Adsorption and diffusion of atomic hydrogen on a curved surface of microporous carbon: A theoretical study

Kayanuma, Megumi; Nagashima, Umpei; Nishihara, Hirotomo; Kyotani, Takashi; Ogawa, Hiroshi

doi:10.1016/j.cplett.2010.06.077

Cited by 39 publications

(29 citation statements)

References 27 publications

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“…55 In addition, its curvature can also influence the reactivity of nanographene. 56 Because of its unique nanostructure, the ZTC framework provides a large number of highly reactive sites. Furthermore, the entire surface of the framework is fully exposed to the electrolyte, 27 and this could further enhance the reactivity.…”

Section: Resultsmentioning

confidence: 99%

Large Pseudocapacitance in Quinone-Functionalized Zeolite-Templated Carbon

Itoi

Nishihara²,

Ishii³

et al. 2013

Bulletin of the Chemical Society of Japan

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Zeolite-templated carbon (ZTC), which can be obtained as a negative replica of a zeolite, consists of buckybowllike nanographenes assembled into a three-dimensional regular network. ZTC is characterized not only by this unique framework structure but also by a very large number of carbon edge sites. In this paper, we report that the edge sites of ZTC are easily functionalized by a large amount of quinone groups through electrochemical oxidation unlike general carbonaceous materials, and the quinone-functionalized ZTC shows a high electrochemical capacitance (ca. 300 500 F g ¹1 ) in an aqueous electrolyte solution (1 M H 2 SO 4 ) as a result of the large pseudocapacitance derived from a quinone/hydroquinone redox couple. Moreover, ZTC keeps its high capacitance even after thousands of charge discharge cycles.Fullerenes, 1 single-walled carbon nanotubes (SWCNTs), 2,3 and graphenes 4,5 are nanocarbon materials with 0D, 1D, and 2D topologies, respectively. Though fullerenes form poorly conductive van der Waals crystals, SWCNTs 6,7 and graphenes 811 are electrically conductive, and are promising as electrode materials for electrochemical capacitors. 12 Their building unit, a graphene sheet, has a large theoretical surface area (2630 m 2 g ¹1 ), and therefore potentially has a large capacitance. However, the actual BrunauerEmmettTeller (BET) surface areas of SWCNTs 13 and graphenes 8 are at most 1250 and 705 m 2 g ¹1 , respectively, because of the aggregation/stacking of the graphene sheets as a result of strong van der Waals interactions. To expose the entire surface, a graphene sheet has to be formed into a self-standing 3D network, like carbon schwarzite 14,15 or pillared graphene, 16 both of which are imaginary materials and have only been proposed theoretically. Thus far our group has demonstrated that it is possible to synthesize a graphene-based architecture with a 3D topology inside the confined-nanospace network of a zeolite crystal, as shown in Figures 1a1c. 1720The zeolite-templated carbon (ZTC) thus obtained consists of a buckybowl-like nanographene assembled into a 3D regular network (Figures 1c and 1d). Both sides of the buckybowllike unit are fully exposed, and, in addition, the narrow nanographene-based framework has a significant number of edge sites. 18 Consequently, ZTC has a very large geometric (theoretical) surface area of 3432 m 2 g ¹1 , and such a large surface area has indeed been observed experimentally.18 ZTC possesses unique spin/magnetic properties 21 and is predicted to have a unique band structure. 22 Moreover, it has a high hydrogen-storage capacity 23,24 and superior performance as an electrode for electrochemical capacitors.2527 Modifications of ZTC with electrochemically active species are expected to further enhance its performance. Graphene-based materials are generally modified by doping of graphene with other functional components such as metal nanoparticles, 2830 metal oxides/ hydroxides, 3134 and conductive polymers. 35 Another modification method is to functionalize graphenes...

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Section: Resultsmentioning

confidence: 99%

Large Pseudocapacitance in Quinone-Functionalized Zeolite-Templated Carbon

Itoi

Nishihara²,

Ishii³

et al. 2013

Bulletin of the Chemical Society of Japan

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“…It is ironic that, in recent years, hydrogen spillover has been more intensively studied in the field of hydrogen storage [8][9][10][11][12][13][14][15][16] rather than in heterogeneous catalysis where the hydrogen spillover concept was first demonstrated.I nh ydrogen storage, hydrogen spillover was used to enhancet he H 2 storage capacities of carbon-based materials by using the chemisorption of atomic hydrogen on their surface. To achieve the increased uptake of H 2 ,a tomic hydrogen generated on the metal catalysts urface should migrate to the carbon support (or adsorbent) surface to form sufficiently stable CÀH [12][13][14][15] and OÀH( with oxygen functional groups) bonds. [16] This means that the carbon supports need to be hydrogenated as ac onsequence of hydrogen spillover for enhancing the H 2 uptake.…”

Section: Understanding Hydrogen Spillover From a Catalysis Point Of Viewmentioning

confidence: 99%

“…[1] If we aim to use hydrogen spillover to enhance hydrogen storage capacity on supports (adsorbents), such driving force should be found in the strongb ond formationb etween the atomic hydrogen and support surface. In the cases of carbonbased adsorbents, the formation of CÀH [12][13][14][15] andO À H [16] bonds on the carbon surface may provide such thermodynamic driving force. In the cases of semiconducting metal oxides such as WO 3 , [3,17,18] MoO 3 , [19] TiO 2 , [20] etc., [21] atomic hydrogen can chemically react with the supports to partially reduce the framework as in the case of Khoobiar's WO 3 experiment.…”

Section: Understanding Hydrogen Spillover From a Catalysis Point Of Viewmentioning

confidence: 99%

Hydrogen Spillover in Encapsulated Metal Catalysts: New Opportunities for Designing Advanced Hydroprocessing Catalysts

2015

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Hydrogen spillover has been one of the most debated concepts in the field of heterogeneous catalysis due to limited ways of studying it. The main controversies in hydrogen spillover, especially from the viewpoint of its catalytic functions, can be mainly attributed to the absence of well‐defined model catalysts that can provide direct proof of the catalytic functions of hydrogen spillover. In this article, we will provide an overview of the recent progress made with encapsulated metal catalysts, which can act as an ideal model catalyst for proving the existence and catalytic functions of hydrogen spillover. We will also demonstrate unique opportunities of using the encapsulated metal catalysts for designing advanced hydroprocessing catalysts with enhanced activity, distinct chemoselectivity, and increased catalyst durability.

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“…Buckybowl C36H12, which is the minimum unit of ZTC and includes three pentagonal carbons, was employed as a model structure [5,11]. The semi-empirical PM3 method was used for static MO calculation, conventional classical MD, and PIMD simulations with Gaussian03 program package [17].…”

Section: Methodsmentioning

confidence: 99%

“…Recently, we have reported hydrogen adsorption site on buckybowl C 36 H 12 , as a fragment of ZTC, and found that the adsorption site of the additional hydrogen atom at out side of buckybowl is more stable than that at edges [11].…”

Section: Introductionmentioning

confidence: 98%