bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Ionic Liquid Interfaces Probed with Spectroscopy and Electrochemistry
Authors: Hailu Amanuel , Horvath Andrew , Shaw Scott K
Published: February 2020

Ionic liquids exhibit heterogeneous structures in both the normal and parallel planes with respect to an interface. The formation of these structures can be almost instantaneous or require hours to develop. The impact of these structures on molecular diffusion and local chemical environment can be significant, impacting tribology, solvation, and catalysis. Our work uses DC and AC electrochemistry, linear and non-linear spectroscopies, probe and optical microscopies, and thermochemistry to examine the IL structures that form near surfaces and within the electrochemical double layer. We probe the dynamics of the order/disorder transitions and attempt to reconcile experimental deviations from predicted, theoretical behaviors (i.e. capacitance or redox). In this talk, we will present series of DC and AC electrochemical data paired with spectroscopic analysis of ionic-liquid interfaces with electrodes to describe the interfacial, or sometimes micron scale ordered structures we observe in IL solvents. We incorporate redox probe molecules to observe the effects of IL ordering on electron transfer. We also probe how the electrochemical system changes in response to diluting the IL with molecular liquid cosolvents (water or acetonitrile). Finally we extend our studies to the electroreduction of carbon dioxide in IL systems, and present preliminary data on the optimization of a mixed IL+cosolvent system on Ag electrodes.

Figure 1
Metal Oxides Solubility in Molten Salt Systems
Authors: Skryptun Igor N
Published: February 2020

The solubility of metal oxides in alkali hydroxide melts and their mixtures with salts has been studied using the method of isothermal saturation at temperate range 673 – 873 K. The effect of temperature on the oxides solubility in melts are satisfactorily described by the linear Schroder – Le Chatellier equation ln C = A + B/T, where A and B are constants, C is concentration of oxide in melt (mole. fract.) and T is temperature (K).

Effective practical used of molten system alkali hydroxide – metal oxide depends on the knowledge of the thermodynamic properties of the system as whole as well as the partial thermodynamic properties of individual components of the system.

Thermodynamic calculations for molten binary and multicomponent systems based on that for saturated solutions meet the following equation: µ
sd = µ
sol. Since the µ
sol = µ
0
a=1(
T, p) + RTln a, where is a chemical potential of supercooled molten oxide and a is the activity of oxide in the melt relative to the supercooled molten oxide as a standard state, that lna = (µ
sd = µ
0)/RT.

Thus the temperature dependence of the activity molten oxide will be described the equation below.

On the other side ln a = ln x + ln λ and Gi
ex = RT In λ , therefore using the experimental data on the solubility of the oxides and solving the above equation we have calculated the excess relative partial molar thermodynamic quantities, which are also listed below.

The results of calculations was showed that the systems molten alkali – oxide are characterized by the deviation from the state of ideal solutions that indicate of interaction between components of the solution.

Figure 1
Importance of Proton Concentration on the Product Selectivity of the CO2 Reduction Reaction
Authors: Varela Ana Sofia , Kroschel Matthias , Ju Wen , Leonard Nathaniel , Arellano Anai , Gozález Eduardo , Bagger Alexander , Rossmeisl Jan , Strasser Peter
Published: February 2020

The electrochemical CO2 reduction reaction (CO2RR) is seen as promising route for converting waste CO2 and excess renewable energy into valuable chemicals and synthetic fuels. During this process a variety of carbon-based products such as CO, HCOOH and hydrocarbons can be formed. The cathode material plays a crucial role on determining the product distribution during the CO2RR. For example, Cu has been found to be an interesting material on which CO2 is directly reduced to alcohols and hydrocarbons. (1) While, Ag based catalyst (2) and metal nitrogen doped materials (MNCs) are considered promising catalyst for the reduction of CO2 to CO.(3)

In addition to the catalysts material, the pH and local pH are known to be key on determining the selectivity of the reaction. In the case of Cu catalysts, we have shown that the ratio between methane and ethylene prodiuction is strongly dependent on the local pH as ethylene formation is not affected by the proton concentration. As result, in conditions in which a high local pH is favored ethylene is the predominant product, while at low pH values CH4 is favored. (4) In the case of carbon base materials, however, the influence of the reaction conditions on the catalytic performance has not been addressed.

Herein we looked into the role of the electrolyte on the selectivity of FeNC materials on CO2RR selectivity. (5) Unlike hydrogen or methane generation, CO production is independent on proton concentration on the NHE scale, suggesting a decoupled proton-electron transfer mechanism for CO formation. The similarity of the reaction mechanism with that of Metal-N macrocyclic complexes is an indication that the Fe centers incorporated to our carbon material indeed behave as the active centers of complex based catalysts.

Furthermore, our results show that on doped carbon catalysts, such as FeNC, the selectivity towards the CO2RR can be conveniently tuned by the proton availability in both aqueous and non-aqueous electrolytes.

References:

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Varela A.S.; Kroschel, M.; Leonard N.D.; Ju W.; Steinberg J.; Bagger A.; Rossmeisl J.; Strasser P. ACS
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Figure 1
(Invited) Gas-Diffusion Electrodes for CO2 Reduction
Authors: Weng Lien-Chun , Bell Alexis T. , Larson David M , Romiluyi Oyinkansola , Weber Adam Z.
Published: February 2020

One of the main challenges towards achieving high-efficiency solar-fuel generators performing CO2 reduction are the mass-transport limitations in traditional aqueous systems due to CO2 interactions/solubility and boundary-layer thickness. To circumvent these issues, gas-diffusion electrodes (GDEs) are considered wherein the CO2 is fed in a vapor form into a porous electrode. In this talk, we will explore the various tradeoffs endemic in GDE architectures. This is accomplished through multiphysics modeling of the cells including breakdowns of the various limiting phenomena. In addition, experimental data on the GDEs for CO2 reduction will be presented using both Ag and Cu-based catalysts. Key is understanding the potential distributions with the GDE and how this along with the observed higher current densities impact product selectivity with Cu-based catalysts. Finally, comments will be made concerning the possibilities of light inclusion in GDEs to enable solar CO2 reduction as well as the benefits of GDEs that extend beyond higher current-density operation including unprecedented control of the local environment compared to traditional, aqueous planar designs.

Acknowledgements

The material is based on work performed at the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, through the Office of Science of the U.S. Department of Energy under award no. DE-SC0004993
Synthesis and Characterization of CuO/TiO2 Photocatodes for the Photoelectrochemical Reduction of CO2
Authors: Reyes Maria de los Angeles , Aguilar Ucán Claudia Alejandra , Ramirez Morales Erik , Sierra Grajeda Juan Manuel , Figueroa Ramirez Sandra Jazmin
Published: February 2020

The carbon dioxide is a very strong and stable molecule, product of fossil fuel combustion and it’s a primary greenhouse gases, currently various studies of de conversion of CO2 to usefull products have been conducted. However, for break the C=O bonds, requires a large external energy. The photoelectrochemical systems have been studied to use the light as the input energy for approach to overcome the high energy barrier of CO2 conversion in to chemicals and fuels in a environment-friendly manner.In this work we report the study of a photocathode material for fuel generation from CO2 reduction in a photoelectrochemical system, nanocompiste thin films of CuO/TiO2 with various concentration of CuO (1%,3%,5%) were prepared with a dip coating and a thermal treatment. The absorption regions, the band gap (Eg), the Anastasa phase, the crystal size and the topography of the surface were identified, using UV-vis spectrophotometry, Raman spectroscopy and Atomic Force Microscopy (AFM) techniques, respectively. It was observed that depending on the percentage of CuO, the Eg of the material decreases from 3.33eV to 3.25eV and increases the absorption in the visible region, this would indicate that less energy is required to activate the surface of the material and to perform the photo-reduction of CO2. And were evaluated in photoelectrochemical cell, with a KHCO3 media, the cyclic voltamperometry reported a catodic peak associated to reduction of CO2 in a -0.57 V vs (SCE) without illumination and a decrease to -0.37 V vs (SCE) whit illumination, this means that the material requires less energy supply for the reduction of CO2 in the presence of light.
Plasmon Enhancement of the CO Oxidation Reaction over Supported Gold Catalysts
Authors: Novello Peter , Liu Jie , Varanasi Pani
Published: February 2020

An active catalyst for the oxidation of CO at all temperatures is essential to ensuring safer air quality. In this study, we demonstrate the use of light to enhance CO oxidation over supported plasmonic gold catalysts, resulting in high activity and more substantial lifetimes at all temperatures ranging from -50 to 250 ֯C. Catalysts are synthesized by impregnation with plasmonic gold nanoparticles with a known size and plasmon resonance frequency. Using experiments which couple light induced desorption of CO2 and regeneration of catalytic activity, we propose a mechanism for light enhancement of gold catalysis. The reaction mechanism is strongly affected by the interaction between hot-electrons generated from relaxation of localized surface plasmon resonances in Au nanoparticles and adjacent species as well as photothermal heating. Through a separation of photothermal heating effects from hot-electron effects, we demonstrate an effective catalyst heating of over 70 oC and an additional nonthermal improvement of catalytic activity surpassing 100%. The hot-electron effects are shown to reactivate gold catalysts by removing surface carbonates which otherwise form in the active sites and poison the catalyst. This more efficient application allows for dramatically increased catalytic activity and catalyst lifetime, demonstrating a new path for highly active CO oxidation and further insight into light and hot-electron enhanced catalysis.
In-Situ Measurement of Exhaled Formaldehyde and Acetone Kinetics As Early-Stage Non-Invasive Markers of Lung Disease Using Nanostructured Polymeric Membranes
Authors: Angelopoulos Anastasios P.
Published: February 2020

Early stage discovery of lung cancer can significantly improve patient prognosis. Unfortunately, the impact of a well-known technique such as computed tomography screening on mortality rates is uncertain. It has been postulated that tumor growth may lead to peroxidation of cell membranes and is responsible for the observed emission of volatile organic compounds (VOC’s) such as acetone and formaldehyde. This observation has stimulated significant recent effort in the measurement of these compounds in exhaled breath. While promising approaches have been developed for analyzing average VOC concentrations in exhaled breath, an unrecognized drawback to current efforts is the presumption that gas partitioning between the blood and gas phases occurs so rapidly that the time averaged concentration of collected VOCs is representative of their saturation concentration in the lungs. In fact, when one considers the mass transport resistances encountered, VOC lung concentration is likely to be time-dependent and any sensing approach must have sufficient time resolution to capture the dynamic evolution of this concentration during a typical breath exhalation period of not more than 40 seconds in a high humidity environment.

In this presentation, we describe development of an optical exhaled gas sensing approach utilizing a nanostructured polymeric membrane that meets these requirements and demonstrates the dynamic evolution of exhaled breath biomarker concentration. We show that the activity of a solid acid catalyst toward the heterogeneous condensation reactions of immobilized resorcinol reagent with gas-phase acetone and formaldehyde can be preserved even at 100% ambient relative humidity through the incorporation of organic acids such as vanillic or tiglic. The reaction produces a colored flavan and poly-condensation products that permits highly selective and sensitive correlation to acetone and formaldehyde concentrations in exhaled breath. Such behavior relies on the complex heterophase morphology of the membrane as will be described.

Figure 1
(Keynote) Wireless Wearable and Implantable Monitoring and Therapeutic Systems for Cardiac Diseases and Neurological Disorders
Authors: Ramasamy Mouli , Varadan Vijay
Published: February 2020

Health and long term care is a growth area for wearable heath monitoring systems. Wearable diagnostic and therapeutic systems can contribute to timely point-of-care of patients with chronic health condition, especially chronic neurological disorders, cardiovascular diseases and strokes that are leading causes of mortality worldwide. Recent progress in nano-bio-tech sensor systems and mobile platforms has resulted in novel wearable health monitoring systems for neurological and cardiovascular disorders. This talk addresses this emerging area with selected videos of subjects for real time measurements and control cardiac and neurological diseases. Combined with state-of-the-art embedded wireless network devices to communicate with smartphone, laptop or directly to remote server through mobile network (GSM,4G-LTE,GPRS), they can function as wearable wireless health- diagnostic systems that are more intuitive to use.
Synthesis of CuInS2 Compound Solar Cell Nanoparticles in an Aqueous Solution By Controlling the Concentration of Metal Complexes
Authors: Satou Kouhei , Yokoyama Shun , Takahashi Hideyuki , Tohji Kazuyuki
Published: February 2020

CuInS2(CIS) is one of the most effective photovoltaic devices for developing high stability and low cost solar cell. Bandgap of CIS is 1.5eV while ideal band gap for solar cell is 1.4eV, so CIS is suitable as solar cell materials. Moreover, unlike Cu(In,Ga)Se2(CIGS), it does not contain toxic materials, such as Se [1]. Until now, CIS solar cells have been synthesized by utilizing gas phase method. However, the gas phase evaporation process needs high energy consumption, high initial cost, and large amount loss of resources. For spreading the solar cells greatly, it is required to develop a method which can resolve the above problems, so it is necessary to synthesize CIS solar cells in liquid method.

Here, we have already developed a synthesizing method of single phase and homogeneous Copper-Indium (CI) alloy nanoparticles in an aqueous solution. In this method, the concentration ratio of the metal complexes in the solution are calculated by using the critical stability constants, and the reduction reaction rate is also controlled. Synthesized CI nanoparticles were spin coated onto substrate and selenized, consequently it shows the photo voltaic effect. Thus, printable solar cell can be formed by using this method. However, CIS2 nanoparticles were not synthesized until now, because of ligand exchange reaction between the complexing agents and Cu and In.

Therefore, in this study, to prevent these undesirable reaction, we tried to control the condition of Cu-In-complexing reagent(s) system precisely by using the calculation. By using these calculation results, CIS2 particles were tried to synthesized in an aqueous solution

Results of calculation indicated that iminodiacetic acid (IDA) was appropriate complexing reagent. In the ternary system of Cu-In-IDA, it was calculated that the Copper comlexes and Indium complexes can be restricted to homogenized species, [(Cu2+)(IDA)] (pH3) and [(In3+)(IDA)2] (pH3) under the condition that the total molar concentration of Copper and Indium ions were 5 mM, respectively.

Based on this calculation, a solution under the above condition was prepared, and both metal complexes were tried to co-sulfurize. As a results, particles with amorphous like morphology were obtained. Therefore, in order to improve the crystallinity, the particles were heated for 30 min at 500 °C under N2 atmosphere. XRD results of heat treated samples indicated that several peaks with a dominant CIS2 peak were observed. Thus, it can be said that CIS2 nanoparticles were successfully synthesized in an aqueous solution, without undesirable ligand exchange reaction during reaction.

These results indicated that homogenize metal complexes system of Cu-In-IDA are essential for the synthesis of CIS2 particles.

In our presentation, detailed and another results will be introduced.

[1]Recent Development of Thin Film Compound Semiconductor Photovoltaic Cells, Wada, Publication of CMC, 2007
Electrochemical Tuning of Ordered Mesoporous Oxides with Spinel and Perovskite Structures for Reversible Control of Magnetization
Authors: Brezesinski Torsten
Published: February 2020

Nanoporous oxides in thin film format have been receiving much attention in recent years, especially because of their potential for next generation device applications. However, the preparation of non-siliceous (mixed-metal) oxides that are structurally and compositionally well-defined is challenging. The primary reason is that both the nucleation and growth of the crystalline phase are usually difficult to control.

Here we describe the block-copolymer-templating synthesis (using an evaporation-induced self-assembly process) of a series of high quality large-pore mesoporous oxides with spinel and perovskite structures, including metal ferrites and mixed-valence manganese oxides, and their characterization by various imaging, diffraction, and spectroscopic methods. Besides, we demonstrate that the general idea of combining nanomagnetism and electrochemical energy storage concepts can be applied to block-copolymer-templated mixed-metal oxide thin films. Using such high-surface-area materials as the working electrode in lithium-ion battery cells or supercapacitors and carefully controlling the charge/discharge potential allows tuning (virtually fully reversible) the magnetism at room temperature without compromising the lattice and/or pore structure.[1-4] The results are exciting and clearly show that both techniques hold potential for application in the fields of micromagnetic actuation and spintronics to name a few.

[1] C. Reitz, P. M. Leufke, R. Schneider, H. Hahn and T. Brezesinski, Chem. Mater.
2014, 26, 5745.

[2] C. Reitz, C. Suchomski, D. Wang, H. Hahn and T. Brezesinski, J. Mater. Chem. C
2016, 4, 8889.

[3] C. Reitz, D. Wang, D. Stoeckel, A. Beck, T. Leichtweiss, H. Hahn and T. Brezesinski, ACS Appl. Mater. Interfaces
2017, 9, 22799.

[4] L. A. Dubraja, C. Reitz, L. Velasco, R. Witte, R. Kruk, H. Hahn and T. Brezesinski, ACS Appl. Nano Mater.
2018, 1, 65.
Super Slippery Surface for Small Volume of Liquid on Superhydrophilic Nanoscale Texture
Authors: Fujikane Masaki
Published: February 2020

In order to realize the excellent functional antifouling coating, the anti-adhesive property is requiring for the material surface. The photocatalyst material such as TiO2 are conventionally used for degrading pollution [1,2]. The superhydrophobic bumps such as lotus leaf structure [3,4], or super slippery surface such as Nepenthes pitcher plant are also conventionally used for self-cleaning function [5,6]. These functional surfaces, however, have been applied in limited practical use due to their difficulties in processability, wearability, permeability and resupplying the lubricant.

This paper reports the first example of super slippery surface using superhydrophilic material, which is opposite approach to generally using superhydrophobic material as mentioned above. The newly discovered superhydrophilic slippery surface has been realized by nanotextured photocatalyst with surface reforming process. Without hydrophobicity or lubricant, it has been succeeded in sliding waterdrops smaller than 5 μL with sliding angle lower than 5° (Fig. 1).

The GaN substrate has been selected as photocatalyst in this study, and 100 nm in diameter SiO2 nanoballs have been dip coated on the substrate in the shape of single layered colloidal crystal following surface modification of the substrate. The nanotexture has been formed by dry etching process with hexagonal closed packed structure SiO2 nanoball etching mask [7–9]. Finally, the nanotextured GaN surface has been modified again to superhydrophilic then the super slippery surface has been finished up [10]. The obtained new phenomenon, i.e. super slips on superhydrophilic surface, is supposed to be affected by the fractal curve at the 3-phase (water, GaN and air) contact line, and by the super low friction coefficient between waterdrop and nanotexture that likes commonly used Cassie-Baxter model.

[1] A. Fujishima & K. Honda, Nature
238, 37–38 (1972).

[2] R. Wang, K. Hashimoto, A. Fujishima, M. Chikuni, E. Kojima, A. Kitamura, M. Shimohigoshi & T. Watanabe, Nature
388, 431–432 (1997).

[3] T. Y. Liu & C. Kim, Science
346, 1096–1100 (2014).

[4] A. Tuteja, W. Choi, M. Ma, J. M. Mabry, S. A. Mazzella, G. C. Rutledge, G. H. McKinley & R. E. Cohen, Science
318, 1618–1622 (2007).

[5] T. S. Wong, S. H. Kang, S. K. Tang, E. J. Smythe, B. D. Hatton, A. Grinthal & J. Aizenberg, Nature
477, 443–447 (2011).

[6] A. R. Parker, C. R. Lawrence, Nature
414, 33–34 (2001).

[7] M. Fujikane, A. Inoue & T. Yokogawa, US patent 8852965 (2014).

[8] M. Fujikane, A. Inoue & T. Yokogawa, US patent 8841220 (2014).

[9] M. Fujikane, A. Inoue & T. Yokogawa, US patent 9209254 (2015).

[10] M. Fujikane, EU patent 17167854.3 (2017).

Figure 1 | Relation between the water volume and the sliding angle for different types of surfaces. The values in parentheses at the end of graph legends indicate static contact angle with 2 μL water probe.

Figure 1
Synthesis and Caracterization of ZrO2/PANI Composite As Electrocaltalyst Support for Direct Alcohol Fuel Cells
Authors: Rivas S. , Calleja Gerardo , Guerra-Balcázar Minerva , Ledesma-García Janet
Published: February 2020

Carbon Vulcan has been widely used as electrocatalyst support despite its susceptibility to electrochemical corrosion. Zirconium oxides are a promising alternative due to its corrosion resistance in acid and alkaline media, the main drawback of these materials are their low conductivity and surface area. Therefore, an alternative to overcome this is, to develop a composite with conducting polymers (CPs) like polyaniline. conducting polymers fulfill the main requirements for fuel cell application: high surface area, to obtain high metal dispersion, suitable porosity, high electrical conductivity, and high stability under fuel cell operational conditions.

In this work Pt as electrocatalyst was supported by chemical reduction onto nanostructured ZrO2 followed by chemical deposition of PAni. Every element of the composite was characterized individually. Zirconium oxide was synthesized by sol-gel technique, using different calcination temperatures (300 and 350 °C), TEM analysis shows that zirconia has a particle size between 100 and 1000nm in a disperse pattern with some agglomerates, the X ray diffraction pattern correspond to an amorphous structure. The surface area was determined by nitrogen adsorption and goes from 60 and 160m2/g depending on calcination temperatures.

PAni was synthetized by chemical method and showed different morphology depending on incubation temperature and with different corresponding conductivity capacities. When the bath temperature was at -16°C a notorious microfibrillar pattern could be seen by SEM analysis, but the sample color was not characteristic of emeraldine (conductor PAni salt). However, when bath temperature was 2 and 20°C, the color allowed to confirm that emeraldine was the PAni phase presented but with porous nanoparticular morphology.

From previous experimental work it is clear that Pt/ZrO2 has a superior performance towards methanol oxidation reaction than Pt/C (20%), especially on alkaline conditions. In this work, the synthesis of PAni over Pt/ZrO2 does not affect the electrocatalytic activity neither in acid or alkaline conditions. Therefore, the low surface area of zirconium could be properly compensated with this conductive polymer. However, stability tests are necessary to consider this composite as adequate substitute for carbon based electrocatalysts supports in direct alcohol fuel cells.
Silver Nanoparticles Supported on Graphene and Graphene Oxide As Catalytic Composites for Application in a Hydrogen Generation Reaction
Authors: Abdel-Fattah Tarek M , Long Julia Madeline , Beveridge Connor , Price Brain , Osborne Justin
Published: February 2020

The limited supply of nonrenewable resources, such as oil and natural gas, as well as the environmental impacts these fuel sources generate has prompted research into the field of renewable and clean sources of energy. A viable candidate to replace nonrenewable resources could come in the form of hydrogen gas, which is recyclable in nature.1 Hydrogen gas is also a more environmentally conscious alternative to fossil fuels, since it generates no harmful emissions unlike fossil fuels.2-3 One obstacle preventing hydrogen gas from being produced on a global scale, as with gasoline, is due to the difficulties associated with harnessing and storing pressurized gas. A solution to this problem can be found in metal hydrides, which are known for their hydrogen releasing capabilities.4 The most favorable metal hydride is sodium borohydride (NaBH4) due to its high hydrogen content (10.8% wt) and its exceptional energy density.4 Sodium borohydride can generate as much as 4 moles of hydrogen gas when reacted with water, however, this reaction proceeds slowly. To accelerate the oxidation of aqueous sodium borohydride, a catalyst is needed. It has been found that graphene supported transition metal catalysts, like silver, can be used to catalyze this reaction.1-5 In this experiment, silver nanoparticles coupled with graphene and graphene oxide scaffold supports were used as the catalytic material for the hydrogen generation reactions. The silver nanoparticles catalyzed reaction was found to preform best under a pH of 7 and a temperature of 30°C producing a rate constant of 0.0026 mol-1sec-1.

References

Liu, B.; Li, Z. A review: Hydrogen generation from borohydride hydrolysis reaction. Journal of Power Sources 2009, 187, 527–534.

Kojima, Y.; Suzuki, K.-I.; Fukumoto, K.; Sasaki, M.; Yamamoto, T.; Kawai, Y.; Hayashi, H. Hydrogen generation using sodium borohydride solution and metal catalyst coated on metal oxide. International Journal of Hydrogen Energy 2002, 27, 1029–1034.

Abdel-Fattah, T. M.; Wixtrom, A. Catalytic Reduction of 4-Nitrophenol Using Nanoparticles on Carbon Nanotubes. ECS J. Solid State Sci. Technol. 2014, 3, M18-M20.

Schlesinger, H.; Brown, H.; Finholt, A.; Gilbreath, J.; Hoekstra, H.; Hyde, E. Sodium Borohydride, Its Hydrolysis and its Use as a Reducing Agent and in the Generation of Hydrogen. J. Am. Chem. Soc. 1952, 75, 215-219.

Kochkar, H., Aouine, Ghorbel, A.,Berhault, G. Shape-Controlled Synthesis of Silver and Palladium Nanoparticles Using β-Cyclodextrin. Journal of Physical Chemistry 2011, 115, 11364-11373.
SEI Formation Vs. Lithium Intercalation: In-Situ AFM Experiments on Graphite and Silicon Electrodes
Authors: Benning Svenja , Chen Chunguang , Notten Peter , Hausen Florian
Published: February 2020

The formation of the solid-electrolyte interphase (SEI) passivation layer on anode materials in lithium ion batteries (LIB) is not yet fully understood at the micro- and nanometer scale. Therefore, experiments under realistic conditions with high spatial resolution are of primary importance. Hence, atomic force microscopy (AFM) is an ideal technique to study in-situ the mechanisms at the electrode-electrolyte interface down to the (sub-) nanometer level.

Within this contribution we present a combined AFM and electrochemical (de-) lithiation study of the electrode-interface for two types of anode materials. Highly oriented pyrolytic graphite (HOPG) as a model system has been investigated in order to observe the topographical and electrochemical properties simultaneously. We find a clear influence of defect structures on the SEI formation process. Furthermore, the structural as well as the mechanical behavior of silicon anodes during (de-) lithiation will be presented. Sputtered silicon thin film electrodes [1] have been used to avoid strain and crack formation [2] on the silicon electrode during lithiation. We will introduce AFM measurements that enable a differentiation between SEI formation and expansion of the silicon electrode upon lithiation. We observed significant variations in the elastic modulus during the (de-) lithiation processes on the silicon electrode that can be directly attributed to the formation of an SEI layer as well as the expansion of the electrode due to the lithium insertion. Additionally, the analysis of the surface roughness will be discussed with respect to (ir-) reversible processes on the electrode surface.

References:

[1] R. Kumar et al., ACS Energy Lett., 2016, 1, 689-697

[2] P. Harks et al., Journal of Power Sources, 2015, 288, 92-105
Synthesis, Characterization and Electrocatalytic Activity for Hydrogen Evolution Reaction of Ternary Transition Metal Borides
Authors: Park Hyounmyung , Fokwa Boniface P.T.
Published: February 2020

Recently, as the concerns on the global warming and the depletion of fossil fuels, the most immediate scientific challenge is developing clean and renewable energy. Hydrogen has focused as one of the promising alternatives to carbon-based fuels because hydrogen is eco-friendly energy.

There are lots of methods to produce hydrogen. One easy and simple way to produce extremely pure hydrogen is water electrolysis, through hydrogen evolution reaction (HER).

Currently, noble metals such as platinum are generally regarded as the state-of-the-art electrocatalysts for improving the kinetics and efficiency of HER. However, their prohibitive price and scarcity limit their application industrially. It is therefore highly desirable to discover highly active and stable HER electrocatalysts composed of inexpensive and earth abundant elements.

In the last few years, boron based materials have been proposed as low-cost alternative electrocatalysts for HER. Recently, binary molybdenum borides (MoB, Mo2B, MoB2 and Mo2B4), iron boride (FeB2) and amorphous cobalt boride (Co2B) were reported to have outstanding catalytic activities for the HER.

In this work, we have synthesized molybdenum-tungsten diborides using solid solution synthesis. We substituted tungsten for molybdenum. The synthesized materials were characterized by X-ray power diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray analysis (EDX) and scanning electron microscope (SEM). Linear sweep voltammetry (LSV) was performed to determine the electrochemical properties by using a three electrodes system, and cyclic voltammetry (CV) was conducted to measure stability.
In Operando Cell Diagnostic with MRI
Authors: Silletta Emilia Victoria , Mohammadi Mohaddese , Ilott Andrew , Ganter Matthew J. , Schauerman Christopher , Jerschow Alexej
Published: February 2020

One of the biggest obstacles in the way of battery technology development is the limited amount of information that one can obtain from the battery mechanism without taking it apart. Here we are presenting a novel non-destructive battery assessment technology that is capable of obtaining crucial information from batteries even when the cells are encased in conductive material. One important application is commercial-type cell-phone batteries, which can be analyzed with this method. The technique is based on measuring the magnetic susceptibility of active ingredients inside an electrochemical cell that is affected by the oxidation state of the materials to give insights into the state of charge (SOC) of the battery, its failure mechanisms and the current distributions. The technique has been demonstrated on various cell types, defects, chemistries, and current level. The measurement is based on Magnetic Resonance Imaging (MRI) techniques, is fast (a couple of seconds), and could be adapted to a range of cell types. The figure shows the schematic setup and examples of images of different cells which are used to diagnose the SOC and the state of health. The technology represents a new opportunity for nondestructive cell diagnostics, and hence could be of great help in the development of next-generation batteries. We demonstrate the identification of defect, state of charge, and classification of cells based on different types of features. The method can also provide localized current distribution measurements.

Figure caption: Magnetic field map measurements for the fully charged cells. (A)-(C) sample placement, and image orientation; (D)-(E) Field maps measured for the cells. Field maps are referenced to the empty holder, giving an absolute field map for the Li-ion cell. (F) Magnetic field maps for the defect cells, with the mean and standard deviation indicated (taken over all of the voxels in each image). The fields are given relative to one of the non-defect cells (not shown).

Figure 1
(Invited) Computational Screening of Single Ion Conducting Polymer Electrolytes Based on sp3 Boron-Poly (ethylene glycol)
Authors: Ramos-Sánchez Guadalupe , Guzmán Gregorio
Published: February 2020

The application of polymer electrolytes in Lithium Ion batteries (LIB), has been proposed as an effective method to alleviate the problems associated to the limited voltage window and safety issues associated to the traditional liquid organic electrolytes. However, polymer electrolytes studied so far based on poly (ethylene glycol) and its derivatives have been unable to reach the required Li+ ionic conductivity needed for a broader application for commercial devices. Common polymer electrolytes contain a polymer with specific chain length at a defined C:O ratio, the conducting salt is added either during the polymerization process or afterwards by a dissolution process; however, the salt is often not completely dissociated while the conduction mechanism has been described as hoping of Li+ (often Li+ and counter ions) between oxygen functional groups and between chains induced by its intrinsic mobility. In order to increase the polymer ionic conductivity, it has been recently proposed the modification of the polymer for the introduction of negatively charge moieties which allows the direct interaction of Li+ with the polymer having no free counter ions; these structures present two big advantages, the Li+ transport number is close to unity and the mobility of Li is not lowered by the presence of the counter Ion. In order to identify the possible modifications to the polymer which allows higher Li conductivity, a detailed study of sp3-Boron Poly (ethylene-glycol) is reported. In this work, by means of density functional theory simulations, different electron withdrawing/donating ligands have been included as modifiers of the Boron site electron density. It was found that the effect of the ligand on the electron density of the Boron site has a great influence on the Bader charge of the boron site and also in the interaction energy with Lithium Ions was. A further study by ab-initio molecular dynamics (AIMD) shows that the mobility of Lithium ion can be modified up to two-fold by the inclusion of withdrawing electron density ligands. This methodology might lead to the discovery of new polymer electrolytes with enhanced Li+ conductivity.
(Invited) Bio-mimic Motion of Gel Material Dispersed with Magnetic Particles
Authors: Shinoda Hayato , Azukizawa Seiji , Maeda Kazuki , Tsumori Fujio
Published: February 2020

In this work, we mixed a gel material and magnetic particles to develop soft magnetic actuators. We also developed a new 3D-printing system with magnetic orientation using the mixture material to realize various motions. Some bio-mimic applications, such as a pumping system of artificial cilia, will be shown as an example.
(Invited) Ultra-Flexible Polymer Nanosheet for Bio and Electronics Applications
Authors: Fujie Toshinori
Published: February 2020

Integration of flexible devices into the living system is expected for advancing medical and healthcare devices, which will realize investigation of biological information at nano-biointerface. Such devices should be compatible to physical and mechanical properties of biological tissues. In this talk, we introduce free-standing polymeric ultra-thin films (referred to as “polymer nanosheets”) as a unique platform of ultra-flexible devices, which comprise tens- to hundreds-of-nanometer thickness close to the scale of biomembranes1. Various polymers (e.g., biodegradable polymers, conductive polymers, elastomers) are applicable as building blocks of polymer nanosheets; those are processed by spincoating, layer-by-layer and gravure coating techniques. The resulting nanosheets showed flexible and physically adhesive property owing to their ultra-thin structure. Polymer nanosheets are also functionalized by printing conductive polymers, nanomaterials or embedding thermo-sensitive dyes2-4. These nanosheet-based devices revealed several types of physiological properties in living organisms at different length scale from cell to tissue to body via functionalized interface, exemplified by temperature mapping of living muscle tissues and electromyogram of human bodies. The nanosheet technology will open a new avenue in the field of biotechnology and biomedicine.

References

T. Fujie, Polym. J., 2016, 48, 773.

A. Zucca, K. Yamagishi, T. Fujie, S. Takeoka, V. Mattoli, F. Greco, J. Mater. Chem. C, 2015, 3, 6539.

T. Miyagawa, T. Fujie, Ferdinandus, T. T. Vo Doan, H. Sato, S. Takeoka, ACS Appl. Mater. Interfaces, 2016, 8, 33377.

M. Okamoto, M. Kurotobi, S. Takeoka, J. Sugano, E. Iwase, H. Iwata, T. Fujie, J. Mater. Chem. C, 2017, 5, 1321.
(Invited) Construction of Soft Materials Composed of Hierarchically Assembled Filamentous Viruses
Authors: Sawada Toshiki
Published: February 2020

Recent studies have revealed that viruses such as filamentous M13 bacteriophages (phages), with a specific affinity for artificial materials or biomolecules, can be utilized to produce various materials. To widen the applicability, the control of phage assemblies is an essential requirement. Herein, we demonstrate solid films composed of regularly assembled phages with high thermal diffusivities. The oriented structures of the phages in the films were characterized in detail. It was revealed that thermal diffusivity of the films with oriented structures prepared by the flow-induced method was higher values than that with the disordered structure. Furthermore, the thermal diffusivity values of the films with nematic- and smectic-liquid crystalline orientated phage structures were slightly different, suggesting phage oriented structures were essential for the thermal diffusivity. The results indicated that thermophysical property of phage films could be controlled by their assembly.
(Invited) DNA Quadruplex Hydrogels: An Application of Synthetic DNA As Bulk Material
Authors: Kuzuya Akinori
Published: February 2020

DNA is a water-soluble and biodegradable polymer, which forms right-handed double helices and carries genetic information in life. Because of its high structure regularity and sequence programmability, DNA has been used as a key component in development of functional nanomaterial. Despite such success in nanoscience, reports on application of DNA to typical material, i.e. hydrogels, are very few, except for some excellent achievements, because preparation of DNA in gram scales usually requires unreasonable costs. One solution for this problem is liquid-phase DNA synthesis method developed by Bonora et al. They used monofunctional MeO-PEG as a soluble polymeric support, which enables coupling reaction of phosphoramidite monomers in liquid phase and can be easily precipitated by ether addition for product separation.

We have applied this system to synthesize DNA-PEG-DNA tri-block copolymer in grams, and successfully prepared biodegradable PEG hydrogels by using higher-order DNA structures, such as G-quadruplexes, for cross-linking points. Aqueous solution of a tri-block copolymer bearing multiple guanosines at the ends, for example, immediately turns into gel upon addition of Na+ or K+ ions at reasonable concentration. Various body-related fluids such as PBS, artificial saliva, sweat, or tear can trigger gelation. The resulting hydrogels are self-healable since the crosslinking points are stable but still reversible structure. Moreover, introduction of toehold sequence realized complete control of such sol-gel transition by the addition of complementary DNA strand.
Development of Hydrogel Fatigue Sensor
Authors: Iijima Tetsuro , Inoue Shota , Saito Azusa , Tamate Hideaki , Khosla Ajit , Kawakami Masaru , Murasawa Go , Furukawa Hidemitsu
Published: February 2020

In recent years, various high-strength gels having strength of several MPa have been developed one after another by devising the internal structure of the gel. They have attracted attention as a new material. High-strength double network gel (DN gel) is a gel consisting of a hard 1st network and a soft 2nd network and have excellent properties such as super low friction, flexibility and biocompatibility. Particle double network gel (P-DN gel) consisting of powdered 1st network and 2nd network is a high strength gel capable of 3D free form fabrication by using 3D gel printer. Utilizing these advantages, there are expectations for soft robot materials and mechanical materials. It is also important to grasp the number of deformation of the gel and how much fatigued it is when the gel material is industrially used. Specifically, by attaching a fatigue sensor to a soft robot, it is possible to predict the optimum time to replace the parts. When it is used for mechanical materials, we need to judge on the necessity of emergency treatment. It will be considered to lead to comfortable use of things.

In this study, we aimed to develop a gel fatigue sensor with reference to the internal structure and destruction phenomenon of P-DN gel. P-DN gels of various compositions were prepared and mechanical tests and evaluation of internal structure by dynamic light scattering were carried out to investigate the physical properties of these gels. As a result, the P-DN gel using super absorbent polymer (SAP) as the 1st gel showed the most suitable physical properties for use as a fatigue sensor.
(Invited) Sliding Dynamics and Mechanical Properties of Slide-Ring Gels
Authors: Mayumi Koichi , Liu Chang , Jiang Lan , Hidaka Yuta , Yokoyama Hideaki , Ito Kohzo
Published: February 2020

To overcome the trade-off relationship between stiffness and toughness of conventional polymer gels with covalent cross-links, introducing dynamical cross-links into polymer network is a promising strategy. A typical example of dynamically cross-linked gels is slide-ring gel, in which polymer chains are cross-linked by rings and the cross-linking points can slide along polymer chains. When slide-ring gels are deformed, the network structure of slide-ring gels is homogenized due to the sliding of the ring molecules, which causes their high deformability [1]. We have recently performed crack propagation tests on slide-ring gels and found that their fracture energy is dominated by the sliding distance of the movable cross-links [2].

In this work, we investigate the relationship between the macroscopic fracture toughness of slide-ring gels and nano-scale sliding dynamics of rings on polymer chains. Slide-ring gels are prepared by cross-linking ring molecules of polyrotaxanes, necklace-like supramolecules consisting of cyclodextrins and polyethylene glycol. The fracture energy of slide-ring gels keeps constant at strain rates below a certain value, and decreases at a high strain rate, where the movable cross-linking points cannot slide and behave like covalent cross-links. From the strain rate dependence of the fracture energy, we have estimated the time scale for the sliding dynamics of cross-links in slide-ring gels.

References

[1] Ito, K., Polym. J., 39, 489 (2007).

[2] Liu, C., Kadono, H., Mayumi, K., Kato, K., Yokoyama, H., Ito, K. ACS Macro Letters, 6, 1409　(2017).

Figure 1
(Invited) Highly Stretchable and Transparent Ionogels as Nonvolatile Conductors for Dielectric Elastomer Transducers
Authors: Mei Chen Yong , Mei Zhang Li , Chen Baohong , lu Jing Jing , Yang Can Hui
Published: February 2020

Large deformation of soft materials is harnessed to provide functions in the nascent field of soft machines. This paper describes a new class of systems enabled by highly stretchable, transparent, stable ionogels. We synthesize an ionogel by polymerizing acrylic acid in ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate ([C2mim][EtSO4]). The ionogel exhibits desired attributes of adequate conductivity (0.22 S m−1), low elastic modulus (∼3 kPa), large rupturing stretch (∼4.6), and negligible hysteresis and degradation after cyclic stretches of large amplitude. Using the ionogel and a dielectric elastomer, we fabricate electromechanical transducers that achieve a voltage-induced areal strain of 140%. The ionogel is somewhat hygroscopic, but the transducers remain stable after a million cycles of excitation in a dry oven and in air. The transparency of the ionogels enable the transducers with conductors placed in the path of light, and the nonvolatility of the ionogels enable the transducers to be used in open air.
Micro-IPN Conversion of DNA Quadruplex Gel for Enhanced Gel-State Lifetime in Water
Authors: Tanaka Shizuma , Yukami Shinsuke , Ohya Yuichi , Kuzuya Akinori
Published: February 2020

DNA is one of popular components to construct intelligent hydrogels, by utilizing the fruits of eager studies in DNA computing and structural DNA nanotechnology. Not only regular duplexes, but also four-stranded structures called G-quadruplex are often used to construct DNA hydrogels because of its attractive features such as metal ion binding capability and quite high thermal stabilities. We have recently reported a new class of DNA hydrogels (DNA quadruplex gel), which utilize G-quadruplexes as crosslinking points. In here, DNA quadruplex gel is a reversible non-covalently bonded type gel whose crosslinking points are formed by hydrogen bonding. Therefore, when DNA quadruplex gel is exposed to a large amount of buffer solution, the equilibrium moves in the direction of dissociation of crosslinking point, and we cannot use DNA quadruplex gel for long time under such conditions. In this study, micro-interpenetrating network (micro-IPN) was introduced into DNA quadruplex gel for improvement of gel-state lifetime in water.