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Junji Nakamura

Bio: Junji Nakamura is an academic researcher from University of Tsukuba. The author has contributed to research in topics: Catalysis & Graphene. The author has an hindex of 49, co-authored 211 publications receiving 10863 citations. Previous affiliations of Junji Nakamura include University of Tokyo & Applied Science Private University.
Topics: Catalysis, Graphene, Carbon nanotube, Carbon, Formate


Papers
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Journal ArticleDOI
22 Jan 2016-Science
TL;DR: In this paper, the oxygen reduction reaction (ORR) active site was characterized by using newly designed graphite (highly oriented pyrolitic graphite) model catalysts with well-defined π conjugation and well-controlled doping of N species.
Abstract: Nitrogen (N)-doped carbon materials exhibit high electrocatalytic activity for the oxygen reduction reaction (ORR), which is essential for several renewable energy systems. However, the ORR active site (or sites) is unclear, which retards further developments of high-performance catalysts. Here, we characterized the ORR active site by using newly designed graphite (highly oriented pyrolitic graphite) model catalysts with well-defined π conjugation and well-controlled doping of N species. The ORR active site is created by pyridinic N. Carbon dioxide adsorption experiments indicated that pyridinic N also creates Lewis basic sites. The specific activities per pyridinic N in the HOPG model catalysts are comparable with those of N-doped graphene powder catalysts. Thus, the ORR active sites in N-doped carbon materials are carbon atoms with Lewis basicity next to pyridinic N.

3,201 citations

Journal ArticleDOI
TL;DR: It is found that Pt particles below 0.5 nm in size are formed on GNS, which would acquire the specific electronic structures of Pt, modifying its catalytic activities.
Abstract: Graphene nanosheet (GNS) gives rise to an extraordinary modification to the properties of Pt cluster electrocatalysts supported on it. The Pt/GNS electrocatalyst revealed an unusually high activity for methanol oxidation reaction compared to Pt/carbon black catalyst. The Pt/GNS electrocatalyst also revealed quite a different characteristic for CO oxidation among the measured catalyst samples. It is found that Pt particles below 0.5 nm in size are formed on GNS, which would acquire the specific electronic structures of Pt, modifying its catalytic activities.

1,028 citations

Journal ArticleDOI
TL;DR: Based on the increased knowledge in controlling ORR performances, bottom-up preparation of N-doped carbon catalysts, using N-containing conjugative molecules as the assemblies of the catalysts is promising.
Abstract: The oxygen reduction reaction (ORR) is a core reaction for electrochemical energy technologies such as fuel cells and metal-air batteries. ORR catalysts have been limited to platinum, which meets the requirements of high activity and durability. Over the last few decades, a variety of materials have been tested as non-Pt catalysts, from metal-organic complex molecules to metal-free catalysts. In particular, nitrogen-doped graphitic carbon materials, including N-doped graphene and N-doped carbon nanotubes, have been extensively studied. However, due to the lack of understanding of the reaction mechanism and conflicting knowledge of the catalytic active sites, carbon-based catalysts are still under the development stage of achieving a performance similar to Pt-based catalysts. In addition to the catalytic viewpoint, designing mass transport pathways is required for O2 . Recently, the importance of pyridinic N for the creation of active sites for ORR and the requirement of hydrophobicity near the active sites have been reported. Based on the increased knowledge in controlling ORR performances, bottom-up preparation of N-doped carbon catalysts, using N-containing conjugative molecules as the assemblies of the catalysts, is promising. Here, the recent understanding of the active sites and the mechanism of ORRs on N-doped carbon catalysts are reviewed.

407 citations

Journal ArticleDOI
TL;DR: The 12 wt% Pt-deposited carbon nanotube electrode gives 10% higher voltages and reduces the Pt usage by 60% in polymer electrolyte fuel cells with hydrogen and oxygen.

269 citations

Journal ArticleDOI
TL;DR: In this article, the structural sensitivity of the water-gas shift (WGS) reaction (CO + H2O → H2+ CO2) over metallic copper is addressed by comparing its kinetics over the atomically clean Cu(110) surface with prior results for Cu(111).
Abstract: The structural sensitivity of the water-gas shift (WGS) reaction (CO + H2O → H2+ CO2) over metallic copper is addressed here by comparing its kinetics over the atomically clean Cu(110) surface with prior results for Cu(111). The surfaces were prepared and characterized with UHV surface analysis (AES, LEED, XPS), then transferred to an attached microreactor for medium-pressure [10–1000 Torr (1 Torr = 101 325/760 Pa)] kinetic measurements and finally returned to UHV for post-reaction surface analysis. For both surfaces, the rate is nearly first-order in H2O pressure and zero-order in CO. Depending upon the temperature, Cu(110) is four- to ten-fold more active than the more densely packed Cu(111) surface. The apparent activation energy is also ca. 7 kcal mol–1(1 cal = 4.184 J) lower on Cu(110). This is attributed to a lower barrier for O—H bond cleavage in the rate-determining step: i.e. the dissociative adsorption of water. Strong evidence for a ‘surface redox’ mechanism involving oxygen adatoms is provided by comparing the known kinetics of reverse WGS with the rate of dissociative CO2 adsorption on Cu(110). A potential-energy diagram is presented which explains the known kinetics and energetics for the elementary steps as occurring in the forward or reverse direction, as well as the overall WGS reaction on clean Cu(110). The influence of adsorbed Cs on the reaction kinetics is also presented, and compared to earlier results on Cs/Cu(111). In both cases, Cs strongly accelerates the reaction. In the case of Cu(110), the rate-determining step is even changed. The reaction mechanism involves Cs · CO3, a and Cs · Oa.

255 citations


Cited by
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Journal ArticleDOI
TL;DR: An overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.
Abstract: There is intense interest in graphene in fields such as physics, chemistry, and materials science, among others. Interest in graphene's exceptional physical properties, chemical tunability, and potential for applications has generated thousands of publications and an accelerating pace of research, making review of such research timely. Here is an overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.

8,919 citations

Journal ArticleDOI
11 Oct 2012-Nature
TL;DR: This work reviews recent progress in graphene research and in the development of production methods, and critically analyse the feasibility of various graphene applications.
Abstract: Recent years have witnessed many breakthroughs in research on graphene (the first two-dimensional atomic crystal) as well as a significant advance in the mass production of this material. This one-atom-thick fabric of carbon uniquely combines extreme mechanical strength, exceptionally high electronic and thermal conductivities, impermeability to gases, as well as many other supreme properties, all of which make it highly attractive for numerous applications. Here we review recent progress in graphene research and in the development of production methods, and critically analyse the feasibility of various graphene applications.

7,987 citations

Journal ArticleDOI
01 Feb 2013-Science
TL;DR: Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.
Abstract: Worldwide commercial interest in carbon nanotubes (CNTs) is reflected in a production capacity that presently exceeds several thousand tons per year. Currently, bulk CNT powders are incorporated in diverse commercial products ranging from rechargeable batteries, automotive parts, and sporting goods to boat hulls and water filters. Advances in CNT synthesis, purification, and chemical modification are enabling integration of CNTs in thin-film electronics and large-area coatings. Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.

4,596 citations

Journal ArticleDOI
TL;DR: The unique advances on ultrathin 2D nanomaterials are introduced, followed by the description of their composition and crystal structures, and the assortments of their synthetic methods are summarized.
Abstract: Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

3,628 citations

Journal ArticleDOI
TL;DR: Approaches, Derivatives and Applications Vasilios Georgakilas,† Michal Otyepka,‡ Athanasios B. Bourlinos,† Vimlesh Chandra, Namdong Kim, K. Kim,§,⊥ Radek Zboril,*,‡ and Kwang S. Kim.
Abstract: Approaches, Derivatives and Applications Vasilios Georgakilas,† Michal Otyepka,‡ Athanasios B. Bourlinos,‡ Vimlesh Chandra, Namdong Kim, K. Christian Kemp, Pavel Hobza,‡,§,⊥ Radek Zboril,*,‡ and Kwang S. Kim* †Institute of Materials Science, NCSR “Demokritos”, Ag. Paraskevi Attikis, 15310 Athens, Greece ‡Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University Olomouc, 17. listopadu 12, 771 46 Olomouc, Czech Republic Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, San 31, Hyojadong, Namgu, Pohang 790-784, Korea Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo naḿ. 2, 166 10 Prague 6, Czech Republic

3,460 citations