27 research outputs found
On Design for Electrochemical Energy Storage Materials
In this dissertation, diverse strategic designs of energy storage materials were explored. The main aims were: affordability and high-performances.
I) on eco-efficient synthesis of 1D intercalation compounds was described; a low-temperature aqueous solution synthesis of nanostructured 1D (molybdenum trioxide) MoO3 was developed. Subsequent self-assembly of the fibers to form large-scale freestanding films in paper-like structure was achieved without any assistance of organic compounds. Indeed, the whole processes, from synthesis to assembly of obtained materials, do not require toxic organic solvents. As an example of the application of our synthesized materials, 1D MoO3, having the width in 50−100 nm, with the length in micro scale, and with thickness in ~10 nm, and the macroscopic oxide papers consisting of 1D MoO3 and carbon materials were applied as the cathode and anode to lithium-ion batteries, respectively. As a cathode material, the 1D MoO3 showed a high rate capability with a stable cycle performance up to 20 A/g due to a short Li+ diffusion path along [101] and less grain boundaries which were achieved by the precise nanostructure control. As an anode material, the composite paper showed the first specific discharge capacity of 800 mAh/g. These findings above indicate not only an affordable, eco-efficient synthesis and assembly of nanomaterials but also show a new attractive strategy towards a possible whole aqueous process for a large-scale fabrication of freestanding oxide papers without any toxic organic solvent.
II) a new energy storage principle using polymeric frameworks was investigated. The new energy storage concept can deliver both high power and high energy. This is because of the novel energy storage nature of designed artificial polymeric frameworks which is different from classical energy storage mechanisms. The main novel discovery was as follows; since CTF-1 is linear stepwise p- and n-dopable polymer, therefore, this framework can store energy as a cathode in the wide working potential with both cation below 3 V versus Li/Li+ and anion above 3 V versus Li/Li+ by Faradaic reaction. Due to this feature, CTF-1 can store high specific capacity of 540 mAh/g. As the result the new energy storage concept which can deliver both high power and high energy was discovered by using a novel polymeric cathode. Unlike typical organic electrodes in sodium battery systems, the CTF-1 has a high specific power of 10 kW/kg, specific energy of 500 Wh/kg, and over 7,000 cycle life retaining 80 % of its initial capacity in half-cells. Indeed, all-organic energy storage devices based on CTF-1 suggested a possibility towards an extremely affordable energy storage device. Recent research on such artificial polymeric frameworks suggests their huge variability to utilize different functional structures which could even further increase power and energy even further when using different starting monomers. This would significantly extend the possibilities of electrical energy storage devices for a sustainable society based on our result. From this point of view, our research strategy which combined the experimental and theoretical study would be a model for further development of this field
Polymeric Frameworks as Organic Semiconductors with Controlled Electronic Properties
The rational assembly of monomers, in principle, enables the design of a
specific periodicity of polymeric frameworks, leading to a tailored set of
electronic structure properties in these solid-state materials. The further
development of these emerging systems requires a combination of both
experimental and theoretical studies. Here, we investigated the electronic
structures of two-dimensional polymeric frameworks based on triazine and
benzene rings, by means of electrochemical techniques. The experimental density
of states was obtained from quasi-open-circuit voltage measurements through
galvanostatic intermittent titration technique, which we show to be in
excellent agreement with first principles calculations performed for two and
three-dimensional structures of these polymeric frameworks. These findings
suggest that the electronic properties do not only depend on the number of
stacked layers but also on the ratio of the different aromatic rings
On Design for Electrochemical Energy Storage Materials
In this dissertation, diverse strategic designs of energy storage materials were explored. The main aims were: affordability and high-performances.
I) on eco-efficient synthesis of 1D intercalation compounds was described; a low-temperature aqueous solution synthesis of nanostructured 1D (molybdenum trioxide) MoO3 was developed. Subsequent self-assembly of the fibers to form large-scale freestanding films in paper-like structure was achieved without any assistance of organic compounds. Indeed, the whole processes, from synthesis to assembly of obtained materials, do not require toxic organic solvents. As an example of the application of our synthesized materials, 1D MoO3, having the width in 50−100 nm, with the length in micro scale, and with thickness in ~10 nm, and the macroscopic oxide papers consisting of 1D MoO3 and carbon materials were applied as the cathode and anode to lithium-ion batteries, respectively. As a cathode material, the 1D MoO3 showed a high rate capability with a stable cycle performance up to 20 A/g due to a short Li+ diffusion path along [101] and less grain boundaries which were achieved by the precise nanostructure control. As an anode material, the composite paper showed the first specific discharge capacity of 800 mAh/g. These findings above indicate not only an affordable, eco-efficient synthesis and assembly of nanomaterials but also show a new attractive strategy towards a possible whole aqueous process for a large-scale fabrication of freestanding oxide papers without any toxic organic solvent.
II) a new energy storage principle using polymeric frameworks was investigated. The new energy storage concept can deliver both high power and high energy. This is because of the novel energy storage nature of designed artificial polymeric frameworks which is different from classical energy storage mechanisms. The main novel discovery was as follows; since CTF-1 is linear stepwise p- and n-dopable polymer, therefore, this framework can store energy as a cathode in the wide working potential with both cation below 3 V versus Li/Li+ and anion above 3 V versus Li/Li+ by Faradaic reaction. Due to this feature, CTF-1 can store high specific capacity of 540 mAh/g. As the result the new energy storage concept which can deliver both high power and high energy was discovered by using a novel polymeric cathode. Unlike typical organic electrodes in sodium battery systems, the CTF-1 has a high specific power of 10 kW/kg, specific energy of 500 Wh/kg, and over 7,000 cycle life retaining 80 % of its initial capacity in half-cells. Indeed, all-organic energy storage devices based on CTF-1 suggested a possibility towards an extremely affordable energy storage device. Recent research on such artificial polymeric frameworks suggests their huge variability to utilize different functional structures which could even further increase power and energy even further when using different starting monomers. This would significantly extend the possibilities of electrical energy storage devices for a sustainable society based on our result. From this point of view, our research strategy which combined the experimental and theoretical study would be a model for further development of this field
On Design for Electrochemical Energy Storage Materials
In this dissertation, diverse strategic designs of energy storage materials were explored. The main aims were: affordability and high-performances.
I) on eco-efficient synthesis of 1D intercalation compounds was described; a low-temperature aqueous solution synthesis of nanostructured 1D (molybdenum trioxide) MoO3 was developed. Subsequent self-assembly of the fibers to form large-scale freestanding films in paper-like structure was achieved without any assistance of organic compounds. Indeed, the whole processes, from synthesis to assembly of obtained materials, do not require toxic organic solvents. As an example of the application of our synthesized materials, 1D MoO3, having the width in 50−100 nm, with the length in micro scale, and with thickness in ~10 nm, and the macroscopic oxide papers consisting of 1D MoO3 and carbon materials were applied as the cathode and anode to lithium-ion batteries, respectively. As a cathode material, the 1D MoO3 showed a high rate capability with a stable cycle performance up to 20 A/g due to a short Li+ diffusion path along [101] and less grain boundaries which were achieved by the precise nanostructure control. As an anode material, the composite paper showed the first specific discharge capacity of 800 mAh/g. These findings above indicate not only an affordable, eco-efficient synthesis and assembly of nanomaterials but also show a new attractive strategy towards a possible whole aqueous process for a large-scale fabrication of freestanding oxide papers without any toxic organic solvent.
II) a new energy storage principle using polymeric frameworks was investigated. The new energy storage concept can deliver both high power and high energy. This is because of the novel energy storage nature of designed artificial polymeric frameworks which is different from classical energy storage mechanisms. The main novel discovery was as follows; since CTF-1 is linear stepwise p- and n-dopable polymer, therefore, this framework can store energy as a cathode in the wide working potential with both cation below 3 V versus Li/Li+ and anion above 3 V versus Li/Li+ by Faradaic reaction. Due to this feature, CTF-1 can store high specific capacity of 540 mAh/g. As the result the new energy storage concept which can deliver both high power and high energy was discovered by using a novel polymeric cathode. Unlike typical organic electrodes in sodium battery systems, the CTF-1 has a high specific power of 10 kW/kg, specific energy of 500 Wh/kg, and over 7,000 cycle life retaining 80 % of its initial capacity in half-cells. Indeed, all-organic energy storage devices based on CTF-1 suggested a possibility towards an extremely affordable energy storage device. Recent research on such artificial polymeric frameworks suggests their huge variability to utilize different functional structures which could even further increase power and energy even further when using different starting monomers. This would significantly extend the possibilities of electrical energy storage devices for a sustainable society based on our result. From this point of view, our research strategy which combined the experimental and theoretical study would be a model for further development of this field
Carbon- and Nitrogen-Based Organic Frameworks
ConspectusThis Account provides an overview of organic, covalent, porous
frameworks and solid-state materials mainly composed of the elements
carbon and nitrogen. The structures under consideration are rather
diverse and cover a wide spectrum. This Account will summarize current
works on the synthetic concepts leading toward those systems and cover
the application side where emphasis is set on the exploration of those
systems as candidates for unusual high-performance catalysis, electrocatalysis,
electrochemical energy storage, and artificial photosynthesis.These issues are motivated by the new global energy cycles and
the fact that sustainable technologies should not be based on rare
and expensive resources. We therefore present the strategic design
of functionality in cost-effective, affordable artificial materials
starting from a spectrum of simple synthetic options to end up with
carbon- and nitrogen-based porous frameworks. Following the synthetic
strategies, we demonstrate how the electronic structure of polymeric
frameworks can be tuned and how this can modify property profiles
in a very unexpected fashion. Covalent triazine-based frameworks (CTFs),
for instance, showed both enormously high energy and high power density
in lithium and sodium battery systems. Other C,N-based organic frameworks,
such as triazine-based graphitic carbon nitride, are suggested to
show promising band gaps for many (photo)Âelectrochemical reactions.
Nitrogen-rich carbonaceous frameworks, which are developed from C,N-based
organic framework strategies, are highlighted in order to address
their promising electrocatalytic properties, such as in the hydrogen
evolution reaction, oxygen reduction reaction (ORR), and oxygen evolution
reaction (OER). With careful design, those materials can be multifunctional
catalysts, such as a bifunctional ORR/OER electrocatalyst.Although
the majority of new C,N-based materials are still not
competitive with the best (usually nonsustainable candidates) for
each application, the framework/N approach as such is still in its
infancy and has already moved organic materials to regions where otherwise
only traditional noble metals or special inorganic semiconductors
are found. As one potential way to enhance the properties of polymeric
frameworks, the idea of catalysts having unique active surfaces based
on Mott–Schottky heterojunctions and related concepts are addressed.In order to integrate all of the above versatile subjects from
synthesis to applications on C,N-based organic frameworks, we begin
the discussion with synthetic concepts and strategies for these frameworks
to distinguish these systems from typical covalent organic frameworks
based on boron oxide rings. Next we focus on the semiconducting properties
of C,N-based organic frameworks in order to show a continuous transition
between CTFs and other systems, such as graphitic carbon nitrides.
At the end, applications of these materials are shown by highlighting
their properties in electrochemical energy storage and photo- and
electrocatalysis
Observations and Theories of Quantum Effects in Proton Transfer Electrode Processes
Quantum tunneling effects play an important role in a variety of chemical reactions considerably affecting the reaction rates via opening the classically-forbidden paths and emerging as highly efficient or selective processes. However, in the case of electrochemical reactions, quantum tunneling effects are less investigated due to complicated nature of chemical interactions at the electrified interfaces. In this review, we summarize the experimental/theoretical concept of electrochemical quantum proton tunneling (EQPT), which is a key element in microscopic electrode processes. First, we review the experimental observations of EQPT, and next, we discuss possible theoretical pictures of the process. This review shows that a combination of a wide spectrum of scientific efforts is required to understand microscopic mechanism of EQPT including development of the precise electrochemistry-oriented experimental techniques and methodologies, formulation of the appropriate theoretical models for specific systems and performance of the advanced computational simulations.</div
Reversible Energy Storage in Layered Copper-Based Coordination Polymers: Unveiling the Influence of the Ligand\u27s Functional Group on Their Electrochemical Properties
Coordination polymers represent a suitable model to study redox mechanisms in materials where both metal cation and ligand undergo electrochemical reactions and are capable to proceed through reversible multielectron-transfer processes with insertion of cation and anion into their open structures. Designing new coordination polymers for electrochemical energy storage with improved performance relays also on the understanding of their structure-properties relationship. Here, we present a family of copper-based coordination polymer with hexafunctionalized benzene ligands forming a kagome-type layered structure, where the in uence of the functional groups in their structure and electrochemical properties is investigated. Their chemical and structural properties have been explored by means of PXRD, and FTIR and Raman spectroscopies, followed by investigation of their electrochemical performance in Li half-cells by CV and galvanostatic cycling techniques. Ex-situ PXRD, Raman, XPS and ToF-SIMS measurements of cycled electrodes have been carried out providing insights into the redox mechanism of these copper-based coordination polymers as positive electrode materials.<br /
Aqueous Solution Process for the Synthesis and Assembly of Nanostructured One-Dimensional α‑MoO<sub>3</sub> Electrode Materials
A low-temperature aqueous solution
synthesis of nanostructured
one-dimensional (1D) molybdenum trioxide (MoO<sub>3</sub>) was developed.
The subsequent self-assembly of the fibers to form large-scale freestanding
films was achieved without any assistance of organic compounds. Indeed,
the whole process, from synthesis to assembly, does not require toxic
organic solvents. As an example of the application of our synthesized
materials, we built two types of half-cell lithium-ion batteries:
(i) the cathode made out of 1D MoO<sub>3</sub>, having the width in
50–100 nm, with the length in micro scale, and with thickness
in ∼10 nm, and (ii) the anode made out of the macroscopic oxide
papers consisting of 1D MoO<sub>3</sub> and carbon materials. As a
cathode material, 1D MoO<sub>3</sub> showed a high rate capability
with a stable cycle performance up to 20 A g<sup>–1</sup> as
a result of a short Li<sup>+</sup> diffusion path along the [101]
direction and less grain boundaries. As an anode material, the composite
paper compound showed a first specific discharge capacity of 800 mAh
g<sup>–1</sup>. These findings indicate not only an affordable,
eco-efficient synthesis and assembly of nanomaterials but also show
a new attractive strategy toward a possible full aqueous process for
a large-scale fabrication of freestanding oxide paper compounds without
any toxic organic solvent