ti, Mn, Ni and Zn, which show off imaginary frequency, demonstrating those structures are not stable. V, Cr, Fe and Co doped graphenes are absence of imaginary frequency, showed that those structures are stable. Finally it is concluded that Cr and Fe doped graphenes are stable, suitable for as a sensor to detect CO molecule.