{"created":"2023-06-20T13:21:26.450097+00:00","id":1653,"links":{},"metadata":{"_buckets":{"deposit":"468f25b3-a80f-45fc-b811-387f247249b8"},"_deposit":{"created_by":21,"id":"1653","owners":[21],"pid":{"revision_id":0,"type":"depid","value":"1653"},"status":"published"},"_oai":{"id":"oai:ir.soken.ac.jp:00001653","sets":["2:427:9"]},"author_link":["0","0","0"],"item_1_creator_2":{"attribute_name":"著者名","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"沼尾, 茂悟"}],"nameIdentifiers":[{}]}]},"item_1_creator_3":{"attribute_name":"フリガナ","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"ヌマオ, シゲノリ"}],"nameIdentifiers":[{}]}]},"item_1_date_granted_11":{"attribute_name":"学位授与年月日","attribute_value_mlt":[{"subitem_dategranted":"2010-03-24"}]},"item_1_degree_grantor_5":{"attribute_name":"学位授与機関","attribute_value_mlt":[{"subitem_degreegrantor":[{"subitem_degreegrantor_name":"総合研究大学院大学"}]}]},"item_1_degree_name_6":{"attribute_name":"学位名","attribute_value_mlt":[{"subitem_degreename":"博士（理学）"}]},"item_1_description_12":{"attribute_name":"要旨","attribute_value_mlt":[{"subitem_description":"　　　Due to the high electronic conductivity and variety of forms, various carbon<br />nanomaterials have been developed in recent years. In particular, porous carbon<br />materials and graphitic carbon materials are very promising as electrode materials<br />in supercapacitors, lithium ion batteries, and fuel cells. Recent demands for<br />electrode materials are oriented toward the development of new porous carbon<br />materials with high conductance both for the electron and ion transportations.<br />However, it has been extremely difficult to combine the properties of porous<br />structures and graphitic ones.<br /><br />　　　We have synthesized silver acetylide (Ag<small>2</small>C<small>2</small> : Ag-C　&equiv;C-Ag) with<br />3D-interconnected frameworks and converted the acetylide to a new carbon<br />material, mesoporous carbon nano-dendrites (MCNDs) with ultra-thin graphitic<br />structure. MCNDs are synthesized by controlling the highly exothermic<br />segregation reaction of silver acetylyde into carbon with porous structure and<br />silver-vapor. The dendroide acetylides were quickly warmed to 250℃ emitting a<br />brilliant flash of raddish orange light with a thunderous sound indicative of the<br />sudden jump of the local temperature to higher than 2000℃. The sudden heating<br />boils off the silver from the main body, leaving 3D-interconnected carbon<br />frameworks, the MCNDs.<br />　　　Raman spectra of MCNDs clearly indicate that carbon frameworks consist<br />of mainly graphitic structure of 1-3 layers. SEM and TEM images as well as<br />EELS spectra show that the main body with ～100 nm radii branches every<br />100-150 nm and are composed of cells with ultra-thin graphitic walls. The BET<br />(Brunauer-Emmett-Teller) surface area of MCNDs was estimated to be 1324-1996<br />m<sup>2</sup>/g from the nitrogen adsorption and desorption isotherm at 77 K, and the<br />adsorption-desorption curves indicate the presence of micropores (pore size: <2<br />nm) and mesopores (2-50 nm) with a continuous size distribution up to 10-20 nm.<br />These results show that the MCND combines porous structures with graphitic<br />ones.<br /><br />　　　One of the most suitable applications of MCNDs is to the supercapacitor<br />electrodes. In this case, the high fluidity of solvent phase is also demanded as well<br />as large surface area. The dendritic structure and the presence of mesopores on the<br />surface area of MCNDs can be well suited for these requirements. In order to<br />examine the electrochemical properties of MCNDs as supercapacitors electrodes,<br />the author assembled Sandwich-type capacitors on a platinum current collector<br />with two carbon electrode sheets consisting mainly of MCND, and<br />polytetrafluoroethylene (PTFE) porous separator were assembled. Cyclic<br />voltammetry of a supercapacitor with MCND electrodes showed good rectangular<br />curves, even at a scanning rate of 300 mV/s and peak current density higher than<br />l0 A/g, suggesting applicability for high current and high-speed charge-discharge<br />capacitors electrodes.<br /><br />　　　The mesopore on the surface area of MCNDs are also available as<br />impregnate sites of catalyst metals and lithium storage metals. We successfully<br />impregnated tin(Sn) and platinum(Pt) metals in the mesopores of MCND through<br />the adsorption of SnCl<small>2</small> or H<small>2</small>[PtCl<small>6</small>]・(H<small>2</small>O)<small>6</small>, and<br /> the reduction with hydrogen gas.<br /><br />　　　Sn nanoparticles with an average size of 10 nm were prepared in the pores<br />of MCNDs by chemical reduction of SnCl<small>2</small> with hydrogen gas for anode materials<br />of lithium ion butteries. The nanoparticles grow with increasing reduction<br />temperature and some pores were occupied with Sn almost entirely. One of the<br />major problems to prevent the practical use of Sn solid single electrodes is poor<br />cycleability due to the large volume changes during lithium alloying and<br />dealloying. However, Sn/MCND composites exhibit significantly enhanced<br />cycling performance for lithium storage. When used as a lithium ion battery, we<br />find that a first discharge capacity of 646 mAh/g and the capacity retain a value of<br />481mAh/g can be obtained after 50 charge and discharge cycles. This improved<br />cycling performance of the Sn/MCND composite could be attributed to its<br />low-density feature caused by dendritic structure of MCND, which has sizable<br />space for the large volume changes during lithium alloying and dealloying.<br /><br />　　　Highly dispersed Pt nanoparticles (Ca. 3 nm) in pores of MCND were also<br />easily prepared through the sonochemical process of a solution of<br />H<small>2</small>[PtCl<small>6</small>].(H<small>2</small>O)<small>6</small> with MCND. This Pt/MCND composite can be used as an<br />electrode of the direct methanol fuel cell (DMFC) for electrochemical oxidation<br />of methanol fuel. We also prepared Pt/AC (AC : high grade activated carbon,<br />Kuraray YP-17) composites for comparison of electrochemical performance.<br />These Pt/MCND and Pt/AC composites were analysed by TEM observation,<br />X-ray diffraction (XRD) and Thermo Gravimetric Analysis (TGA). These<br />structural analyses show that the average size and quantity of Pt particles on the<br />surface of carbon matrix are very similar to each other. The electrochemical active<br />surface areas and methanol electro-oxidation properties of these catalysts were<br />investigated by cyclic voltammetry. As a result, the Pt/MCND composites<br />indicated higher electrochemical activities than that of Pt/AC composites. The<br />electrochemically active surface area is estimated from the CV curve of the<br />Pt/MCND electrode in 0.5 mol/L H<small>2</small>SO<small>4</small> solution to be 62.1 m<small>2</small>g. It is 1.3 times as<br />large as that of the Pt/AC electrode. The excellent performance of the Pt/MCND<br />composite could be attributed to the dendritic structure and the graphitic structure<br />of MCND, which has sizable space for the high fluidity of the solvent and gases<br />for efficient catalytic reaction.","subitem_description_type":"Other"}]},"item_1_description_18":{"attribute_name":"フォーマット","attribute_value_mlt":[{"subitem_description":"application/pdf","subitem_description_type":"Other"}]},"item_1_description_7":{"attribute_name":"学位記番号","attribute_value_mlt":[{"subitem_description":"総研大甲第1315号","subitem_description_type":"Other"}]},"item_1_select_14":{"attribute_name":"所蔵","attribute_value_mlt":[{"subitem_select_item":"有"}]},"item_1_select_8":{"attribute_name":"研究科","attribute_value_mlt":[{"subitem_select_item":"物理科学研究科"}]},"item_1_select_9":{"attribute_name":"専攻","attribute_value_mlt":[{"subitem_select_item":"07 構造分子科学専攻"}]},"item_1_text_10":{"attribute_name":"学位授与年度","attribute_value_mlt":[{"subitem_text_value":"2009"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"NUMAO, Shigenori","creatorNameLang":"en"}],"nameIdentifiers":[{}]}]},"item_files":{"attribute_name":"ファイル情報","attribute_type":"file","attribute_value_mlt":[{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2016-02-17"}],"displaytype":"simple","filename":"甲1315_要旨.pdf","filesize":[{"value":"377.3 kB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"要旨・審査要旨","url":"https://ir.soken.ac.jp/record/1653/files/甲1315_要旨.pdf"},"version_id":"512e0c30-7b5b-483f-ba35-1e51a64335cd"},{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2016-02-17"}],"displaytype":"simple","filename":"甲1315_本文.pdf","filesize":[{"value":"15.8 MB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"本文","url":"https://ir.soken.ac.jp/record/1653/files/甲1315_本文.pdf"},"version_id":"f296373c-14b3-4d0a-a4af-4c91ac823292"}]},"item_language":{"attribute_name":"言語","attribute_value_mlt":[{"subitem_language":"eng"}]},"item_resource_type":{"attribute_name":"資源タイプ","attribute_value_mlt":[{"resourcetype":"thesis","resourceuri":"http://purl.org/coar/resource_type/c_46ec"}]},"item_title":"Synthesis and Electrochemical Studies of Mesoporous Carbon Nano-Dendrites","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"Synthesis and Electrochemical Studies of Mesoporous Carbon Nano-Dendrites"},{"subitem_title":"Synthesis and Electrochemical Studies of Mesoporous Carbon Nano-Dendrites","subitem_title_language":"en"}]},"item_type_id":"1","owner":"21","path":["9"],"pubdate":{"attribute_name":"公開日","attribute_value":"2011-01-14"},"publish_date":"2011-01-14","publish_status":"0","recid":"1653","relation_version_is_last":true,"title":["Synthesis and Electrochemical Studies of Mesoporous Carbon Nano-Dendrites"],"weko_creator_id":"21","weko_shared_id":-1},"updated":"2023-06-20T15:57:42.406101+00:00"}