bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Differential Reference Concentration Cell Method for Determination of Thermodynamic Factors in Concentrated Binary Electrolytes
Authors: Wang Andrew , Hou Tianhong , Monroe Charles W
Published: February 2020

Accurate models of ion transport in isothermal binary solutions require measurements of various properties, including ionic conductivity, salt diffusivity, cation transference number (t0
+), and the thermodynamic Darken factor (χ). In this work a novel method is proposed to quantify composition-dependent values of χ(1-t0
+).

Recent studies of highly concentrated “solvent-in-salt” electrolytes suggest a strong variation of transference number with respect to composition. In fact t0
+ for electrolyte systems may double in magnitude in the highly concentrated regimes.1

Previous studies have quantified the Darken factor by assuming that t0
+ is relatively constant across the concentration range of interest. Furthermore, concentration-cell experiments typically fix arbitrary reference concentrations that may be far from the test concentration across the liquid junction. Such methods employ integral values of t0
+; the accuracy of thermodynamic properties, and thereby numerical models, may be compromised if there are substantial concentration differences and concomitant local changes in t0
+.2 An alternative approach to concentration-cell experiments would apply differential forms of the equations relating potential difference, composition, thermodynamic factor, and cation transference number.3

We propose a novel approach to concentration-cell experiments in which a matrix of liquid-junction potentials banded about a variable reference concentration is employed. Coupled with independent t0
+ measurements, this 3-dimensional surface for potential difference can be numerically fitted to reliably and accurately determine differential values of the thermodynamic factor χ across the solubility range of an electrolyte. The feasibility of the method is demonstrated with the electrolyte lithium hexafluorophosphate in propylene carbonate (LiPF6:PC) to determine concentration-cell liquid-junction potential (U) across a wide concentration range (0M-3M). Transference-number measurements via Hittorf-cell experiments are then used to isolate χ from differential measurements of χ(1-t0
+) as a function of electrolyte particle fraction (y).

Suo, L., Hu, Y. S., Li, H., Armand, M. & Chen, L. A new class of Solvent-in-Salt electrolyte for high-energy rechargeable metallic lithium batteries. Nat. Commun.
4, 1–9 (2013).

Lundgren, H., Scheers, J., Behm, M. & Lindbergh, G. Characterization of the Mass-Transport Phenomena in a Superconcentrated LiTFSI:Acetonitrile Electrolyte. J. Electrochem. Soc.
162, A1334–A1340 (2015).

Newman, J. & Thomas-Alyea, K. E. Electrochemical Systems. (John Wiley & Sons, 2004).

Figure 1
Artificial Neuron Based on TiO2 Cbram for Neuromorphic Computing
Authors: Kim Dong-Won , Kwon Ki-Hyun , Kim Hea-Jee , Jin Soo-Min , Yang Hun-Mo , Kim Ji-Yeon , Park Jea-Gun
Published: February 2020

Recently, CMOS-based artificial neurons have successfully implemented neuron functions such as integrate and fire (IF) or leaky integrate and fire (LIF). In general, CMOS-based artificial neurons use capacitors to implement integration function of neuron. In this case, required RC time constant is about few milliseconds. And it requires large area of capacitor more than 1000F2. Therefore, it is necessary to develop capacitor-less artificial neuron to achieve high neuronal density. In this works, we implemented the integration function of neurons using CBRAM instead of capacitors. For the neuron device, CuTe/TiO2/TiN CBRAM cell was fabricated as shown in figure 1a. The neuron device has W bottom electrode with ~113 nm2 pattern size and 10 nm-thick TiO2 layer, and 200 nm-thick CuTe top electrode with 60 μm2 size. The TiO2-based CBRAM showed a typical bi-stable I-V curve as shown in figure 1b. The CBRAM cells showed negative differential resistance (NDR) during reset process. And it showed integrate characteristic when consecutive negative voltage pulse was induced to top electrode of the CBRAM cell. Figure 1c shows integrate characteristic of TiO2-based CBRAM cell. As shown in figure 1c, as the voltage pulse is applied, current gradually decreases. Also as amplitude of voltage pulse increased, the change of current became greater. Because the area of the CBRAM cell is only 4F2, it is expected that area of artificial neuron can be significantly reduced by replacing conventional capacitor based neuron. We will present how the CBRAM cell can be used to implement artificial neuron.

Figure 1
(Dielectric Science and Technology Division Thomas D. Callinan Award Address) Colorful Adventures in the Field of Dielectrics Science: Some Highs and Lows with a Touch of a Chilly Forecast
Authors: King Sean W.
Published: February 2020

Dielectric materials are utilized throughout semiconductor microelectronic devices for a variety of applications ranging from passive electrical isolation and charge storage to more functional etch stopping and diffusion barriers and more active layers such as humidity sensing and solid state electrolyte materials. Just in the past two decades alone, the semiconductor industry has researched and adopted a vast array of new dielectric materials with exceptionally high or low values of dielectric permittivity (k). While scaling of these so called high-k and low-k dielectrics may have reached their limits, numerous additional applications for dielectric materials continue to emerge as the industry seeks to adopt new methods for patterning nanoscale features and considers a dizzying array of beyond CMOS devices.

In this talk, I will discuss my colorful adventures over these past two decades as a dielectric materials scientist starting with molecular beam and atomic layer epitaxy of III-N nitrides to plasma enhanced chemical vapor deposition of low-k dielectrics and back to atomic layer deposition of high-k dielectrics (various misadventures in between will also not be neglected!). It has been an exciting journey and I will use it to highlight the multi-disciplinary nature of dielectric science as well as illustrate how something that was once old can be reimagined to fulfill the needs of future beyond CMOS devices. I will further address some of the future challenges and opportunities presented for dielectric materials that have been created by the new patterning methods and beyond CMOS devices now under consideration. We will conclude by reviewing the unique obstacles that dielectric materials present for the realization of advanced cryogenic quantum computing architectures and the necessary associated research vectors to prevent dielectrics from becoming quantum computing’s Achilles heel.
(Invited) 2D Materials for Nanoelectronics: Prospects and Materials Integration Challenges
Authors: Wallace Robert M
Published: February 2020

The size reduction and economics of integrated circuits, captured since the 1960’s in the form of Moore’s Law, is under serious challenge. Current industry roadmaps reveal that physical limitations include reaching aspects associated with truly atomic dimensions, and the cost of manufacturing is increasing such that only 2 or 3 companies can afford leading edge capabilities. To address some of the “conventions;” material’s physical limitations, “2D materials” such as graphene, phosphorene, h-BN, and transition metal dichalcogenides have captured the imagination of the research community for advanced applications in nanoelectronics, optoelectronics, and other applications. [1,2] Among 2D materials “beyond graphene,” some exhibit semiconducting behavior, such as transition-metal dichalcogenides (TMDs), and present useful bandgap properties for applications even at the single atomic layer level. Examples include “MX2”, where M = Mo, W, Sn, Hf, Zr and X = S, Se and Te.

In addition to the potentially useful bandgaps at the monolayer thickness scale, the atomically thin layers should enable thorough electric field penetration through the channel, thus enabling superior electrostatic control. Further, with such thin layers, the integration with suitable gate dielectrics can result in a mobility enhancement. Applications “beyond CMOS” are also under exploration. From an interface perspective, the ideal TMD material may ne expected to have a dearth of dangling bonds on the surface/interface, resulting in low interface state densities which are essential for efficient carrier transport. The ideal TMD materials have much appeal, but the reality of significant densities of defects and impurities will surely compromise the intrinsic performance of such device technologies. This presentation will examine the state-of-the-art of these materials in view of our research on semiconductor device applications, and the challenges and opportunities they present for electronic and optoelectronic applications. [3,4]

This research was supported in part by the Semiconductor Research Corporation (SRC) NEWLIMITS Center and NIST through award number 70NANB17H041 and the Erik Jonsson Distinguished Chair at the University of Texas at Dallas.

References

[1] Z. Lin, et al., APL Materials, 6, 080701 (2018)

[2] N. Briggs, et al., 2D Materials, in press (2019)

[2] S. J. McDonnell and R.M. Wallace, JOM
. in press (2018).DOI: 10.1007/s11837-018-3156-x

[2] S. J. McDonnell and R.M. Wallace, Thin Solid Films, 616, 482-501 (2016); and references therein.
(Invited) Time Resolved Spectroscopy of Charge Carriers in TiO2 Anatase and Rutile Single Crystals. Effect of Oxygen Defects and Electrons/Holes Scavengers
Authors: Katsiev Khabiboulakh , Idriss Hicham
Published: February 2020

In an effort to probe into the fundamentals of charge carriers dynamics relevant to photo-catalytic materials, we have performed femtosecond time resolved spectroscopy (TRS) on anatase and rutile single crystals in the gas phase as well as in aqueous environment. By studying the effect of pump fluence, differences in charge carrier recombination rates and nature between both crystals were observed. The time constants for carrier recombination are two orders of magnitude slower for anatase (101) when compared to those of rutile (110) single crystal. Bulk defects introduced by sample reduction via annealing in ultra-high vacuum resulted in faster recombination rates for both polymorphs. Both surfaces (fresh and reduced) probed by pump fluence dependence measurements revealed that the major recombination channel in fresh and reduced anatase and reduced rutile is the first-order Shockley–Reed mediated. The effect of a hole trapping agent (ethanol) and of electron trapping agents (Ag+ and Ce4+ cations) is investigated over TiO2(110) rutile single crystal. Ethanol adsorption resulted in increasing the transient absorption signal in the 700-950nm with a slight decrease of their lifetime. No change was seen in the 500nm region commonly attributed to the presence of holes. The decay of the 700-950 nm signal mainly composed of two components is considerably perturbed by the presence of Ag+ or Ce4+ cations, which may indicate its surface origin. Work in progress to extract kinetic information from the study of the concentration effect of these metal cations in both the “nominally” hole and electron transient absorption regions.
(Invited) Organic Molecular Electrets: Multifaceted Complexity of Dipole Effects on Charge Transfer
Authors: Vullev Valentine Ivanov
Published: February 2020

Electric dipoles are everywhere. While they provide potentially important paradigms for controlling charge transfer (CT), dipole effects on CT still remain largely unexplored. CT is among the most fundamental processes responsible for sustaining life on earth and for ensuring the functionality of a range of energy and electronic devices that are an intricate part of everyday life. Therefore, we pioneer the concept of bioinspired molecular electrets that, in addition to possessing large macrodipoles, also can mediate long-range CT. (Electrets are systems with ordered electric dipoles, i.e., they are the electrostatic analogies of magnets.) Our electret designs are based on polypeptides composed of non-native aromatic beta-amino acids. We observe that even a single electret residue induces rectification of CT that surpasses what is reported for similar systems utilizing polypeptide helices composed of native amino acids. While dipoles generate enormous fields around them, the strength of these localized fields significantly decays with distance. Therefore, we incorporate the dipoles within the participants in the CT steps. It allows us to observe unprecedentedly large dipole effects on the CT kinetics.5 A decrease in solvent polarity increases the rates of CT. It appears counterintuitive, and it should be the other way around: polar media stabilizes the formed charged CT states and thus increases the rates of photoinduced CT in the Marcus normal region. Concurrently, polar media screens the dipole-generated fields and suppresses their effects on CT. For non-polar solvents, changing the dipole orientation can alter the reduction potentials of the photosensitizers with hundreds of millivolts. Therefore, a careful balance between the two opposing polarity effects allows us to demonstrate CT in lipophilic media, such as toluene. For non-polar solvent, we observe enhancement of electron-transfer (ET) rates along the dipole, while ET against the dipole is completely suppressed. By modifying the semi-classical CT theory, we quantify such experimentally observed dipole effects for the first time. In addition to affecting the reduction potentials and thus the Franck-Condon aspects of the CT kinetics, the molecular electrets reveal that dipoles can also drastically change the CT rates by altering the donor-acceptor electronic coupling. This discovery contradicts the accepted notion about dipole effects on CT, where the focus is on the Franck-Condon nuclear aspects of the kinetics and the electronic contributions are considered insignificant. Our findings not only lead to rethinking the fundamentals of dipole effects on CT, but also open new avenues for development of unprecedented paradigms for organic electronics and energy materials.
A Smart Glove with Integrated Triboelectric Nanogenerator for Self-Powered Gesture Recognition and Language Expression
Authors: Pao Yu-Ping , Chiu Che-Min , Lin Zong-Hong
Published: February 2020

Flexible electronics with great functional characteristics have proved to be a stepping stone in the field of wearable devices. Amongst all, gesture sensing techniques have been widely studied for human-machine interfaces. In this paper, we propose a self-powered gesture sensing system which has the capability of distinguishing hand gestures by measuring the triboelectric nanogenerator (TENG) output signal. The sensor was attached on the back of the hand and the displacement of tendons was sensed to detect the gestures. Furthermore, we have established a set of rules to define the relationship between gestures and corresponding English letters. Therefore, the proposed sensor can further serve as an electronic sign language translator by converting gestures into words. In addition, we can integrate this system into gloves to enhance the applicability and utility of the developed system. At the same time, the humidity resistance and durability of the device was tested and validated. Overall, we have developed a real time self-powered back-of-hand sensing system which can recognize and represents various hand gestures.
(Invited) Self-Powered Wearable and Implantable Electrical> Stimulation Devices for Medical Treatments
Authors: Wang Xudong
Published: February 2020

Electrical stimulation (ES) is a widely used therapeutic treatment strategy. It showed significantly positive results in treating a variety of diseases, biological disorders, and neurological problems. Today, the emergence of wearable devices is rapidly reshaping the development of medical devices, pushing them from conventional bulky and rigid silicon electronics to flexible and primarily polymer-based systems. Among many types of functions, nanogenerators are developed as a unique device for converting biomechanical energy into electrical pulses. Besides using it directly as a power source, this pulsed electricity can be applied directly as a ES signal for therapeutic treatment. In our recent research, we successfully implemented such an electromechanical system for skin wound healing and vagus nerve stimulation for obesity control. An electrical stimulation bandage was developed by integrating a flexible nanogenerator and a pair of dressing electrodes on a flexible substrate. Rat studies demonstrated rapid closure of a full-thickness rectangular skin wound within 3 days as compared to 12 days of usual contraction-based healing processes in rodents. From in vitro studies, the accelerated skin wound healing was attributed to the electric field-facilitated fibroblast migration, proliferation and transdifferentiation. In another work, an implanted vagus nerve stimulation system was developed. The device comprises a flexible and biocompatible nanogenerator that is attached on the surface of stomach. It generates biphasic electric pulses in responsive to the peristalsis of stomach. The electric signals generated by this device stimulates the vagal afferent fibers to reduce food intake and achieve weight control. This strategy is successfully demonstrated on rat models. Within 100 days, the average body weight is controlled at 350 g, 38% less than the control groups. Both results bring a new concept in electrical therapeutic technology that is battery-free, self-activated and directly responsive to body activities.
(Invited) Electrochemical Tuning Sensing and Catalytic Performance of Catalytic Materials -from Nanoscale to Atomic Scale
Authors: Huang Jing-Fang
Published: February 2020

In this talk, we will introduce two facile methods for the preparation of a nanoporous Ag foam and a promising electrocatalyst for the oxygen reduction reaction (ORR). Ag has a high electrical and thermal conductivity, low cost, and is relatively abundant in the earth compared to other Pt-group metals. Unlike Pt-related noble metals, the poor hydrogen evolution reaction (HER) activity of Ag in acidic environments makes it rarely considered as a potential HER electrocatalyst. We demonstrate a spongy-like highly nanoporous Ag foam obtained using a simple Ag surface treatment through the repetitively electrochemical anodic formation of AgBr/cathodic reduction back to Ag exhibited Pt-like high HER activities. Bimetallic Pt-Ni with Pt on the outermost layer and an innermost layer enriched in Ni, referred to as (Pt3Ni(Pt-skin), is a promising configuration of electrocatalyst for the ORR in fuel cells. We prepare a core (Pd)/shell (Pt3Ni(Pt-skin)) catalyst (Pt3Ni(Pt-skin)/Pd/C) from Zn underpotential deposition (UPD) on a Ni UPD modified Pd/C catalyst, facilitating Pt atomic layer-by-layer growth on the Ni surface through the galvanic replacement process. The Pt3Ni(Pt-skin) thin layer with ultra-low Pt loading presents not only a breakthrough in Pt specific activity and Pt mass activity, both of which were superior to state-of-the-art Pt-Ni catalysts, but also in high durability owing to the perfect Pt3Ni(Pt-skin) construction
(Invited) Nanowire-Enabled Low-Voltage Electroporation for Microbial Inactivation in Water
Authors: Xie Xing
Published: February 2020

Pathogens in water and liquid food can be inactivated by pulsed electric field treatment (PEFT), a process that induces irreversible electroporation on cell membranes. As a physical disinfection method, PEFT is fast (e.g., 6-log inactivation in 100 ms) and effective broadly to all pathogens, including “superbugs” that are resistant to multiple antimicrobials. Moreover, no chemicals are consumed and no disinfection byproducts generated during PEFT. PEFT has been applied to inactivate many microorganisms in various water and liquid food samples, but the practical implementation in water and food industry is limited by the high energy consumption to sustain a high-strength electric field (e.g., >10 kV/cm) and technical challenges to achieve such electric field without the risk of arcing. These limitations can be overcome by low-voltage-powered (e.g., <5 V) locally enhanced electric field treatment (LEEFT). The electrodes installed in a LEEFT device are modified with nanowires so that the electric field is not uniform but enhanced locally near the tips of the nanowires due to the “lightning rod effect.” The microorganisms present in such regions can be effectively inactivated. In this talk, some recent progress on the electrode development and mechanism studies of the LEEFT technology will be covered.
(Invited) Nanoporous Titaninum Nitride Electrodes for Neural Probes
Authors: Cheng Mark Ming-Cheng
Published: February 2020

We report corrosion-resistant and high-capacity implantable nanoporous titanium nitride (TiN) electrodes for neural probes applications Traditionally, the TiN electrodes are prepared using reactive sputtering techniques and have limited surface areas. To research smaller electrodes to minimize tissue damage, high aspect ratio TiN nanotube structures were fabricated using electrochemical anodization of Ti wires followed by high-temperature nitration. The specific charge capacity of nanoporous TiN correlates proportional with the surface area and pore size.

According to Shannon criteria, an empirical rule in neural engineering for possibility of tissue damage from electrical stimulation, the recommended limit density of a stimulation pulse is 30 μCcm-2 for a geometric surface area of 0.06 cm2. Nevertheless, the charge injection capacity of chronically implanted electrodes has shown degraded over the time (within one month to a year), including sputtered iridium oxide (SIROF), porous platinum and tungsten. One of the challenges for these implantable electrodes involves irreversible reduction and oxidation reactions occurring at the electrode surface through faradic or pseudocapacitive charge transfer. On the other hand, TiN has different mechanism of charge injection (through capacitive double layers). TiN has been shown promising electrode material in neural implants thanks to its super electrical conductivity, biocompatibility and chemical stability. TiN is also known for physiologically inert and corrosion resistant. To increase the spatial resolution of neural stimulation, small electrodes with high surface areas are more desirable. To the best of our knowledge, TiN nanotubes electrodes have not been studied in the literature for neural implants. Compared to tungsten electrode, the impedance and morphology of nanoporous TiN was found stable over a long-term in stress tests (at an elevated temperatures in phosphorous buffered solution).
High Efficient Bi2Te3 Thermalcatalyst for Environmental Disinfection
Authors: Chan Shuen-Wen , Lin Yu-Jiung , Lin Zong-Hong
Published: February 2020

The highly reactive nature of reactive oxygen species (ROS) makes it widely used in environmental and health related fields. Conventionally, there are only two kinds of catalysts used for ROS generation, photocatalysts and piezocatalysts. However, their usage is limited due to various environmental and physical factors. Over the past few years, it has paved the way for the development of a novel catalyst which relies on temperature difference for ROS generation, called thermalcatalyst. Being the most important environmental factor in daily life, temperature exactly has a tremendous potential for applications. In this study, the experiment using thermoelectric materials as thermalcatalysts to generate ROS by controlling the temperature difference was performed. Furthermore, the produced ROS can kill the bacteria because of oxidative damage, which makes the thermalcatalyst ideal for disinfection. In order to increase the practicality in daily life, bismuth telluride (Bi2Te3), serving as the thermalcatalyst, was coated on the carbon fiber fabrics (Bi2Te3@CFFs) as an antibacterial filter. In conclusion, the results present that the thermoelectric material such as Bi2Te3 exhibited the significant antibacterial activity, providing a great potential for ROS-related applications.
(Invited) Wearable Sweat Sensors
Authors: Javey Ali
Published: February 2020

Wearable sensor technologies play a significant role in realizing personalized medicine through continuously monitoring an individual’s health state. To this end, human sweat is an excellent candidate for non-invasive monitoring as it contains physiologically rich information. In this talk, I will present our recent advancements on fully-integrated perspiration analysis system that can simultaneously measure sweat metabolites, electrolytes and heavy metals, as well as the skin temperature to calibrate the sensors' response. Our work bridges the technological gap in wearable biosensors by merging plastic-based sensors that interface with the skin, and silicon integrated circuits consolidated on a flexible circuit board for complex signal processing. This wearable system is used to measure the detailed sweat profile of human subjects engaged in prolonged physical activities, and infer real-time assessment of physiological state of the subjects.
“Inverse Strain Effect in Atomic Scale” - Enhanced Hydrogen Evolution Activity and Durability in Cu Substituted Binary Chalcogenide
Authors: Sarma Saurav Chandra , Mishra Vidyanshu , Mary K. A. Ann , Roy Soumyabrata , Peter Sebastian C.
Published: February 2020

Since preceding decades, the demand for hydrogen production through water splitting has increased exponentially. In addition to highly active catalyst, we require our catalyst to be stable for several hours and days. We report herein a ternary chalcogenide-based compound, (CuPd)17Se15, with electrochemical stability for 30000 cycles towards hydrogen evolution reaction. In addition, this work provide a unique strategy of improving activity through the introduction of tensile strain by the substitution of small and low cost copper atoms (inverse strain effect) at the active site (larger size than Cu) of the compound. Pd atom being in +2 oxidation state adsorbs hydrogen very weakly and Se, in its elemental state, binds weakly to H* adsorbate. However, the presence of Pd modulates the electronic structure of Se to have ∆GH* close to zero and favors the progress of the reaction. Cu substitution further lowers ∆GH*, thus favoring the reaction. This unique synergistic effect between the two processes is accountable for better activity, high stability of 30000 cycles and significantly high TOF of 126.3 s-1 for (CuPd)17Se15. We deconvoluted the strain, ligand and ensemble effect to understand the factors behind the enhancement of the activity.

Figure 1. (a) Linear sweep voltammogram of the Cu-substituted catalyst showing prolonged stability of the catalyst even after 30000 cycles and (b) comparison of the Tafel slope of the catalyst before and after the degradation test. (c) Schematic representation of different possible sites of Cu substitution and (d) comparison of the change in Gibbs free energy of adsorption of H* before and after Cu substitution.

Figure 1
Unraveling Oxygen Electrocatalysis Mechanisms and Investigating the Role of Vulcan Carbon on a Thin Film Oxygen Deficient Perovskite La0.6Sr0.4CoO3-
δ
Authors: Mattick Victoria F , Jin Xinfang , White Ralph E. , Huang Kevin
Published: February 2020

Alkaline-based metal-air batteries require a low-resistance, bifunctional oxygen electrode to perform fast oxygen electrocatalysis during charging and discharging cycles. However, achieving good oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) bifunctionality has proven challenging. In this work, a perovskite-structured and oxygen-deficient oxide, La0.6Sr0.4CoO3-
δ (LSCO), has been investigated as a model bifunctional thin-film oxygen electrode for alkaline metal-air cells. The rotating disk electrode (RDE) configuration in combination with common electrochemical techniques such as linear sweep voltammetry (LSV) and cyclic voltammetry (CV) were applied to characterize the behavior of the ORR and OER taking place on LSCO in 0.1 M KOH solution. The results show that the oxygen electrocatalysis process on LSCO in the alkaline media follows a multistep charge-transfer pathway. A physics-based, generalized electrochemical model, encompassing two sequential 2e- steps with HO2
- as an intermediate species and one parallel 4e- step, along with peroxide dissolution, has been established to account for the multi-step charge transfer behavior with very satisfactory results, yielding a series of important electrode kinetic parameters for the elementary reactions considered. After forming the base concept of oxygen electrocatalysis on the LSCO, the effect of the Vulcan carbon (XC-72R) mass ratios on the ORR/OER were also investigated and a synergistic effect between the perovskite-oxide and the XC-72 was observed to affect the reaction mechanism. Finally, the bifunctionality of the LSCO towards ORR was clearly elevated through the addition of a commercial, noble-metal 20% wt Pt/C, where even the slightest addition of the Pt/C dominated the ORR trending and the smallest amounts of LSCO trumped the OER characteristic profiles.

Keywords: oxygen electrocatalysis; perovskite-oxide; rotating disk electrode, linear sweep voltammetry.
Encapsulation of Metallic Electrocatalysts in Graphitic Shells
Authors: Khani Hadi , Grundish Nicholas S. , Wipf David O , Goodenough John B.
Published: February 2020

Developing highly efficient, cost effective, and environmentally friendly electrocatalyts for the oxygen reduction and oxygen evolution reactions (ORR and OER) and the hydrogen evolution reaction (HER) are of interest for sustainable and clean energy technologies, including metal–air batteries, solar and fuel cells, and water splitting. Herein, we report the screening of electrocatalytic activities of a series of graphite-coated metallic iron (Fe), cobalt (Co), and nickel (Ni) nanoparticles along with their corresponding binary and ternary alloys towards the OER, ORR, and HER in alkaline media. The synthesis of the metallic compounds encapsulated in graphitic shells proceeds via a two-step sol–gel and carbothermal reduction procedure. The X-ray diffraction patterns of the obtained powders revealed a single-phase purity among all the single, binary and ternary compounds. The result of XRD, XPS and TEM characterizations revealed a chemical and morphological transformation from those of graphite-coated metallic compositions to an exfoliated graphite network with metal oxide and hydroxide phases upon their electrochemical activation in KOH solution. The characterization of electrochemically activated samples revealed that the graphite-coated Ni0.5Fe0.5 and Co0.6Fe0.4 nanoparticle precursors exhibit remarkable enhanced electrocatalystic activities for OER and HER/ORR, respectively. The screened electrocatalysts have shown promising onset potentials and current densities as well as durable electrocatalytic performance for their respective reaction.
(Invited) Degradation Aspects of Electrocatalysts and Materials in PEM Water Electrolyzers
Authors: Carmo Marcelo
Published: February 2020

When coupled to renewable but nonetheless intermittent power sources such as wind or solar, polymer electrolyte membrane (PEM) electrolyzers are intended to be in operation for tens of thousands of hours [1]. Hence, the long-term behavior of catalyst coated membranes (CCMs) under some specific operating characteristics is of great importance. Previous durability studies have focused on electrolyzers operating at constant current input, showing little to no significant degradation (<4µVh) after 40.000 h at moderate conditions (25 cell stack, around 50°C and 1,3 A/cm²)[2]. In another study, constant and highly variable operation mode was compared for three used stacks after 7.500 h and indicated that variable operation might result in higher cell decay [3]. To the best of our knowledge, no durability data has been published yet, that fundamentally contrasts the effects of defined dynamic load profiles and constant operation on the cell decay in single cell tests. This is particularly crucial, since coupling PEM electrolysis to renewable power sources involves dealing with fluctuating power inputs, startup, and shutdown incidents that for PEM fuel cells are known to accelerate degradation.

In this study we demonstrate for the first time, the different effect of a constant and defined dynamic operation on the cell decay. For this purpose, durability tests were performed using state-of-the-art PEM electrolysis cells. The physicochemical characteristics were comprehensively addressed and the main process constraints (e.g., electrical, reaction, and transport) were analyzed. Exceptional improvements could be demonstrated using new membrane and catalyst materials enhancing performance, gas separation, and overall durability. Our results also show an effect of the operation mode on the degradation rate. Moderate conditions of 1 A/cm² show no significant degradation after 1000h. This is in line with the above mentioned results for commercial electrolyzer units. At higher current densities significant degradation rates were found. This study undeniably suggests coupling PEM electrolyzers to intermittent power sources under long term operation, contributing to transformative knowledge in the field of energy conversion and storage.

[1]. M. Carmo, D. Fritz, J. Mergel and D. Stolten, International Journal of Hydrogen Energy, 38, 4901-4934 (2013)

[2] Katherine Ayers, presented at the DOE Fuel Cell Technologies Program Webinar, May 23, 2011

[3] 2013 Annual Merit Review Proceedings, II.A.2, Renewable Electrolysis Integrated Systems Development and Testing
3D Micro Porous Cobalt−Iron−Phosphorus Electrocatalyst for Overall Water Splitting
Authors: Kim HyoWon , Oh SeKwon , Cho EunAe , Kwon HyukSang
Published: February 2020

3D Co-Fe-P microstructure based on electrodeposition was synthesized for high performance oxygen and hydrogen evolution reaction catalysts. Preferentially, Fe/Co ratio of Co-Fe-P film was optimized to 1.1 and exhibited the highest activity for the oxygen evolution. It is related with the transfer of the valence electron from Co to Fe and P. Based on these characteristics and Cu foam microstructure, 3D porous Co-Fe-P foam was fabricated. The Co-Fe-P foam had 94 times larger electrochemical active surface area (ECSA) than the Co-Fe-P film with similar Fe/Co ratios of 1.1, resulting in a high activity for the oxygen evolution reaction (294 mV at 10 mA/cm2) and hydrogen evolution reaction (73 mV at 10 mA/cm2) in 1 M KOH solution. The electrodeposited Co-Fe-P foam itself can be directly used without binder, and microstructure of the electrode can be engineered by controlling the electrodeposition condition, leading to the enlarged ECSA and improved performance. This study offers a facile and controllable synthesis of catalyst and electrode through an easy electrodeposition process.
A 10kW Class Ti/Mn Redox Flow Battery
Authors: Kaku Hirokazu , Yamaguchi Hideyuki , Dong Yong-Rong , Tatsumi Ryouta , Miyatake Kenichiro , Moriuchi Kiyoaki , Tsutsui Yasumitsu , Shigematsu Toshio
Published: February 2020

Large-scale energy storage systems play an important role in the effective use of renewable energy such as wind and solar power. Redox flow batteries (RFBs) have attracted a great deal of attention because of high-speed response, the independent design of power and energy, and advantages in safety. RFBs consist of tanks of electrolyte which store chemical energy and electrochemical cells which reversibly convert chemical energy to electricity. All-vanadium RFBs are widely used as the most mature technology while other various redox species can also be utilized as the electrolyte.

Among redox species applicable in aqueous solution, we have reported an electrolyte of titanium and manganese. The discharged state consists of Ti (IV) and Mn (II), both of which are widely available from abundant and low-cost resources. An energy density of 23.5 kWh/m3 is achievable due to the two-electron reaction of manganese on the positive side [1]. Main issues of the Ti/Mn RFB are the precipitation of MnO2 over time in the positive electrolyte and its low power density. As for the precipitation, a systematic research on the effect of mixing Ti (IV) into the positive electrolyte revealed that Ti (IV) ions change the morphology and the crystal structure of MnO2 as well as the electrochemical property of the positive electrolyte [2]. The other issue of low power density can be overcome by thermal treatment of carbon electrodes [3]. Moreover, the low permeability of ions in the Ti/Mn electrolyte contributes to the high coulombic efficiency even when a thin membrane is used. We have reported that the combination of a heat-treated carbon electrode and a thin membrane led to the highest energy efficiency, which was 84.3% with a current density of 200 mA/cm2 [4].

In this work, long-term cycle test was performed in a scaled-up system in order to further investigate the reliability of Ti/Mn RFBs. The evaluation system was designed to be approximately 10 kW×1h. In charge-discharge cycle tests, it was confirmed that the cell performance was stable over 100 cycles. A stable energy density over 14 kWh/m3 was successfully confirmed with a current density of 200 mA/cm2. The coulombic efficiency remained over 99%. The characteristics of this Ti/Mn RFB will be discussed in details 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., ECS Trans., 75 (18), 27 (2017).

[4] H. Kaku et. al., ECS Trans., 77 (11), 173 (2017).
(Invited) Status and Future Perspectives of Redox Flow Batteries
Authors: Yang Z. Gary
Published: February 2020

The trends of growing renewable penetration and demand of reliable, flexible, clean and affordable electricity have driven ever increasing interests of electrical energy storage (EES). Applications of EES as utility assets have seen significant growth around the globe in the past few years. Among varied EES technologies, batteries that convert chemical energy into electricity or vice versa offer quick response and unparalleled flexibility and have thus been one of the most developed and commercialized. Particularly, redox flow batteries (RFB’) have been among the leader in emerging battery technologies for utilities, independent power producer, microgrid, and commercial and industrial customers. Unlike other battery chemistries, such as lead-acid and Li-ion or generally classified as solid-state batteries, RFB’ were developed specifically for utility applications. With energy stored in liquid electrolytes and without ionic diffusion in the solid electrodes, these batteries work in a unique way that enables a set of unique advantages over the solid-state batteries. These may include separated design of energy (kWh) and power kW), a superior cyclability, a long life and full access to rate capacities over the life. More importantly, the RFB so far, including vanadium RFB’ or VRFB’, Zn-halide, etc., most use aqueous electrolytes and are inherent safe. The unique advantages, along with the performance flexibility demonstrated allow for stacking benefits for a safe EES solutions of a maximized value to customers.

As emerging technologies, however, RFB’ have found a limited share in the early market that has been dominated by Li-ion batteries lately. Though there have been many deployments in the fields, the RFB’ are still being optimized to achieve a full maturity and have not yet produced at scales. Pressure is also on to reduce costs and make competitive in the markets. This paper will review progress and challenges of the redox flow battery industry and technology development and share perspectives in future directions.
(Invited) Performance Improvements and Cost Considerations of the Vanadium Redox Flow Battery
Authors: Skyllas-Kazacos Maria
Published: February 2020

Since the initial development of the All-Vanadium Redox Flow Battery (VRFB) at UNSW Sydney Australia in the mid 1980s, considerable improvements in performance have been achieved through electrode modification and new cell designs that have led to significant increases in power density and reduecd stack costs. These improvements are allowing VRFB manufacturers to achieve the cost structures required for a range of energy storage applications and have led to extensive commercialisation of the technolology around the world. In this paper a brief overview of the main advances in electrodes and cell design will be presented, together with results from modelling and simulation studies that can be used to optimise stack design and battery performance.
(Invited) Zinc Based Flow Battery for Stationary Energy Storage
Authors: Li Xianfeng
Published: February 2020

Key words: flow battery, zinc based, energy storage, prospects and challenges

Zn2+/Zn redox couple attracts more and more attention in flow battery due to its characteristics of high solubility, low cost electrochemical reversibility and environmental friendly. Until now, many zinc based flow battery systems such as zinc-bromine1, zinc- nickle and zinc-iron2,3 etc. have been investigated, which have very promising prospect for stationary energy storage. Among them, zinc-bromine is one of the most successfully example of zinc based flow battery system, while zinc nickle and zinc iron systems have obtained tremendous developments recently. At the same time, many new zinc based systems such as zinc iodine have been proposed and demonstrated great advantages in some aspects such as energy density. However, secondary batteries that use zinc electrodes typically exhibit short lifetimes, because of problems with undesirable zinc morphology especially zinc dendrites, that form during charge. Hence, the challenge is to deposit a compact, uniform and free of dendrite layer that ensure a long cycle secondary negative electrode.

In recent years, DICP devoted to Zinc based batteries and implemented several demonstrations on zinc bromine flow batteries in different fields.

Therefore, in this presentation we will introduce the research and development status of zinc based flow batteries at DICP.

References:

1 Wang, C. et al. Cage-Like Porous Carbon with Superhigh Activity and Br2 - Complex-Entrapping Capability for Bromine-Based Flow Batteries. Adv. Mater. 29, 1605815, (2017).

2 Xie, C., Duan, Y., Xu, W., Zhang, H. & Li, X. A Low‐Cost Neutral Zinc–Iron Flow Batterywith High Energy Density for Stationary Energy Storage. Angew. Chem. Int. Ed., 47, 14953-14957, (2017).

3 Yuan, Z., Duan, Y., Liu, T., Zhang, H. & Li, X. Toward a low cost alkaline zinc-iron flow battery with a polybenzimidazole custom membrane for stationary energy storage. iScience, (2018). doi:10.1016/j.isci.2018.04.006
A Low-Cost and Robust Aqueous Organic Redox Flow Battery
Authors: Yang Bo , Murali Advaith , Nirmalchandar Archith , Jayathilake Buddhinie Srimali , Surya Prakash G. K. , Narayanan S. R.
Published: February 2020

Aqueous Organic Redox Flow Batteries (ORBAT) are attractive for large-scale energy storage. Quinone based ORBATs have the advantages of being low cost and also environmentally-friendly. However, it has been a challenge to find electrolyte materials that are stable because of the reactivity of the organic molecules with water. For grid-scale energy storage systems to be commercially viable, it is desirable that the levelized cost of energy storage (LCOS) is <5 cents/kWh and the operational life of the system is >10 years.

The flow battery research at the University of Southern California (USC) has previously identified the causes for capacity fade ORBATs operating on quinones. We have demonstrated molecular design strategies to prevent chemical transformations by the Michael reaction with water [1] and acid-catalyzed proto-desulfonation [2]. We have also demonstrated operational approaches to mitigate capacity fade by crossover through the proton exchange membrane separator [2].

Recently, we have developed a highly efficient redox flow battery system based on low-cost water soluble redox materials, which can deliver electricity at the target levelized cost of storage (LCOS) of 5 cents/kWh-cycle. The highly durable molecules at the positive and negative electrode have shown the ability to be discharged at current densities as high as 840 mA/cm2 (Figure 1). We have performed stable charge/discharge cycling experiments for over 700 cycles at 200 mA/cm2 (Figure 2) without any measurable capacity fade.

The system is distinguished by the remarkably low cost of redox materials of $6.5/kWh, the lowest cost for any known type of redox flow battery. Based on our preliminary tests and understanding of the chemical stability of the water-based solutions of the active materials, we can expect the system to realize the targets for long operational life. The ultra-low cost of redox materials, the inherent stability of redox materials, and the high efficiency during charge and discharge, gives this organic flow battery system a competitive edge over other systems.

References

[1] L. Hoober-Burkhardt et al., “A New Michael-Reaction-Resistant Benzoquinone for Aqueous Organic Redox Flow Batteries,” J. Electrochem. Soc., vol. 164, no. 4, pp. A600–A607, 2017.

[2] A. Murali et al., “Understanding and Mitigating Capacity Fade in Aqueous Organic Redox Flow Batteries,” J. Electrochem. Soc., vol. 165, no. 7, pp. A1193–A1203, 2018.

Figure 1
Enhancing Cell Performances of High Ni-Content NCM cathode By Surface Modification with SiO2
Authors: Kim Hyun-Soo , Lee Seung-Hwan , Park Gumjae , Jin Bong-Soo
Published: February 2020

Recently, there is a growing demand for high-energy lithium ion batteries in order to apply to electric vehicles, hybrid electric vehicle, uninterruptible power supplies and portable devices. The cathode active material of three component layered LiNixCoyMnzO2 (NCM, 0≤x, y, z <1) delivers superior electrochemical performances, which is highly dependent on the composition of Ni, Co and Mn in the NCM. The high Ni content contributes to a high capacity and reduction in cost while sacrificing the long-term stability.

In this paper, we prepared SiO2 coated LiNi0.8Mn0.1Co0.1O2 cathode and investigated the effect of SiO2 coating layer on the electrochemical performances and thermal behavior. The SiO2 coated LiNi0.8Mn0.1Co0.1O2 cathode delivers outstanding electrochemical performances. Therefore, we believe that SiO2 coated LiNi0.8Mn0.1Co0.1O2 cathode is beneficial approach for high performance and reliability lithium ion batteries.

SiO2 coated LiNi0.8Mn0.1Co0.1O2 delivers high initial capacity of 200.7 mAh g-1 as well as the excellent cycleability (capacity retention of 87.3 % after 100 cycles at 0.5 C) and rate capability (82.2% at 2C). Such improvements are attributed to the SiO2 coating, which can suppress the irreversible phase transformation and play a role in obstacle to protect the LiNi0.8Mn0.1Co0.1O2 from electrolyte.