Adsorption energy of oxygen molecules on graphene and two-dimensional tungsten disulfide

Abstract

Adsorption of gas molecules on the surface of atomically layered two-dimensional (2D) materials, including graphene and transition metal dichalcogenides, can significantly affect their electrical and optical properties. Therefore, a microscopic and quantitative understanding of the mechanism and dynamics of molecular adsorption and desorption has to be achieved in order to advance device applications based on these materials. However, recent theoretical calculations have yielded contradictory results, particularly on the magnitude of the adsorption energy. Here, we have experimentally determined the adsorption energy of oxygen molecules on graphene and 2D tungsten disulfide using temperature-programmed terahertz (THz) emission microscopy (TPTEM). The temperature dependence of THz emission from InP surfaces covered with 2D materials reflects the change in oxygen concentration due to thermal desorption, which we used to estimate the adsorption energy of oxygen molecules on graphene (~0.15 eV) and tungsten disulphide (~0.24 eV). Furthermore, we used TPTEM to visualize relative changes in the spatial distribution of oxygen molecules on monolayer graphene during adsorption and desorption. Our results provide much insight into the mechanism of molecular adsorption on the surface of 2D materials, while introducing TPTEM as a novel and powerful tool for molecular surface science.The successful isolation of monolayer graphene in 2004 and its remarkable properties found subsequently have paved the way for a new research field of two-dimensional (2D) atomic layer materials [1][2][3][4] . Many other 2D materials have since been discovered with a wide range of characteristics, from metallic to semiconducting to insulating, opening up exciting new opportunities for the development of devices based on monolayers, bilayers, and heterostructures of 2D materials [5][6][7][8] . However, since these materials typically consist of one or a few atomic layers, their properties are extremely susceptible to perturbations from their environment. Exposure to gases, for example, has been shown to drastically affect their electrical and optical properties [9][10][11][12][13][14][15] , which means that in order to realize 2D-materials-based devices, it is crucial to understand and control the influence of gas adsorption and desorption dynamics on their properties.Of the possible gas adsorbates/contaminants, oxygen (O 2 ) is one of the most important because not only it significantly alters the properties through doping, it is also the second most abundant gas in the atmosphere and is therefore highly likely to affect the performance of devices in practical applications. Though theoretical simulations proved to be useful in understanding the interaction of O 2 molecules and/or O atoms with 2D materials, conflicting results for the adsorption energies were obtained due to the inability of the approximation functionals used to properly describe the dispersion forces [16][17][18][19][20][21][22][23] . Knowing the correct value of the adsorption ...

Revealing the role of the 1T phase on the adsorption of organic dyes on MoS2 nanosheets

“…In addition, various properties of the adsorbents (such as geometrical conguration, hydrophobicity, size, and substituent chemical groups) were investigated. 37,38 With the progress in fabricating 2D MoS 2 nanosheets, molecular adsorption on its surface have been recently computationally investigated, where defects arising from Mo or S vacancies can lead to an enhancement of its adsorption and catalytic properties. 39,40 Edges of MoS 2 nanoparticles, where the atomic coordination of the Mo and S atoms is different from the bulk, provide active sites that can anchor various functional groups, adsorb various gases, and catalyse hydrogen evolution reactions.…”

Diffusion Monte Carlo study of O2 adsorption on single layer graphene

“…are a little higher than the experimentallyreported value of -0.15 eV for the O 2 adsorption energy on graphene 26. This leads us to explore the graphene surface for more favorable adsorption sites for O 2 than either a bridge or a hollow site and to investigate in the process diffusion mobility of O 2 on the graphene surface.…”

“…[23][24][25] Recently, the adsorption energy of O 2 on graphene was experimentally measured using temperature-programmed terahertz emission microscopy. 26 However, detailed information about the adsorption site and equilibrium distance along with its preferred 3 molecular orientation is yet to be accurately determined.…”

Terahertz Emission Functionality of High‐Temperature Superconductors and Similar Complex Systems

“…2020, 8,1900892 mentation of THz emission spectroscopy to 2D systems is a viable and credible approach to realizing such ultrafast optical control. [128][129][130][131][132][133][134][135][136][137][138][139][140][141] In the specific area of active metamaterials research, combining the electronic and magnetic control with the optical THz functionality of metamaterials promises several new possibilities for the technological utility of THz light-matter interaction. [136,137] Thus, material research by and for THz technology is one of the most exciting research fields where we can study the intrinsic nature of materials and devices.…”