bluuebunny/crossref_metadata_2025 huggingface dataset:
Developing Plasmonic Imaging Technique to Understand Battery Solid Electrolyte Interface Formation and Li Nucleation in-Situ
Authors: Shan Xiaonan , Yang Chaojie
Published: February 2020

During the operation of lithium-ion battery (LIB), a solid electrolyte interface (SEI) layer forms on the anode electrode materials due to side reactions with the electrolyte solvent and salt. It is essential to the performance of LIBs and it decides the initial capacity loss, self-discharge characterizstics, cycle life and safety. Therefore to understand the SEI formation is extremely important for battery research. Currently, most of characterization methods of SEI are based on electron microscope, although powerful, it is difficulty to directly map the SEI formation in-situ.

We have developed a novel plasmonic imaging technique to image the local SEI formation and measure the electrochemical reaction of the anode electrodes. Unlike conventional electrochemistry that measures the electrical current from entire electrode, the plasmonic-based electrochemical microscope (PECM) technique is based on sensitive imaging of surface plasmonic signal caused by electrochemical reaction, which is measured optically, thus allowing for fast and non-invasive imaging of electrode processes. PECM can image localized chemical reactions on the electrode surface ins-situ, this information will be extremely important for us to understand SEI formation and electrochemical reaction on the anode electrode. The electrochemical reaction will always be accompanied by a conversion of the chemical species between oxidized and reduced states, and plasmonic imaging is extremely sensitive to the species generated (or consumed) on electrode materials. Therefore, the PECM has great potential to characterize the local electrochemical reactions and energy storage process.
7li Chemical Shift Imaging to Detect Microstructural Growth in All Solid-State Batteries
Authors: Marbella Lauren E , Zekoll Stefanie , Kasemchainan Jitti , Emge Steffen , Bruce Peter G. , Grey Clare P.
Published: February 2020

All solid-state batteries potentially offer safe, high energy density electrochemical energy storage, yet are plagued with issues surrounding Li microstructural growth and subsequent cell death. We use 7Li magnetic resonance chemical shift imaging and electron microscopy to track Li microstructural growth in the garnet solid-electrolyte, Li6.5La3Zr1.5Ta0.5O12. Here, we follow the early stages of Li microstructural growth during electrochemical cycling – from the formation of Li on the electrode surface to dendritic Li connecting both electrodes in a symmetrical cell and correlate these changes with electrochemistry (e.g. short circuiting). During these experiments, we observe changes at both the stripping and plating interfaces during Li microstructural growth, indicating heterogeneities in both Li removal and deposition. At low current densities, 7Li MRI detects the formation of Li microstructures in cells before obvious electrochemical signatures indicating their presence are observed.
Carbon Nanostructures and Nanocapsules: Preparation and Biological Behaviour
Authors: DaRos Tatiana
Published: February 2020

The potentiality of Carbon Nanostructures (CNSs) and Nanocapsules (i.e. filled nanostructures) are already known but there still is a lot to be explored and unraveled. For example the conjugation with many biocompatible and/or bioactive units are reported but there is still room to development and exploitation of the peculiar characteristics of the carbon-based nanoconstructs. Preparation of new and more biocompatible materials, removal of salts externally deposited on nanocapsules, functionalization of filled materials, interactions with cellular components and possible alterations of cellular and biological pathways are issues to be addressed in the perspective of a better comprehension of CNSs potentialities and are devoted to the development of actual clinical applications.
(Invited) Fast-Scan Nanogap Voltammetry at Double-Carbon-Fiber Ultramciroelectrodes
Authors: Amemiya Shigeru
Published: February 2020

In this presentation, we discuss theory [1] and experiment [2] of double-carbon-fiber (CF) ultramicroelectrodes (UMEs) with nanometer-wide gaps to voltammetrically obtain high time resolution, signal-to-background ratio, and kinetic selectivity for dopamine (DA) against ascorbic acid (AA). The novel nanogap-based electrodes are fabricated by using a pair of ~7 µm-diameter CFs, which are inserted into a double-bore glass capillary, heat-pulled, and milled by focused-ion-beam technology to yield ~50 µm-long double-cylinder UMEs separated by a nanometer-wide gap without extensive nanolithography or nanoscale electrode positioning required for other nanogap electrodes. Double-CF UMEs are characterized electrochemically by investigating the redox cycling of the Ru(NH3)6
3+/2+ couple across a nanogap between voltammetric generator and amperometric collector electrodes to achieve quasi-steady states at fast scan rates of 100 V/s, which is ~1000 times faster than reported with any nanogap-based electrochemical cell. Importantly, the transient background of the amperometric collector response is suppressed ~100 times in comparison with that of the voltammetric generator response to enable the quantitative analysis of the collector response against the cycled generator potential without background subtraction. Finite element analysis of oxidative amperometric responses to Ru(NH3)6
2+ at the collector electrode at up to 100 V/s yield consistent gap widths of ~0.18 µm and a standard electron-transfer rate constant of 0.9 cm/s. Moreover, nanogap-mediated redox cycling can be initiated by DA oxidation at the generator electrode to largely improve the DA selectivity of the collector response against AA, which is also oxidized at the generator electrode to immediately and irreversibly produce a redox-inactive species, thereby minimizing the corresponding collector response. The probe-type design of double-CF UMEs as well as their high DA selectivity against AA is attractive for in-vivo applications.

[1] Pathirathna, P.; Balla, R. J.; Amemiya, S. “Simulation of fast-scan nanogap voltammetry at double-cylinder ultramicroelectrodes.” J. Electrochem. Soc., Focus Issue on the Brain and Electrochemistry Honoring R. Mark Wightman and Christian Amatore, 2018, 165, G3026.

[2] Pathirathna, P.; Balla, R. J.; Amemiya, S. “Nanogap-based electrochemical measurements at double-carbon-fiber ultramicroelectrodes.” Anal. Chem.
2018, 90, 11746.
(Invited) Advances in NIR Fluorescent Swnt Sensors for Biomedical Applications
Authors: Strano Michael
Published: February 2020

Our laboratory at MIT has been interested in how carbon nanosensors, such as those based on carbon nanotubes and graphene, can be applied to problems in precision medicine. Specifically, we are working on nIR fluorescent nanosensors based on single walled carbon nanotubes capable of implantation in-vivo for the continuous, real time, persistent monitoring of a wide range of important analytes in the human body. Precision medicine motivates the need for specific measurements and analysis of data on individuals within a complex human population. To address the challenge of adapting sensor platforms to different analytes of interest to stable, molecular recognition interfaces, we invented at MIT a technique called Corona Phase Molecular Recognition (CoPhMoRe) whereby synthetic, non-biological recognition sites are created from the three-dimensional structure of an adsorbed heteropolymer, selected from a combinatorial library once adsorbed to a nIR fluorescent single walled carbon nanotube. This platform is well suited for precision medicine due to the long term photostability of the CNT, and the label free nature of the detection, as well as lack of photobleaching. Our carbon nanotube sensors have been developed for a variety of important biomolecules such as, radical oxygen species, radical nitrogen species, carbohydrates such as glucose, and even proteins such as fibrinogen and insulin. The ability to implant a carbon nanotube sensor and measure the concentration of an analyte continuously and in real time will give physicians the data they need to assess the needs of individual patients.
(Invited) Modeling Insights into Optical Properties of Functionalized Carbon Nanotubes
Authors: Tretiak Sergei
Published: February 2020

Chemical functionalization or ‘doping’ (e.g., with oxygen or diazonium salt agents) of carbon nanotube surfaces recently emerged as a promising path to address these issues. Our quantum-chemical modeling have shown that chemical surface adducts locally alter the pi-conjugated network of the nanotube surface and lead to a spatial confinement of the electronically excited wavefunctions. Experimental low temperature photoluminescence studies reveal a complex structure of electronic states and their dynamics induced by surface modifications. Our simulations suggest an association of these spectroscopic features with deep trap states tied to different specific chemical species. Engineering of interfacial surface structures of single-chirality nanotube materials with dopant-induced defects then allowed us for accurate control over energy transfer and luminescence properties. Overall, these results suggest that covalent doping chemistry is a powerful route toward harnessing dynamics of excitons and charges in carbon nanotubes leading to new enhanced optical behaviors.
Mediatorless, Reversible Optical Nanosensor Enabled through Enzymatic Pocket Doping
Authors: Zubkovs Vitalijs , Schuergers Nils , Lambert Benjamin Paul , Ahunbay Esra , Boghossian Ardemis Anoush
Published: February 2020

Single-walled carbon nanotubes (SWCNTs) exhibit intrinsic near-infrared fluorescence that benefits from indefinite photostability and tissue transparency, offering a promising basis for in vivo biosensing. Existing SWCNT optical sensors that rely on charge transfer for signal transduction often require exogenous mediators that compromise the stability and biocompatibility of the sensors. This study presents a reversible, mediatorless, near-infrared glucose sensor based on glucose oxidase-wrapped SWCNTs (GOx-SWCNTs). GOx-SWCNTs undergo a selective fluorescence increase in the presence of aldohexoses, with the strongest response toward glucose. When incorporated into a custom-built membrane device, the sensor demonstrates a monotonic increase in initial response rates with increasing glucose concentrations between 3 × 10−3 and 30 × 10−3 M and an apparent Michaelis–Menten constant of KM(app) ≈ 13.9 × 10−3 M. A combination of fluorescence, absorption, and Raman spectroscopy measurements suggests a fluorescence enhancement mechanism based on localized enzymatic doping of SWCNT defect sites that does not rely on added mediators. Removal of glucose reverses the doping effects, resulting in full recovery of the fluorescence intensity. The cyclic addition and removal of glucose is shown to successively enhance and recover fluorescence, demonstrating reversibility that serves as a prerequisite for continuous glucose monitoring.
Long Life Fully Reversible Lithium-CO2 Battery
Authors: Ahmadiparidari Alireza , Curtiss Larry A , Salehi-Khojin Amin
Published: February 2020

Although far less studied, lithium-CO2 (Li-CO2) batteries are attractive energy storage systems for fulfilling the demand for the future large-scale applications such as electric vehicles and grid systems due to their higher specific energy density (~1876 Wh/kg) compared to those of commonly used lithium-ion (~265 Wh/kg) and lead-acid (~30-40 Wh/kg) batteries. However, the major challenges with these batteries are the low cyclability and poor reversibility of discharge products (e.g., Li2CO3 and carbon) during the battery cycling. An ideal system must operate in carbon neutral conditions in order to reversibly balance the electrochemical reactions during discharge and charge processes.

In this work, using molybdenum disulfide nanoflakes as a cathode catalyst combined with an ionic liquid and dimethyl sulfoxide hybrid electrolyte, we have obtained a Li-CO2 battery with a long cycle life while maintaining a carbon neutrality in the system. The battery shows a superior cycle life of 500 for a fixed 500 mAh/g capacity per cycle and a remarkable deep discharge capacity of 60,000 mAh/g, which are by far the best cycling stability and highest capacity reported in Li-CO2 batteries, respectively. The presented Li-CO2 battery system demonstrates for the first time that C-O bond making and breaking chemical transformations can be used in energy storage systems with a long cycle life, in addition to the widely studied alkali metal (Li, Na, K) – oxygen bond making and breaking transformations. Theoretical calculations are used to provide insight into the reaction mechanisms for the reversible formation and decomposition of the products during the discharge and charge processes. The achievement of a reversible, long cycle life Li-CO2 battery helps to improve Li-CO2 chemical performance and energy storage systems.
Possibility of Using Petroleum Coke As Reducing Agent for V2O5 in Solid-Phase Synthesis of Li3V2(PO4)3
Authors: Kuzmina Elena , Isyangulov Ilgam , Chudova Nadezhda , Prosochkina Tatyana , Karaseva Elena , Kolosnitsyn Vladimir
Published: February 2020

Nowadays, electrochemical batteries are playing an important role in the development of technology in various fields – consumer electronics, electric transport, and stationary energy storage systems. The main requirements for modern batteries are high specific energy and low cost. State of art lithium-ion batteries have the highest specific energy, but their cost is quite high, and that limits their production volume. Therefore, a relevant problem is the development of new low-cost electrode materials with a high specific energy.

One of the most promising compounds for positive electrodes of lithium-ion batteries is lithium vanadium phosphate Li3V2(PO4)3. It has the same safety in operation as LiFePO4, and at the same time has a higher specific capacity of 197 mA·h/g vs. 170 mA·h/g in LiFePO4, and provides lithium-ion batteries higher average discharge voltage. The lithium-ion batteries with positive electrodes based on Li3V2(PO4)3 have an average discharge voltage of 4.1 V and with LiFePO4 have 3.3 V [1].

The main raw material for lithium-vanadium phosphate is vanadium pentoxide (V2O5). V5+ reduces to V3+ in the process of synthesis Li3V2(PO4)3.

The aim of the present work was to study the possibility of using petroleum electrode coke as a reducing agent in the solid-phase synthesis of lithium vanadium phosphate Li3V2(PO4)3.

The following reagents were used: Li2CO3 (>99.9%), NH4H2PO4 (>98%), V2O5 (>99%), petroleum electrode coke. The reagents were milled to a homogeneous mixture in a mortar, then pressed into pellets in a hydraulic press at a pressure of 6 tons per cm2. The synthesis was carried out at a temperature of 800 °C in a tubular furnace in an argon atmosphere for 5 hours. Electrodes of the following composition (% wt.) were made of the synthesized material: 80% Li3V2(PO4)3, 10% Super P, 10% LA-132. 1M LiPF6 in mixture of DMC:EMC:EC:PA (1:1:2:1 by vol.) was used as an electrolyte, Celgard®3501 was used as a separator, lithium metal foil (100 µm) was used as the negative electrode.

On the 1st cycle, the discharge capacity of the cells was 130 mA∙h/g(Li3V2(PO4)3) for cells being cycled in the potential range of 3.0-4.2 V and 160 mA∙h/g(Li3V2(PO4)3) in the range of 3.0-4.8 V.

According to obtained results, it can be concluded that petroleum electrode coke can be used as a reducing agent in the solid-phase synthesis of Li3V2(PO4)3. In order to improve the characteristics of Li - Li3V2(PO4)3 cells, it is necessary to optimize the synthesis method.

This work was performed as part of a Government Order to Ufa Institute of Chemistry of the Russian Academy of Sciences by the Ministry of Science and Higher Education of the Russian Federation (Theme No. AAAA-A17-117011910031-7), Russia.

References

[1]. S.W. Choi, Da. H. Kim, S.H. Yang, M.Y. Kim, M. S. Lee, Journal of Industrial and Engineering Chemistry,
52 (2017), 314-320.
Mathematical Modeling of Primary Zn/MnO2 Alkaline Batteries
Authors: Chadderdon Xiaotong
Published: February 2020

In this work, a mathematical model based on porous electrode theory was developed in COMSOL Multiphysics to simulate discharge behavior of primary Zn/MnO2 alkaline batteries. The model integrates microscopic and macroscopic phenomena through incorporation of species diffusion in pseudo-2D geometries for both the anode and cathode. The predicted battery performance shows good agreement with experiments under various constant-current and current-interrupt discharge conditions. These results provide battery design engineers better understanding of polarization sources and insights that would otherwise be laborious to obtain.
Elastomeric Polyethylene Glycol-b-Polypropylene Glycol-b-Polyethylene Glycol Dimethacrylate Polymer Network As Polymer Electrolyte Membrane for Li-Ion Batteries
Authors: Narute Suresh T , Marin Angel Juan C , Cavicchi Kevin , Kyu Thein
Published: February 2020

In an effort to fabricate stretchable, superionic, hydrophobic, stable solid-state polymer electrolyte membrane (PEM), polyethylene glycol-b-polypropylene glycol-b-polyethylene glycol dimethacrylate (PPPDA) photocurable precursor was synthesized. This precursor was used in ternary mixtures consisting of ethylene carbonate (EC) plasticizer, and lithium trifluorosulphonyl imide salt (LiTFSI) which were melt-mixed to obtain isotropic solution over a wide compositional range. On photopolymerization, the ternary mixture formed a completely amorphous and transparent membrane. This polymer membrane exhibits ionic conductivity of about 10-3 S/cm, improved thermal and moisture resistance, and superior tensile properties as compared to the polyethylene glycol diacrylate (PEGDA) based PEMs. The polymeric membrane showed a wide electrochemical window on testing with half cells consisting of stainless steel (SS)/PEM/Li Foil. In order to evaluate the electrochemical performance of the polymeric membranes, half cells comprising LiFePO4/PEM/Li foil were tested using cyclic voltammetry and charge/discharge cycling performance.
Design, Synthesis, and Characterization of a Water–Stable Li+ ion-Conducting Sulfonate-Based Neutral Metal-Organic Framework
Authors: Panda Dillip K. , Palukoshka Andrei , Ibrahim Faysal , Sourav Sourav
Published: February 2020

The desire for ion permeable electrode separators in rechargeable batteries has led to an increase in interest in lithium ion-conducting metal-organic frameworks (MOFs). A novel, water-stable, 2D sheet-like neutral Cu (I) −sulfonate MOF, could be the first example of significant lithium ion-conductivity in a neutral, practically solvent-free, not post-synthetically modified MOF. The naphthalenediimide (NDI) ligands of this MOF are capable of simultaneously binding guest lithium ions to its carbonyls and uncoordinated sulfonate oxygen atoms, while charge diffuse perchlorate anions coordinate through anion−π interaction. When made into pristine MOF pellets, the intrinsic electrical conductivity was rather poor (4.65x10−10 S/m) at room temperature. This was due to deficient electron delocalization pathways and charge carrier density. Yet, upon the insertion of LiClO4, the ionic conductivity grew by a factor of 106 to 2.3x10−4 S/m and the activation energy for the charge carrier transport to 0.167 eV. To show the impact of the Li+ binding, the MOF was treated with Bu4NClO4, and the conductivity was essentially unchanged from the original value. The lack of conductivity can be attributed to the size exclusion and facile removal of large uncoordinated Bu4N+ cations. Thus, this presents a new strategy to develop ion-conducting sulfonate MOFs for potential battery applications
9 Kw VRFB Experimental Facility: Early Results from a Multichannel Electrochemical Impedance Spectroscopy
Authors: Guarnieri Massimo , Trovo' Andrea
Published: February 2020

A Vanadium redox flow battery test facility of industrial size (IS-VRFB) has been recently built at the Energy Storage and Conversion Laboratory of University of Padua in order to investigate the performance potential of scaling-up from small-scale single-cell bench experiments. The facility is built around a 40-cell 600-cm­
2 active-area stack and two 550-litre tanks. The facility is provided with advanced electronic bidirectional power supply, multiphysics instrumentation and data acquisition and control system. This paper reports on the commissioning of a multichannel Electrochemical Impedance Spectroscopy (EIS) system, tailored for such large stack, capable of operating in the range 0-30 kHz, with bias currents up to 400 A. Results from early experimental campaign will be also reported, which show the lack of uniformity among cells and how differences enlarge with increasing battery load conditions. Results can be instrumental in addressing the design of flow patterns inside a large stack.

References

Alotto, M. Guarnieri and F. Moro, “Redox flow batteries for the storage of renewable energy: A review,” Renew Sus. Energ Rev. 29, (2014): 325–335.

Guarnieri, A. Trovò, A. D’Anzi, P. Alotto, “Developing vanadium redox flow technology on a 9-kW 26-kWh industrial scale test facility: design review and early experiments”, Appl Energy, 230 (2018) 1425-1434. DOI: 10.1016/j.apenergy.2018.09.021.

Trovò, G. Marini, A. Sutto, P. Alotto, M. Giomo, F. Moro, M. Guarnieri, “Standby thermal model of a vanadium redox flow battery stack with crossover and shunt-current effects”, Appl Energy, 240 (2019) 893-906.

Trovò, A. Saccardo, M. Giomo, F. Moro, M. Guarnieri, “Thermal modeling of industrial-scale vanadium redox flow batteries in high-current operations”, J Power Sources, in print.

Figure 1
Ion-Sieving Carbon Nanoshells for Deeply Rechargeable Zn-Based Aqueous Batteries
Authors: Wu Yutong , Liu Nian
Published: February 2020

As an alternative to lithium-ion batteries, Zn-based aqueous batteries feature non-flammable electrolyte, high theoretical energy density, and abundant materials. However, a deeply rechargeable Zn anode in lean electrolyte configuration is still lacking. Different from the solid-to-solid reaction mechanism in lithium-ion batteries, Zn anodes in alkaline electrolyte go through a solid-solute-solid mechanism (Zn-Zn(OH)4
2--ZnO), which introduces two problems. First, discharge product ZnO on the surface prevents further reaction of Zn underneath, which leads to low utilization of active material and poor rechargeability. Second, soluble intermediate changes Zn anode morphology over cycling. In this work, we report an ion-sieving carbon nanoshell coated ZnO nanoparticle anode, synthesized in a scalable way with controllable shell thickness, to solve the problems of passivation and dissolution simultaneously. The nano-sized ZnO prevents passivation, while microporous carbon shell slows down Zn species dissolution. Under extremely harsh testing conditions (closed cell, lean electrolyte, no ZnO saturation), this Zn anode shows significantly improved performance than Zn foil and bare ZnO nanoparticles. The deeply rechargeable Zn anode reported is an important step towards practical high-energy rechargeable aqueous batteries (e.g. Zn-air batteries). And the ion-sieving nanoshell concept demonstrated is potentially beneficial to other electrodes such as sulfur cathode for Li-S batteries.
Controlling the Electrochemical Properties of Spinel Intercalation Compounds
Authors: Kolli Sanjeev Krishna , Van der Ven Anton
Published: February 2020

Many spinel intercalation compounds are well known for their high ionic conductivity and high voltage in Li-ion batteries. In this study, we investigate the effects of changing the (i) guest cation valence, (ii) guest cation size, and (iii) host ionicity on the site preference and, in turn, intercalation behavior of spinel compounds. We examine the model spinels of CoO2 and TiS2 from first-principles and choose intercalants of Li, Na, and Mg to investigate the parameters of interest. Our results indicate that larger guest cations prefer octahedral coordination of anions within the spinel framework. Electrostatic interactions cause the guest cations to reside on tetrahedral sites within the spinel framework for spinel hosts that are more ionic in nature. These competing factors dictate the site preference and electrochemical properties of spinel intercalation compounds. We propose simple design principles that suggest that Na intercalation into Co, Ni, or Mn oxide spinels would result in fast sodium ion diffusion and therefore make them promising candidates for Na-ion batteries.

Figure 1
(Invited) Formation, Characterization and Applications of Nanowire Films Formed By Anodizing of Metals
Authors: Habazaki Hiroki , Wada Keisuke , Zhu Chunyu , Aoki Yoshitaka
Published: February 2020

Anodizing of metals and alloys is a simple electrochemical process to form various nano-structured oxide films, including self-ordered nanoporous and nanotubular films. Typical examples are nanoporous alumina films with honeycomb morphology and nanotubular array of anodic titanium oxide. Recently, several nanowire-type anodic films have been prepared on metals, including aluminum, copper and zinc. The formation mechanism of of the nanowire films may be different from those of the nanoporous and nanotubular anodic films. Here, our recent studies on the formation, characterization and applications of the anodic nanowire films on metals are presented.

When zinc plate was anodized at a constant voltage in KHCO3 aqueous electrolytes, nanowires were covered on the entire zinc surface. From the SEM observations, it was found that pits were initially formed on zinc surface. The low-voltage SEM observations disclosed that some small pits were covered with a thin passive film, and in such pits nanowires were preferentially nucleated probably because of the increased concentration of dissolved Zn2+ ions in the pits. Then, the nanowires were grown radially over the pits and covered the entire zinc surface.

The nanowires were not composed of ZnO. XPS and FT-IR analyses of the nanowire films indicated the presence of carbonate and hydroxide species; the nanowire consisted of basic zinc carbonate. TEM observations confirmed the single crystalline nature of the as-formed nanowires. The basic zinc carbonate was converted to ZnO without changing the nanowire morphology by heat treatment in air, although single crystalline nanowires changed to polycrystalline one. In addition, slit-type nanopores were introduced into the nanowires so that the specific surface area of the nanowire films was highly enhanced by the heat treatment.

The nanowire films exhibits unique wettability to liquids. The as formed nanowire films showed superhydrophilicity with a water contact angle close to 0o and after organic coating the surface changed to superhydrophobic with a water contact angle greater than 150o. Such surface may have many potential applications.
Formation of Porous Alumina Film By Indirect Oxidation Under AC Electric Field
Authors: Asoh Hidetaka , Ishino Mami , Miura Sayuri , Hashimoto Hideki
Published: February 2020

In recent years, there has been renewed interest in bipolar electrochemistry, which deals with reactions occurring on unconnected conductive objects placed between outer electrodes, due to its potential applications in various fields ranging from sensing to the fabrication of functional materials. In most of the studies regarding bipolar electrochemistry, a direct current (DC) electric field is applied between the driving electrodes, and an inhomogeneous reaction field on the bipolar electrode is used. Based on the polarization of both sides of a bipolar electrode under a DC electric field, the electrochemical redox reactions on each part of a bipolar electrode can be controlled. In our previous study, we investigated the application of an alternating current (AC) electric field for surface coating of aluminum and successfully formed porous alumina films on unconnected aluminum by indirect oxidation under an AC electric field without a direct electrical connection (“AC-bipolar anodization”) 1, 2). A common strategy applied in bipolar anodization is to use the interfacial potential differences between the driving electrodes under a DC electric field, resulting in the asymmetrical formation of oxide films (e.g., gradients in the thickness of the porous layer and pore diameter) on a metal substrate used as a bipolar electrode. On the other hand, we focused on bipolar anodization under an AC electric field as uniform surface treatment for aluminum. With the above background, we continued our preliminary work and tried to fabricate Pt/alumina composite on an unconnected aluminum substrate using one-pot electrochemical synthesis in a single electrolyte 3). This synthetic approach overcomes the drawbacks of conventional methods in terms of the operation efficiency and will lead to the development of various functional composites using one-pot synthesis. In terms of basic research, potential applications of our developed method will be also discussed.

H. Asoh, M. Ishino, H. Hashimoto, RSC Adv., 6, 90318 (2016).

H. Asoh, M. Ishino, H. Hashimoto, J. Electrochem. Soc., 165, C295 (2018).

H. Asoh, S. Miura, H. Hashimoto, ACS Appl
.
Nano Mater., in press (2019).
Mg Thin Film Pit Growth and Anomalous Hydrogen Evolution
Authors: D avila Gabbardo Aline , Viswanathan Gopal B , Frankel Gerald S.
Published: February 2020

New technologies and applications for Mg require further improvements of its corrosion resistance. Fundamental comprehension of the Mg corrosion mechanisms is necessary to address the issue, as the Mg corrosion behavior is unexpected from the theory of electrochemical kinetics. The anomalous hydrogen evolution phenomenon (anomalous HE) exhibit by Mg, also known as the negative difference effect (NDE), is still an unresolved issue. Recent research suggests that the anomalous HE is a consequence of a surface change during dissolution. The proposed mechanisms debate the location of the phenomenon on the surface. The phenomenon is proposed to happen at the corroded areas behind the corrosion front, in the dark corrosion products left behind the corrosion front and/or at the active dissolving sites. New techniques and experimental data are needed to further address the discussion.

In this work, the 2D pit growth method is used to study the anomalous HE phenomenon on Mg with the aim to provide further experimental evidence towards an explanation. The method is called 2D pitting because the sample is a thin metallic film deposited on an inert substrate, so the pit depth is constant and limited to the film thickness. By analyzing 2D pit growth, it is possible to accurately track the active dissolving surface and to measure the anodic, net and cathodic current densities. The hydrogen evolution current density was shown to increase with increasing applied potentials in the ohmic/activation control region, which is direct evidence for the anomalous HE behavior. In addition, the results clearly demonstrated that the anomalous HE phenomenon happens at the active dissolving site, which in this case is the 2D pit wall. Anomalous HE did not occur at the corroded areas behind the corrosion front, which in the case of a 2D pit is the inert substrate. It also did not occur in the corrosion product, which in this case was broken and lifted out by the hydrogen bubbles being electrically disconnected from the Mg matrix. The 2D pits were also evaluated at high applied potentials where a salt film precipitated on the active dissolving surface. The results showed that the anomalous HE rate decreased in the transport control region approaching zero at the limiting current density. In this case, the rate of hydrogen evolution was limited by water diffusion through the salt film to reach the active surface. It was also shown by TEM/EDX analysis that impurities do not accumulate at the pit wall and cannot account for anomalous HE. The results support the idea that the actively dissolving Mg surface is the site of anomalous HE, and that, in the absence of a salt film, the dissolving surface is extremely catalytic to the HE process.
Using Macro and Micro Electrochemical Methods to Understand the Corrosion Behavior of Stainless Steel Thermal Spray Coatings & Mg/Al Diffusion Couples
Authors: Mauzeroll Janine
Published: February 2020

High-velocity oxygen fuel (HVOF) thermal spray coatings are desirable for their excellent erosion resistance. However, the fabrication process can lead to a decrease in corrosion resistance in comparison to the original bulk material. Stainless steel coatings on stainless steel substrates were produced using varying deposition parameters to investigate the corrosion properties of the resulting composite steels and elude the corrosion mechanism. Potentiodynamic polarization measurements carried out in corroding environments demonstrated the rate of degradation of the Fe-Cr alloy. After short immersion periods, both the coatings and sintered powder pellets for the same alloy showed iron-like active corroding behavior and no passivation regions on the anodic branch. Over time, the coating’s corrosion behavior began to change to signify similar results to that of pure chromium. Ex-situ electron microscopy and elemental composition revealed a Cr oxide rich layer left on the coating’s surface. Furthermore, chemical etching and digestion revealed microstructural changes between the powdered material and the bulk sheet metal such as Cr rich inclusions, known to be responsible for initiating intergranular corrosion. Micro electrochemical techniques including scanning electrochemical microscopy and scanning micro capillary method were employed over the coatings and powdered material, respectively, to prove that the lack of protective passivity the thermal spray coatings possess is mostly inherited from the atomized powdered stainless steel material.
Electrochemical Investigation of Oxygen Reduction Reaction on Type 316L Stainless Steel in NaCl Solutions in a Confined Space
Authors: Tada Eiji , Jang Junho , Ooi Azusa , Nishikata Atsushi
Published: February 2020

Steel plate joints are commonly produced in the manufacturing process of steel structures such as automobiles and bridges. The steel plate joints suffer from aqueous corrosion in atmospheric environments. Especially, severe corrosion is often observed in the confined spaces between the steel plates because aqueous electrolytic solutions can be kept in the spaces. In this case, corrosion reaction rate of the steels in the confined space is basically controlled by the reduction reaction rate of dissolved oxygen. Therefore, it is important to estimate oxygen reduction reaction rate in the confined spaces to predict corrosion deterioration of steel plate joints. In this study, electrochemical investigation of oxygen reduction reaction rate in a confined space was performed.

The material used in this study was austenitic stainless steel type 316L bar with various diameters from 5 to 20 mm. The type 316L bar was cut into a small cylindrical piece and the piece was embedded in epoxy resin after being contacted with a lead wire. The surface of the embedded stainless steel sample was ground with SiC papers down to JIS200 grit and then cleaned ultrasonically in EtOH. Test solutions were aqueous NaCl of different concentrations from 0.05wt% to 5wt%. The solutions were prepared with Milli-Q water and reagent grade sodium chloride.

For the electrochemical measurements, the sample was set horizontally in a plastic vessel and then an acrylic rod of 20 mm in diameter, which was used as a crevice former, was placed above the sample surface to make a confined space between the sample and the rod. The gap between the sample surface and the rod was changed from 20 um to 200 um by using a laser displacement meter. Electrochemical measurements were conducted by a conventional three electrode method with a platinum wire (Pt) and a Ag/AgCl in a saturated KCl (SSE) as a counter electrode (CE) and a reference electrode (RE), respectively. Cathodic polarization curves for the sample were measured with various gaps at a potential sweep rate of 0.5mV/s.

Cathodic polarization behavior for the sample measured in the confined spaces was similar as that measured in a bulk solution; a limiting current region due to oxygen reduction reaction was observed on the samples of various diameters in a confined space. It was confirmed that the limiting current density decreased with decreasing in the gap. This is attributed to be the difference in the oxygen diffusion rate on the sample in the confined space.
(Invited) Phase Change Materials for Non-Volatile Memories : Properties and Optimization through Ab Initio Simulation
Authors: Raty Jean-Yves
Published: February 2020

Phase Change Materials are emerging as active components of non-volatile memories thanks to their ability to switch extremely rapidly from a conducting crystal to a more semiconducting glassy. Using Ab Initio simulations, we address the structure and some properties of the glassy phase, like aging, but also go back to the description of bonding in the crystalline phase.

We develop a two-dimensional map based on a quantum-topological description of electron sharing and electron transfer in binary solids. This map intuitively identifies the fundamental nature of ionic, metallic, and covalent bonding in a range of elements and binary materials. Furthermore, it highlights a distinct region where phase change materials are found and for which bonding has been qualified as ‘metavalent’ [1,2]. Extending this map into the third dimension by including physical properties of application interest, we show that bonding in metavalent compounds differs from the our usual views of bonding. This map could be used to help designing new materials: by searching for desired properties in a 3D space and then mapping this back onto the 2D plane of bonding.

[1] J.Y. Raty, M. Schumacher, P. Golub, V. Deringer, C. Gatti and M. Wuttig Advanced Materials, (2018) 1806280

[2] M. Wuttig, V. Deringer, X. Gonze, C. Bichara and J.Y. Raty, Advanced Mater. (2018) 1803777

Work funded by F.R.S.-FNRS & the Region Wallonne (CECI Tier-1) and the Federation Wallonie-Bruxelles (ARC AIMED)
Electrodeposition Carbon with Improved Performance As Anode Material for Lithium-Ion Batteries (LIBs)
Authors: Ahmed Zahoor , Hughes Matthew , Donne Scott W
Published: February 2020

Electrolytic reduction of molten carbonates (Li, K-Na) has been suggested as a practical approach to improve the performance of lithium-ion batteries as anode material. However, to achieve the desired carbon phase is still a challenge, and this area needs more exploration. Herein, novel carbonaceous were synthesized by using molten carbonates as an exciting new method of producing carbons for battery applications. The electrochemical properties Galvanostatic charge-discharge, cycle ability, rate performance and cyclic voltammetry were enhanced by using the electrodeposited anode as a comparison to the pure commercialized artificial graphite. As a consequence, the modified carbon anode material exhibits superior initial discharge capacity 334 mAh g-1 at 0.1C with coulombic efficiency of 95.70% and 255 mAh g-1 at 1C with a capacity retention (coulombic efficiency) of 85.8% (100%) after 100 cycles in the potential window of 0.01-2V (vs Li/Li+). In comparison pure artificial graphite exhibit only 316 mAh g-1 at 0.1C, corresponding to lower first coulombic efficiency of 89.26% and 195 mAh g-1 at 1C with capacity retention (coulombic efficiency) of 83.8% (94%) after 100 cycles. The great improvement in the de-/lithiation kinetic can be accredited to the enhancement in apparent lithium ion diffusion coefficient.
Electrodeposited Mcraly Coatings for Gas Turbine Engine Applications
Authors: Zhang Ying , Bates Brian
Published: February 2020

Electrolytic codeposition is a promising alternative process for fabricating MCrAlY coatings (where M = Ni, Co, or Ni + Co) for protecting high-temperature components used in various industrial gas turbine engines. The coating process involves codeposition of CrAlY-based particles and a metal matrix of Ni, Co, or (Ni,Co), followed by a diffusion treatment to convert the composite coating to the desired MCrAlY microstructure. Despite the advantages of low cost and non-line-of-sight, this coating process is less known compared to electron beam-physical vapor deposition and thermal spray processes for manufacturing high-temperature coatings. This presentation provides an overview of the electrodeposited MCrAlY coatings for gas turbine applications, highlighting the unique features of this coating process and some important findings in the past 30 years. Recent coating development progress from a collaborative research project between Tennessee Tech University and Oak Ridge National Laboratory will be presented. The effects of additional elements (e.g., Ta, Si and Hf) on the coating oxidation/corrosion performance will be discussed.
All Electrodeposited Nanowire Array Based Tandem Junction Photoelectrochemical Devices
Authors: Cheng Wei , Rassoolkhani Alan , Koonce Jonathan G , Lee Joun , Mubeen Syed
Published: February 2020

Large-scale solar fuel production using semiconductor based photoelectrochemical (PEC) system requires inexpensive, efficient and stable devices that can provide photovoltages sufficient to overcome both the thermodynamic and overpotential losses of the redox reaction. Here we report all electrodeposited multi-junction PEC devices for solar fuel production using serially connected CdSe based and CdTe based Schottky barrier junctions with photovoltages exceeding 1.0 V. These PEC devices are synthesized inside nanoporous alumina membranes with each nanoscale solar conversion units physically and electronically isolated from each other, making the entire device fault tolerant. The alumina membranes also serve to protect the semiconductor from chemical and PEC corrosion.
Molybdenum Electrorefining in Ionic Liquids
Authors: Gunnell Ethan Mitchel , Avery Ashley , Ying Andrew , Gunnell LaGrande , Stoddard Michael , Memmott Matthew , Harb John N.
Published: February 2020

Molybdenum is a valuable refractory metal used to harden and protect metal alloys. Additionally, certain nuclear reactors can be used to produce Mo99, a valuable radioactive isotope with important medical applications. To qualify for medical use, the isotope must be isolated in high purity molybdenum. One method of metal purification is electrorefining. Electrorefining consists of anodically dissolving a target metal of inadequate purity, and then depositing it onto a substrate at a higher purity. Conventional aqueous-based electrolytes are not suitable for Mo electrorefining owing to their instability in the potential range needed for Mo deposition and the tendency of molybdenum to form insoluble oxides. Ionic liquids offer the wider electrochemical window needed to process Mo. Such liquids are often referred to as ‘designer solvents’ due to the plethora of possible constituents that can render different properties. The purpose of this study was to explore Mo electrorefining in ionic liquids, and to identify solvents with properties suitable for this type of molybdenum purification.

In this study, the effectiveness of molybdenum electrorefining was examined in a few different ionic systems, including choline-chloride-based deep eutectic systems. Cyclic voltammetry was utilized to determine oxidation and reduction potentials given against an Ag/Ag+ reference electrode. Deposits were characterized with EDX and morphologies examined with SEM. Furthermore, faradaic efficiencies and methods for optimizing deposition were determined.

Our findings show that the effectiveness of a solvent for Mo electrorefining is determined by the coordinating nature of the solvent. Weakly coordinating ligands, such as BF-
4, are not ideal for electrorefining because Mo ion replenishment via anodic dissolution is inhibited by low solubility. Ethylene glycol-choline chloride, which is more strongly coordinating, has shown effective dissolution at room temperature. In addition, deposition has been observed in this DES at temperatures above 80° C with aggressive stirring, indicating that it is transport controlled. Despite low faradaic efficiencies for deposition, deposit morphology and adherence can be improved through pulse deposition. This is believed to be the first report of molybdenum deposition or electrorefining in a deep eutectic solvent.
Enhanced Capacitive Deionization Performance with Activated Carbon Loaded in Graphite Felt Framework
Authors: Wang Yang , Lado Julio , Vázquez-Rodríguez Inés , Santos Cleis , Garcia - Quismondo Enrique , Palma Jesus , Anderson Marc Arlen
Published: February 2020

Capacitive Deionization (CDI) is an emerging technology for brackish water desalination. So far, very promising electrode materials with excellent performance have been only tested on a small scale, mainly, because of scalability issues. With the desire of finding a stable and easy to scale electrode from an engineering point of view, advances from the energy storage field have been implemented here. In this fashion, 3D composites were prepared using the highly conductive macrostructure of a graphite felt (GF) as electron transfer channel and the microstructure of activated carbon (AC) to furnish ionic adsorption sites (GF-AC). The electrochemical characterization of the 3D composite at small scale showed a larger total ion storage capacity as compared to an AC film electrode prepared with the same active material. Moreover, the composite also shows a great stability that the specific capacitance retention is high after 5000 charge/discharge cycles. The 3D composite was was then tested in a 1-Cell CDI System (10 cm2) reaching high salt adsorption capacity (SAC) values and charge efficiency. Subsequently, long-term operation testing resulted only in a 30% SAC capacity loss after more than 100 cycles. Finally, the system was scaled to a 9-Cell Stack (300 cm2 electrodes) and was able to demonstrate excellent CDI performance. In general, the 3D electrodes provide several advantages for capacitive deionization, including a well-dispersed amount of active material with high mass loading, a simple preparation, easy scalability and good cycling stability. Therefore, we believe that GF-AC electrodes hold promise for large-scale CDI practical applications.