bluuebunny/crossref_metadata_2025 huggingface dataset:
Facile Synthesis of Graphene Quantum Dots By Microplasma-Assisted Electrochemistry
Authors: Yang Jhih-Siang , Chiang Wei-Hung
Published: February 2020

In recent years, Graphene-based materialshave attracted much attention due to their superior physical and chemical characteristics. However, these characteristics depend on their size and structure. Among these materials are zero-dimensional Graphene quantum dots (GQDs) with sizes defined lower than 100 nm. The electrons could be confined by the structure and let material possess semiconductor characteristic. They are also non-toxic and biocompatible making them widely applicable in biosensing, biomaging. Currently, most methods of synthesis GQDs involve high temperature, costly and complex processes unfavorable to its development. Here we report a facile and rapid process to synthesize GQDs through a microplasma-assisted electrochemistry method. And also, we provide a methodology to study physical and chemical effects on the photoluminescence properties.

Microplasmas are defined as gaseous discharges formed in electrode geometries where at least one dimension is less than 1mm. It can be operated with an aqueous solution as an electrode. Energetic species including radicals, ions and electrons formed in the microplasma are capable of initiating electrochemical or non-electrochemical reactions below the electrolyte and produce GQDs. Detailed materials characterizations including UV-Vis, Raman, FTIR, XPS and Photoluminescence spectroscopies, and microscopies including TEM and AFM suggest the developed microplasma-assisted electrochemistry method possess the ability to produce GQDs. The analytic results demonstrate as-product have blue emission with quantum yield of closing 1.5%. Raman spectrum show G, D and 2D band signals typical for carbon containing materials. Size distribution from TEM imaging show an average size of 4.9 nm. Its photoluminescence properties exhibit excitation-dependent emission, suggesting microplasma technology can possibly control its surface state and structure. Moreover, we also investigated its physical and chemical effects towards GQDs PL properties by adjusting plasma operating conditions and various precursors in the electrolytes, respectively. Increasing exposure time consequently shifts GQDs PL peak to the red spectrum suggesting particle size was increased, with reference to the quantum confinement theory. Similar effect was observed for using amine precursors having COOH functional groups as it generate more defects on GQDs surface, thus emitting lower energy. Our study provides the insight to understand the fundamental factors to control the GQDs emission energies.

Figure 1
Composition, Morphology and Electrical Properties of Electroplated Bite Thin Films
Authors: Hong Kimin , Suh Hoyoung , Noh Jinsung , Kim Jihyun , Jin Younghwan
Published: February 2020

Bismuth telluride(BiTe) is known as a promising material for thermoelectric devices. In this study, we fabricated BiTe thin films by using electrodeposition method and investigated the composional variation depending on the process parameters such as electrolyte composition, plating potential and thermal annealing temperatures. We prepared working electrodes by coating 50 nm of Au on P-type Si(100) wafers using electron-beam deposition method. The plating electrolyte was composed of Bi(NO3)3-5H2O, TeO2 and HNO3, where the concentration of Bi and Te ions varied from 1 mM to 30 mM. Electroplating was carried out with a potentiostatic method with the plating potential from –0.15 V to 0.1 V. As we changed the plating potential, we could observe that the relative contents of Bi and Te in the thin films could be adjusted in a continuous manner and that thin films changed from N-type to P-type semiconductor. The thin films were annealed by RTA with the annealing temperature between 220 and 260oC and the annealing time between 1 and 120 min. By annealing the films, the grain size of BiTe increased from 40 nm to 90 nm and the electrical resistivity increased from 2 uΩ·m to 8 uΩ·m. Maximum electromotive force was –1005 μV and highest power factor was 8.3 mW/m·K2.
Conductive Membrane Coatings for High Rate Vanadium Redox Flow Batteries
Authors: Shah Andrew , Joo Yong Lak
Published: February 2020

Global electricity production from renewable sources has grown dramatically in recent years. The intermittent nature of renewable forms of electricity generation has proven difficult to incorporate into regional electrical grids. Grid-scale electricity storage methods are a promising solution to the inefficiencies of unpredictable electricity generation. Redox flow batteries have demonstrated the ability to be used as reasonably low-cost, long-term, grid-scale electrical storage methods. Specifically, vanadium redox flow batteries (VRBs) have been of special interest due to their chemical stability, long life cyclability, and potential for high electrical capacity compared to other redox chemistries. Accompanying these advantages are some research challenges. There have been a number of efforts to improve the electrical conductivity of VRBs by physically or chemically altering the electrodes of the cell. Most VRBs use a carbon or graphite felt as a porous cathode and anode of the battery – the large surface area from the felt is used to increase the number of reaction sites at which the redox reaction can occur. Many modifications to the electrodes have been investigated, including using various highly conductive carbons, metal catalysts, and covering the carbon felt with hydrophilic surface groups. Less attention has been spent improving the membrane surface properties to improve electrical conductivity in the cell. A new approach to improve the rate capability of VRBs involves improving the electrical conductivity of the surface of the membrane itself using air-assisted electrospray deposition of conductive carbons mixed with a binder.

A conductive coating of carbon nanotubes (CNTs) and Nafion dispersion in water was used to coat a Nafion 117 membrane via air-assisted electrospraying to improve the rate capability and cycling performance of VRBs. It was found that electrospraying a highly conductive coating directly onto the surface of the membrane allowed for stable cycling performance at nearly double the current density that was afforded by the pristine Nafion membrane. A templating technique was used during the electrospraying process to allow for alternating domains of coated and uncoated membrane surface, which helped reduce the restriction of proton transport across the membrane, further improving rate capability and capacity retention of the VRB. The interfacial resistance between the membrane and the electrode was greatly diminished with the addition of a very small mass (<0.05 mg/cm2) of CNTs. This method has shown to be a fast, simple, and scalable technique for improving the rate capability of vanadium redox flow batteries, with the potential for extension to other redox flow battery systems.
Development of Intermediate Temperature Sodium Nickel Chloride Rechargeable Batteries: Polymer Seals and Cathode Formula
Authors: Chang Hee Jung , Lu Xiaochuan , Jung Keeyoung , Sprenkle Vincent , Li Guosheng
Published: February 2020

Large scale battery technologies have gained more attention as electric energy storage devices for renewable energy applications and grid stabilization. Due to growing safety concerns, high material costs and a limited cycle life, conventional lithium ion battery technologies have a limited portfolio for stationary applications. Recently, the sodium-nickel chloride (Na-NiCl2) battery has been under consideration as an alternative battery technology for stationary energy applications.[1] Yet, there are a number of challenges, such as the high operating temperature and high cost of hermetic sealing technologies, that hinder a further market penetration.

Typically, a tubular type Na-NiCl2 battery is operated at a high temperature above 280°C to obtain a reasonable electrochemical performance. Our recent work has demonstrated that a planar type Na-NiCl2 battery can achieve remarkable electrochemical performance over 1000 cycles even at an intermediate temperature (IT) of 190°C.[2] The lower operating temperature allows for the development of cost-effective sealing technology that uses conventional high temperature polymers as sealing materials.[3] We also demonstrate the Ni content in the cathode can be greatly reduced by 30% compared to that of the conventional Na-NiCl2 battery. Long term cell tests using the advanced cathode formula show a stable battery performance over 250 cycles.[4]

Therefore, our work suggests that developing polymer sealing technology and advanced low Ni-content cathode materials at intermediate operating temperatures might provide a new breakthrough to Na-NiCl2 batteries for practical stationary energy storage applications.

REFERENCES

J. L. Sudworth, J. Power Sources, 51 (1994) 105-114.

G.S. Li, X.C. Lu, J.Y. Kim, K.D. Meinhardt, H.J. Chang, N.L. Canfield, V.L. Sprenkle, Nat. Commun., 7 (2016) 10683.

H. J. Chang, X. Lu, J. F. Bonnett, N. L. Canfield, S. Son, Y. Park, K. Jung, V. L. Sprenkle, and G. Li. (submitted)

H. J. Chang, X. Lu, K. Jung, V. L. Sprenkle, and G. Li. (in preparation)
Development of Bifunctional Catalysts/Electrodes for Rechargeable Zn-Air Batteries in Alkaline and Near-Neutral Electrolyte
Authors: Jayasayee Kaushik , Bathgate Cameron , Oates Rose , Hanetho Sidsel Meli , Tolchard Julian Richard , Colmenares Luis , Labonnote-Weber Sophie , Kube Alexander , Juel Mari
Published: February 2020

In the framework of the EU funded project ZAS (Zinc Air Secondary innovative nanotech based batteries for efficient energy storage); we aim at improving the cycle life performance of secondary Zn-air batteries using low cost nanostructured materials and production methods. However, the goal is challenging due to the degradation of electrodes during cycling, which results in a rapid reduction in (storage) capacity. Furthermore, in order to improve the overall reversibility of the zinc-air battery it is necessary to understand the current limitations, requirements and challenges for each cell component (viz. anode, electrolyte, and cathode) and their interaction. Through close interaction between computer simulations and experimental testing, ZAS will select and develop electrodes to achieve its targets.

For rechargeable metal-air batteries, bifunctional air electrodes should be capable of catalyzing both the oxygen reduction and oxygen evolution reaction (ORR and OER, respectively) efficiently. In Zn-Air systems where aqueous alkaline and near-neutral electrolyte is used, it is not necessary to use a pure noble metal catalyst; instead it is possible to implement typical transition metal oxides such as perovskites, pyrochlores and spinels, individual oxides, and their mixture. This presentation will describe the achievements in the development of nanostructure bifunctional catalysts/electrodes in ZAS so far. Oxide materials of spinel and perovskite structures is being synthesized and electrochemically assessed in both alkaline and near-neutral electrolyte. The catalyst synthesis methods have comprised of a modified Pechini route, flame spray pyrolysis and regular spray pyrolysis. Physical methods such as specific surface area (BET), XRD and SEM have been used to characterize the catalysts.

The electrocatalytic activity of the bifunctional catalysts is determined by polarization measurements through rotating disk electrodes and a lab-scale screening method. Promising catalysts were further tested through half-cell and full-cell setups to systematically investigate the performance and lifetime. By constructing a database of the results, comparison of the relationship among the physicochemical and electrochemical characteristics from the different synthesis routes has been benchmarked.

Figure 1
Direct Visualization of Electrochemical Reactions in Porous Electrodes By Fluorescence Microscopy Using a Quinone-Based Flow Battery
Authors: Wong Andrew A. , Aziz Michael J. , Rubinstein Shmuel
Published: February 2020

As flow batteries gain attention for potential deployment for grid-scale energy storage, a deeper understanding of micro-scale phenomena, particularly electrochemical reactions within porous electrodes, is becoming increasingly important to predict and improve performance. In the past few years, aqueous-soluble organic molecules such as quinones have been increasingly studied because of their potential to be abundant, inexpensive active electrolytes for flow batteries. Furthermore, redox-active quinones can also have distinct fluorescence signatures enabling direct, in situ reaction-flow mapping using fluorescence microscopy. In contrast to many other in situ techniques used to characterize flow batteries, fluorescence microscopy enables fast (<100 ms) high resolution imaging enabling detailed understanding of reactions and fluid flow within porous electrodes.

In this study, we use fluorescence microscopy to bridge the micro-scale (<10 μm) and macro-scale (>2 cm) reaction-flow properties of flow batteries by mapping quinone reduction in flow past individual fibers and within bulk electrodes. To gain a deeper understanding of the reaction-advection-diffusion profile around individual fibers, spanning filaments are mounted perpendicular to the fluid flow using 3D-printed supports. The resulting quinones flow profile is imaged while passing a reducing current through the spanning fiber. This information is then correlated to bulk properties of porous electrodes.

Bulk properties of porous electrodes are also evaluated by fluorescence microscopy while operating a quinone-based flow battery at various fluid flow rates and electronic current densities. The abstract image here shows a snapshot of how reaction distributions can vary at low fluid flow rates. The results suggest that microscopically-heterogeneous, macroscopically-homogeneous electrode materials such as porous carbon papers can lack the full utilization of their surface area, and provide an opportunity for exploring improved electrode architectures. The results of this work aim to illuminate possibilities for improving the performance of flow batteries for grid-scale energy storage.

Figure 1
Study of Electrochemical Double Layer at Low Concentration and Voltage
Authors: Jain Aman
Published: February 2020

Worldwide research has identified electrical energy storage as one of the key areas for rapid advancement. There is a need of efficient storage and utilisation of electricity generated by intermittent sources to make a smooth transition of motor vehicles from traditional energy sources to electrically driven sources. This process highly depends on the development of high energy and power densities’ energy storage devices. Researchers have identified super-capacitors as one of the promising candidates for this purpose. Super-capacitors have a higher power density, but a lower energy density in comparison to other traditional energy and power devices. In future, they may find applications in various devices like hybrid vehicles. However, to achieve this target, it is crucial to maximise the energy density of super-capacitors. The focus of the paper is on the synthesis of electrodes using activated carbon mixed with polytetrafluoroethylene as the binder and soaking these electrodes in propylene carbonate. The aim is to maximise the energy density of prepared super-capacitors by varying electrolyte concentration, surface potential and dielectric constant of the medium. The dielectric constant was varied by varying the volumes of ethylene carbonate in propylene carbonate. A scrutinised binary model for net medium dielectric constant calculation was selected from literature to compare experimental values with theoretical values. Moreover, the transitional behaviours of the stern and diffuse layers capacitance with electrolyte concentration were also analysed using the modified Gouy-Chapman-Stern Model.

Keywords: Activated Carbon; Energy Density; Gouy-Chapman-Stern; Super-capacitor
A High-Performance Bismuth Decorated Carbon Cloth Electrode for Vanadium Redox Flow Batteries
Authors: Jiang Haoran , Zeng Yikai , Ren Yuxun , Zhou Xuelong , Shyy Wei , Zhao Tianshou
Published: February 2020

The fluctuated and intermittent nature of renewable energies, such as solar energy and wind energy, presents an imperative need to develop reliable, efficient and cost-effective large scale energy storage systems. Among the state-of-art large scale energy storage technologies, vanadium redox flow batteries (VRFBs) attract the most attention due to the advantages of decoupling power and energy, excellent electrochemical reversibility, no cross-contamination and long cycle life [1,2]. Even though, the widespread application of VRFBs is still hindered by the high capital cost, mostly resulting from the large stack size and precious redox-active materials [3]. In this regard, a VRFB capable of operating at high current density with deep charge/discharge depth is highly desirable, because the improved current density and charge/discharge depth will lead to the reduced stack size and the increased usage of electrolyte, respectively. However, the high current density would inevitably increase the cell polarization, resulting in the declining battery efficiency as well as electrolyte utilization. As a critical component of VRFBs system, the electrode exerts a significant influence on the battery performance since it contributes to the system polarization through not only the ohmic polarization, but also the activation polarization and concentration polarization. Thus, an idea electrode for VRFBs should have high surface activity and specific surface area to decrease activation loss, high electrical conductivity to decrease ohmic loss and high hydraulic permeability to decrease concentration loss [4].

In this work, a high-performance bismuth decorated carbon cloth electrode is prepared for VRFBs. Due to the thin thickness, low tortuosity and broad pore distribution ranging from 5 to 100 μm [5], carbon cloth electrode shows low electrical resistance and high permeability. In addition, the electrodeposited bismuth can effectively catalyze the vanadium redox reactions to increase the surface activity [6]. Our preliminary results show that the battery assembled with the present electrode delivers a high energy efficiency over 80 % at the high current density of 320 mA cm-1 for more than 100 cycles. Further experimental results will be disclosed at the meeting.

References:

[1] G.L. Soloveichik, Chem. Rev. 115 (2015) 11533-11558.

[2] M. Ulaganathan, V. Aravindan, Q. Yan, S. Madhavi, M. Skyllas‐Kazacos, T.M. Lim, Adv. Mater. Interface, 3 (2016) 1500309.

[3] A. Crawford, V. Viswanathan, D. Stephenson, W. Wang, E. Thomsen, D. Reed, B. Li, P. Balducci, M. Kintner-Meyer, V. Sprenkle, J. Power Sources. 293 (2015) 388-399.

[4] X. Zhou, Y. Zeng, X. Zhu, L. Wei, T. Zhao, J. Power Sources. 325 (2016) 329-336.

[5] K. Yoshizawa, K. Ikezoe, Y. Tasaki, D. Kramer, E.H. Lehmann, G.G. Scherer, J. Electrochem. Soc. 155 (2008) B223-B227.

[6] B. Li, M. Gu, Z. Nie, Y. Shao, Q. Luo, X. Wei, X. Li, J. Xiao, C. Wang, V. Sprenkle, Nano Lett., 13 (2013) 1330-1335.
Stable Organic Redox Flow Batteries in Nonaqueous Electrolytes
Authors: Wei Xiaoliang , Zhang Lu , Duan Wentao , Hu Dehong , Yang Zheng , Vijayakumar Murugesan , Liu Jun , Wang Wei , Sprenkle Vincent , Mueller Karl T
Published: February 2020

Redox flow battery is a promising stationary energy storage technology, which is ascribed to the separation of energy and power leading to excellent design flexibility and scalability. To overcome the limitation of narrow electrochemical window of traditional aqueous flow batteries, considerable attention has been paid to develop nonaqueous flow systems with the hope to increase the energy density. However, the reported nonaqueous flow batteries are limited by low energy density, low rate performance, and more critically, poor cyclability.

Here we report our efforts to explore the mechanisms of capacity fading and to improve the cycling stability of nonaqueous flow batteries based on organic redox-active materials.1-3 Promising organic redox candidates have been identified and structurally tailored to increase their solubilities, redox activities, and chemical stability. A rational molecular design protocol has been proposed and validated for developing stable organic flow batteries. Electrolyte engineering is also found to play a role in tuning the electrochemical performance and stability of nonaqueous flow batteries.

References

(1) X. Wei, W. Xu, J. Huang, L. Zhang, E. Walter, C. Lawrence, M. Vijayakumar, W. A. Henderson, T. Liu, L. Cosimbescu, B. Li, V. Sprenkle, W. Wang, Angew. Chem. Int. Ed.
2015, 54, 8684.

(2) X. Wei,* W. Duan, J. Huang, L. Zhang, B. Li, D. Reed, V. Sprenkle, W. Xu, W. Wang, ACS Energy Lett.
2016, 1, 705.

(3) W. Duan, R. S. Vemuri, J. D. Milshtein, S. Laramie, R. D. Dmello, J. Huang, L. Zhang, D. Hu, M. Vijayakumar, W. Wang, J. Liu, R. M. Darling, L. Thompson, K. Smith, J. S. Moore, F. R. Brushett, X. Wei, J. Mater. Chem. A, 2016, 4, 5448.

Figure 1. The cycling performance of a nonaqueous organic flow battery, showing excellent cycling stability for 50 cycles. The organic redox-active materials are shown.2

Figure 1
Enhanced Performance of Ti/Mn Redox Flow Battery
Authors: Kaku Hirokazu , Kawagoe Yoshiyasu , Dong Yong-Rong , Tatsumi Ryouta , Moriuchi Kiyoaki , Shigematsu Toshio
Published: February 2020

Large-scale batteries play an important role in the effective use of renewable energy like wind and solar power. Redox flow batteries (RFBs) offer high-speed response, independent design of power and energy, and high safety advantages, which have attracted much attention. RFBs consist of tanks of electrolyte that store chemical energy and electrochemical cells that reversibly convert chemical energy to electricity. Various RFBs can be classified into aqueous RFBs and non-aqueous RFBs, according to the electrolyte. Among aqueous RFBs, all-vanadium RFBs are the most mature technology and have been used in practical applications.

We have reported a Ti (IV) and Mn (II) mixed aqueous electrolyte which is applied for a Ti/Mn RFB. The aqueous Ti/Mn RFB shows a high energy density of 23.5kWh/m3 [1], and provides a low-cost option. The precipitation of MnO2 particles generated from instable Mn3+ ion can be greatly suppressed by mixing Ti and Mn for both positive and negative electrolytes [2]. However, the current density (50mA/cm2) remained low and needed to be improved. In the previous study, we succeeded to enhance the reactivity of both positive and negative electrodes by the thermal treatment of carbon electrodes. The full-cell performance was improved to the energy efficiency of 83.2% at 100mA/cm2
　[3].

For further enhancement of the cell performance, the resistivity of the membrane also needs to be considered. In this study, we investigate various ion exchange membranes for the Ti/Mn RFB. Some membrane samples are pretreated to achieve lower resistivity. The improved cell performance is confirmed with the appropriate membrane. We will also discuss the ion crossover and the coulombic efficiency of various membranes. In addition, the cell performance is affected by the state of the precipitation of MnO2 in the Ti/Mn RFB. The condition of the electrolyte (SOC, MnO2precipitation, flow rate, etc.) should be considered at the same time. The cell components and the electrolyte condition will be discussed comprehensively in the presentation.

References

[1] Y. R. Dong et. al., ECS Trans., 69(18), 59 (2015).

[2] H. Kaku et. al., ECS Trans., 72(10), 1 (2016).

[3] Y. R. Dong et. al., PRiME meeting, 26 (October, 2016).

Acknowledgements

This work is financially supported by Ministry of Economy, Trade and Industry (METI). This work is technically supported by The National Institute of Advanced Industrial Science and Technology (AIST).
Micelle Mediated Extraction of Neodymium and Electrochemical Characterization of AOT Reverse Micelles
Authors: Anderson Shannon , Kalu Egwu Eric , Clark Clayton , Nilsson Mikael
Published: February 2020

The extraction and separation of metal ions in the lanthanide series using the liquid-liquid extraction (LLX) technique poses a major challenge due to the chemical similarities of the metals. Hence, interest exists in devising a technique to improve the separation factor. The anionic surfactant, AOT, is proposed to pre-concentrate the metal from an aqueous phase through third phase formation and increasing the conductivity of the organic phase of a LLX experiment so an electric field can be applied to drive the extraction. Surfactants within LLX experiments have been shown to from a third phase and it is theorized that this phase is predominantly the surfactant and target metal, thus pre-concentrating the metal. The use of an imposed external field (electrochemical) to improve the LLX has been explored in the literature with limited success due to conductivity issues. In this work, the use of reverse micelle solutions containing water/AOT/n-dodecane for pre-concentrating Nd and water/AOT-HDEHP/n-dodecane for improved electrical conductivity is explored. The results of a feasibility study of the pre-concentration and electrochemical modulated extraction of neodymium (Nd) using the reverse micelles/microemulsions will be presented.

A concentration of 0.2 M AOT in n-dodecane was used to form a third phase in the extraction/pre-concentration of Nd from an aqueous solution using LLX. At and above an initial Nd concentration of 12 mM, third phase formed. As the initial concentration of the Nd increased, more Nd was extracted from the aqueous phase. Post-extraction washing of the organic phase resulted in approx. 56% of the Nd being accounted for. ICP will be used to determine if there is Nd in the third phase. Below an initial Nd concentration of 10 mM, third phase did not form and Nd was extracted. Post-extraction washing of the organic phase resulted in approx. 90% of the Nd being account for.

Electrochemical impedance (EIS) technique was used to determine the effect of molar content of water, Wo, and temperature on the reverse micelle solution conductivity. Results showed that as Wo increases, conductivity increases until the reverse micelles burst and form a biphasic system. Addition of HDEHP caused a significant drop in solution conductivity. Temperature has a mild effect on increasing the conductivity. Limited to applying 7 V, electrochemical extraction showed small improvement in Nd extraction percent over traditional LLX. The extraction percent of Nd in a liquid-liquid extraction cell containing reverse micelles and the mechanism of electrochemical modulated liquid-liquid metal ion extraction will be discussed.
Electrochemical Reduction of Molybdenium Compounds to Form Molybdenium Powder
Authors: Akpinar Bengisu , Erdogan Metehan , Karakaya Ishak
Published: February 2020

Molybdenum (Mo) is a refractory metal and mostly used as an alloying agent in cast iron, steels and superalloys to enhance hardenability, strength, toughness and corrosion resistance. It also finds other uses either in the form of a pure metal or an element in, for example, lubricants and catalysts. Traditional metal production methods are not suitable for molybdenum because pure molybdenum has very high melting point and has a tendency to get oxidized at low temperatures. Hydrogen reduction of molybdenum oxide is a very common way for Mo production but, it has two stages during process. At the second stage, the reduction process needs very high temperatures, therefore, high energy consumption and special equipment requirement is essential.

FFC Cambridge process [1] based on electrochemical reduction of solid compounds was considered as an alternative way to produce molybdenum at relatively low temperatures. Similar to reduction of WO3 [2], loss of molybdenum as molybdenum oxychloride from MoO3 in CaCl2 containing molten salts is inevitable [3]. MoS2 powder pressed and sintered at 400oC to form pellets were used as starting material for electrochemical formation of pure Mo in molten CaCl2-NaCl salt mixture under argon gas at 800oC. A constant voltage in the range 1 to 3.0V was applied between MoS2 cathode and graphite anode. When the process was terminated at a prescribed time, the cathode was removed from the molten salt, cooled in argon, washed with water in air to dissolve the solidified salt, and then dried at about 100oC in vacuum before further analysis employing XRD, SEM and EDS.

[1] G.Z. Chen, D. J. Fray, T. W. Farthing, Direct Electrochemical Reduction of Titanium Dioxide to Titanium in Molten Calcium Chloride, Nature, 407 (2000), 361-364.

[2] M. Erdoğan, İ. Karakaya, Electrochemical Reduction of Tungsten Compounds to Produce Tungsten Powder, Metallurgical and Materials Transactions B, 41B (2010), 798-804.

[3] W.T. Thompson, C.W. Bale, and A.D. Pelton: Facility for the Analysis of Chemical Thermodynamics (FACT), McGill University Montreal, Royal Military College of Canada in Kingston, E´cole Polytechnique, Montreal, Canada, 1985.
Molecular Dynamics Simulations of Lithium Ion Transport through Solid Electrolyte Interface Layer
Authors: Muralidharan Ajay , Chaudhari Mangesh , Rempe Susan , Pratt Lawrence R
Published: February 2020

Lithium ion transport through solid electrode interface (SEI) layer is elusive to molecular simulation studies due to lack of composition information and force field parameters available for organic SEI layer. Last decade, dilithium diethylene carbonate (Li2EDC) was suggested as the primary component of SEI layer using experiments and quantum mechanical simulations. We applied classical, non-polarizable OPLS-AA force field parameters to model SEI layer of Li2EDC molecules. Long time-scale molecular simulations at various temperatures (333, 500, 700K) were performed to calculate structural and transport properties of lithium ion in EDC. Vibrational power spectral analysis suggested two prominent modes of lithium vibrations at frequencies 400 and 650 cm-1 in EDC and pure ethylene carbonate solvents. These vibrational modes were further confirmed in Gaussian electronic structure calculations results. Self part of time dependent correlation function calculated using van Hove function confirm that EDC is crystalline compared to pure ethylene carbonate.

Sandia National Laboratories (SNL) is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's (DOE) National Nuclear Security Administration under Contract DE-AC04-94AL85000.
The Electrochemical Reduction of Organic Acids on Anatase-Type TiO2 Nanoparticles – a Theoretical Approach
Authors: Juhasz Gergely
Published: February 2020

The electrochemical reduction of organic acids on anatase-type TiO2electrode has been recently reported by Yamauchi [1]. Such an electrochemical reaction has a potential to produce alcohol products with high selectivity and efficiency, which can be used as alternative fuel. However so far the reaction is reported only for oxalic acid, and other acids like acetic acid cannot be reduced.

This reaction raise many questions, including the mechanism or the electrochemical steps as well as the role of the anatase electrode. We used Density Functional Tight Binding (DFTB ) method to study the interaction between organic acids and possible intermediates of the reduction reaction. For the simulation, models of the (101) surface of anatase as well as nanoparticle models were also used.

TiO2 nanoparticles, unlike surface slab models, always have a strong dipole moment, which interfere with absorption of organic acids as well as the solvent water molecules. The morphology of the nanoparticles has also a strong influence on the bandgap of TiO2: calculations showed an approx. 0.5 eV smaller gap for the nanoparticles. The decrease of the gap were mostly due to the significantly lower LUMO energy levels when they are compared to surface models (Figure 1). These low energy LUMO levels are due to edge effects and are expected to play an important role in the electrochemical reduction over these nanoparticles.

Calculations showed very strong absorption of the acids on the anatase models (in order of 150 kJ/mol). Such a strong absorption of the carboxyl group may actually protect it from the reduction. We hypothesized that one of the carboxyl group of oxalic acid acts as an anchor, while the reduction reaction is taking place mostly on the other side of the molecule. This would also explain why ordinary carboxylic acids like acetic acid cannot be reduced under the same conditions.

Reference:

[1] R. Watanabe, M. Yamauchi, M. Sadakiyo, R. Abe and T. Takeguchi, Energy Environ. Sci., 2015, 8, 1456–1462.

Figure 1
First-Principles Study of Ultrathin Coating Layer on Cathode Particles in Lithium Ion Batteries
Authors: He Yufang , Park Jonghyun
Published: February 2020

An ultra-thin film coating via Atomic Layer Deposition (ALD) is a viable approach for enhancing battery performance significantly. Despite several demonstrations of this improvement, still the fundamental understanding on the role of thin film is unclear, especially, regarding to interaction between the active material and the coated layer. In this work, an investigation was conducted via a first-principles calculation, focused on interfacial reaction, charge analysis and structural change of coating layer, and lithium ions transport mechanism during lithiation. Comparison between CeO2 and Al2O3 layers could explain the experimental observation, where CeO2 coating showed better performance. One interesting finding was that lithium ions in the coating layer can intercalate easily to the active materials, which was ignored in the several previous work in literature. This gives us an important clue for the reason of why ALD coating is beneficial to battery.
Powder Pulse Electrodeposition for Additive Manufacturing
Authors: Abbott Andrew P , Cihangir Salih , Ryder Karl S
Published: February 2020

Electrodeposition is commonly used for the deposition of metallic and composite coatings. It is useful as it can coat complex 3D structures and can be used for the deposition of alloys. There are a few disadvantages; it is relatively slow to build up thick coatings and in some cases the current efficiency can be low.

In this study a fundamentally different method for carrying out electrodeposition is demonstrated which can potentially be used for additive manufacturing. Here instead of dissolving metal from the anode and depositing it on the cathode a powder of the coating metal is put in contact with the cathode and pulse plating sequentially dissolves metal from the powder and then deposits it between the powder grains. By this method super-efficient deposition (efficiency >100%) can be achieved and thick layers can quickly be deposited.

This can in principle be carried out in any media but in this study ionic liquids were used to increase the current efficiency of the process. The method is demonstrated using both zinc and copper. It is shown that using these media certain crystal planes can be promoted and ordered deposits are obtained. In addition the same technique was used to deposit composite materials by staring with a mixture of metal powder with ceramic powders, such as alumina, silicon carbide. The morphology of the surfaces was characterized using SEM, X-ray diffraction, and 3D optical microscopy techniques.
(Invited) AlN and ScAlN Contour Mode Resonators for RF Filters
Authors: Henry Michael David , Timon Robert , Young Travis R , Nordquist Chris , Griffin Ben
Published: February 2020

A very strong technological market pull for wide bandgap semiconductor devices comes from the piezoelectric properties of aluminum nitride (AlN). Portable wireless products are expanding in their use of AlN films as RF devices in bulk acoustic wave (BAW) and surface acoustic wave (SAW) filters with substantial performance properties over other semiconductor materials. To maintain market dominance properties such as size, integration costs, and filter performance metrics continue to improve. Metrics closely coupled to material properties such as piezoelectric coupling coefficient (k2
eff) and quality factor (Q) arising from material sputtering conditions directly impact key filter parameters such as insertion loss, bandwidth, and rejection, and these properties have been intensely investigated as have device and filter architecture. To improve versatility, alternate resonator designs are emerging that combine micromachining and different piezoelectric coefficients such as d31 instead of d33. These contour mode resonators (CMR) differ slightly from BAW and SAW since resonator frequency is determined lithographically and devices are suspended which provides the opportunity to provide multiple frequencies on a single die with reduction of cross talk and integration on top of CMOS.

This work will discuss our efforts in utilizing CMRs to achieve a wide range of operating frequencies on a single die with improved performance. In this presentation we will discuss our RF sputter deposition process for creating high-performance AlN films, as well as plasma etching and integration techniques for fabricating CMRs. Fabricated devices spanning a range of 400 MHz to 3 GHz will be demonstrated with spur modal interaction discussed. Further, early investigations into scandium aluminum nitride (ScAlN) suggest that metrics such as Q and K2
eff can substantially improve simultaneously while still providing a wide frequency range of devices.
Optical Reflectivity of Spin-Coated Multilayered ZnO and Al:ZnO Thin Films
Authors: Buckley Darragh , McCormack Robert , McNulty David , Zubialevich V.Z. , Parbrook Peter J. , O'Dwyer Colm
Published: February 2020

Zinc oxide (ZnO) and its doped counterparts such as Al:ZnO are extensively investigated as indium-free alternatives for oxide electronics including solar cells, light emitting diodes and also display technologies. For the latter application, thin film transistor (TFT) devices are the building-block structures. High fidelity TFTs require conductive channel materials, with good field effect mobility for majority carriers and tunable optical transparency. Controlling growth, doping, crystallization, and thickness of thin films of these materials is required in order to improve and control physical properties, primarily electronic conductivity and optical transparency. With the advent of flexible electronics and curved TFT-based display panels, low cost, solution-processed methods are important and provide scalable coating methods on a range of substrates.

This work demonstrates the changes to the morphology, crystalline structure, optical reflectivity and electrical conductance of solution-processed ZnO thin films by the inclusion of an aluminium dopant during spin-coating. The is work also determines the compositional chemical state of the Al:ZnO structures compared to ZnO using X-ray photoelectron spectroscopy in conjunction with detailed X-ray diffraction and transmission electron microscopy examination of the film morphology. We also demonstrate a method of determining the optical thickness of multilayer thin films using simple, non-destructive angle-resolved reflectance measurements. Using optical interference, the optical thickness of the multi-layered deposited ZnO and Al:ZnO can be determined and show good agreement with the thicknesses measured by transmission electron microscopy of electron transparent lamellar cross-sections.

We also show the visible and near-infra red (VIS-NIR) light spectroscopy of ZnO and Al:ZnO multi-layered thin film structures grown on oxidized silicon substrates also define the growth conditions and processing to provide tunable antireflection coatings of ZnO and AZO.
Abnormal I-V Characteristics of Nanoparticle Based Al / ZnO / Au Diodes
Authors: von Seggern Heinz , Mundt Paul
Published: February 2020

Au/ ZnO(np)/ Al diodes produced by spin coating of ZnO nanoparticle (np) dispersions exhibit abnormal I-V characteristics compared to sputtered Au/ ZnO(sp)/ Al diodes produced by reactive oxygen-ion sputtering (sp) of the ZnO layer. Whereas the reactive ion sputtered diode shows the energetically expected injection from the Al electrode under positive bias (forward bias), the spin-coated ZnO(np) diode displays an inverse I-V characteristic. Since Al is used as bottom electrode in both kind of diodes the expected formation of a native Al2O3 layer is unlikely to be responsible for the different I-V characteristics. SEM micrographs of the diode’s cross section indicate that most likely the geometrical structure of the contact of the ZnO nanoparticles with the native Al/Al2O3 layer on the one side and the tip-like shape of the Au top-electrode on the other side are responsible for the drastic decrease of the injection probability of electrons under forward bias and for the strong increase of the current under reverse bias. A simple tunnelling model shows that the existance of air filled voids at the ZnO-Al2O3/Al interface can explain the strongly reduced injection current under forward bias. The strongly increased injection current under reverse bias (using the nomenclature of the sputtered device) can also be understood by the nanoparticulate structure of the ZnO top surface where deposition of Au onto the ZnO(np) surface leads to an enlarged surface area and a tip-like surface structure in contrast to a smooth interface in the case of sputtered ZnO. These Au-tips lead to high local electric fields which can explain the observed strong increase of the injection current under reverse bias. The same inverse I-V characteristics can be observed for an Au/ZnO(np)/Au device supporting strongly the proposed mode of operation of the nanoparticles on the injection processes. Characteristics of different diodes will be compared and observed diode characteristics will be rationaled by theoretical considerations along the above lines of argumentation. Possible impact on already published and more complex device structures like light emitting diodes and organic solar cells will be discussed comprising all functional nanoparticulate ZnO- layers.
(Invited) Surface Plasmon Resonance Sensors for Biomolecular Chirality
Authors: Liu Mingzhao , Lu Fang , Tian Ye , Su Dong , Gang Oleg
Published: February 2020

Surface Plasmon Resonance Sensors for Biomolecular Chirality

Mingzhao Liu, Fang Lu, Ye Tian, Dong Su, and Oleg Gang

A chiral object, i.e., one that is distinguishable from its mirror image, interacts differently with photons of left-hand (+) and right-hand (-) circular polarizations. The difference in the absorption part is known as circular dichroism (CD), which is usually observed for biomolecules with one or more chiral centers and is widely used to probe their molecular stereometry. Such probing has an increasingly broad importance for biomedical and pharmacological fields due to synthesis/separation/detection of homochiral species, biological role of chiral organization, and structural response to environmental conditions and enantiomeric drugs. Recent theoretical and experimental works demonstrated that the CD signal from chiral organic molecules could appear in the plasmonic band when they are coupled with plasmonic particles. This talk will cover an intriguing case in which non-chiral plasmonic nanoparticles are surrounded by a monolayer of DNA molecules that have chirality arising from its individual nucleobases and helix structure. It is found that the surface plasmon-induced CD is very sensitive to the nonchiral plasmonic nanoparticles’ shape and chemical composition. We identify gold/silver core/shell nanocubes as most effective by providing a giant, 2 orders of magnitude CD enhancement in a near-visible region, while DNA’s native CD signal appears at much higher energy. The discovered phenomenon opens novel opportunities in ultrasensitive probing of biomolecules and for novel optical nanomaterials based on the chiral elements.
(Invited) Tuning Physicochemical Properties of MoS2 By Mechanical Strain
Authors: Zheng Xiaolin
Published: February 2020

Monolayers of 2D materials have ultrahigh mechanical strength, which enables application of very large elastic strains (e.g., ~11% for MoS2 and 25% for graphene). The ability of sustaining such large elastic strain offers unprecedented opportunities to engineer the physicochemical properties by applying mechanical strain. In this talk, I will present two examples on the effect of strain on the properties of MoS2 layer. The first example shows that elastic tensile strain reduces the bandgap of MoS2. When a gradient strain field is applied to MoS2 monolayer, the created bandgap gradient acts as an efficient funnel of photogenerated excitons that leads to enhanced photoluminescence. The second example shows that when elastic strain is applied to the sulfur vacancy on the basal planes of monolayer 2H-MoS2, the strain modifies the local electronic structure and catalytic activity. The proper combination of S-vacancy and strain allows us to achieve higher intrinsic activity for hydrogen evolution reaction than the edge site of MoS2.
Multifunctional Textile for Energy Harvesting and Self-Powered Sensing Applications
Authors: Jao Yun-Ting , Chang Ting-Wei , Lin Zong-Hong
Published: February 2020

With the rise of wearable electronic technology, the market value of related devices is predicted to exceed $12 billion in 2018. However, the supply of sufficient electricity to operate such devices over an acceptable duration of time without employing a large-sized battery has remained a major challenge for the development. Therefore, the concept of power suit which can harvest renewable energy from the environment to charge the battery in wearable electronic devices has been proposed. In this study, we developed textile-based triboelectric generator to harvest mechanical energy from human motions. The electric outputs generated from the triboelectric generator reached 200 V, 0.1 mA, and 1.5 W/m2. In addition, we also functionalized the textile-based triboelectric generator with self-powered sensing properties. Through the selection of triboelectric materials, the as-developed generator further became self-powered sensors for humidity and ions detection. We believe that the textile-based triboelectric generator can be combined with other healthcare sensors to become smart clothing products in the near future.
A Self-Powered Active Antibacterial System Controlled by Human Motions
Authors: Chou Ting-Mao , Ke Yi-Yun , Lin Zong-Hong
Published: February 2020

Pathogenic bacteria that give rise to diseases every year is a major health concern around the world. In recent years, tellurium-based nanomaterials have been approved as new and efficient antibacterial agents. In this research, we developed a new approach to directly grow tellurium and tellurium-gold nanowires (Te and Te-Au NWs) onto commercial carbon fiber fabrics and demonstrated that they remain the good antibacterial effect. In addition, we also showed that when connecting the as-prepared carbon fiber fabrics to a triboelectric nanogenerator, a self-powered antibacterial system was constructed. During the operation of triboelectric nanogenerator, the generated electricity contributed to electroporation of bacteria and electrolysis of Te and Te-Au NWs. These factors resulted in a combination effect and consequently kill the bacteria in an efficient way. Upon increasing the amplitude and frequency of electric output, the self-powered antibacterial system exhibited more enhanced performance to inhibit the bacteria growth. These results indicate that the as-prepared carbon fiber fabrics and self-powered antibacterial system can be integrated with clothing products in the near future.