Shinobu Sekine - Academia.edu (original) (raw)
Papers by Shinobu Sekine
Meeting abstracts/Meeting abstracts (Electrochemical Society. CD-ROM), Dec 22, 2023
ECS Meeting Abstracts, 2017
Polymer electrolyte fuel cells (PEFCs) are already put into the market as the power source for hy... more Polymer electrolyte fuel cells (PEFCs) are already put into the market as the power source for hydrogen fuel cell vehicles (FCVs), but further technical advancement is necessary to achieve both higher cell performance and lower cost required for wider distribution. Regarding the latter requirement, a precious metal-free cathode is an attractive alternative and various candidates have been examined such as nonprecious metal-containing or metal-free carbon-based catalysts, metal oxides, oxynitrides, and metal chalcogenides [1]. In spite of extensive researches, however, the cell performances and stabilities using those materials are still significant lower than conventional Pt-based cells. Another approach for a precious metal-free cathode is to flow a catholyte containing oxidized-state redox mediator through porous carbon electrode. The system is similar to a redox flow battery, and the reduced-state mediator is oxidized with air in another compartment (we call this system as "...
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
ECS Meeting Abstracts, 2020
Polymer electrolyte fuel cell (PEFC) is one of the candidates to replace automotive power sources... more Polymer electrolyte fuel cell (PEFC) is one of the candidates to replace automotive power sources using fossil fuels. For this purpose, we need to overcome three major criteria: cost, performance, and durability. One of the important topics of PEFC durability is how to keep its catalyst activity for oxygen reduction reaction (ORR). The catalyst activity is product of the electrochemical surface area (ECSA) and activity per surface area. A central issue of catalyst durability is the loss of ECSA over time. This ECSA is approximately the same as the effective surface area of the catalyst. To maximize the ECSA, the radius of catalyst particles is in the order of nano meters. In this study we focus on the ECSA loss of PtCo alloy catalysts on carbon support. These alloy catalysts have much higher activity for ORR than traditionally used Pt1. Our model of ECSA loss combines the following two mechanism: (i) Co dissolution from the surface of the alloy catalyst, (ii) Pt dissolution from smal...
PROBLEM TO BE SOLVED: To provide a solid electrolyte membrane having low interfacial resistance b... more PROBLEM TO BE SOLVED: To provide a solid electrolyte membrane having low interfacial resistance between the other members constituting a fuel cell and itself, and an excellent power generating property, and to provide a membrane-electrode assembly using the same. SOLUTION: The solid electrolyte membrane has a reinforcing member at its inside, and the difference between the SP value of the reinforcing member and the SP value of a solid electrolyte membrane main body is equal to or smaller than the value shown in expression 1. COPYRIGHT: (C)2006,JPO&NCIPI
Journal of Physics: Condensed Matter, 2020
We analyzed the electronic and structural properties of an α-Keggin type molybdenum-based polyoxo... more We analyzed the electronic and structural properties of an α-Keggin type molybdenum-based polyoxometalate (POM) [[PMo12O40]3-] and its capacity for reduction reaction via H adsorption using Ab Initio calculations based on density functional theory (DFT). We also determined the change in the electronic properties brought about by vanadium substitutional doping, and its effect on the capacity of POM to adsorb H atom. We found that the optimal substitutional doping of 4 vanadium per one unit of POM is adequate to maintain its structural stability. Furthermore, increasing dopant concentration changes charge redistribution such that it induces charge transfer to an initially less active sites for H adsorption on pristine POM. This may increase the possibility of creating active sites from an initially inert H adsorption sites and allows for a higher density of H adsorption. This phenomenon could be relevant for chemical reactions that initially requires high number of pre-adsorbed H atoms.
ECS Transactions, 2018
One of the fundamental hurdles for further commercialization of fuel cell vehicles (FCV) using po... more One of the fundamental hurdles for further commercialization of fuel cell vehicles (FCV) using polymer electrolyte membrane fuel cells (PEMFC) is their upper limitation of operating temperature. Operating temperature of current PEMFC is much lower than that of internal-combustion engines and it makes FCV require huge radiators for high power operation. Raising operating temperature is beneficial for downsizing and cost reduction for FCV system because it downsizes not only cooling system but also PEMFC stack. One of the root causes of this limitation is the decrease in proton conductivity of the membrane during long term operation. In order to avoid the decrease in proton conductivity, reducing the contamination of metal cations in the membrane is an effective way. Metal cations, which contaminate into the membrane during operation, reduce the proton conductivity of the membrane due to decrease in the proton path in the membrane. Proton conductivity loss by contamination of metal cations is critical for the high temperature performance. In order to reduce cation contamination into the membrane, it is necessary to understand its mechanism. An in-situ measurement for the amount of metal cations should be helpful to understand the phenomena. For this reason, we propose an in-situ quantitative measurement for cation contamination ratio in PEMFC. Electrochemical impedance spectroscopy (EIS) was adapted to the measurement because cation transport inside the membrane was expected to be detectable with EIS. Experimental results showed that EIS spectrum under a certain condition reflects metal cation contamination ratio strongly, which was proposed to be an indicator of cation contamination ratio. The mechanism of EIS spectrum change is explained theoretically by a numerical simulation using a simple model of cation and water transport. Detail of the measurement will be shown in the conference. Therefore this EIS measurement is proposed for the analysis of metal cation contamination mechanisms in PEMFC. Further study will elucidate the impact of catalyst layer, membrane and metal cation species against the EIS spectrum.
Organometallics, 2017
Dicationic thiolate-bridged diruthenium complexes bearing sterically bulky alkane substituents on... more Dicationic thiolate-bridged diruthenium complexes bearing sterically bulky alkane substituents on the thiolate ligands such as [Cp*Ru(μ-S i Pr) 2 Ru(OH 2)Cp*](OTf) 2 have been found to work as effective catalysts toward oxidation of molecular dihydrogen into protons and electrons in protic solvents such as water and methanol. DFT calculations indicate that the sterically bulky alkane substituent in the complex plays an important role in facilitating the reaction step of the coordination of molecular dihydrogen.
The Proceedings of the National Symposium on Power and Energy Systems, 2011
The new power control algorithm to improve freeze startability of the TOYOTA FCH 塾 adv is reviewe... more The new power control algorithm to improve freeze startability of the TOYOTA FCH 塾 adv is reviewed in this papeL lhis new algorithrn is using the 血 herent eapacitance characteristics of the fUel cell in order to adjust the output power response of the fUel cell to the target power of 出 e vehicles ． The algorithm is combined with fUel cell operation method to warm rapidly ， called Rapid Wann − Up Operation． 』 is operation is based on ： concentration overvoltage increase and Gonversion eMciency decrease by limiting oxygen or hydrogen supply ． As a result ， the FCHV − adv has been capable of starting at a temperature of − 30 ℃ ．
Molecular Crystals and Liquid Crystals, 2014
The dynamics and stochastic aspect of the vortices that occur in a smectic-A liquid crystal close... more The dynamics and stochastic aspect of the vortices that occur in a smectic-A liquid crystal close to its nematic-smectic A transition point is investigated. Using the analogy between our target system and the superfluid system, we discuss following two topics: The first topic is the formulation of the equation of motion of the vortex center, and the other one is the analysis of the random behavior of the vortices.
Advances in Natural Sciences: Nanoscience and Nanotechnology, 2013
We propose a simple mechanical model describing viscoelasticity, cavitation growth and crack prop... more We propose a simple mechanical model describing viscoelasticity, cavitation growth and crack propagation during the debonding process in pressure-sensitive adhesives (PSAs). Typical materials of PSA are made of block copolymers and they are usually very soft and highly dissipative, and can stick on a variety of surfaces under low pressure in short time. The debonding process of PSA is governed by very complicated dynamics, for example, deformation of the adhesive layer, cavity expansion and coalescence. Our model is a modified version of that proposed by Yamaguchi et al (2006 Eur. Phys. J. E 20 7). We extended his simple model to be applicable to the final rupture process and applied the model to some cases, where we studied the effects of the change of PSA layer's thickness, separation speed and friction coefficient. Our results are qualitatively in good agreement with the experimental data.
SAE Technical Paper Series, 2011
ECS Transactions, 2011
The Toyota FCHV-adv that was released in 2008 has a cruising range in actual driving conditions o... more The Toyota FCHV-adv that was released in 2008 has a cruising range in actual driving conditions of more than 500 km and can be started in temperatures as low as -30°, thereby overcoming two of the major obstacles to the practical adoption of FCVs. Toyota is continuing to resolve technical issues to popularize FCVs. For example, Toyota aims to reduce the cost to about 1/20 by further development work. In addition to improving commercial appeal, the widespread adoption of FCVs depends on the establishment of basic hydrogen infrastructure. Toward 2015, Car manufactures including Toyota are continuing to cooperate with governments and energy businesses to establish infrastructure and make the necessary modifications to laws and regulations. This article summarizes the technical progress for FCVs
Transactions of Society of Automotive Engineers of Japan, 2019
Meeting abstracts/Meeting abstracts (Electrochemical Society. CD-ROM), Dec 22, 2023
ECS Meeting Abstracts, 2017
Polymer electrolyte fuel cells (PEFCs) are already put into the market as the power source for hy... more Polymer electrolyte fuel cells (PEFCs) are already put into the market as the power source for hydrogen fuel cell vehicles (FCVs), but further technical advancement is necessary to achieve both higher cell performance and lower cost required for wider distribution. Regarding the latter requirement, a precious metal-free cathode is an attractive alternative and various candidates have been examined such as nonprecious metal-containing or metal-free carbon-based catalysts, metal oxides, oxynitrides, and metal chalcogenides [1]. In spite of extensive researches, however, the cell performances and stabilities using those materials are still significant lower than conventional Pt-based cells. Another approach for a precious metal-free cathode is to flow a catholyte containing oxidized-state redox mediator through porous carbon electrode. The system is similar to a redox flow battery, and the reduced-state mediator is oxidized with air in another compartment (we call this system as "...
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
ECS Meeting Abstracts, 2020
Polymer electrolyte fuel cell (PEFC) is one of the candidates to replace automotive power sources... more Polymer electrolyte fuel cell (PEFC) is one of the candidates to replace automotive power sources using fossil fuels. For this purpose, we need to overcome three major criteria: cost, performance, and durability. One of the important topics of PEFC durability is how to keep its catalyst activity for oxygen reduction reaction (ORR). The catalyst activity is product of the electrochemical surface area (ECSA) and activity per surface area. A central issue of catalyst durability is the loss of ECSA over time. This ECSA is approximately the same as the effective surface area of the catalyst. To maximize the ECSA, the radius of catalyst particles is in the order of nano meters. In this study we focus on the ECSA loss of PtCo alloy catalysts on carbon support. These alloy catalysts have much higher activity for ORR than traditionally used Pt1. Our model of ECSA loss combines the following two mechanism: (i) Co dissolution from the surface of the alloy catalyst, (ii) Pt dissolution from smal...
PROBLEM TO BE SOLVED: To provide a solid electrolyte membrane having low interfacial resistance b... more PROBLEM TO BE SOLVED: To provide a solid electrolyte membrane having low interfacial resistance between the other members constituting a fuel cell and itself, and an excellent power generating property, and to provide a membrane-electrode assembly using the same. SOLUTION: The solid electrolyte membrane has a reinforcing member at its inside, and the difference between the SP value of the reinforcing member and the SP value of a solid electrolyte membrane main body is equal to or smaller than the value shown in expression 1. COPYRIGHT: (C)2006,JPO&NCIPI
Journal of Physics: Condensed Matter, 2020
We analyzed the electronic and structural properties of an α-Keggin type molybdenum-based polyoxo... more We analyzed the electronic and structural properties of an α-Keggin type molybdenum-based polyoxometalate (POM) [[PMo12O40]3-] and its capacity for reduction reaction via H adsorption using Ab Initio calculations based on density functional theory (DFT). We also determined the change in the electronic properties brought about by vanadium substitutional doping, and its effect on the capacity of POM to adsorb H atom. We found that the optimal substitutional doping of 4 vanadium per one unit of POM is adequate to maintain its structural stability. Furthermore, increasing dopant concentration changes charge redistribution such that it induces charge transfer to an initially less active sites for H adsorption on pristine POM. This may increase the possibility of creating active sites from an initially inert H adsorption sites and allows for a higher density of H adsorption. This phenomenon could be relevant for chemical reactions that initially requires high number of pre-adsorbed H atoms.
ECS Transactions, 2018
One of the fundamental hurdles for further commercialization of fuel cell vehicles (FCV) using po... more One of the fundamental hurdles for further commercialization of fuel cell vehicles (FCV) using polymer electrolyte membrane fuel cells (PEMFC) is their upper limitation of operating temperature. Operating temperature of current PEMFC is much lower than that of internal-combustion engines and it makes FCV require huge radiators for high power operation. Raising operating temperature is beneficial for downsizing and cost reduction for FCV system because it downsizes not only cooling system but also PEMFC stack. One of the root causes of this limitation is the decrease in proton conductivity of the membrane during long term operation. In order to avoid the decrease in proton conductivity, reducing the contamination of metal cations in the membrane is an effective way. Metal cations, which contaminate into the membrane during operation, reduce the proton conductivity of the membrane due to decrease in the proton path in the membrane. Proton conductivity loss by contamination of metal cations is critical for the high temperature performance. In order to reduce cation contamination into the membrane, it is necessary to understand its mechanism. An in-situ measurement for the amount of metal cations should be helpful to understand the phenomena. For this reason, we propose an in-situ quantitative measurement for cation contamination ratio in PEMFC. Electrochemical impedance spectroscopy (EIS) was adapted to the measurement because cation transport inside the membrane was expected to be detectable with EIS. Experimental results showed that EIS spectrum under a certain condition reflects metal cation contamination ratio strongly, which was proposed to be an indicator of cation contamination ratio. The mechanism of EIS spectrum change is explained theoretically by a numerical simulation using a simple model of cation and water transport. Detail of the measurement will be shown in the conference. Therefore this EIS measurement is proposed for the analysis of metal cation contamination mechanisms in PEMFC. Further study will elucidate the impact of catalyst layer, membrane and metal cation species against the EIS spectrum.
Organometallics, 2017
Dicationic thiolate-bridged diruthenium complexes bearing sterically bulky alkane substituents on... more Dicationic thiolate-bridged diruthenium complexes bearing sterically bulky alkane substituents on the thiolate ligands such as [Cp*Ru(μ-S i Pr) 2 Ru(OH 2)Cp*](OTf) 2 have been found to work as effective catalysts toward oxidation of molecular dihydrogen into protons and electrons in protic solvents such as water and methanol. DFT calculations indicate that the sterically bulky alkane substituent in the complex plays an important role in facilitating the reaction step of the coordination of molecular dihydrogen.
The Proceedings of the National Symposium on Power and Energy Systems, 2011
The new power control algorithm to improve freeze startability of the TOYOTA FCH 塾 adv is reviewe... more The new power control algorithm to improve freeze startability of the TOYOTA FCH 塾 adv is reviewed in this papeL lhis new algorithrn is using the 血 herent eapacitance characteristics of the fUel cell in order to adjust the output power response of the fUel cell to the target power of 出 e vehicles ． The algorithm is combined with fUel cell operation method to warm rapidly ， called Rapid Wann − Up Operation． 』 is operation is based on ： concentration overvoltage increase and Gonversion eMciency decrease by limiting oxygen or hydrogen supply ． As a result ， the FCHV − adv has been capable of starting at a temperature of − 30 ℃ ．
Molecular Crystals and Liquid Crystals, 2014
The dynamics and stochastic aspect of the vortices that occur in a smectic-A liquid crystal close... more The dynamics and stochastic aspect of the vortices that occur in a smectic-A liquid crystal close to its nematic-smectic A transition point is investigated. Using the analogy between our target system and the superfluid system, we discuss following two topics: The first topic is the formulation of the equation of motion of the vortex center, and the other one is the analysis of the random behavior of the vortices.
Advances in Natural Sciences: Nanoscience and Nanotechnology, 2013
We propose a simple mechanical model describing viscoelasticity, cavitation growth and crack prop... more We propose a simple mechanical model describing viscoelasticity, cavitation growth and crack propagation during the debonding process in pressure-sensitive adhesives (PSAs). Typical materials of PSA are made of block copolymers and they are usually very soft and highly dissipative, and can stick on a variety of surfaces under low pressure in short time. The debonding process of PSA is governed by very complicated dynamics, for example, deformation of the adhesive layer, cavity expansion and coalescence. Our model is a modified version of that proposed by Yamaguchi et al (2006 Eur. Phys. J. E 20 7). We extended his simple model to be applicable to the final rupture process and applied the model to some cases, where we studied the effects of the change of PSA layer's thickness, separation speed and friction coefficient. Our results are qualitatively in good agreement with the experimental data.
SAE Technical Paper Series, 2011
ECS Transactions, 2011
The Toyota FCHV-adv that was released in 2008 has a cruising range in actual driving conditions o... more The Toyota FCHV-adv that was released in 2008 has a cruising range in actual driving conditions of more than 500 km and can be started in temperatures as low as -30°, thereby overcoming two of the major obstacles to the practical adoption of FCVs. Toyota is continuing to resolve technical issues to popularize FCVs. For example, Toyota aims to reduce the cost to about 1/20 by further development work. In addition to improving commercial appeal, the widespread adoption of FCVs depends on the establishment of basic hydrogen infrastructure. Toward 2015, Car manufactures including Toyota are continuing to cooperate with governments and energy businesses to establish infrastructure and make the necessary modifications to laws and regulations. This article summarizes the technical progress for FCVs
Transactions of Society of Automotive Engineers of Japan, 2019