The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Jun-ichi Ozaki - One of the best experts on this subject based on the ideXlab platform.
-
Development of Carbon Alloy catalysts for a polymer electrolyte fuel cell
Carbon, 2015Co-Authors: Jun-ichi Ozaki, Yasuo ImashiroAbstract:Using hydrogen as an energy source is the most promising option to construct a society with low Carbon dioxide emission. We are dreaming to establish such a world by using Carbon materials to produce, store and use hydrogen. The present paper provides an explanation of the Carbon Alloy cathode catalysts for polymer electrolyte fuel cells, which we have discovered and nurtured to the level of platinum catalysts. The paper explains the necessity of developing non-platinum cathode catalysts and our ideas for Carbon Alloy cathode catalysts, to meet the demand. It then gives our research results on the active sites for oxygen reduction reaction (ORR) of the Carbon Alloy catalysts by comparing them with results from other researchers on non-platinum cathode catalysts. The paper concludes that the ORR active sites of our catalysts are disordered Carbon structures formed on the Carbon Alloy catalysts. Lastly, the paper describes our efforts to improve the catalytic activity, where our latest Carbon Alloy catalysts with the highest cell performance are presented. [TANSO 2014 (No. 265) 204–212.]
-
Effects of graphite oxide additions on the oxygen reduction reaction activity of a Carbon Alloy catalyst for a polymer electrolyte fuel cell cathode
Carbon, 2015Co-Authors: Takuya Maie, Saki Tsuboi, Jun-ichi OzakiAbstract:The effects of graphite oxide (GO) additions on the oxygen reduction reaction (ORR) activity of Carbon Alloy catalysts were examined in order to develop high performance cathode catalysts for polymer electrolyte fuel cell. Different amounts of GO were mixed with a Carbon Alloy precursor consisting of phenolic resin and phthalocyanine iron, followed by Carbonization at 800 °C. Thermogravimetry revealed that the GO addition changed the Carbonization behavior of the precursor. The formation of a nanoshell structure was observed under TEM for the Carbons derived from precursors containing less than 50% GO. The ORR activities of the obtained Carbons in 0.5 M H 2 SO 4 varied with the GO content showing a maximum at 40% GO. A similar trend was obtained for the relation between the N/C atomic ratio determined by XPS and the GO content; the contribution of edge nitrogen species such as pyrrole/pyridone and pyridine types to the ORR activity was suggested. The results indicate that the GO addition to the Carbon Alloy precursors improved the ORR activity, and that it was caused by the introduction of edge nitrogen species. [TANSO 2014 (No. 265) 159–164.]
-
preparation of Carbon Alloy catalysts for polymer electrolyte fuel cells from nitrogen containing rigid rod polymers
Journal of Power Sources, 2010Co-Authors: Masayuki Chokai, Masataka Taniguchi, Shogo Moriya, Katsuyuki Matsubayashi, Tsuyoshi Shinoda, Yuta Nabae, Shigeki Kuroki, Teruaki Hayakawa, Masaaki Kakimoto, Jun-ichi OzakiAbstract:Abstract ‘Carbon Alloy Catalysts’ (CAC), non-precious metal catalysts for the oxygen reduction reaction (ORR), were prepared from various kinds of nitrogen-containing rigid-rod aromatic polymers, polyimides, polyamides and azoles, by Carbonization at 900 °C under nitrogen flow. The catalytic activity for ORR was evaluated by the onset potential, which was taken at a current density of −2 μA cm −2 . Carbonized polymers having high nitrogen content showed higher onset potential. In particular, CACs derived from azole (Az5) had an onset potential of 0.8 V, despite being was prepared without any metals.
-
x ray absorption analysis of nitrogen contribution to oxygen reduction reaction in Carbon Alloy cathode catalysts for polymer electrolyte fuel cells
Journal of Power Sources, 2009Co-Authors: Hideharu Niwa, Jun-ichi Ozaki, Koji Horiba, Yoshihisa Harada, Masaharu Oshima, Takashi Ikeda, Kiyoyuki Terakura, Seizo MiyataAbstract:The electronic structure of nitrogen introduced into various Carbon-based cathode catalysts for the polymer electrolyte fuel cell (PEFC) is investigated using X-ray absorption spectroscopy (XAS). The profile of π* peaks at the pre-edge of N 1s XAS spectra is used to determine the chemical state of nitrogen, which can be an indicator of oxygen reduction reaction (ORR) activity. It is found that catalysts with a relatively larger amount of graphite-like nitrogen exhibit a higher ORR activity than those with a relatively larger amount of pyridine-like nitrogen. We propose that effective doping with graphite-like nitrogen is a practical guideline for the synthesis of active Carbon Alloy catalysts.
-
Carbon Alloy catalysts active sites for oxygen reduction reaction
Journal of Physical Chemistry C, 2008Co-Authors: Takashi Ikeda, Masaharu Oshima, Kiyoyuki Terakura, Mauro Boero, Shengfeng Huang, Jun-ichi OzakiAbstract:Nitrogen-doped Carbon-based catalysts are attracting increased interest as potential Pt-free electrode catalysts for polymer electrolyte fuel cells. In this computational study, we inspect possible oxygen adsorption and reduction processes on various models for the exposed edges of these catalysts. The dynamics of an O2 molecule solvated in water, which mimicks the cathode environment, shows that O2 adsorption depends on the morphology and the atomic structure of the system. We show that Carbon Alloys with N dopants at specific sites can exhibit metal-free catalytic activity.
Kiyoyuki Terakura - One of the best experts on this subject based on the ideXlab platform.
-
active sites and mechanisms for oxygen reduction reaction on nitrogen doped Carbon Alloy catalysts stone wales defect and curvature effect
Journal of the American Chemical Society, 2014Co-Authors: Guoliang Chai, Takashi Ikeda, Kiyoyuki TerakuraAbstract:Carbon Alloy catalysts (CACs) are promising oxygen reduction reaction (ORR) catalysts to substitute platinum. However, despite extensive studies on CACs, the reaction sites and mechanisms for ORR are still in controversy. Herein, we present rather general consideration on possible ORR mechanisms for various structures in nitrogen doped CACs based on the first-principles calculations. Our study indicates that only a particular structure of a nitrogen pair doped Stone–Wales defect provides a good active site. The ORR activity of this structure can be tuned by the curvature around the active site, which makes its limiting potential approaching the maximum limiting potential (0.80 V) in the volcano plot for the ORR activity of CACs. The calculated results can be compared with the recent experimental ones of the half-wave potential for CAC systems that range from 0.60 to 0.80 V in the reversible-hydrogen-electrode (RHE) scale.
-
x ray absorption analysis of nitrogen contribution to oxygen reduction reaction in Carbon Alloy cathode catalysts for polymer electrolyte fuel cells
Journal of Power Sources, 2009Co-Authors: Hideharu Niwa, Jun-ichi Ozaki, Koji Horiba, Yoshihisa Harada, Masaharu Oshima, Takashi Ikeda, Kiyoyuki Terakura, Seizo MiyataAbstract:The electronic structure of nitrogen introduced into various Carbon-based cathode catalysts for the polymer electrolyte fuel cell (PEFC) is investigated using X-ray absorption spectroscopy (XAS). The profile of π* peaks at the pre-edge of N 1s XAS spectra is used to determine the chemical state of nitrogen, which can be an indicator of oxygen reduction reaction (ORR) activity. It is found that catalysts with a relatively larger amount of graphite-like nitrogen exhibit a higher ORR activity than those with a relatively larger amount of pyridine-like nitrogen. We propose that effective doping with graphite-like nitrogen is a practical guideline for the synthesis of active Carbon Alloy catalysts.
-
Carbon Alloy catalysts active sites for oxygen reduction reaction
Journal of Physical Chemistry C, 2008Co-Authors: Takashi Ikeda, Masaharu Oshima, Kiyoyuki Terakura, Mauro Boero, Shengfeng Huang, Jun-ichi OzakiAbstract:Nitrogen-doped Carbon-based catalysts are attracting increased interest as potential Pt-free electrode catalysts for polymer electrolyte fuel cells. In this computational study, we inspect possible oxygen adsorption and reduction processes on various models for the exposed edges of these catalysts. The dynamics of an O2 molecule solvated in water, which mimicks the cathode environment, shows that O2 adsorption depends on the morphology and the atomic structure of the system. We show that Carbon Alloys with N dopants at specific sites can exhibit metal-free catalytic activity.
Takashi Ikeda - One of the best experts on this subject based on the ideXlab platform.
-
active sites and mechanisms for oxygen reduction reaction on nitrogen doped Carbon Alloy catalysts stone wales defect and curvature effect
Journal of the American Chemical Society, 2014Co-Authors: Guoliang Chai, Takashi Ikeda, Kiyoyuki TerakuraAbstract:Carbon Alloy catalysts (CACs) are promising oxygen reduction reaction (ORR) catalysts to substitute platinum. However, despite extensive studies on CACs, the reaction sites and mechanisms for ORR are still in controversy. Herein, we present rather general consideration on possible ORR mechanisms for various structures in nitrogen doped CACs based on the first-principles calculations. Our study indicates that only a particular structure of a nitrogen pair doped Stone–Wales defect provides a good active site. The ORR activity of this structure can be tuned by the curvature around the active site, which makes its limiting potential approaching the maximum limiting potential (0.80 V) in the volcano plot for the ORR activity of CACs. The calculated results can be compared with the recent experimental ones of the half-wave potential for CAC systems that range from 0.60 to 0.80 V in the reversible-hydrogen-electrode (RHE) scale.
-
x ray absorption analysis of nitrogen contribution to oxygen reduction reaction in Carbon Alloy cathode catalysts for polymer electrolyte fuel cells
Journal of Power Sources, 2009Co-Authors: Hideharu Niwa, Jun-ichi Ozaki, Koji Horiba, Yoshihisa Harada, Masaharu Oshima, Takashi Ikeda, Kiyoyuki Terakura, Seizo MiyataAbstract:The electronic structure of nitrogen introduced into various Carbon-based cathode catalysts for the polymer electrolyte fuel cell (PEFC) is investigated using X-ray absorption spectroscopy (XAS). The profile of π* peaks at the pre-edge of N 1s XAS spectra is used to determine the chemical state of nitrogen, which can be an indicator of oxygen reduction reaction (ORR) activity. It is found that catalysts with a relatively larger amount of graphite-like nitrogen exhibit a higher ORR activity than those with a relatively larger amount of pyridine-like nitrogen. We propose that effective doping with graphite-like nitrogen is a practical guideline for the synthesis of active Carbon Alloy catalysts.
-
Carbon Alloy catalysts active sites for oxygen reduction reaction
Journal of Physical Chemistry C, 2008Co-Authors: Takashi Ikeda, Masaharu Oshima, Kiyoyuki Terakura, Mauro Boero, Shengfeng Huang, Jun-ichi OzakiAbstract:Nitrogen-doped Carbon-based catalysts are attracting increased interest as potential Pt-free electrode catalysts for polymer electrolyte fuel cells. In this computational study, we inspect possible oxygen adsorption and reduction processes on various models for the exposed edges of these catalysts. The dynamics of an O2 molecule solvated in water, which mimicks the cathode environment, shows that O2 adsorption depends on the morphology and the atomic structure of the system. We show that Carbon Alloys with N dopants at specific sites can exhibit metal-free catalytic activity.
Shigehiko Tateno - One of the best experts on this subject based on the ideXlab platform.
-
Carbon depleted outer core revealed by sound velocity measurements of liquid iron Carbon Alloy
Nature Communications, 2015Co-Authors: Yoichi Nakajima, Saori Imada, Kei Hirose, Tetsuya Komabayashi, Haruka Ozawa, Shigehiko TatenoAbstract:The relative abundance of light elements in the Earth’s core has long been controversial. Recently, the presence of Carbon in the core has been emphasized, because the density and sound velocities of the inner core may be consistent with solid Fe7C3. Here we report the longitudinal wave velocity of liquid Fe84C16 up to 70 GPa based on inelastic X-ray scattering measurements. We find the velocity to be substantially slower than that of solid iron and Fe3C and to be faster than that of liquid iron. The thermodynamic equation of state for liquid Fe84C16 is also obtained from the velocity data combined with previous density measurements at 1 bar. The longitudinal velocity of the outer core, about 4% faster than that of liquid iron, is consistent with the presence of 4–5 at.% Carbon. However, that amount of Carbon is too small to account for the outer core density deficit, suggesting that Carbon cannot be a predominant light element in the core. The composition of the Earth's core, particularly the light elements present, is not well constrained. Here, the authors report sound velocities of liquid iron-Carbon Alloy as measured at very high pressures using inelastic X-ray scattering and suggest that Carbon cannot be predominant in the outer core.
Sabine Szunerits - One of the best experts on this subject based on the ideXlab platform.
-
surface plasmon resonance on gold and silver films coated with thin layers of amorphous silicon Carbon Alloys
Langmuir, 2010Co-Authors: Larbi Touahir, Rabah Boukherroub, Jean-noël Chazalviel, Joanna Niedziolkajonsson, E Galopin, Anne Chantal Gougetlaemmel, I Solomon, Mikhail Petukhov, F Ozanam, Sabine SzuneritsAbstract:The paper reports on a novel surface plasmon resonance (SPR) substrate architecture based on the coating of a gold (Au) or silver (Ag) substrate with 5 nm thin amorphous silicon−Carbon Alloy films. Ag/a-Si1−xCx:H and Au/a-Si1−xCx:H multilayers are found to provide a significant advantage in terms of sensitivity over both Ag and Au for SPR refractive index sensing. The possibility for the subsequent linking of stable organic monolayers through Si−C bonds is demonstrated. In a proof-of-principle experiment that this structure can be used for real-time biosensing experiments, amine terminated biotin was covalently linked to the acid-terminated SPR surface and the specific streptavidin−biotin interaction recorded.
-
Amorphous silicon-Carbon Alloys for efficient localized surface plasmon resonance sensing.
Biosensors and Bioelectronics, 2009Co-Authors: Elisabeth Galopin, Larbi Touahir, Joanna Niedziółka-jönsson, Rabah Boukherroub, Anne Chantal Gouget-laemmel, Jean-noël Chazalviel, François Ozanam, Sabine SzuneritsAbstract:This paper describes a novel platform for preparing localized surface plasmon resonance (LSPR) sensing surfaces. It is based on the coating of gold nanostructures deposited on glass with an amorphous silicon-Carbon Alloy overcoating. The interest in coating the Au NSs with an amorphous silicon-Carbon Alloy resides in the possibility of incorporating carboxyl functions directly onto the surface via Si-C covalent bonds. This permits the use of hyrdosilylation reactions to modify the sensor surface. The use of this multilayer structure for the detection of hybridization events is discussed.