bluuebunny/crossref_metadata_2025 huggingface dataset:
Etching Studies of Mo in Aqueous Solutions
Authors: Lee Sang-Min , Jung Chan-Yong , Lee Chi-Woo
Published: February 2020

Molybdenum (Mo) has been a choice of substrate metal for chalcopyrite or kesterite solar cells because of its low thermal expansion coefficient, high melting point, good thermal and electrical conductivity, and high wear resistance. Mo surface, however, is almost always covered with molybdenum oxides, unless kinetic limitations prevail. Previously, we reported the mild electrochemical conditions of forming molybdenum blue as well as molybdenum oxides colored in yellow and red in aqueous solutions. Figure 1 shows the representative changes in resonance frequency and current observed when the potential was applied to the molybdenum/quartz in aqueous solutions. The starting potential was –0.7 V, where the resonance frequency was set to be at the base line. As the potential was scanned up to –0.1 V, apparently the anodic current flew and simultaneously the resonance frequency increased. Near –0.1 V, the sharp increase in current as well as resonance frequency was observed, suggesting the significant dissolution of molybdenum into the solution as molybdenum ions. In this work we wish to report the results of electrochemical quartz crystal microbalance studies of etching of molybdenum in aqueous solutions. The present results may be important in relation to cleaning or polishing of molybdenum, which has been traditionally performed in strong acidic solutions such as mixtures of phosphoric acid and sulfuric acid. Details will be presented at the meeting.

Acknowledgements

Acknowledgements are made for SACHEM’s supply of some samples used in this work. Helpful discussions with Drs. Craig Allen and Paul Vermeulen are greatfully acknowledged.

References.

1. Sang-Min Lee, Young-Ho Kim, Mi-Kyung Oh, Suk-In Hong, Hang-Ju Ko, and Chi-Woo Lee, J. Korean Electrochem. Soc. 13, 89-95 (2010).

2. Sang-Min Lee and Chi-Woo Lee, Bull. Korean Chem. Soc. 33, 1443 (2012)

3. Viswanathan S. Saji and Chi-Woo Lee, Electrochem. Acta, 137, 647-653 (2014).

4. Viswanathan S. Saji, Chan-Yong Jung and Chi-Woo Lee, J. Electrochem. Soc. 162, D465-D479, (2015).

 

Figure 1
Mechanistic Study of Methanol Oxidation over Platinum Electrode in Alkaline Aqueous Solutions
Authors: Kubota Ryoma , Okanishi Takeou , Muroyama Hiroki , Matsui Toshiaki , Eguchi Koichi
Published: February 2020

Hydrogen is a clean fuel for stationary, mobile and transportation applications, particularly for fuel cells, but its storage and delivery are still major issues. To overcome these problems, hydrogen has been stored and transported via other chemical compounds, such as alcohols, hydrocarbons, ammonia, etc. Methanol is a promising hydrogen career due to its high volumetric energy density and ease in handling and storage. Direct methanol fuel cells (DMFCs) have been mainly studied with acidic electrolytes and the methanol oxidation mechanism has been clarified to some extent in recent years [1]. However, rare and expensive Pt–based electrocatalysts are normally used in DMFCs. One promising approach to improve this problem is using alkaline electrolytes because of the potential use of non–Pt catalysts. Nevertheless, there are few studies on the methanol oxidation mechanism in alkaline media. In this study, the electrochemical oxidation of methanol over Pt electrode in an alkaline solution was investigated using linear sweep voltammetry and in situ attenuated total reflection infrared (ATR–IR) spectroscopy.

　The oxidation current of methanol was observed at approximately 0.4–0.9 V in 0.25 M KOH–0.25 M CH3OH in the linear sweep voltammogram (LSV). In the time–resolved IR spectra acquired simultaneously with the LSV, two characteristic bands ascribable to the adsorbed formic acid species (HCOOad) were detected at 1800 cm–1 and 2000 cm–1 in the potential range of 0.1–0.3 V, and their intensity decreased with an increase in potential [2]. Alternatively, the new bands attributable to the aldehyde species (H
x
CHOad) appeared at 0.2 V in the same wavenumber range. These bands shifted to higher wavenumber with a rise in the potential probably due to the dipole–dipole coupling effect [3], and disappeared above 0.8 V. These results clarified that the formic acid species was oxidized in the initial step of methanol oxidation, followed by the aldehyde species.

Therefore, aldehyde species and formic acid species were found to be the intermediates of the methanol oxidation. Since the aldehyde species existed over Pt electrode even at higher potential of 0.8 V, the development of the electrocatalysts active for the H
x
CHOad oxidation reaction will be required for the enhancement of methanol oxidation in alkaline media.

REFERENCES

[1] N. M. Markovic, H. A. Gasteiger, P. N. Ross Jr, Electrochim. Acta, 40 (1995) 91–98

[2] G. Samjeske, M. Osawa, Angew. Chem. Int. Ed., 117 (2005) 5840–5844.

[3] Y. Y. Yang, J. Ren, H. X. Zhang, Z.Y. Zhou, S. G. Sun, W. B. Cai, Langmuir, 29 (2013) 1709–1716.
Crystal Structures and Electrochemical Properties of Li2TiO3 - LiMeO2 (Me = Cr, V and Mn) Binary System
Authors: Kobayashi Yuki , Yabuuchi Naoaki
Published: February 2020

Lithium ion batteries are used not only as power sources for portable electronic devices but also for electric vehicles, and the demand for further increase in the energy density is still growing. In this study, we focus on the layered oxide, Li2TiO3, and trivalent chromium, vanadium and manganese ions are substituted for lithium and titanium ions according to the formula of x Li2TiO3 – (1 – x) LiMeO2 (x = 0.5; Me = Cr, V and Mn) binary system. These samples are further reformulated as Li1.2Ti0.4Me0.4O2. Li1.2Ti0.4Me0.4O2 samples were prepared by solid-state reaction from stoichiometric amounts of Li2CO3, TiO2 (anatase type), Cr2O3, V2O3 and Mn2O3 at 900 – 1100 oC in Ar. The results of X-ray diffraction and structural analysis by Rietveld analysis on Li1.2Ti0.4Me0.4O2 (Me = Cr, V and Mn) samples reveal that crystal structures of the samples are different depending on the substituted ions. The Cr- and V-substituted samples crystallize into a layered rocksalt structure (α-NaFeO2 type). Perfect cation ordering is found for the Cr-substituted sample whereas partial anti-site defects between lithium sites (3b sites) and transition metal sites (3a sites) are noted for the V-substituted sample. In contrast, the Mn-substituted sample crystallizes into a cation disordered rocksalt structure. Electrochemical properties of Li1.2Ti0.4Me0.4O2 (Me = Cr, V and Mn) after ball-milling with carbon are evaluated in Li cells at room temperature or 50 oC (Figure 1). Although Li2TiO3 is electrochemically inactive, Li1.2Ti0.4Me0.4O2 delivers reversible capacities of >200 mAh g–1. Reversible capacity of the Mn-substituted sample reaches 300 mAh g–1 at 50 oC, and moreover such large capacity originates from the charge compensation by oxide ions.[1]

From these results, we will discuss the possibility of Li2TiO3-based electrode materials as positive electrode materials for rechargeable lithium batteries.

Reference

 [1] N. Yabuuchi, Y. Kobayashi et al., submitted.

Figure 1
A Study on Making a Stable Loop Profile and Improving Bonding Time in Wire Bonding Process
Authors: Nam KwanHyub , Ryu JangWoo , Lee Sungho , Kim Hyunjoong
Published: February 2020

Wire bonding is one of the most important processes in assembly of semiconductor. And the most competitive technology in wire bonding is making advanced loop profile. Therefore, as the growth of high-density and high-stacked die packages, it is essential to develop a highly lowed loop profile because wire bonding process is so sensitive in the semiconductor trend. Making a lowed loop profile is a key technology for today’s wire bonders. However, the conventional Folded Loop (FL) profile always accompanies many problems, such as critical faults due to un-stability at the neck of wire loop and long bonding time due to a lot of folding steps. These kinds of problems cause much of the un-efficient operation in the wire bonding. Therefore, we should develop an advanced loop profile to meet using more stable loop profile and applying speedy bonding time. The usual folded type loop profile can be developed by improving the shape of wire neck formation and reducing the kink steps for making lowed neck formation. In this paper, we propose a Very-Very Lowed Loop (VVLL) profile and it is the improved method to realize a fast and reliable loop profile in wire bonding process.

Fig.1 shows that the result of the conventional FL profile and its 6-folding steps.

Fig.2 describes 4-folding steps of the proposed VVLL profile and the bonding results.

Fig.3 includes the critical problems of FL profile appeared at the loop neck position. Cracks are caused by 6-folding steps and direct touching of a capillary tool. In addition, the loop variation is also happened due to bouncing effects while realizing loop trajectory.

Fig.4 depicts the advantages of VVLL. By decreasing the number of bending steps, it is possible to deconcentrate the stress and to reduce variation in the neck position of wire loop.

Fig5 is shown how the one cycle bonding time is speedy by converting the folding method from FL to VVLL. It can reduce 2-steps of folding motion.

To sum up, VVLL profile is significantly efficient to realize a fairly lowed and stable loop profile for state of the art high-tech semiconductor.

REFERENCE

 

Harman, George G. Wire bonding in microelectronics. McGraw-Hill, 2010

Brunner, Jon, Ivy Wei Qin, and Bob Chylak. "Advanced wire bond looping technology for emerging packages." Electronics Manufacturing Technology Symposium, 2004.

Wang, Fuliang, Yun Chen, and Lei Han. "Modeling and experimental study of the kink formation process in wire bonding." Semiconductor Manufacturing, IEEE Transactions on 27.1 (2014): 51-59.

Figure 1
Deposition and Dissolution of Lithium through a Lithium Carbonate Thin Film in an Ionic Liquid Electrolyte
Authors: Kotake Hiroki , Tachikawa Naoki , Yoshii Kazuki , Katayama Yasushi
Published: February 2020

Li-ion batteries are used widely for portable energy storages because of large capacity. Generally, the carbonate-based organic solvents are used as the electrolytes. Most of these organic solvents decompose during the first charge, resulting in formation of the solid electrolyte interphase (SEI) film, which plays an important role for Li-ion batteries on the active materials. Although there are many reports about the SEI film, its nature and function have not been clarified yet. We have already reported that lithium phosphorous oxynitride (LiPON) film acts as an artificial SEI film in 1-butyl-1-methylpyrrolidinium (BMP+) and 1-ethyl-3-methylimidazolium (EMI+) bis(trifluoromethylsulfonyl)amide (TFSA–) ionic liquids containing LiTFSA, and LiTFSA-glyme solvate ionic liquid. [1,2] Ionic liquids are expected to be the alternative electrolytes for Li-ion batteries, since ionic liquids have low flammability and low volatility, which are expected to improve safety of the batteries. However, the SEI film formed by the decomposition of ionic liquids is not preferable for deposition and dissolution of lithium. In this study, deposition and dissolution of lithium through a Li2CO3 thin film prepared by RF magnetron sputtering were investigated in BMPTFSA containing LiTFSA.

 The Li2CO3 thin film was characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractrometer, and X-ray photoelectron spectrometer (XPS). All the electrochemical measurements were performed using an airtight three-electrode cell. The Ni electrode with or without the Li2CO3 thin film was used as a working electrode. Li foil was used as a reference and counter electrode. After electrochemical measurements, the electrode was washed with dimethyl carbonate (DMC) and characterized by SEM and XPS.

 SEM observation and XPS measurement showed that the Ni substrate was covered with the Li2CO3 thin film completely. The Li2CO3 thin film on the substrate was X-ray amorphous. However, the crystalline domains were observed sparsely by TEM observation. The deposition and dissolution of lithium were possible through the Li2CO3 thin film in BMPTFSA containing 1 M LiTFSA. Although the cathodic current attributed to the decomposition of the electrolytes was observed on the Ni electrode, it was suppressed on the Ni electrode with the Li2CO3 thin film. These results indicate that the Li2CO3 thin film has the possibility to act as an artificial SEI film. The depth analysis by XPS revealed that lithium deposited between the Li2CO3 thin film and Ni electrode. From AC impedance measurement, the ionic conductivity of the Li2CO3 thin film was estimated to be 1.3 × 10−8 S cm−1.

 

References

[1] N. Tachikawa, R. Furuya, K. Yoshii, M. Watanabe, Y. Katayama, Electrochemistry, 83, 846 (2015).

[2] R. Furuya, N. Tachikawa, K. Yoshii, Y. Katayama, and T. Miura, J. Electrochem. Soc., 162, H634 (2015).
Noncovalent Functionalization�of Quinone Derivatives on 2D Graphene for High Performance Pseudocapacitive Electrodes
Authors: Boota Muhammad , Chen Chi , Bécuwe Matthieu , Miao Ling , Gogotsi Yury
Published: February 2020

Redox-active organic materials have recently gained significant attention from small to large scale energy storage systems due to their natural abundance and sustainability.1,2 However, they degrade upon moderate cycling mainly due to their poor conductivity, which limits their usage. One option to tackle this issue is to deposit organic materials on conductive carbons. Herein, we report 3D interconnected xerogel composed of 2,5-dimethoxy-1,4-benzoquinone (DMQ) decorated on reduced graphene oxide sheets (DMQ@rGO), via one-step hydrothermal method. The DMQ performed dual role in the composite: 1) it provided high redox capacitance and 2) served as a spacer to mitigate rGO sheet aggregation. When binder-free optimized composition of DMQ@rGO was tested as a pseudocapacitive electrode, it showed high capacitance (650 F/g, 780 F/cm3 at 5 mV/s) and excellent capacitance retention of 99% after 25000 cycles at 50 mV/s in 1 M H2SO4. Furthermore, we used density functional theory calculations to explore the charge storage mechanism, binding energies, adsorption orientation of the molecules, charge redistribution and density of the states.

References:

1 B. Huskinson, M. P. Marshak, C. Suh, S. Er, M. R. Gerhardt, C. J. Galvin, X. Chen, A. Aspuru-Guzik, R. G. Gordon and M. J. Aziz, Nature, 2014, 505, 195–8.

2 M. Boota, B. Anasori, C. Voigt, M.-Q. Zhao, M. W. Barsoum and Y. Gogotsi, Adv. Mater., 2015, 28, 1517–22.
Vertical Distribution of Ammonium Ion Concentration to the Air-Cathode of a Single-Chamber Microbial Fuel Cell
Authors: Motoyama Ayuri , Ichihashi Osamu , Hirooka Kayako
Published: February 2020

A microbial fuel cell (MFC) is a promising technology for wastewater treatment that can achieve removal of organic matter from wastewater and electricity generation simultaneously. In addition, it is known that not only organic matter but also ammonia in wastewater can be removed by single chamber microbial fuel cell (SCMFC). However, little is known of this ammonia removal mechanism. Some researchers reported that reduction of ammonium ion concentration occurred through biological nitrification / denitrification process by biofilm on the surface of an air-cathode in the SCMFC. Meanwhile, there is another hypothesis that ammonia volatilization occurs through the air-cathode as a result of decrease in the degree of ammonia dissociation and promotion of conversion to ammonia molecule, induced by local pH increase near the air-cathode. However, no direct evidence about the ammonia volatilization has not been reported. Therefore, in this study, SCMFC with a new (biofilm-less) air-cathode was operated and vertical distribution of ammonium ion concentration to the air-cathode was measured. If ammonia volatilization occurs, a sharp decrease in the concentration must be observed near the air-cathode. In our previous study, the vertical pH distribution to the air-cathode was measured with an ion selective microelectrode. Therefore, we applied this method to a micro-ammonium ion electrode.

 The concentration of ammonium ion at 10 mm from the air-cathode was 2 mM and there was a trend to decrease gradually as it approached to the air-cathode. Especially, the concentration of ammonium ion decreased sharply at approximately 0.6 mm from the air-cathode, and it became less than one-tenth within the distance of 0.5 mm. In our previous study under almost the same operational condition, the maximum pH was observed on the surface of the air-cathode, and it was about 9.3. Since the fraction of ammonium ion dissociation under this pH is about 50 % at most, the sharp decrease in the ammonium ion concentration cannot be explained only by this reason. Hence, something that caused the decrease in ammonium ion concentration must have happened near the air-cathode. The effect of nitrification can be denied because the biofilms were not formed on the surface of the air-cathode. From these above reasons, it is natural to think that ammonia volatilization through the air-cathode occurred in this study.

 

Acknowledgments

 This research was financially supported by Grant-in-Aid for Japan Society for the Promotion of Science Fellows (Project No. 15J0490902).

Figure 1
In Situ Tuning of Magnetization Via Double Layer Charging and Topotactic Li Insertion in Polymer-Templated Mesostructured Thin Films
Authors: Reitz Christian , Brezesinski Torsten
Published: February 2020

Mesostructured mixed-metal oxide thin films have received much attention in recent years, as they have great potential for future device applications. Advances in polymer templating over the past years have enabled the preparation of a variety of important materials in the form of thin films. However, despite the progress made, complex metal oxides (other than binary systems) often exhibit an ill-defined nanoscale structure after thermally-induced crystallization and removal of the porogen, mainly for stability reasons.

Here, we describe the self-assembling synthesis of large-pore mesoporous mixed-metal oxides, with special emphasis on La1–x
Ca
x
MnO3 (LCMO) and alpha-LiFe5O8 (LFO). Electron microscopy, GISAXS, XRD, XPS, TOF-SIMS, and RBS all show that these materials can be templated to produce high quality thin films that are phase pure and thermally stable to over 600 °C. For LCMO, we demonstrate that the surface charge carrier density can be tuned by double layer charging using an ionic liquid electrolyte.[1] Peak-to-peak magnetization modulation values of up to 10% have been achieved, (to our knowledge) the highest thus far reported for electrolyte-gated mixed-valence manganese oxides. Furthermore, we demonstrate that the topotactic Li insertion into LFO allows for the intriguing possibility of controlling the r.t. bulk magnetic state in a highly reversible manner. Overall, both approaches are promising and should be applicable to other magnetic nanomaterials.

[1] C. Reitz, P. M. Leufke, R. Schneider, H. Hahn, and T. Brezesinski, Chem. Mater. 26, 5745 (2014).
Synthesis, Morphology Control and Deposition of CeO2 Nanocrystals Toward Thin Film
Authors: Ozawa Masakuni , Hattori Takashi , Kobayashi Katsutoshi
Published: February 2020

Cerium dioxide (CeO2, ceria) is one of the most important materials toward electrolyte materials of solid oxide fuel cells. Since physicochemical and electrical properties of CeO2 vary with the particle dimension, morphology control of CeO2 on nanometer scale has been the key subject to realize the optimal properties for each application. Fabrication of CeO2 nanocrystals with remarkable morphologies such as nano-cubes is the first step in development of nanometer-scaled SOFC. In this study, CeO2 nanocrystals of around 5 nm in diameter were prepared by a hydrothermal route using potassium oleate as a stabilizing agent in the same manner as described in the previous papers. And then, nanocrystals were dispersed on crystal substrate toward thin film device.
Direct Evaluation about Structure and Optical Property of Individual Multi-Shell Quantum Dot By TEM
Authors: Uehara Masato , Sato Yohei , Terauchi Masami
Published: February 2020

Quantum dots (QDs) such CdSe nanocrystals attract much attention owing to their promising applications in light emitting devices and biomedical tags. They are usually coated by the wider band materials such CdS and ZnS in order to improve the photoluminescence quantum yield together with the chemical protection. However, it is not clarified the relationship between optical properties and core/shell particle structure, and we should optimize the coating treatment condition and the core/shell structure (shape and thickness), throughout many experiments.

It is important to clarify the relationship between optical properties and particle structure. Direct evaluation about the optical properties of the individual particles is very effective. As we all know, TEM is a powerful tool for the shape structure evaluation of nanoparticle. In addition, even the optical properties from UV to NIR of individual single nanoparticles can be evaluated by the HR-EELS using the monochromator TEM.

In this study, we have investigated the particle structure and optical property using advanced TEM technique. We have synthesized CdSe, CdSe/CdS and CdSe/CdS/ZnS multi-shell particles. The optical properties of individual single nanoparticles have been evaluated by HR-EELS using the monochromator TEM in addition to the usual particle structure evaluation by HR-STEM and EDX.

All nanoparticles were synthesized in an organic solvent with some ligands such as amine, oleic acids and trioctylphoshine. The synthesized and refined core CdSe particles were re-heated together with CdS raw material in an organic solvent, and we have obtained the CdSe/CdS core/shell particles. The CdSe/CdS/ZnS core/shell/shell particles have been also obtained in the similar treatments. We have evaluated the particle size and shape by STEM. Their size and shape was homogeneous. CdSe core particles were spherical and ca. 5 nm. CdSe/CdS and CdSe/CdS/ZnS particles were cubic shape, and ca. 10 nm and 15 nm. In STEM-EDX analysis, we have been able to confirm the core/shell and core/shell/shell structure. We could obtain some spectral structures attributed to interband transitions in the CdSe core and CdS shell by EELS analysis. However, the spectral structure about ZnS outer shell could be hardly confirmed. This would be attributed the low crystallinity of ZnS. Through the detail investigation of spectra, dielectric property of multi-shell nanoparticle is clarified and relation with the photo luminescent property will be discussed.

[Acknowledgement] The research was partially supported by JSPS KAKENHI Grant Number 26286026, Grant-in-Aid for Scientific Research (B). In addition, this STEM observation was partly supported by Advanced Characterization Platform of the Nanotechnology Platform Japan sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.
Study about Electrostatic Deposition of CdTe Quantum Dots on Glassy Carbon Electrodes
Authors: Muñoz Eduardo Carlo , Navarrete Emilio Alonso , Rojas Víctor , Romero Mario , Henríquez Rodrigo Gonzalo , Schrebler Ricardo Silvio , Córdova Ricardo Alejandro
Published: February 2020

Quantum Dots (QDs) are semiconductor nanocrystals. These materials are characterized for its continuous absorption spectra at wavelengths ranging from ultraviolet to visible. This feature is directly related to the size of the nanoparticle. Considering their applications, these materials can be employed in solar cells, lasers, light emitting diodes, electronic devices, among others [[i],[ii]]. However, one of the most attractive applications for QDs has been as sensors or biosensor.

In this work, the synthesis of CdTe Quantum Dots was carried out in aqueous media using Na2TeO3 and CdCl2 as precursors of Te2- and Cd2+ ions, respectively, mercaptosuccinic acid (MSA) as capping agent and NaBH4 as reducing agent. The QDs obtained as colloids were purified and characterized by transmission electron microscopy (TEM), while their optical properties were characterized by UV-visible spectroscopy. After, an electrostatic deposition of the QDs on a Glassy Carbon (GC) electrode was done. This last was carried out applying a positive potential value regarding to the zero charge potential of the electrode in an aqueous media, and the influence of the potential value, deposition time was determined by means cyclic voltammetry. A study of surface conductivity changes of the glassy carbon electrodes after QDs deposition was performed by means Scanning Electrochemical Microscopy (SECM). With this was possible to observe aggregates of CdTe QDs deposited on GC electrodes indicating a possible irreversible electrostatic deposition.

[
[i]
] R. Debnath, J. Tang, D. Barkhouse, X. Wang, A. Pattantyus-Abraham, L. Brzozowski, L. Levina, and E. Sargent, J. Am. Chem. Soc. 132 (2010) 5952-5953.

[
[ii]
] P. Kamat, K. Tvrdy, D. Baker, and J. Radich, Chem. Rev. 110 (2010) 6664-6688.

Figure 1
Supported Heterogeneous Gold Nanoparticles As a Catalyst for the 4-Nitrophenol Hydrogenation Reaction
Authors: Abdel-Fattah Tarek M , Jusino Angelica
Published: February 2020

Bulk gold cannot oxidize in air and is known for its minimal reactive ability with many chemical reagents. Because of this, bulk gold is known to be chemically inert, and this low activity is due to the particle sizes.1 However, gold nanoparticles (AuNPs) are the most highly active of catalyst due to the lack of a stable oxide (unlike most elements).2–4 As the Fermi potential of metal nanoparticles becomes more negative, they exhibit a substantial decrease in potential. The result of this unique property allows them to behave as catalysts in electron transfer processes, such as hydrogenation reactions. Electrical, optical, and catalytic properties are frequently seen in small nanomaterials and gold nanoparticle catalysts show excellent potential for the selective oxidation or hydrogenation of organic substrates.1,5 It is believed that gold nanoparticles will be key building blocks for many disciplines in the 21st century. For example, their individual particle size behaviors, and the electronic, magnetic and optical properties (quantum size effect), show great promises to the catalysis, nanotechnology, and biological field.2–4

Four different sizes of nanoparticles were synthesized and then suspended on four different economically favorable supports. The catalytic properties were investigated in this study with the reduction of 4-nitrophenol, a common hydrogenation reaction. Kinetics of the catalysis was monitored with UV-Vis spectrophotometry and samples were characterized with both transmission electron microscopy (TEM) and X-ray fluorescence (XRF). It was found that all reactions followed first order kinetics. Activated carbon did not behave as a catalytic surface, but was found to absorb the nitrophenol for all nanoparticle sizes. Glass wool and the largest AuNP (53.5nm) proved to be the best support by providing the fastest rate constants. This heterogeneous catalyst was also found to be recyclable.

REFERENCES

1) Abdel-Fattah, T. M. & Wixtrom, A. Catalytic reduction of 4-nitrophenol using gold nanoparticles supported on carbon nanotubes. ECS J. Solid State Sci. Technol. 3, M18–M20 (2014).

2) Seoudi, R. & Said, D. A. Studies on the Effect of the Capping Materials on the Spherical Gold Nanoparticles Catalytic Activity. World J. Nano Sci. Eng. 01, 51–61 (2011).

3) Daniel, M.-C. & Astruc, D. Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology. Chem. Rev. 104, 293–346 (2004).

4) Heddle, J. Gold Nanoparticle-Biological Molecule Interactions and Catalysis. Catalysts 3, 683–708 (2013).

5) Huang, J. et al. Ag Dendrite-Based Au/Ag Bimetallic Nanostructures with Strongly Enhanced Catalytic Activity. Langmuir 25, 11890–11896 (2009).
Growth Mechanism of Silver Nanowires By Polyol Process and Their Application for Transparent Conductive Thin Film
Authors: Hsu Hsun-Feng , Hong Liang-Zheng , Lin Cheng-Fu , Lyu Cheng-Han
Published: February 2020

One-dimensional nanowires have attracted intense interest due to their unique photo-electric, magnetic and thermal conductive characteristics. Silver nanowire (Ag NW) based thin films have been recently used as transparent conductive films because of their high optical transparency, low sheet resistance and flexibility. Previous studies have demonstrated that polyol process, one of widely used method for Ag NWs chemical synthesis, could be used to produce Ag NWs by adding Cl- ions with appropriate concentration in the process. Besides Ag NWs, Ag particles could also be formed with addition of much higher or lower Cl- ions. However, optimal reaction time and concentration of Cl-ions for Ag NWs synthesis have rarely been reported.

In this study, Ethylene Glycol (EG) solution with AgNO3was prepared and added in EG solution with Polyvinylpyrrolidone (PVP) for Ag NW formation. Mechanism of Ag NW formation was investigated by adding different amount of NaCl for different reaction time.

The results show that Ag nanoparticles were initially formed and gradually turned into nanowires because of PVP addition.
However, Ag NWs would gradually shorten while growing at critical length in the reaction. This interesting phenomenon could be explained by the reducing of surface energy. Furthermore, the longest Ag NWs could be obtained under condition of optimal reaction time and concentration of Cl-ions. These Ag NWs were prepared as transparent conductive thin films for optical transmittance and electrical conductivity measurements. Transparent conductive thin films with long AgNWs have better conductivity than short ones, and their stability would be further increased while coating the Polymethylmethacrylate (PMMA) as protective layer.
Ionic Current Rectification in a Conical Nanopore: Influence of Salt
Authors: Yang Shu-Tuan , Lin Chih-Yuan , Hsu J.P. , Tseng Shiojenn
Published: February 2020

Because it is capable of mimicking the ion channels of living organisms, the ionic transport in an artificial nanopore has drawn the attention of many researchers, recently. A considerable amount of efforts has also been made on relevant analyses due to the fast advances in nanotechnology and wide potential applications. As the linear size of a channel is down to the order of Debye length (or thickness of electric double layer), the overlapping of electric double layers yields distinctive electrokinetic phenomena. These include, for example, ion concentration polarization, ion selectivity, and ion current rectification. Ion current rectification is the phenomenon that a nanopore shows a diode-like current-voltage behavior, or the preference for ionic current in a certain direction when an electric potential is applied. For charged nanopores, ion current rectification might arise from several reasons, such as asymmetric pore geometry, imposed salt gradient, and bipolar surface properties. In the present study, the influence of electroosmotic flow on the behavior of the ion current rectification in a conical nanopore connecting two large identical reservoirs is investigated. In particular, the effect of the type of salt is examined by considering LiCl, NaCl, and KCl. We show that neglecting electroosmotic flow is capable of influencing ion current rectification both quantitatively and qualitatively. If electroosmotic flow is neglected, the rectification factor at each level of the applied electric potential bias across the two reservoirs for the case of LiCl (KCl) is always the largest (smallest). However, if electroosmotic flow is taking into account, the relative magnitude of the rectification factors for various salt depends upon the level of the applied electric potential bias. This behavior is consistent with the experimental observation in the literature, and can be explained by the degree of ion deplection/enrichment in a nanopore.
Aerosol Synthesis of Mesoporous Carbon Spheres with High Electrochemical Double-Layer Capacitance
Authors: Min Byeong Ho , Jung Kyeong Youl
Published: February 2020

Mesoporous carbons have received much attention as the electrode materials for electrical double layer capacitors (energy storage) or capacitive deionization (separation) due to the advantages of large surface area, tunable pore size, chemically inert and good conductivity. The electrode materials are known as a key factor determining the performance of capacitors. A lot of carbons with different forms including activated carbon (AC), carbon nanotubes (CNTs), mesoporous carbon, and graphene have been used as the electrode materials for energy storage devices. Carbons should have a proper pore structure in order to exhibit good electrochemical properties. Thus, it is important to design porous carbons via a proper synthetic method. The spray pyrolysis as a representative aerosol process is a powerful tool and has been used to prepare various functional materials. In this work, mesoporous carbon particles with high capacitance were prepared by the spray pyrolysis using sucrose as a carbon source. To increase the mesopores, a new strategy was developed. The key idea is to add TEOS into the precursor solution with the carbon source. The physical and electrochemical properties of the resulting carbons were characterized by using N2 isotherm, Raman, SEM, TEM, CV, and EIS analysis. The prepared carbons have a spherical shape and a graphitic structure. The use of TEOS was revealed to effectively improve the generation of mesopores. The synthesized carbons have the specific surface area of 1480 m2/g and the pore size of about 4 nm. According to the electrochemical analysis, the prepared mesoporous carbons exhibit high specific capacitance of 332 F/g at current density of 1 A/g, which is about 75% higher compared with the commercial activated carbon (189 F/g). The improved capacitance is mainly attributed to the mesoporous structure helpful for the ion transportation. The suggested new strategy for the spray pyrolysis could produce high mesoporous carbons which were revealed to be profitable for electrode materials with high capacitance.
Impedance Spectra Associated with Metal Deposition at the Negative Electrode from Contaminated Metal Particles at the Positive Electrode in a Lithium Ion Battery
Authors: Nakajima Hironori , Inada Akiko , Kitahara Tatsumi , Nagata Yusaku
Published: February 2020

Lithium ion batteries have the issue of internal short circuiting by the electrodeposition of metal at the negative electrode. This deposition follows the dissolution of contaminated metal particles incorporated into the positive electrode in manufacturing process. Thus, we have investigated the dissolution­/deposition behavior of metals such as copper, nickel, iron, and stainless steel so far1. We also proposed a diagnosis method for the incorporation of the metal particles by electrochemical impedance spectroscopy, taking advantage of characteristic changes of the impedance spectra (phase angle) between 10-­1 Hz1. In the present study, we investigate the time variation of the impedance spectra associated with the growth of the metal deposits at the negative electrode.

Test cells were assembled with positive electrodes of metal plates of iron, nickel and stainless steel, electrolyte solution of ethylene carbonate (EC)/diethylcarbonate (DEC) (1:1 vol.) containing 1 M LiPF6, and negative electrodes of graphite mixed with PVDF binder.

Potential between the metal plates and the negative electrode was maintained at 4.2 V by a potentio/galvanostat to electrochemically dissolve the metal plate at the positive electrode and deposit the metals at the negative electrode, while the negative electrode was maintained at 0.3 V against a lithium wire in the test cell by an auxiliary potentio/galvanostat to reproduce the potentials in a lithium ion battery.

We observe the metal deposits at the negative electrodes from the iron, nickel and stainless steel plates by FE-SEM and EDX. Time variations of the phase angle in the impedance spectra between 10­-1 Hz for the above metal deposits are correlated with the metal growth, taking into account the impedance of the SEI layer at the metal surface.

1. Hironori Nakajima, and Tatsumi Kitahara, Diagnosis Method to Detect the Incorporation of Metallic Particles in a Lithium Ion Battery, ECS Trans., Vol. 68, 2, 59-74 (2015).
Flexible Wire-Shaped Supercapacitors in Parallel Double Helix Configuration with Stable Electrochemical Properties Under Static/Dynamic Bending
Authors: Guo Kai , Li Huiqiao
Published: February 2020

Wire-shaped flexible supercapacitors (SCs) have aroused much attention due to their small size, light weight, high flexibility and deformability. However, the previously reported wire-shaped SCs usually involve complex assembly process and encounter potential structural instability, and the influence of dynamic bending on the electrochemical stability of wire-shaped SCs is also not clear. Here, a parallel double helix wire-shaped supercapacitor (PDWS) protocol has been developed with two symmetric titanium@MnO2 fiber electrodes winded on a flexible nylon fiber by a simple and reliable process. The PDWSs show an operate voltage of 0.8 V, a high capacitance of 15.6 mF cm-2
and an energy density of 1.4 μWh cm-2. Due to rational structure design, the PDWSs demonstrate excellent mechanical and electrochemical stability under both static and dynamic deformations. Over 3500 bending cycles, 88.0% of the initial capacitance can still be retained. In terms of dynamic bending, it is found that the cyclic voltammetry curves show periodically fluctuations simultaneously with the bending frequency and the intensity of fluctuation increases with higher bending frequency, while the dynamic capacitance is almost not affected. With extraordinary mechanical flexibility and excellent electrochemical stability, the high performance PDWS is considered to be a promising power source for wearable electronics.

Figure 1
Pseudocapacitance and Excellent Cyclability of Quinones on 2D Graphene
Authors: Boota Muhammad , Chen Chi , Bécuwe Matthieu , Miao Ling , Gogotsi Yury
Published: February 2020

Electrochemically active organic materials are attractive solution for the energy storage devices due to their natural abundance, relatively low cost, structural diversity and sustainability.1,2 Conducting polymers are well studied organic systems for the supercapacitors and batteries.3,4 Although, they exhibit high initial capacitance, their structural degradation due to ion doping/undoping leads to capacitance fade upon moderate cycling. Thus, it is needed to explore new organic materials which offer high redox capacitance, and longer cycling lifespan for the energy storage devices.

Herein, we report 3D interconnected xerogel composed of redox-active 2,5-dimethoxy-1,4-benzoquinone (DMQ) decorated on reduced graphene oxide sheets (DMQ@rGO), via one-step hydrothermal method. The DMQ not only provided fast two-electron redox but also yielded an open-structured hierarchical architecture by acting as a spacer between the rGO sheets. When binder-free optimized composition of DMQ@rGO was tested as a pseudocapacitive electrode, it showed high capacitance (650 F/g, 780 F/cm3 at 5 mV/s) and excellent capacitance retention of 99% after 25000 cycles at 50 mV/s in 1M H2SO4. Furthermore, density functional theory calculations are used to elucidate the charge storage mechanism, binding energies, adsorption orientation of DMQ, charge redistribution and density of the states. Our combined experimental and theoretical results determine that careful selection of the quinone structure, conductive substrate and electrode architecture altogether play a crucial role for high capacitance and long cycling performance.

1 B. Huskinson, M. P. Marshak, C. Suh, S. Er, M. R. Gerhardt, C. J. Galvin, X. Chen, A. Aspuru-Guzik, R. G. Gordon and M. J. Aziz, Nature, 2014, 505, 195–8.

2 M. Boota, B. Anasori, C. Voigt, M.-Q. Zhao, M. W. Barsoum and Y. Gogotsi, Adv. Mater., 2015, 28, 1517–22.

3 D. Vonlanthen, P. Lazarev, K. a. See, F. Wudl and A. J. Heeger, Adv. Mater., 2014, 26, 5095–5100.

4 M. Boota, M. P. Paranthaman, A. K. Naskar, Y. Li, K. Akato and Y. Gogotsi, ChemSusChem, 2015, 8, 3576–3581.
US DOE Electric Vehicle Battery R&D Progress and Plans
Authors: Howell David
Published: February 2020

The Department of Energy’s Vehicle Technology Office (DOE-VTO) funds high-reward/high-risk research conducted by national laboratories, universities, and industry – to develop low-cost and high-performance automotive batteries necessary for the consumer acceptance of hybrid and plug-in electric vehicles (PEV) in the marketplace. In fiscal year 2015, VTO battery R&D funding totaled about $80 million. Current battery technology performance is far below its theoretically possible limit and in the near-term, opportunity exists to more than double the battery pack specific energy for lithium-ion technology by using new high-capacity cathode materials, higher voltage electrolytes, and by replacing graphite anodes with high capacity silicon or tin-based intermetallic alloys. In the longer term, certain “beyond Li-ion” battery chemistries) offer the possibility of specific energy values significantly higher than those of current lithium-ion batteries as well as the potential of significantly-reduced battery cost. Despite recent promising advances, more R&D is needed to achieve the requisite performance, lifetime and reduced cost needed for these new battery technologies to enter the market. The status of VTO-funded advanced automotive battery R&D projects for FY 2014-15 will be discussed in this talk and associated issues will be highlighted.
Thick Electrode Designs for Lithium Ion Batteries
Authors: Chiang Yet-Ming
Published: February 2020

A typical lithium-ion cell contains about 25 individual materials layers per 1 mm of stack thickness, an evolutionary result after a quarter century of technology development that remains non-optimal from materials cost and volume utilization viewpoints.  This talk will discuss recent work at MIT and 24M Technologies on thick electrode designs that can reduce materials cost from non-energy-storing components while delivering necessary electrochemical kinetics and remaining highly manufacturable.  24M has developed a new semisolid electrode technology and manufacturing method that yields electrodes with several times the thickness and area capacity of conventional lithium ion electrodes, yet has transport kinetics rapid enough for all but very high power applications.  The semisolid lithium ion cells have significantly fewer inactive component layers than conventional lithium-ion cells of similar performance, and can be produced by a radically simpler process that obviates most of the electrode fabrication unit operations in conventional Li-ion, thereby lowering both materials and manufacturing cost.  At MIT, magnetic alignment methods that produce low tortuosity porosity from sacrificial pore formers have been developed, that are rapid, scalable, and naturally produce aligned porosity favorably oriented normal to the electrode plane.

Support for this work by the U.S. Department of Energy through the ARPA-E program, the Vehicle Technologies Office of EERE, and the Advanced Battery Materials Research (BMR) program is gratefully acknowledged.
Fail-Safe System for High Energy Density Power Li-Ion Batteries
Authors: Mao Huanyu
Published: February 2020

As longer driving range becomes an important feature for pure electric vehicles, higher energy density power batteries are needed.  However, the battery safety for higher energy density power batteries has been an obstacle.   An idea of “Fail-Safe” and its measures can largely reduce the risk of using high energy density power Li – Ion batteries. This talk will describe how our Fail-Safe system working to prevent the overall packs disasters when few cell had thermo runaway inside the battery pack.
Morphological Evolution of Multilayer Ni/NiO Thin Film Anodes during Lithiation
Authors: Evmenenko Guennadi , Fister Timothy T , Buchholz Donald Bruce , Esbenshade Jennifer , Chen Xiao , Li Qianqian , Wu Jinsong , Dravid Vinayak , Fenter Paul , Bedzyk Michael J.
Published: February 2020

We focus on in-operando structural evolution of model Li-ion battery anodes, which are comprised of multi-bilayer Ni/NiO films with active NiO layers sandwiched between buffer Ni layers. The films were deposited on sapphire via pulsed laser deposition (PLD). The morphological changes accompanying lithiation were tracked via in-situ and ex-situ X-ray reflectivity (XRR) and cross-sectional transmission electron microscopy in a series of films produced by systematically varying the thicknesses of active and buffer layers (20 Å to 200 Å) and the number of periodic bilayers (1 to 5). The key results of these combined studies are:

Complete lithiation of all the active NiO layers occurs only when the thickness of the buffer Ni layers is less than ~50 Å. For fully lithiated films, the active NiO layers doubled in thickness while being converted to Li2O layers and the reduced Ni from the NiO migrated to the bordering Ni buffer layers. This uniaxial lithiation process of multi-bilayer anodes started at the top and progressed toward the bottom of the stack. The expansion was accompanied initially by lateral inhomogeneities, which diminished over time leading to laterally uniform lithiated Li2O/Ni multilayers.

Ni layers with a thickness >50 Å present a kinetic barrier for the diffusion of lithium ions. This results in a partial lithiation of Ni/NiO multilayer anodes such that only the top NiO layer is lithiated.

XRR shows that for the 5-bilayer Ni/NiO films, the electron density of the fully lithiated layers is a constant (no density fluctuations). This attests that the reduced Ni is rather uniformly distributed inside the Li2O matrix after the completion of the conversion reaction. This contrasts the situation for 2-bilayer Ni/NiO films. Here, low-density regions are observed inside the fully lithiated active layers near the Ni interlayers.

For the fully lithiated Ni/NiO 5-bilayer films, the thickness of the Ni layers increases by 6-7 Å (roughly two atomic diameters of Ni), suggesting segregation of reduced Ni at the Ni/lithiated NiO layers. Consistent with this, the thickness of the Ni layer increases by 3-4 Å when only the top NiO layer is lithiated (for Ni thickness >50 Å, see 2 above).

In my presentation, I will discuss the mechanisms of the observed structural transformations. These are the first systematic studies of vertically digitized multilayer anodes that precisely determine the relationships between the morphological changes and the film architecture during lithiation.

This research was supported by the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
AlOOH-Based Nanocomposite Separators for Enhanced Safety and Performance
Authors: Avison David William , Carlson Steve , Sloan Ben
Published: February 2020

The separator, while typically regarded as an inactive component of the battery, is widely recognized as being critical to cell efficacy and safety; the importance of their role in cell design and overall battery performance has become increasingly important with the move to higher energy density storage systems to meet industry needs.

The present paper outlines the many key functions that separators serve in lithium-ion batteries and describes a separator design – specifically, AlOOH-based nanocomposite membranes – which addresses several critical safety concerns for high performance lithium-ion batteries, while maintaining cell longevity. These nanoporous membranes exhibit an extremely narrow pore size distribution, outstanding dimensional stability, excellent compression resistance, and very high thermal conductivity.  Safety and cell performance characteristics are correlated with fundamental materials and separator design parameters using a range of analytical techniques, characterization methods, and cell abuse tests. Opportunities for enhanced functionality are discussed.