Faculty Profiles - NAKANISHI Kazuki

Papers - NAKANISHI Kazuki

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Nanostructured titanium phosphates prepared via hydrothermal reaction and their electrochemical Li- and Na-ion intercalation properties Reviewed

Zhu, Y., Hasegawa, G., Kanamori, K., Kiyomura, T., Kurata, H., Hayashi, K., Nakanishi, K.

Crystengcomm Vol. 19 ( 31 ) page： 4551 - 4560 2017.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

In this report, we demonstrate a facile and versatile methodology for synthesizing a series of titanium phosphates (TiPs) with various morphologies. The hydrothermal reactions of TiO2 in different concentrations of H3PO4 aq. yield 4 types of crystal structures with diverse shapes, such as nanoparticles, nanorods and nanosheets, which are assembled into a variety of flower-like morphologies. The dependence of the crystal phases and morphologies of TiPs on the synthesis conditions have been comprehensively investigated. This synthetic process can be further extended to other TiP derivatives incorporated with guest cations (e.g. NH4+ and Na+) simply by adding the corresponding phosphate salts to the starting composition, which leads to the morphological variation associated with the change of the crystal phase. The mechanism for the formation of the TiPs is discussed in terms of the stable Ti-based ion species relying on the pH value of the reaction solution. In addition, the correlation between the crystal structures and morphologies of TiPs and their electrochemical Li- and Na-ion storage behaviors are demonstrated as well, which discloses the different tendencies of morphological effects between the Li- and Na-ion systems.

DOI： 10.1039/c7ce01123g

Ultralow-Density, Transparent, Superamphiphobic Boehmite Nanofiber Aerogels and Their Alumina Derivatives (vol 27, pg 3, 2015) Reviewed Open Access

Gen D Hayase, Kazuya Nonomura, George Hasegawa, Kazuyoshi Kanamori, Kazuki Nakanishi

CHEMISTRY OF MATERIALS Vol. 29 ( 12 ) page： 5413 - 5413 2017.6

Fabrication of hydrophobic polymethylsilsesquioxane aerogels by a surfactant-free method using alkoxysilane with ionic group Reviewed Open Access

Hayase, Gen, Nagayama, Shuya, Nonomura, Kazuya, Kanamori, Kazuyoshi, Maeno, Ayaka, Kaji, Hironori, Nakanishi, Kazuki

Journal of Asian Ceramic Societies Vol. 5 ( 2 ) page： 104 - 108 2017.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier B.V.

Phase separation control is an important factor to prepare a porous monolith by an aqueous sol–gel reaction. Here, we report a surfactant-free synthesis method to obtain hydrophobic polymethylsilsesquioxane aerogels by copolymerizing a cationic-functionalized alkoxysilane N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride. The resultant materials have low-density, high visible-light transmittance, and high thermal insulating equivalent to those of prepared under the presence of surfactant.

DOI： 10.1016/j.jascer.2017.02.003

Functionalization of hierarchically porous silica monoliths with polyethyleneimine (PEI) for CO2 adsorption Reviewed

Guo, Xingzhong, Ding, Li, Kanamori, Kazuyoshi, Nakanishi, Kazuki, Yang, Hui

Microporous and Mesoporous Materials Vol. 245 page： 51 - 57 2017.6

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

A novel CO2 sorbent was prepared by modifying polyethyleneimine (PEI) on hierarchically porous silica (HPS) monoliths with well-defined macro-mesopores through wet impregnation method. HPS monoliths before and after functionalization were characterized by scanning electron microscopy (SEM), differential thermal analysis/thermogravimetry (DTA/TG), fourier transform infrared spectroscopy (FT-IR) and nitrogen adsorption/desorption analysis (BET), and the CO2 adsorption-regeneration properties of as synthesized sorbents were investigated by thermogravimetric analysis (TG). The effects of loaded PEI amount as well as adsorption temperature and CO2 partial pressure on the CO2 adsorption performance of the as-prepared sorbents were also studied. The results showed that the porous structure of HPS-PEI sorbents was preserved after functionalization, while the specific surface area and pore volume decreased with increasing amount of amines to some extent. The use of PEI had a remarkable improvement on the CO2 adsorption capacity. With the increasing amount of PEI loaded, the CO2 adsorption capacity improved significantly. The highest CO2 adsorption capacity of 2.44 mmol (g sorbent)-1 was obtained at 75 degrees C in the CO2 partial pressure of 100 kPa for the HPS loaded with 60 wt% PEI. Adsorption/desorption cycles indicated that the PEI-modified HPS sorbents had a good stability and regeneration. (C) 2017 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.micromeso.2017.02.076

Transparent Ethenylene-Bridged Polymethylsiloxane Aerogels: Mechanical Flexibility and Strength and Availability for Addition Reaction Reviewed

Shimizu, Taiyo, Kanamori, Kazuyoshi, Maeno, Ayaka, Kaji, Hironori, Doherty, Cara M., Nakanishi, Kazuki

Langmuir Vol. 33 ( 18 ) page： 4543 - 4550 2017.5

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Transparent, low-density ethenylene-bridged polymethylsiloxane [Ethe-BPMS, O-2/2(CH3)Si-CH=CH-Si(CH3)O-2/2] aerogels from 1,2-bis(methyldiethoxysilyl)ethene have successfully been synthesized via a sol-gel process. A two-step sol-gel process composed of hydrolysis under acidic conditions and polycondensation under basic conditions in a liquid surfactant produces a homogeneous pore structure based on cross-linked nanosized colloidal particles. Visible-light transmittance of the aerogels varies with the concentration of the base catalyst and reaches as high as 87% (at a wavelength of 550 nm for a 10 mm thick sample). Gelation and aging temperature strongly affect the deformation behavior of the resultant aerogels against uniaxial compression, and the obtained aerogels prepared at 80 C-circle show high elasticity after being unloaded. This highly resilient behavior is primarily derived from the rigidity of ethenylene groups, which is confirmed by a comparison with other aerogels with similar molecular structures, ethylene-bridged polymethylsiloxane and polymethylsilsesquioxane. Applicability of the addition reaction using a Diels-Alder reaction of benzocyclobutene has also been investigated, revealing that a successful addition takes place on the ethenylene linkings, which is verified using Raman and solid-state NMR spectroscopies. Insights into the effect of molecular structure on mechanical properties and the availability of surface functionalization provided in this study are important for realizing transparent aerogels with the desired functionality.

DOI： 10.1021/acs.langmuir.7b00434

Silicone-Based Organic-Inorganic Hybrid Aerogels and Xerogels. Reviewed

Shimizu, Taiyo, Kanamori, Kazuyoshi, Nakanishi, Kazuki

Chemistry (Weinheim an der Bergstrasse, Germany) Vol. 23 ( 22 ) page： 5176 - 5187 2017.4

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

Aerogels are attracting increasing attention due to their high thermal insulation ability as well as unique properties such as high porosity, surface area, and transparency. However, low mechanical strengths, originating from their unique porous structure, impede handling, formability, mass production, and extended applications. This minireview focuses on the strengthening of aerogels by several organic-inorganic hybridization strategies. In particular, successful strengthening methodologies, which employ organo-substituted alkoxysilanes as the single precursor for the sol-gel preparations, developed by the authors are highlighted. Moreover, improvements in compressive strength and elasticity lead to monolithic aerogel-like xerogels through ambient pressure drying. Correlations between structures in different length scales (e.g., molecular, network, and pore structure levels) and resultant mechanical properties are discussed for further understandings and better design toward mechanically improved aerogels/xerogels and their applications.

DOI： 10.1002/chem.201603680

Transparent polyvinylsilsesquioxane aerogels: investigations on synthetic parameters and surface modification Reviewed

Shimizu, Taiyo, Kanamori, Kazuyoshi, Nakanishi, Kazuki

Journal of Sol-Gel Science and Technology Vol. 82 ( 1 ) page： 2 - 14 2017.4

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

Systematic investigations on the effect of synthetic conditions onto the properties of polyvinylsilsesquioxane (CH2=CHSiO3/2) aerogels have been conducted. As previously reported, transparent polyvinylsilsesquioxane aerogels can be obtained by utilizing a liquid surfactant as a solvent and a two-step sol-gel reaction involving hydrolysis catalyzed by a strong acid and subsequent polycondensation by a strong base. In this study, effects of base catalyst, gelation and aging conditions, amount of surfactant and concentration of acid catalyst have been investigated. With the optimized synthetic condition, the value of light transmittance reaches as high as 70% (at the wavelength of 550 nm for a 10-mm thick sample). Applicability of addition reactions utilizing thiol-ene reactions and hydrosilylation has also been surveyed. Thiol-ene reactions are relatively effective and can modify surface hydrophobicity and mechanical properties of polyvinylsilsesquioxane aerogels. In the case of hydrosilylation, a partial addition of a hydrosilane compound onto the polyvinylsilsesquioxane gel surface can be observed. Addition reactions, in particular thiol-ene reactions, are found to be profitable for implementing chemical functionality on the transparent aerogels.

DOI： 10.1007/s10971-017-4339-6

Highly Flexible Hybrid Polymer Aerogels and Xerogels Based on Resorcinol-Formaldehyde with Enhanced Elastic Stiffness and Recoverability: Insights into the Origin of Their Mechanical Properties Reviewed

Hasegawa, George, Shimizu, Taiyo, Kanamori, Kazuyoshi, Maeno, Ayaka, Kaji, Hironori, Nakanishi, Kazuki

Chemistry of Materials Vol. 29 ( 5 ) page： 2122 - 2134 2017.3

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Flexible low-density materials, such as aerogels and polymer foams, have received increasing attention as energy absorbers and cushions that protect artificial products and human bodies. Microscopic geometry is a crucial factor determining their mechanical functions, i.e. strength and toughness (flexibility). However, it is a formidable challenge to combine these two properties because they are mutually elusive in general; stiff materials are brittle, while flexible ones are soft. Here, we demonstrate lightweight porous polymeric materials based on a common phenolic resin, resorcinol-formaldehyde (RF) gels, with salient combinatorial properties of high stiffness (up to 100 MPa) and good recoverable compressibility (against 80-90% strain), which can deliver remarkable energy absorption and dissipation performances repetitively. The detailed investigation reveals that the unique mechanical features originate from the synergetic effect of interdigitated hard and soft components in polymer matrices as well as exquisitely designed highly branched microstructures both generated through the spontaneous supramolecular self-assembly of the nonionic block copolymer (F127) and RF oligomer, which is essentially analogous to how natural organisms create biological structural materials, e.g. nacre and bone.

DOI： 10.1021/acs.chemmater.6b04706

Amine/Hydrido Bifunctional Nanoporous Silica with Small Metal Nanoparticles Made Onsite: Efficient Dehydrogenation Catalyst Reviewed

Zhu, Yang, Nakanishi, Takahiro, Kanamori, Kazuyoshi, Nakanishi, Kazuki, Ichii, Shun, Iwaida, Kohji, Masui, Yu, Kamei, Toshiyuki, Shimada, Toyoshi, Kumamoto, Akihito, Ikuhara, Yumi H., Jeon, Mina, Hasegawa, George, Tafu, Masamoto, Yoon, Chang Won, Asefa, Tewodros

Acs Applied Materials & Interfaces Vol. 9 ( 1 ) page： 36 - 41 2017.1

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Multifunctional catalysts are of great interest in catalysis because their multiple types of catalytic or functional groups can cooperatively promote catalytic transformations better than their constituents do individually. Herein we report a new synthetic route involving the surface functionalization of nanoporous silica with a rationally designed and synthesized dihydrosilane (3-aminopropylmethylsilane) that leads to the introduction of catalytically active grafted organoamine as well as single metal atoms and ultrasmall Pd or Ag-doped Pd nanoparticles via on-site reduction of metal ions. The resulting nanomaterials serve as highly effective bifunctional dehydrogenative catalysts for generation of H-2 from formic acid.

DOI： 10.1021/acsami.6b12972

Grafted Polymethylhydrosiloxane on Hierarchically Porous Silica Monoliths: A New Path to Monolith-Supported Palladium Nanoparticles for Continuous Flow Catalysis Applications Reviewed

Pelisson, Carl-Hugo, Nakanishi, Takahiro, Zhu, Yang, Morisato, Kei, Kamei, Toshiyuki, Maeno, Ayaka, Kaji, Hironori, Muroyama, Shunki, Tafu, Masamoto, Kanamori, Kazuyoshi, Shimada, Toyoshi, Nakanishi, Kazuki

Acs Applied Materials & Interfaces Vol. 9 ( 1 ) page： 406 - 412 2017.1

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Polyrnethylhydrosiloxane has been grafted on the surface of a hierarchically porous silica monolith using a facile catalytic reaction between Si-H and silanol to anchor the polymer. This easy methodology leads to the functionalization of the surface of a silica monolith, where a large amount of free Si-H bonds remain available for reducing metal ions in solution. Palladium nanoparticles of 15 nm have been synthesized homogeneously inside the mesopores of the monolith without any stabilizers, using a flow of a solution containing Pd2+. This monolith was used as column-type fixed bed catalyst for continuous flow hydrogenation of styrene and selective hydrogenation of 3-hexyn-1-ol, in each case without a significant decrease of the catalytic activity after several hours or days. Conversion, selectivity, and stereoselectivity of the alkyne hydrogenation can be tuned by flow rates of hydrogen and the substrate solution, leading to high productivity (1.57 mol g(Pd)(-1) h(-1)) of the corresponding cis-alkene.

DOI： 10.1021/acsami.6b12653

Low-density, transparent aerogels and xerogels based on hexylene-bridged polysilsesquioxane with bendability Reviewed

Aoki, Yosuke, Shimizu, Taiyo, Kanamori, Kazuyoshi, Maeno, Ayaka, Kaji, Hironori, Nakanishi, Kazuki

Journal of Sol-Gel Science and Technology Vol. 81 ( 1 ) page： 42 - 51 2017.1

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

Low-density, transparent aerogels based on a hexylene-bridged polysilsesquioxane ([O1.5Si-(CH2)(6)SiO1.5](n)) network have been prepared for the first time via a simple sol-gel process. An optimized base-catalyzed onestep hydrolysis-polycondensation process of a bridged alkoxysilane precursor 1,6-bis(trimethoxysilyl) hexane in a low-polarity solvent N,N-dimethylformamide allows for the formation of a pore structure of a length scale of several tens nanometers, resulting in low-density, transparent aerogels after supercritical drying. Because of the incorporated organic moiety that bridges the silicon atoms in the network, these aerogels show higher flexibility and strength against compression and bending as compared to silica aerogel counterparts. In addition, minimizing the residual silanol groups in the network by a surface modification with hexamethyldisilazane has further improved resilience after compression and bending flexibility and strength, due to the decreased chance of the irreversible formation of the siloxane bonds upon compression. The resulting trimethylsilylated hydrophobic gels have been subjected to ambient pressure drying to obtain xerogels, resulting in low-density (0.13 g cm(-3), 90 % porosity), transparent (71 % transmittance) xerogels. These results are promising for the development of transparent thermal superinsulators applicable to window insulating systems that manage heat transfer in a more efficient way.

DOI： 10.1007/s10971-016-4077-1

Effects of nanostructured biosilica on rice plant mechanics Reviewed Open Access

Sato, Kanako, Ozaki, Noriaki, Nakanishi, Kazuki, Sugahara, Yoshiyuki, Oaki, Yuya, Salinas, Christopher, Herrera, Steven, Kisailus, David, Imai, Hiroaki

Rsc Advances Vol. 7 ( 22 ) page： 13065 - 13071 2017

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

Nanostructured amorphous silica in rice plants (biosilica or plant opal) plays an important role in plant growth related to food production. However, the same silica has a structural supporting role as well that has not been uncovered. The current study focuses on the structural design of the two main types of biosilicas in rice plants for the improvement of their mechanical properties. One structural motif is platelike silicas, which cover most of the surfaces of leaf blades. Another is fan-shaped silicas, which are aligned inside leaf blades, providing a stiff backbone. These biosilica structures consist of 10-100 nm diameter nanoparticles. The mechanical properties, such as hardness and Young's modulus, of the biosilicas are associated with their relative density. Thus, the rice plant mechanics is inferred to be designed by changing the packing of the nanoparticles. Silica plates consisting of loosely packed particles have relatively low density and high flexibility enabling coverage of leaf blade surfaces, while fan-shaped silicas, which consist of tightly packed nanoparticles, are rigid to support the leaf blades as a backbone.

DOI： 10.1039/c6ra27317c

Highly Efficient Encapsulation of Ingredients in Poly(methyl methacrylate) Capsules Using a Superoleophobic Material Reviewed

Takei, Takayuki, Araki, Kiyotaka, Terazono, Keita, Ozuno, Yoshihiro, Hayase, Gen, Kanamori, Kazuyoshi, Nakanishi, Kazuki, Yoshida, Masahiro

Polymers & Polymer Composites Vol. 25 ( 2 ) page： 129 - 134 2017

Language：English Publishing type：Research paper (scientific journal) Publisher：ISMITHERS

Increasing the efficiency of encapsulation of ingredients into spherical capsules can decrease the manufacturing costs of the capsules. Ingredients can be encapsulated with high efficiency (>99%) into nondegradable hard resin capsules prepared by polymerization of spherical droplets of trimethylolpropane trimethacrylate (TRIM) monomer placed on a superoleophobic material. Poly(methyl methacrylate) (PMMA) resin is a more versatile capsule material than poly-TRIM resin. In this study, the efficiency of encapsulation in PMMA resin capsules prepared from methyl methacrylate (MMA) monomer was investigated. To reduce the volatility of the MMA monomer, pre-polymerized MMA was used for capsule preparation. Although non-volatile a-tocopherol and doxorubicin could be encapsulated in the capsules with high efficiency by heat polymerization at 60 degrees C for 3 h, the efficiency for volatile tetradecane was much lower (approximately 60%) because it evaporated. Furthermore, even when using pre-polymerized MMA, more than 70% of the prepolymer evaporated during polymerization. To prevent the evaporation of tetradecane and the prepolymer, ultraviolet photopolymerization was adopted because it was faster and could be conducted at a lower temperature. The photopolymerization prevented the evaporation of the prepolymer and increased the efficiency of encapsulation of tetradecane (approximately 90% efficiency). This polymerization system is effective for encapsulation of ingredients in PMMA capsules with high efficiency.

DOI： 10.1177/096739111702500202

Transparent Ethylene-Bridged Polymethylsiloxane Aerogels and Xerogels with Improved Bending Flexibility Reviewed

Taiyo Shimizu, Kazuyoshi Kanamori, Ayaka Maeno, Hironori Kaji, Kazuki Nakanishi

LANGMUIR Vol. 32 ( 50 ) page： 13427 - 13434 2016.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Transparent, monolithic aerogels with nano sized colloidal skeletons have been obtained from a single precursor of 1,2-bis(methyldiethoxysilyl)ethane (BMDEE) by adopting a liquid surfactant and a two-step process involving strong-acid, followed by strong-base, sol gel reactions. This precursor BMDEE forms the ethylene-bridged polymethylsiloxane (EBPMS, O-2/2(CH3)Si-CH2CH2-Si(CH3)O-2/2) network, in which each silicon has one methyl, two bridging oxygens, and one bridging ethylene, exhibiting an analogous structure to that of the previously reported polymethylsilsesquioxane (PMSQ CH3SiO3/2) aerogels having one methyl and three bridging oxygen atoms. Obtained aerogels consist of fine colloidal skeletons and show high visible-light transparency and a flexible deformation behavior against compression without collapse. Similar to the PMSQ aerogels, a careful tuning of synthetic conditions can produce low-density (0.19 g cm(-3)) and highly transparent (76% at 550 nm, corresponding to 10 mm thick samples) xerogels via ambient pressure drying by solvent evaporation due to their high strength and resilience against compression. Moreover, EBPMS aerogels exhibit higher bending strength and bending strain at break against the three-point bending mode compared to PMSQ aerogels. This improved bendability is presumably derived from the introduced ethylene-bridging parts, suggesting the potential for realizing transparent and bendable aerogels in such polysiloxane materials with organic linking units.

DOI： 10.1021/acs.langmuir.6b03249

Monolithic acidic catalysts for the dehydration of xylose into furfural Reviewed Open Access

Yang Zhu, Kazuyoshi Kanamori, Nicolas Brun, Carl-Hugo Pelisson, Nirmalya Moitra, Francois Fajula, Vasile Hulea, Anne Galarneau, Kazuyuki Takeda, Kazuki Nakanishi

CATALYSIS COMMUNICATIONS Vol. 87 page： 112 - 115 2016.12

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

We report the application of hierarchically porous zirconium phosphate monoliths with high surface area as acidic heterogeneous catalysts for the dehydration of xylose into furfural. Analyses by NH3-temperature programmed desorption and P-31 solid state NMR reveal the presence of both Lewis and Bronsted acid sites in the as-synthesized zirconium phosphate monolith and that calcined at 600 degrees C. High accessibility and availability of the acidic sites and easy separation of the monolith from the liquid medium result in good catalytic activity (initial reaction rate for furfural production as 8.7 mmol g(cat)(-1) h(-1)) with easy handling of the catalyst. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.catcom.2016.09.014

Transparent, Highly Insulating Polyethyl- and Polyvinylsilsesquioxane Aerogels: Mechanical Improvements by Vulcanization for Ambient Pressure Drying Reviewed

Taiyo Shimizu, Kazuyoshi Kanamori, Ayaka Maeno, Hironori Kaji, Cara M. Doherty, Paolo Falcaro, Kazuki Nakanishi

CHEMISTRY OF MATERIALS Vol. 28 ( 19 ) page： 6860 - 6868 2016.10

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Silica aerogels are unique porous materials possessing high visible-light transparency and low thermal conductivity. However, the practical applications are limited due to the native fragility of silica, and a lot of research focuses on the improvement of mechanical properties by organic inorganic hybridization, and so forth. Here, the first synthesis of polyethylsilsesquioxane (PESQ CH3CH2SiO1.5) and polyvinylsilsesquioxane (PVSQ CH2=CHSiO1.5) aerogels is reported. The resultant PESQand PVSQ aerogels obtained through a two-step acid-base sol-gel reaction in a surfactant-based solution exhibit visible-light transmittance and flexibility against compression without collapsing. The microstructural variations of these aerogels are systematically investigated by positron annihilation lifetime spectroscopy (PALS) in order to clarify the differences in properties derived from substituent groups. Furthermore, a post cure on the PVSQ wet gel using a radical initiator induces polymerization of vinyl groups in the solid network, resulting in mechanically reinforced aerogels with higher compressive modulus and resilience. This chemical modification, similar to vulcanization in silicone rubber materials, helps to produce xerogels with comparable properties to those of aerogels via ambient pressure drying. Since the resultant xerogel obtained from the vulcanization of PVSQ shows sufficiently low thermal conductivity of 15.3 m(-1) K-1, these novel polysilsesquioxane materials are promising for transparent aerogels/xerogels superinsulators.

DOI： 10.1021/acs.chemmater.6b01936

The XVIII International Sol-Gel Conference: Sol-Gel 2015 was held in Kyoto, Japan, September 6-11, 2015 Reviewed Open Access

Kazuki Nakanishi

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY Vol. 79 ( 2 ) page： 241 - 241 2016.8

Facile preparation of well-defined macroporous yttria-stabilized zirconia monoliths via sol-gel process accompanied by phase separation Reviewed

Guo, Xingzhong, Song, Jie, Ren, Jing, Yang, Fanger, Kanamori, Kazuyoshi, Nakanishi, Kazuki

Journal of Porous Materials Vol. 23 ( 4 ) page： 867 - 875 2016.8

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

Yttria-stabilized zirconia monoliths with well-defined macropores and high porosity have been successfully fabricated via sol-gel process accompanied by phase separation. Propylene oxide acts as an acid consumer to mediate sol-gel process, and poly (ethylene oxide) is used to induce phase separation. Ethylene glycol is applied as chelating agent, and formamide serves as drying control chemical additive to inhibit cracking during drying stage. Proper proportion of the starting compositions allows the generation of well-defined macroporous YSZ monoliths with co-continuous skeletons and porosity as high as more than 60 %. The dried gels are amorphous and crystalline of ZrO2 precipitates after heat treatment between 400 and 1200 A degrees C without formation of monoclinic ZrO2, which indicating a wide application prospects.

DOI： 10.1007/s10934-016-0143-x

Studies on electrochemical sodium storage into hard carbons with binder-free monolithic electrodes Reviewed

George Hasegawa, Kazuyoshi Kanamori, Naokatsu Kannari, Jun-ichi Ozaki, Kazuki Nakanishi, Takeshi Abe

JOURNAL OF POWER SOURCES Vol. 318 page： 41 - 48 2016.6

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Hard carbons emerge as one of the most promising candidate for an anode of Na-ion batteries. This research focuses on the carbon monolith derived from resorcinol-formaldehyde (RF) gels as a model hard carbon electrode. A series of binder-free monolithic carbon electrodes heat-treated at varied temperatures allow the comparative investigation of the correlation between carbon nanotexture and electrochemical Na+-ion storage. The increase in carbonization temperature exerts a favorable influence on electrode performance, especially in the range between 1600 degrees C and 2500 degrees C. The comparison between Li+- and Na+-storage behaviors in the carbon electrodes discloses that the Na+-trapping in nanovoids is negligible when the carbonization temperature is higher than 1600 degrees C. On the other hand, the high temperature sintering at 2500-3000 degrees C enlarges the resistance for Na+-insertion into interlayer spacing as well as Na+-filling into nanovoids. In addition, the study on the effect of pore size clearly demonstrates that not the BET surface area but the surface area related to meso- and macropores is a predominant factor for the initial irreversible capacity. The outcomes of this work are expected to become a benchmark for other hard carbon electrodes prepared from various precursors. (C) 2016 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2016.04.013

Hierarchically Porous Carbon Monoliths Comprising Ordered Mesoporous Nanorod Assemblies for High-Voltage Aqueous Supercapacitors Reviewed

George Hasegawa, Kazuyoshi Kanamori, Tsutomu Kiyomura, Hiroki Kurata, Takeshi Abe, Kazuki Nakanishi

CHEMISTRY OF MATERIALS Vol. 28 ( 11 ) page： 3944 - 3950 2016.6

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

This report demonstrates a facile one-pot synthesis of hierarchically porous resorcinol-formaldehyde (RF) gels comprising mesoporous nanorod assemblies with two-dimensional (2D) hexagonal ordering by combining a supramolecular self-assembly strategy in the nanometer scale and phase separation in the micrometer scale. The tailored multilevel pore system in the polymer scaffolds can be preserved through carbonization and thermal activation, yielding the multimodal porous carbon and activated carbon (AC) monoliths. The thin columnar macroframeworks are beneficial for electrode materials due to the short mass diffusion length through small pores (micro- and mesopores). By employing the nanostructured AC monolith as a binder-free electrode for supercapacitors, we have also explored the capability of "water-in-salt" electrolytes, aiming at high-voltage aqueous supercapacitors. Despite that the carbon electrode surface is supposed to be covered with salt-derived decomposition products that hinder the water reduction, the effective surface area contributing to electric double-layer capacitance in 5 M bis(trifluoromethane sulfonyl)imide (LiTFSI) is found to be comparable to that in a conventional neutral aqueous electrolyte. The expanded stability potential window of the superconcentrated electrolyte allows for a 2.4 V-class aqueous AC/AC symmetric supercapacitor with good cycle performance.

DOI： 10.1021/acs.chemmater.6b01261

Other Link： http://orcid.org/0000-0002-8069-4780

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