Hydrogen physisorption capacities of mechanically milled activated carbon powders in a H2 atmosphere using a gravimetric method

Shindo, Kazuhiko; Kondo, Toshihiko; Sakurai, Yasuhisa

doi:10.1016/j.jallcom.2004.02.019

Cited by 14 publications

(15 citation statements)

References 12 publications

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“…15,16 Adsorption of H 2 on carbon materials has been studied by many authors. [17][18][19][20][21][22][23][24][25] But these investigations have been directed toward use of carbon materials as hydrogen storage materials, and not as catalyst support in PEMFCs.…”

Section: Introductionmentioning

confidence: 99%

Surface Self-Diffusion and Mean Displacement of Hydrogen on Graphite and a PEM Fuel Cell Catalyst Support

2009

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Quasielastic neutron scattering (QENS) measurements together with equilibrium molecular dynamic (EMD) simulations have been performed to investigate the surface interaction between hydrogen molecules and a carbon material commonly used in polymer electrolyte membrane fuel cells (PEMFC), called XC-72. Half a monolayer of molecular hydrogen was adsorbed on to the carbon material at 2 K. QENS spectra were recorded at the time-of-flight spectrometer IN5 at 40,45, 50, 60, 70, 80, and 90 K. Simultaneously the pressure was measured as a function of time to monitor the equilibrium surface coverage at each temperature. By using the Chudley and Elliott model for jump diffusion we found the diffusion coefficient at each temperature. At 350 K, a typical fuel cell temperature, the temperature function was extrapolated to a self-diffusion coefficient of 2.3 × 10 -7 m 2 /s. We simulated graphite in contact with hydrogen molecules using EMD simulation. We simulated the system at different temperatures from 70 to 350 K in 20 deg intervals and for five numbers of H 2 molecules N H 2 ) 50, 100, 150, 200, and 300. The graphite was made of 9 sheets of graphene in a sandwich. The surface self-diffusion was found from the mean-square displacement, and the values from EMD simulations are the same order of magnitude as the experimental values at 90 K, but systematically higher, probably due to the ideal surface. From EMD simulation, we also calculated the average time between adsorption and desorption events on the surface. This was used to find the mean displacement of the hydrogen molecules between adsorption and desorption. This result showed that H 2 molecules can move 80 Å at ambient temperatures and pressures, along the surface. Using these data, we conclude that catalyst support material in PEMFC contributes to the transport of reactant.

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Section: Introductionmentioning

confidence: 99%

Surface Self-Diffusion and Mean Displacement of Hydrogen on Graphite and a PEM Fuel Cell Catalyst Support

2009

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“…If this is true, we be- lieve that the hydrogen capacity of AC stored by mechanical milling depends on the initial pressure of the H 2 introduced into the milling pot. This is because the physisorption capacity increases with increasing H 2 pressure [8]. We then examined whether the hydrogen storage capacity is influenced by H 2 pressure.…”

Section: Hydrogen Pressure Dependencementioning

confidence: 99%

“…5. We assume that the physisorption capacity might be small at 0.8 MPa H 2 because it measured by a gravimetric method was less than 0.05 wt.% at 1 MPa H 2 and room temperature [8].…”

Section: Hydrogen Pressure Dependencementioning

confidence: 99%

Influence of milling conditions on hydrogen storage capacities of activated carbon mechanically milled in an H2 atmosphere

Shindo

Kondo

Sakurai

2005

Journal of Alloys and Compounds

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“…Hydrogen storage capacities in porous materials such as carbon nanomaterial, zeolites and crystalline coordination polymers at room and liquid nitrogen temperatures have been studied extensively [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Carbon materials are largely investigated in this field.…”

Section: Introductionmentioning

confidence: 99%

“…Kopac and Erdogan [12] studied sorption characteristic of H 2 and N 2 in ACs with different particle sizes in a temperature range of 303-473 K using a dynamic technique and evaluated the adsorption equilibrium constant and heat of adsorption values of H 2 and N 2 on the carbon samples. Shindo et al [13] investigated the hydrogen physisorption characteristics of mechanically milled AC powders using thermal desorption spectroscopy and the pressure-composition-temperature method. It was observed that hydrogen molecules were easily desorbed in hydrogenated milled AC and the hydrogen physisorption capacity of hydrogenated milled AC was smaller than that of the host AC, as the specific surface area of the host AC was reduced by milling.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen sorption characteristics of Zonguldak region coal activated by physical and chemical methods

Kopaç

Toprak

2009

Korean J. Chem. Eng.

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Hydrogen sorption characteristics of activated carbons (ACs) produced by physical and chemical activations from two coal mines (Kilimli and Armutcuk) in the Zonguldak region, Turkey were investigated by a volumetric technique at 77 K. H 2 adsorption isotherms were obtained on the samples exposed to pyrolytic thermal treatments in a temperature range of 600-900 o C under N 2 flow and chemical activation using different chemical agents such as KOH, NH 4 Cl, ZnCl 2 from the two mines. Experimental hydrogen adsorption isotherm data at 77 K were used for the evaluation of the adsorption isotherm constants of the Brunauer-Emmett-Teller (BET) and the Langmuir models, and also the amount of hydrogen adsorbed on the various samples was evaluated by using the adsorption isotherm data. Higher hydrogen adsorption capacity values were obtained for all the heat and the chemically treated activated carbon samples from the Kilimli coal samples than Armutcuk. The amount of H 2 adsorbed on the original Kilimli coal samples was 0.020 wt%, and it was increased to 0.89 wt% on the samples pyrolyzed at 800 o C. The highest value of hydrogen adsorption obtained was 1.2 wt% for the samples treated with KOH+NH 4 Cl mixture at 750 o C followed by oxidation with ZnCl 2 . It was shown that chemical activations were much more effective than physical activations in increasing the surface area, pore volume and the hydrogen sorption capacities of the samples.

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Hydrogen physisorption capacities of mechanically milled activated carbon powders in a H2 atmosphere using a gravimetric method

Cited by 14 publications

References 12 publications

Surface Self-Diffusion and Mean Displacement of Hydrogen on Graphite and a PEM Fuel Cell Catalyst Support

Surface Self-Diffusion and Mean Displacement of Hydrogen on Graphite and a PEM Fuel Cell Catalyst Support

Influence of milling conditions on hydrogen storage capacities of activated carbon mechanically milled in an H2 atmosphere

Hydrogen sorption characteristics of Zonguldak region coal activated by physical and chemical methods

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