Programme

O.12 -- Oral, VCTP-45

Date: Tuesday, 13 October 2020

Time: 11:40 - 12:00

Adsorption of Toxic Gases on Pristine Graphene, Graphene/h-BN and Graphene/$\alpha$-SiO2 Heterostructures: Density Functional Theory Calculations

Ba Lich Pham (1), Viet Bac T. Phung (2), Van An Dinh (1,3)

(1) Nanotechnology Program, VNU Vietnam Japan University, Luu Huu Phuoc street, My Dinh, Nam Tu Lien, Hanoi, Vietnam (2) Institute of Sustainability Science, VNU Vietnam Japan University, Luu Huu Phuoc street, My Dinh, Nam Tu Lien, Hanoi, Vietnam (3) Center for Atomic and Molecular Technologies, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan

In this study, the adsorption properties of five toxic gases in the atmosphere CO2, CO, NH3, NO, NO2 onto the surface of pristine graphene and graphene on substrates of h-BN and α-SiO2 are studied systematically using the density functional theory (DFT). All considered gases are physically adsorbed on graphene-based surface. With reference to the adsorption characteristics and electronic properties of considered toxic gases on different substrates, $\alpha$-SiO2 has been predicted as the good substrate to enhance the selectivity for NO, NO2 gas sensing compared to h-BN substrate. The band structures and density of states (DOS) analysis results show that the interaction between h-BN and alpha-SiO2 with $\pi$ and $\pi^*$ states of the C atoms in graphene breaks the symmetry of graphene and small band gap occurs at the Dirac cone. New bands originating from different substrates modify the band structure of pristine graphene and open a band gap of 0.05 eV in Graphene/h-BN and 1.75 eV in Graphene /$\alpha$-SiO2, respectively. These changes in band gap from zero in pristine graphene to 1.75 eV in Graphene/$\alpha$-SiO2 suggests the potential use of Graphene/$\alpha$-SiO2 for gas sensing applications. During adsorption, the considered toxic gases CO2, CO, NH3, NO, NO2 cause a change in the electronic structure of graphene. By DOS analysis of adsorption systems, we found that the highest occupied molecular orbitals (HOMO) of these gas molecules shift backward the Fermi level, suggesting the charge donation tendency of gas molecules to the graphene on substrates. The enhancement of sensitivity and selectivity of graphene-based gas sensing materials by introducing different substrates as h-BN or $\alpha$-SiO2 are discussed in detail..

Presenter: Phung T. V. Bac