• Title, Summary, Keyword: hydrogen adsorption

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Understanding the Mechanism of Hydrogen Adsorption into Metal Organic Frameworks (Metal-Organic Framework의 수소 흡착 메커니즘의 이해)

  • Lee, Tae-Bum;Kim, Dae-Jin;Yoon, Ji-Hye;Choi, Sang-Beom;Kim, Ja-Heon;Choi, Seung-Hoon
    • 한국신재생에너지학회:학술대회논문집
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    • pp.634-637
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    • 2005
  • Hydrogen adsorption mechanism onto the porous metal-organic frameworks (MOFs) has been studied by density functional theory calculation. The selected functionals for the predict ion of interact ion energies between hydrogen and potential adsorption sites of MOF was utilized after the evaluation with the various functionals for interaction energy of $H_2C_6H_6$ model system the adsorption energy of hydrogen molecule into MOF was investigated with the consideration of the favorable adsorption sites and the orientations. We also calculated the second favorable adsorption sites by geometry optimization using every combination of two first absorbed hydrogen molecules. Based on the calculation of first and second adsorption sites and energies, the hydrogen adsorption into MOF follows a cooperative mechanism in which the initial metal sites initiate the propagation of the hydrogen adsorption on the whole frameworks. In addition, it was found that the interaction strength between the simple benzene ring with hydrogen is significantly reinforced when the benzene ring has been incorporated into the framework of MOFs.

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The Relationships between the Porosity of Activated Carbon and Hydrogen Adsorption Capacity (활성탄의 기공도와 수소홀착능 사이의 관계)

  • JIN, Hangkyo
    • Transactions of the Korean hydrogen and new energy society
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    • v.14 no.4
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    • pp.305-312
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    • 2003
  • A study is presented of the adsorption capacity of a number of different activated carbons for hydrogen at 100 bar aad 298 K. The hydrogen adsorption isotherm was measured by isothermal gravimetric analysis, using a microbalance. The effect of activated carbon's porosity on hydrogen adsorption capacity is surveyed. It is concluded that hydrogen adsorption capacity of activated carbon is lineally increased according to the increase of specific surface area and total pore volume, It seems that microporosity is more contributive than mesoporosity. Most of the adsorbed quantity is due to physical adsorption and chemisorption is negligible, In this work, 0.79 wt.% of hydrogen adsorption capacity is reached.

Low Temperature Adsorption of Hydrogen on Nanoporous Materials

  • Jhung, Sung-Hwa;Yoon, Ji-Woong;Kim, Hye-Kyung;Chang, Jong-San
    • Bulletin of the Korean Chemical Society
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    • v.26 no.7
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    • pp.1075-1078
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    • 2005
  • Hydrogen adsorption on various porous materials have been studied with a volumetric method at low temperature in the pressure of 0-760 torr. Their hydrogen uptakes depend at least partly on microporosity rather than total porosity. However, it is also necessary to consider other parameters such as pore size and pore architecture to explain the adsorption capacity. The heat of adsorption and adsorption-desorption-readsorption experiments show that the hydrogen adsorption over the porous materials are composed of physisorption with negligible contribution of chemisorption. Among the porous materials studied in this work, SAPO-34 has the highest adsorption capacity of 160 mL/g at 77 K and 1 atm probably due to high micropore surface area, micropore volume and narrow pore diameter.

Determination of the Frumkin and Temkin Adsorption Isotherms of Underpotentially Deposited Hydrogen at Pt Group Metal Interfaces Using the Standard Gibbs Energy of Adsorption and Correlation Constants

  • Chun, Jinyoung;Jeon, Sang K.;Chun, Jang H.
    • Journal of the Korean Electrochemical Society
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    • v.16 no.4
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    • pp.211-216
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    • 2013
  • At Pt(111), Pt(100), Pt, and Rh interfaces, the Frumkin adsorption isotherm of underpotentially deposited hydrogen (UPD H) and related electrode kinetic data are determined using the standard Gibbs energy of adsorption. The Temkin adsorption isotherm of UPD H correlating with the Frumkin adsorption isotherm of UPD H is readily determined using the correlation constants between the Temkin and Frumkin or Langmuir adsorption isotherms. At the Pt(111), Pt(100), Pt, and Rh interfaces, the lateral repulsive interaction between the UPD H species is interpreted using the interaction parameter for the Frumkin adsorption isotherm. The lateral repulsive interaction between the UPD H species at the Pt(111), Pt(100), Pt, and Rh interfaces is significantly different from the lateral attractive interaction between the overpotentially deposited hydrogen (OPD H) species at Pt, Ir, and Pt-Ir alloy interfaces.

Effect of hydrogen on adsorption of hydrocarbon fragments on graphene

  • Cho, Sangmo
    • Proceeding of EDISON Challenge
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    • pp.464-466
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    • 2014
  • We investigate the effect of hydrogen on adsorption of hydrocarbon molecules on graphene with density functional theory (DFT) calculations. In this study, we calculate the binding energies of hydrogen molecule, carbon atom and other hydrocarbon fragments such as CHx (x=1, 2, 3, 4) on graphene to find the most stable adsorption site. Then, to study the effect of hydrogen, we investigate the adsorption of hydrocarbon fragments in the presence of hydrogen atoms on graphene.

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Improvement of Accuracy for Determination of Isosteric Heat of Hydrogen Adsorption (부피법을 이용한 저온 등량 수소 흡착열 측정법 개선)

  • Oh, Hyunchul
    • Korean Journal of Materials Research
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    • v.27 no.3
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    • pp.127-131
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    • 2017
  • Isosteric heat of hydrogen adsorption is one of the most important parameters required to describe solid-state hydrogen storage systems. Typically, it is calculated from adsorption isotherms measured at 77K (liquid N2) and 87K (liquid Ar). This simple calculation, however, results in a high degree of uncertainty due to the small temperature range. Therefore, the original Sievert type setup is upgraded using a heating and cooling device to regulate the wide sample temperature. This upgraded setup allows a wide temperature range for isotherms (77K ~ 117K) providing a minimized uncertainty (error) of measurement for adsorption enthalpy calculation and yielding reliable results. To this end, we measure the isosteric heats of hydrogen adsorption of two prototypical samples: activated carbon and metal-organic frameworks (e.g. MIL-53), and compared the small temperature range (77~87K) to the wide one (77K ~ 117K).

Investigation of the Hydrogen Storage Mechanism of Expanded Graphite by Measuring Electrical Resistance Changes

  • Im, Ji-Sun;Jang, Seung-Soon;Lee, Young-Seak
    • Bulletin of the Korean Chemical Society
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    • v.33 no.9
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    • pp.3033-3038
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    • 2012
  • The hydrogen storage mechanism of graphite was studied by measuring the electrical resistance change. Graphite was expanded and activated to allow for an easy hydrogen molecule approach and to enlarge the adsorption sites. A vanadium catalyst was simultaneously introduced on the graphite during the activation process. The hydrogen storage increased due to the effects of expansion, activation, and the catalyst. In addition, the electrical resistance of the prepared samples was measured during hydrogen molecule adsorption to investigate the hydrogen adsorption mechanism. It was found that the electrical resistance changed as a result of the easy hydrogen molecule approach, as well as of the adsorption process and the catalyst. It was also notable that the catalyst improved not only the hydrogen storage capacity but also the speed of hydrogen storage based on the response time. The hydrogen storage mechanism is suggested based on the effects of expansion, activation, and the catalyst.

Adsorption Characteristics of Hydrogen Sulfide on Iron Hydroxide-based Adsorbent (수산화철계 흡착제의 황화수소 흡착 특성)

  • Ryu, Seung Hyeong;Seo, Youngjoo;Park, Joonwoo;Kim, Shin Dong;Park, Seong Soon
    • Journal of Korea Society of Waste Management
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    • v.34 no.5
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    • pp.468-473
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    • 2017
  • This study was carried out to examine the characteristics of hydrogen sulfide adsorption using an iron hydroxide-based adsorbent. The prepared adsorbent was discussed with regard to its adsorption capacity and analyzed via surface analysis methods to illustrate the physical characteristics of hydrogen sulfide adsorption. As the drying temperature increased, the adsorption capacity of the adsorbent decreased from 29.15wt% to 22.73wt%. The adsorption capacity was decreased as the space velocity increased and showed an adsorption capacity of about 3.65 at $3,157.6h^{-1}$. The effect of sulfur dioxide was to decrease the adsorption capacity from 29.15wt% to 27.94wt%. The adsorbent exhibited the amorphous type in its physical appearance based on XRD and EDS analysis.

The Evaluation of CO Adsorbents Used in PSA Process for the Purification of Reformed Hydrogen (개질 수소 정제용 PSA 공정을 위한 CO 흡착제의 성능 평가)

  • PARK, JIN-NAM
    • Transactions of the Korean hydrogen and new energy society
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    • v.27 no.6
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    • pp.628-635
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    • 2016
  • Natural gas reformed hydrogen is used as a fuel of fuel cell vehicle, PSA process is used for the purification of reformed hydrogen. In this study, the performance of CO adsorbent in PSA process was evaluated. Zeolite adsorbents used in the commercial PSA process is used. The physical and chemical properties of adsorbents were characterized using BET apparatus, XRD, and FE-SEM. The breakthrough apparatus modified from GC was used for the CO breakthrough experiment, the quantitative analysis of CO adsorption capacity was performed using CO breakthrough curve. Zeolite 10X and 13X showed superior CO adsorption capacity than activated alumina. The CO adsorption capacity of zeolite 10X is more than twice of zeolite 13X even the BET surface area is low. It seems that the presence of $Ca^{2+}$ cation in zeolite 10X is beneficial to the adsorption of CO.

Accurate Determination of Hydrogen Adsorption on Metal Materials Considering the Equations of State and its Influential Errors

  • Cho, Won-Chul;Park, Chu-Sik;Han, Sang-Sup
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • pp.1229-1230
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    • 2006
  • Adsorption isotherms of hydrogen by step-by-step method are widely used. However, the relations between the equations of state and the accumulated errors produced by step-by-step method and the mechanical errors of pressure or temperature controller were not analyzed. Considering the influence of various errors on the equations of state, we could find out the factors and compare the performance of the equations of state.

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