bluuebunny/crossref_metadata_2025_split 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
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).