Transport properties of H2 confined in carbide-derived carbons with different pore shapes and sizes

Härmas, Riinu; Palm, Rasmus; Russina, Margarita; Kurig, Heisi; Grzimek, Veronika; Härk, Eneli; Koppel, Miriam; Tallo, Indrek; Paalo, Maarja; Oll, Ove; Embs, Jan Peter; Lust, Enn

doi:10.1016/j.carbon.2019.08.041

Cited by 21 publications

(19 citation statements)

References 36 publications

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“…Details of adsorption process and diffusion of liquid and gas phases in nano-and mesoporous materials are crucial in many industrial processes, e.g. catalysis, separation [26], development of novel materials for hydrogen storage [27].…”

Section: Diffusion Of Liquid and Gases In Nanoand Mesoporous Materialsmentioning

confidence: 99%

Dynamics studied by Quasielastic Neutron Scattering (QENS)

Kruteva

2021

Adsorption

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Quasielastic neutron scattering (QENS) allows measurement of the molecular displacements in time and space, from pico- to tens of nanoseconds and from Ångstroms to nanometers, respectively. The method probes dynamics from fast vibrational modes down to slow diffusive motion. Every scattering experiment leads to a dynamic structure factor $$S\left( {\vec Q,\omega } \right)$$ S Q → , ω or its spatial and temporal Fourier transform (van Hove correlation function $$G\left( {\vec r,t} \right)$$ G r → , t ). This shows exactly where the atoms are and how they move. In this manuscript the basics of the QENS method are presented and a few examples highlighting the potentials of QENS are given: (i) diffusion of liquids and gases in nano- and mesoporous materials; (ii) hydrogen dynamics in a high temperature polymer electrolyte fuel cell (HT-PEFC) and (iii) influence of the surface interactions on polymer dynamics in nanopores.

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Section: Diffusion Of Liquid and Gases In Nanoand Mesoporous Materialsmentioning

confidence: 99%

Dynamics studied by Quasielastic Neutron Scattering (QENS)

Kruteva

2021

Adsorption

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“…The maximum diffusivity ( D 0 ) and activation energy ( E a ) of hydrogen isotopes can be calculated by the Arrhenius equation (Equation ()). [ 31,32 ]

\begin{matrix} D = D_{0} e^{- E_{normala} / RT} \end{matrix}

where R is the universal gas constant. Figure shows the Arrhenius plot for temperature‐dependent diffusivity at a loading pressure of 18 mmol g −1 of hydrogen isotopes.…”

Section: Figurementioning

confidence: 99%

“…The maximum diffusivity (D 0 ) and activation energy (E a ) of hydrogen isotopes can be calculated by the Arrhenius equation (Equation ( 4)). [31,32]…”

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confidence: 99%

Elucidation of Diffusivity of Hydrogen Isotopes in Flexible MOFs by Quasi‐Elastic Neutron Scattering

et al. 2021

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porous materials, the diffusion measurements can be used to obtain detailed microgeometric information about porous materials. [7] Therefore, fine control of homogeneously distributed pore size and morphology in porous media is required to understand the fundamental physical adsorption and diffusion processes.Among the various nanoporous materials available, metal-organic frameworks (MOFs) are a promising candidate for investigating the adsorption and diffusion characteristics of gas separation/purification application because of their crystallinity and tunability of the pore structure. To date, however, only a few MOFs have been utilized to investigate the application of diffusivity to gas separation either experimentally (e.g., pulsed-field-gradient (PFG) NMR and quasi-elastic neutron scattering (QENS)) or through molecular dynamic simulations. [8][9][10][11] Stallmach et al. used PFG NMR to study the diffusion of hydrocarbons, such as methane, ethane, n-hexane, and benzene, in MOF-5 and revealed for the first time the diffusivity correlation between the surface area and the pore size. [8] Similarly, Pusch et al. explored CO 2 and CH 4 self-diffusion in ZIF-8 at elevated pressure and found that the former diffuses slightly faster than the latter. They also used QENS to observe the microscopic molecular dynamics in porous frameworks. [9] Using QENS measurements, Rives et al. investigated the dynamics of xylene isomers (m-, o-, and p-xylene) in MIL-47(V) and found that the diffusion increases with the increase in temperature. [10] Russina et al. also reported the Kinetic-quantum-sieving-assisted H 2 :D 2 separation in flexible porous materials is more effective than the currently used energy-intensive cryogenic distillation and girdle-sulfide processes for isotope separation. It is believed that material flexibility results in a pore-breathing phenomenon under the influence of external stimuli, which helps in adjusting the pore size and gives rise to the optimum quantum-sieving phenomenon at each stage of gas separation. However, only a few studies have investigated kinetic-quantumsieving-assisted isotope separation using flexible porous materials. In addition, no reports are available on the microscopic observation of isotopic molecular transportation during the separation process under dynamic transition. Here, the experimental observation of a significantly faster diffusion of deuterium than hydrogen in a flexible pore structure, even at high temperatures, through quasi-elastic neutron scattering, is reported. Unlike rigid structures, the extracted diffusion dynamics of hydrogen isotopes within flexible frameworks show that the diffusion difference between the isotopes increases with an increase in temperature. Owing to this unique inverse trend, a new strategy is suggested for achieving higher operating temperatures for efficient isotope separation utilizing a flexible metal-organic framework system.Molecular diffusion in nanoporous materials for processes such as adsorption, separation, and catalysis is one ...

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“…An interesting group has been termed sorbent materials [2,3]. These include, among others, carbon nanotubes [4][5][6], boron nitride nanotubes [7,8], inorganic and organic fullerenes [9,10], graphene nanoflakes [11,12], porous carbons [13][14][15][16][17][18][19], mesoporous silica [3], metal-organic frameworks (MOFs) [19], covalent-organic frameworks (COFs) [20], and clathrates [21]. In these, hydrogen is bound to the substrate by physisorption forces [22,23], so the systems are good hydrogen adsorbers only at low temperature.…”

Section: Introductionmentioning

confidence: 99%