First principles investigation of hydrogen physical adsorption on graphynes' layers

Abstract

Graphynes are 2D porous structures deriving from graphene featuring triangular and regularly distributed subnanometer pores, which may be exploited to host small gaseous species. First principles adsorption energies of molecular hydrogen (H 2 ) on graphene, graphdiyne and graphtriyne molecular prototypes are obtained at the MP2C level of theory. First, a single layer is investigated and it is found that graphynes are more suited than graphene for H 2 physical adsorption since they provide larger binding energies at equilibrium distances much closer to the 2D plane.In particular, for graphtriyne a flat minimum located right in the geometric center of the pore is identified. A novel graphite composed of graphtriyne stacked sheets is then proposed and an estimation of its 3D arrangement is obtained at the DFT level of theory. In contrast to pristine graphite this new carbon material allow both H 2 intercalation and out-of-plane diffusion by exploiting the larger volume provided by its nanopores. Related H 2 binding energies for intercalation and in-pore adsorption are around 0.1 eV and they could lead to high storage capacities. The proposed carbon-based layered material could represent a safer and potentially cheaper alternative for hydrogen on-board storage than conventional solutions based on cryogenic liquefaction and/or high compression. PACS numbers:2

Adsorption of molecular hydrogen on coronene with a new potential energy surface

“…The choice of the MP2C approach relies on its capability to provide accurate estimations for the interaction energies in weakly bound noncovalent systems, ranging from RG-coronene 37 or benzene-benzene 41 up to moleculeannulenes [42][43][44] , at an affordable computational cost. DFT-SAPT estimations of the interaction energies are in general more expensive in terms of computing time, but they have been also performed in order to provide alternative results of well known reliability 45,46 and unaffected by the basis set superposition error (BSSE).…”

“…As opposed to chemical dissociative processes, physical adsorption energy is typically in the meV regime and therefore the overall mechanism becomes relevant at low temperatures [13][14][15] . Physisorption on PAHs can be directly considered, on the other hand, as a model to study hydrogen storage 16,17 . The characterization of phase diagrams and the heat capacity of systems formed by layers of H 2 on either graphite or graphene has been the goal of numerous investigations in the [18][19][20][21][22][23][24][25] .…”

Enhanced competitive adsorption of CO2 and H2 on graphyne: A density functional theory study

“…1 In particular, graphyne has been recognized as a promising material for energy storage applications, such as for electrodes in batteries or fuel cells, hydrogen storage mediums, and catalysts supporting noble metals. [10][11][12][13][14] For physisorption of molecules at low temperature, activated carbons, zeolites, and metal organic frameworks (MOFs), have been used since materials with a large surface area and ordered porosity lead to a high gas uptake capacity. 14 In this paper, we have focused on the adsorptive ability of graphyne, based on its effective shape and chemical properties.…”

“…[10][11][12][13][14] For physisorption of molecules at low temperature, activated carbons, zeolites, and metal organic frameworks (MOFs), have been used since materials with a large surface area and ordered porosity lead to a high gas uptake capacity. 14 In this paper, we have focused on the adsorptive ability of graphyne, based on its effective shape and chemical properties. In recent years, adsorption using graphyne, as a storage material for H 2 , CO, and O 2 , has been reported.…”

“…Bartolomei et al investigated the hydrogen adsorption capacity of a graphyne monolayer through binding energy calculations. 14 Lu et al presented a comparative study for hydrogen in metals on graphyne nanotubes and graphyne monolayers with first-principles calculations. 15 In addition, using the adsorption property of a single layer of graphyne, Ma et al and Kang et al demonstrated the ability of the material to act as a catalyst substrate for noble and single metals, through chemical reactions between CO and O 2 .…”