bluuebunny/crossref_metadata_2025 huggingface dataset:
Hematite/TiO2 Heterostructure Photoanodes for Efficient Solar-to-Fuel Conversion
Authors: Jayasayee Kaushik , Balasingam Suresh Kannan , Sunde Svein , Srinivas Thangavel , Lee Jae Sung , Manivasagam Thirugnasambandam
Published: February 2020

Photoelectrochemical (PEC) water splitting is a promising route for the conversion of solar energy into energy rich hydrogen fuel using water as a reactant. Synthesis of highly efficient semiconductor photoelectrode is the key challenge in this field. The photoelectrode should absorb a major part of visible light from the sunlight, the valence band and conducting band edge of semiconductor should be straddled with the oxygen evolution and hydrogen evolution potential, good stability in electrolyte medium and efficient charge transport properties in the semiconductor. So far, no single electrode satisfies all such criteria. In the quest of suitable semiconductor photoelectrodes, hematite (α-Fe2O3) is the earth abundant material, which has an optimum band gap of around 2.1 eV, high theoretical solar-to-hydrogen (STH) efficiency of 16.8%, a suitable band edge position for water splitting reaction and the good stability in broad pH electrolyte medium. However, the hematite suffers from the short hole-diffusion length, poor electronic conductivity, high electron-hole recombination rate, slow charge-transfer kinetics and sluggish oxygen evolution reaction (OER) kinetics still limits its practical STH efficiency. To mitigate these issues, we have developed hematite/TiO2 bi-layered photoanodes for enhanced charge separation and reduced recombination of electron-holes. The direct growth of the heterostructures with different thicknesses is achieved by the facile electron beam evaporation route via formation of metallic thin films followed by high temperature calcination in air atmosphere. The physico-chemical properties of as synthesized photoelectrodes are characterized using XRD, SEM and TEM. The photoelectrochemical properties are measured using linear sweep voltammetry, chronoamperometry and impedance spectroscopy under 1-sun illumination using three-electrode setup with platinum wire as a counter electrode and RHE as a reference electrode in 1 M KOH electrolyte. For comparison purpose, the dark current is also measured using the same experimental setup in the absence of light.
Prospects for Validation of PEM Fuel Cell Models Using Current Distribution
Authors: Beruski Otávio , Perez Joelma
Published: February 2020

Complex systems have a lot to gain from computational models, as they provide information out of reach of most individual experimental techniques. The possibility of providing full control over variables and parameters of a given system, as well as enabling the comparison of mathematical approaches, are a few of the many advantages of employing a well-developed computational model. Such is the case for fuel cells, notorious for its complex interactions between micro, meso and macro-scale components, and difficulty in obtaining reliable information from its dynamics. However, it is of high importance that the models be continuously improved and validated, not only against the already established empirical data, but also against new techniques that provide furtherinsights in the system. In this context, an ongoing work is being developed to provide robust data from current distribution, a rather unused technique when it comes to PEM fuel cell model validation, in order to further improve model development and provide a complementary dataset for validation. It is seen that, when using a simple 3D model of a 50 cm2 PEM fuel cell, with a well-established mathematical formulation, it is possible to reproduce most of the experimental polarization curve, within one deviation, despite the uncertainties on material properties (upper graph in Figure). On the other hand, the current distribution greatly differs between the experimental and computational results, even qualitatively (lower graph in Figure: applied current 3.0 A, current values normalized by sum over all collection points). In general, the same behavior is observed throughout the polarization curve and for different inlet flow rates. Although the lack of proper characterization of the electrode materials may be partially to blame, the consistent differences in the spatial distribution of the current points to broader issues: i) the polarization curve is rather insensitive to finer properties of the system, being a poor result for validation; and ii) the lack of accuracy of widely used mathematical formulations in describing the spatial dependency of variables of interest, in this case current, even in a relatively small device and conservative conditions. These preliminary results and the observed tendencies add to the growing consensus that greater efforts are needed in order to develop and validate useful fuel cell models. In particular, it is suggested that current distribution results, if available, provide more information and greater constraints for fuel cell development and validation, than when relying solely on polarization curves.

Figure 1
(Keynote) Mechanisms in Ion Conducting Polymer Materials By Broadband Electrical Spectroscopy (BES)
Authors: Di Noto Vito , Vezzù Keti , Negro Enrico , Bertasi Federico , Pagot Gioele , Nawn Graeme , Pace Giuseppe
Published: February 2020

The charge transfer mechanisms of ion conducting polymer materials (ICPMs) is of crucial importance both for fundamental research and for a host of practical applications, including primary and secondary batteries, fuel cells, dye-sensitized solar cells, supercapacitors and sensors. A wide variety of ICPMs has been proposed, based on: (a) different families of polymer electrolytes; (b) ionic liquids (ILs); and (c) classical ion-conducting ceramics. In these materials, the long-range charge transfer events take place owing to complex processes, which involve several possible relaxation phenomena, such as: (a) ion hopping events between ion coordination sites; (b) relaxation modes of the host matrix; and (c) polarization effects occurring at the interfaces between the different domains characterizing the materials. Broadband electrical spectroscopy (BES) is a powerful tool for the accurate investigation of the roles played by electrical relaxation events in the charge transfer processes. Indeed, BES allows to carefully detect the fundamental relaxations governing the long-range charge transfer mechanisms and to correlate them to the morphology of ion-conducting materials. This presentation overviews results of the application of BES in the study of the charge transfer mechanisms of a variety of ICMs, including: (a) polymer electrolytes based on alkaline and alkaline-earth ions; (b) pristine and hybrid inorganic-organic proton-conducting and anion-conducting membranes. The general phenomena and the fundamental theory underlying the interpretation of the events characterizing the electric response of the materials is also described. Finally, the models adopted for the interpretation of conductivity mechanisms are described and a unified conductivity mechanism is proposed.
Ion Transport in Single-Ion Conducting Polymer Electrolytes for Lithium Batteries
Authors: Upadhyay Sunil , Schaefer Jennifer L.
Published: February 2020

Electrochemical energy storage devices are increasingly desired for consumer vehicle electrification and renewable power utilization. Safety and performance of batteries is strongly dictated by the performance of the electrolyte. Polymer electrolytes offer advantages over liquid and inorganic solid-state electrolytes, as they are non-leakable and non-volatile, yet flexible. Single-ion conducting electrolytes that eliminate ion concentration gradients offer further advantages: greater electrochemical stability allowing for higher voltage cells, lower interfacial impedance, and higher theoretical charge/discharge rates. Single-ion conducting polymer electrolytes may simply be created by titration of an ionomer with the active ion – Li+ in a Li-ion battery, for example. Unfortunately, the drastically low ionic conductivity of single-ion conducting polymer electrolytes without added solvent has precluded their commercial application thus far. Improved understanding of lithium ion transport mechanisms is critical for the development of high performance electrolytes. Our efforts in this area are focused on understanding ion states and ion transport in two distinct classes of single-ion conducting polymers. The first class of materials of interest are polyethers with highly dissociable tethered anions, where the research focus is to understand ion-pair dissociation and ion states that contribute to conduction. The second class of materials of interest are ionomers with solely non-polar polymer components, where we aim to understand ion transport through ionic domains.
Tunable-High Performance Sustainion™ Anion Exchange Membranes for Electrochemical Applications
Authors: Sajjad Syed D. , Gao Yan , Liu Zengcai , Yang Hongzhou , Masel Rich
Published: February 2020

This paper will describe the development and applications of Dioxide Materials’ new brand of novel Sustanion™ polymer Anion Exchange Membranes (AEMs). The styrene backbone of these membranes is functionalized in various degrees by the imidazolium functional group and includes other additives to yield several compositions for tailoring the properties and performance of these membranes. The advantage of using the Sustanion™ membranes over any commercially available AEM technologies is demonstrated in terms of their significantly higher anionic conductivities in Figure 1. Furthermore, the membranes are stable and maintain these conductivities when exposed to 1M KOH at 60 oC for up to a period of at least 1500 hours.

We have corroborated these finding by testing these membranes in-situ CO2 and water electrolyzers. Our results speak for themselves. The CO2 electrolyzers have run under 3V at 200 mA/cm² with a voltage rise of only between 4 and 6 µV/hr for 3700 hours. Keep in mind, these currents are more than a factor of 4 higher than our closest competitor. For water electrolyzers, our Sustainion™ membranes have helped us embark on the Holy Grail of base metal catalysts using NiFe on stainless steel anodes and NiFeCo cathodes. We can maintain 1 A/cm² at 1.9V at 60oC in 1M KOH for 200 hours with less than 5 mV voltage variation. This is unprecedented since under the same conditions, we have failed to find a single instance in literature of values surpassing the above results by including even high loadings of precious metal catalysts. The cell is still running.

As such, we are expecting to offer these membranes for beta-testing by various academic and industry groups. Based on our current findings, we envision the Sustainion™ membranes making similar breakthroughs in applications of alkaline anion exchange based fuel cells, flow batteries and even electrodiyalsis among other untapped electrochemical applications.

Acknowledgement

Parts of this work were supported by ARPA-E under contracts DE-AR0000345 and DE-AR0000684 and by 3M. The opinions here are those of the authors and may not reflect the opinions of ARPA-E or 3M. Assistance from colleagues, collaborators and friends from 3M are gratefully acknowledged.

Figure 1
Pentablock Ionomer Based TEOS-TIP Hybrid Nanocomposites: Morphology, Physical Properties, and Ion Transport
Authors: Huang Fei , Zheng Wenjian , Cornelius Chris
Published: February 2020

Nowadays, pure materials cannot embody all the physical, chemical, and mechanical properties required for a given application. Therefore, hybrid inorganic-organic composite materials were created to fill this critical void. The hybrid composites depend not only the properties of individual components, but also on the interfacial interactions between inorganic and organic phases. The significance of this work is to control the interaction-structure-property relationships of hybrid inorganic-organic nanocomposites in many applications such as fuel cells, lithium-ion batteries, biomimetic actuator, and water purification.

The PBC based hybrid organic-inorganic films were synthesized based on tetraethylorthosilicate (TEOS), titanium isopropoxide (TIP), and poly(t-butylstyrene-b-hydrogenated isoprene-b-sulfonated styrene-b-hydrogenated isoprene-b-t-butylstyrene) or pentablock copolymer (PBC) via sol-gel chemistry. A ternary phase diagram was estibalished to understand the homogeneity of TEOS-TIP sol-gel system dependent on initial sol composition and reaction conditions leading to controllable materials. All hybrid PBC-TEOS-TIP membranes exhibited higher water uptake than unmodified PBC membranes. Proton conductivity increased 80% from 58 mS/cm for unmodified PBC film to 85 mS/cm for hybrid nanocomposite film due to the role TEOS-TIP within it. This can be attributed to the partial charge transfer from the titanate’s inorganic domains to sulfonate groups that promote acid dissociation and proton attraction. The PBC’s microphase-separated morphology changed from well-ordered lamella-like structure to a random and homogenous distribution of ionic domains with increasing TIP concentration, which was observed from AFM and SAXS results. TGA analyses revealed a decrease in degradation temperature due to titanate's catalytic character, and DMA results demonstrated reduced polymer chain mobility caused by inorganic-organic interactions. Finally, these PBC-TEOS-TIP hybrid composites were used as proton-exchange membranes (PEM) for hygroden fuel cells.
The Effect of Litfs and Epoxy on Epoxy Based Adhesive Polymer Electrolyte for Mediator Structural Supercapacitor
Authors: Wang Yuchen , Qiao Xiaoyao , Zhang Chen , Zhou Xiangyang
Published: February 2020

Structural energy storage devices have drawn the attention of many researchers because load-carrying components can store electrical energy. Structural supercapacitor (SC) is a fast charging energy storage device and a component that withholds mechanical loading. We used an epoxy based adhesive polymer electrolyte for structural mediator-enhanced SCs. The epoxy based adhesive polymer electrolyte was composed of polyvinylidene fluoride (PVDF), lithium trifluoromethanesulfonate (LiTFS), and epoxy. In this work, the effects of LiTFS and epoxy on electrochemical and mechanical properties are investigated. The mass ratio of PVDF:LiTFS were 2:1, 1:1, 1:2 and 1:4 in this study whereas the concentration of epoxy was 0%, 10%, 20%, 30%, 40% and 50%. The ionic conductivity was evaluated by measuring the total conductivity and the electronic conductivity. The ionic conductivity decreases with the increase of epoxy concentration. The ionic conductivity reaches the maximum when PVDF:LiTFS=1:2 which is 0.015 S/cm. Mediators or redox species were used to dope the adhesive polymer electrolyte in the electrodes. The cyclic voltammetry (CV) curves of structural mediator-enhanced SCs fabricated using the epoxy based polymer electrolytes correlate with the trend of ionic conductivity. Tension tests were performed to evaluate Young’s modulus of mediator-enhanced SCs. The results indicate that epoxy component plays the key role to mechanical properties. Considering both electrochemical and mechanical properties, the best composition of the epoxy based electrolytes is defined.
Lithium Battery Casualty Detection and Mitigation Developments for Navy Platforms
Authors: Schwartz Jessica , Wartelsky Michael , Winchester Clinton
Published: February 2020

The growing need for large lithium batteries and lithium battery powered equipment aboard submarines provides major challenges to the US Navy; two of these challenges include (1) early battery casualty detection and (2) containment or mitigation of hazards associated from lithium-based battery casualties. Lithium ion rechargeable batteries used within research unmanned undersea vehicles (UUV) was abusively tested inside of its vehicle and was instrumented with water mitigation and various types of presumptive pre/post casualty onset detection sensors. These efforts were conducted under the requirements for the Navy’s Lithium Battery Safety Program, Naval Sea Systems Command Instruction 9310.1C and related documents as guidance for need. This effort followed similar recent works for the storage and carriage of large form lithium and lithium-ion batteries conducted preciously. This paper will review the results of these tests conducted by the Naval Surface Warfare Center, Carderock Division (NSWCCD), Naval Undersea Warfare Center, Newport (NUWC NWPT) and the Naval Research Center (NRL) over the past six years. These efforts have enabled the carriage and deployment of lithium battery powered systems from surface platforms and are expected to enable the deployment from undersea platforms.
Battery Internal Short Circuit Detection
Authors: Zhang Mingxuan , Ouyang Minggao , Lu Languang , He Xiangming , Feng Xuning , Liu Lishuo , Xie Xiaoyi
Published: February 2020

Internal short circuit (ISCr) is one of the major safety concerns of lithium batteries, and may result in thermal runaway of batteries. The detection of ISCr in battery is critical for preventing thermal runaway and promoting electrical vehicle safety. In this research, the electrical characteristics of the ISCr of lithium ion batteries are analyzed through the battery equivalent circuit model (ECM). An ISCr detection method is developed based on battery consistency inside the battery pack. The proposed ISCr detection method adopts the recursive least square (RLS) algorithm basing on the mean-difference model (MDM). The proposed method first estimates the basic parameters of the MDM, then calculates the characteristic parameters, such as the differential of the voltage and the fluctuation function of the internal resistance, derived from the basic parameters of the MDM. These characteristic parameters largely vary from their normal values once ISCr occurs, thereby enable the battery management system to achieve ISCr detection. The effectiveness of the proposed method is validated through experiments. The proposed ISCr detection method is integrated into battery management system (BMS) of vehicles and yields satisfactory performance.
Conductive Polymer for Reversible Overcharge Protection in Lithium-Ion Batteries
Authors: Wang Bin
Published: February 2020

Great improvement in the safety of lithium ion battery is needed to meet the full requirements of electric vehicles(EV). Among these safety hazards, overcharge has long been recognized as a primary concern because it can lead to dangerous events such as thermal runaway,fire and explosion. The electroactive polymer approach utilizes the unique electronic properties of the polymers to form a reversible resistive shunt between the current collectors and protect the cell from overcharging. The process is self-activated by voltage, and it does not pose interference during normal cell charge and discharge.

In this work, we report the recent progress in cell overcharge protection for high-energy-density lithium ion batteries. By incorporating the reversible electroactive polymers into highly porous membrane separators, we demonstrate that the composites can provide reversible and stable overcharge protection for a variety of cell chemistries. The results for the protection of Li1.05Mn1.95O4 or LiNi0.8Co0.15Al0.05O2 electrode will be discussed. Both cells were protected at a steady state voltage of 4.5 V for well over 100 cycles.
Characterizing the Ionic Transport through Nanoporus AAO Membranes: Effect of Surface Charge Due to Biomolecule Functionalization
Authors: Gosai Agnivo , Shrotriya Pranav
Published: February 2020

Nanoporous anodic aluminum oxide (NAAO) membranes have been utilized as sensing platforms for a variety of chemical/biological targets in recent years. NAAO membrane based sensors are attractive due to the low cost, simple instrumentation and fast response time. Traditionally, biomolecule functionalized NAAO membranes have been used as working electrodes in electrochemical sensors. Afterwards due to binding with the target molecule, the electrical characteristic of the working electrode (for e.g. impedance) is changed which is calibrated with different concentrations of the target species.

Previous research has primarily focused on recognition of target molecule by characterizing the impedance change of the working electrode. In the present work, we have conducted experiments to understand how the ionic transport (of the electrolyte) across the NAAO membrane is affected due to the functionalization of biomolecules. We have used electrochemical impedance spectroscopy (EIS) to analyze the effect of different biomolecules on the membranes.

As a test example, we have chosen the thrombin binding aptamer as the sensing molecule and human alpha thrombin as the target molecule in the experiments. The NAAO membranes were sputter coated with gold and the effect of sputtering on the pore size was analyzed through scanning electron microscope (SEM). Afterwards the membrane was functionalized with thiolated thrombin binding aptamer (TBA). Then the membrane was placed in a custom made electrochemical cell and a four-electrode system was utilized to measure the impedance change across the membrane. The electrolyte was maintained at a physiological pH value. When the system was treated with thrombin protein, upon binding with the TBA, it produced a change in the impedance, which was characterized by EIS. We have repeated the experiments for different pore diameters, different sputtering time and concentrations of thrombin. A negative control experiment was also carried out to check the effect of other proteins on the system.

Finally, we have modeled the system using a modified Randles circuit to look at the contribution of protein-aptamer binding on the following parameters: resistance due to the pores, capacitance of the membrane and the electrolytic resistance. We have found that there is a positive correlation between these parameters and successful binding of the biomolecules which in turn can be utilized to calibrate the ionic transport across the membrane as well as utilize the system as a sensor for target proteins.
Improvement of Electrochemical ORR Activity and Its Durability with Pt Electrocatalyst Nanoparticles Anchored on MOx/Cup-Stacked Carbon Nanotube in Acidic Aqueous Media
Authors: Ando Fuma , Tanabe Toyokazu , Gunji Takao , Kaneko Shingo , Ohsaka Takeo , Matsumoto Futoshi
Published: February 2020

In order to prepare the sample that exhibits the enhancement of oxygen reduction reaction (ORR) and improvement of its durability for the ORR in acidic aqueous solutions, Pt nanoparticles (NPs) were deposited on TiO2 moieties which was coated on a cup-stacked carbon nanotube (CSCNT) as a electron-conducting support material. The TiO2 moieties on which Pt NPs were deposited contribute to both enhancement of ORR and improvement of durability of ORR electrocatalytic activity by the electronic interaction between Pt NPs and TiO2 and anchor effect of rough TiO2 by which Pt NPs are anchored, resulting in the inhibition of aggregation of Pt NPs during potential cycling. The two functions of TiO2 moieties could realize large improvement of the electrocatalytic performance for ORR in Pt NPs/TiO2/CSCNT. The formation of nanostructure of Pt NPs on TiO2 and surface structure of the Pt NPs were characterized with transmission electron microscope (TEM). The electronic states of Pt and Ti atoms were measured with X-ray photoelectron spectroscopy (XPS). The results obtained with TEM and XPS supported our consideration on the improvement of ORR activity and its durability.
Flexible Paper Photodetectors Based on 2D BN Nanosheets
Authors: Lin Chun-Ho , Tsai Meng-Lin , Fu Hui-Chun , He Jr-Hau
Published: February 2020

The market for printed and flexible electronics, key attributes for internet of things, is estimated to reach $45 billion by 2016 and paper-based electronics shows great potential to meet this increasing demand due to its popularity, flexibility, low cost, mass productivity, disposability, and ease of processing. However, conventional flexible devices made of paper and plastic substrates are expected to have thermal issues due to their poor thermal conductivity. In this work, we demonstrated flexible solar-blind deep-ultraviolet (DUV) sensors based on 2D boron nitride nanosheets (BNNSs) composited paper with good detectivity (up to 8.05 × 1010 cm Hz1/2/W), fast recovery time (down to 0.393 s), great thermal stability (146 W/m K, 3-order-of-magnitude larger than conventional flexible substrates), high working temperature (up to 200 oC), excellent flexibility and bending durability (showing repeatable ON/OFF switching during 200-time bending cycles). This shows great potential to be a key component to solve thermal problems and fully activate flexible electronics for meeting the demand of internet of things.
Stretchable Smart Skin Based on 2D Piezoelectric Semiconductors
Authors: Wang Ruoxing , Wu Wenzhuo
Published: February 2020

Capturing the stimuli from ambient environment and having response are critical to exploring the world. This not only requires a complex integration of heterogeneous components but also lacks a direct interface between the (opto)electronics and the working environment. Moreover, all existing technologies require a power source, which complicates the system design and limits operation schemes. Stretchable electronic devices are particularly desirable for practical applications because of the high mechanical deformability and adaptability enabling their integration with three-dimensional biological systems. In this work, we built up a monolithic piezoelectric nanogenerator system as self-powered wearable devices for use in physiological detecting on human body. The stretchable electrodes were directly printed on soft substrates with designed patterns. Subsequently, two-dimensional ZnO nanosheets were selectively grown on electrodes without any decrease of electrode conductivity. ZnO nanosheets with thin thickness which is more flexible compared with common ZnO nanowires, can generated charges under tiny mechanically deformation and sustainably perform non-invasive physiological functions, e.g. detection of pulses, by harvesting power from human body. This research is expected to have a positive impact and immediate relevance to many societally pervasive areas, e.g. biomedical monitoring, consumer electronics, and human-machine interface.
Simultaneous Optical and Electrochemical Imaging of Shewanella Oneidensis
Authors: Calhoun Margaret C , Crisostomo David , Cliffel David E
Published: February 2020

Shewanella oneidensis is an electroactive bacterium that has the ability to harvest electrons from insoluble metals in its environment for biological processes via dissimilatory metal reduction (DMR). There are 4 mechanisms by which S. oneidensis accomplishes these reductions: direct contact of the outer cell membrane to the metals, protein “nanowires” that extend from the cell surface, metal chelators that solubilize the metals, and small molecule electron shuttles. While evidence suggests S. oneidensis predominately utilizes soluble electron shuttles for DMR, it has yet to be directly proven. If the exact mechanism or mechanisms could be elucidated, S. oneidensis could be employed in a fuel cell that rids polluted water of metal contaminants in the process of generating electricity.

For this research, scanning electrochemical microscopy (SECM) was used to investigate the DMR processes of S. oneidensis. By coupling SECM to an inverted microscope, we optically imaged the bacteria during two-dimensional electrochemical measurements. Combined with advances in carbon ultra-micro electrode fabrication, this optical-SECM was used for high resolution scans of S. oneidensis biofilms, as well as planktonic bacteria.
Sol-Gel Synthesis and Photoluminescent Investigation of SrZnV2O7:Eu3+ Nanophosphors
Authors: Khatkar Satyender Pal
Published: February 2020

Sol-gel Synthesis and Photoluminescent Investigation of SrZnV2O7:Eu3+ Nanophosphors

S.P. Khatkar1*, V.B. Taxak1, Mandeep Dalal1

1Department of Chemistry, Maharshi Dayanand University, Rohtak -124001, India

*Corresponding Author: Tel: +919813805666

E-mail: s_khatkar@rediffmail.com

Recently, opto-electronic study of rare earth doped inorganic host materials emerged out as one of the most proficient field in nanotechnology. White LEDs exhibit excellent advantages such as more economical power consumption, longer life, being mercury-free and less pollution as compared to the conventional halogen and incandescent lamp. However, white LEDs using GaN based chip system have poor color rendering index and low chromatic stability under different driving currents. Therefore, near UV-LEDs coated with RGB phosphor offer effective and attractive solution for the problem of white light emission with lower color temperature. In present work, europium doped SrZnV2O7 nanophosphor was successfully synthesized via sol-gel approach in nano range with particle size in 70-90 nm range confirmed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The crystallinity of pure phased nanophosphor in monoclinic lattice with the P121/n1 (14) space group was confirmed through X-ray diffraction analysis. The nanophosphor yields strong red emission at 616 nm attributed to 5D0→ 7F2 transition of Eu3+ ion when excited at 395 nm with optimum concentration for maximum luminescence was 4 mol%. The photoluminescent excitation and emission spectra of synthesized samples suggest their potential application in phosphor converted white LEDs with NUV excitation.
Au Core-TiO2 Shell Nanoparticles Produced By RT Atomic Layer Deposition
Authors: Hirose Fumihiko , Kanomata Kensaku , Miura Masanori , Kukuchi Ko , Ahmmad Bashir , Kubota Shigeru
Published: February 2020

Core-shell nanoparticles consist of core materials coated with different kinds of films, where new functional material properties are expected by the combination of core and shell materials. In our laboratory, we have been developing the Au-core-oxide-semiconductor shell particles which must be used for the electron channel material. By using the metal core, we can form the particle chain between two adjacent electrodes by using an electrostatic force where the shell material works as a semiconductor channel. We also expect the nanoparticle chain can be formed at a two-dimensional space in a lipid bilayer that could be used for the bio sensors and field effect sensors. We report on the room temperature atomic layer deposition producing the core-shell particles and the related experiments in the presentation.
Cu-Ni-Mo-P/C Electrocatalyst for the Co-Generation of Energy and Fine Chemicals from Glycerol Electrooxidation
Authors: Elendu Oyidia , Kalu Egwu Eric , Yeboah Yaw D.
Published: February 2020

CuNiMoP/C synthesized using a mixture of sodium hypophosphite and formaldehyde as reducing agents in a single electroless bath has been used as anode side catalysts for the oxidation of glycerol. The copper to nickel ratio in the electroless deposits was 9. The ratio of NaOH/glycerol charged to the anode side of an unstirred divided electrochemical reactor at the beginning of the electro-oxidation was 4. The cathode (platinum) was depolarized with oxygen during each oxidation. The anode and cathode compartments were separated by an anion exchange membrane.

Using voltammetry and high pressure liquid chromatography, we show that changing the potential applied at a CuNiMoP/C anode affects both glycerol conversion and product yield/selectivity. The applied anode potentials studied ranged from 0.5 V - 1.3 V (versus Ag/AgCl in satd KCl). The major liquid products obtained were glyceraldehyde, dihydroxyacetone, oxalic acid, lactic acid and tartronic acid at room temperature. Glycerol conversions ranged from 20% to 30% for six to eight hour operations.

Electrochemical characterization of the CuNiMoP/C gave a Tafel slope of 130 mV/decade, and an exchange current density of 1.8 mA/cm2. Electrochemical impedance spectroscopy was carried out between 25 0C and 80 0C to study the effect of temperature on impedances, since the higher temperature approximate actual liquid fuel cell conditions. Some preliminary results on the CuNiMoP/C stability while in use, determined from 72 hours uninterrupted use of the electro-catalysts for glycerol electro-oxidation, will also be presented.

These results have important implications for portable applications with a direct alkaline glycerol fuel cell.

Figure 1
A Molten Salt Electrolysis Procedure to Form Al-Sc Alloys
Authors: Polat Çağlar , Erdogan Metehan , Karakaya Ishak
Published: February 2020

Recently, alloys such as Al-Sc and Al-Mg-Sc came to the forefront due to the reinforcement effect of scandium on the properties of aluminum such as mechanical strength, thermal stability, resistance to recrystallization, resistance to intergranular fracture and corrosion

[1]. The main scandium source for these aluminum alloys is the Sc2O3 by-product obtained during uranium (U), tungsten (W) or tantalum (Ta) production. It has been shown that it is possible to produce Sc by the molten salt electrolysis method with dissolution of Sc2O3 in Na3ScF6 as in the Hall-Héroult process [2]. This scandium can be used to produce Al-Sc alloy in-situ, provided that required amount of aluminum was already present in the reactor. Furthermore, the production of Al-Sc alloy by the dissolution of Sc2O3 in a molten salt containing CaCl2, in which the solubility of oxide ions is very large has been reported [3]. The Al-Sc alloy formation by the reduction of other Sc containing compounds in a molten salt containing CaCl2 was investigated in this study. The preliminary tests revealed that Al3Sc intermetallic was successfully formed and distributed homogeneously throughout the Al matrix as confirmed by the XRD, SEM-EDS and optical microscopy analyses. As can be seen in the optical micrograph shown in Figure (a), due to the long electrolysis and the high voltage applied, calcium contamination was observed by the presence of black Al4Ca eutectics in between the white faceted Al3Sc intermetallics. On the other hand, in the optical micrograph shown in Figure (b), it can be seen that the calcium contamination was inhibited by changing the electrolysis duration and the voltage while keeping the homogeneous distribution of Al3Sc.

References

[1]Ahmad, Z. (2003). The properties and application of scandium-reinforced aluminum. JOM, 55(2), 35-39.

[2] Vickery,R.C. Production of scandium and yttrium. U.S. Patent No 3,111,467, 1963

[3] Harata, M., Yasuda, K., Yakushiji, H., & Okabe, T. H. (2009). Electrochemical production of Al–Sc alloy in CaCl2–Sc2O3 molten salt. Journal of Alloys and Compounds, 474(1), 124-130.

Figure 1
Electrochemical Reduction of Solid Silica to Form Silicon in Molten Salts
Authors: Akpinar Bengisu , Erdogan Metehan , Ergul Emre , Akduman Baris , Karakaya Ishak
Published: February 2020

Nowadays, Silicon is the most critical element in solar cells and/or solar chips. Silicon having 98 to 99% Si as being metallurgical grade, requires further refinement/purification processes such as zone refining [1,2] and/or Siemens process [3] to upgrade it for solar applications. A promising method, based on straightforward electrochemical reduction of oxides by FFC Cambridge Process [4], was adopted to form silicon from porous SiO2 pellets in molten CaCl2 and CaCl2-NaCl salt mixture [5]. It was reported that silicon powder contaminated by iron and nickel emanated from stainless steel cathode, consequently disqualified the product from solar applications. SiO2 pellets sintered at 1300oC for 4 hours, were placed in between pure silicon wafer plates to defeat the contamination problem. Encouraging results indicated a reliable alternative method of direct solar grade silicon production for expanding solar energy field.

[1] P.R. Mei, S.P.Moreira, E.Cardoso, A.D.S.Cortes, F.C.Marques, “Purification of metallurgical silicon by horizontal zone melting”, Sol. Energ. Mat. Sol., 98 (2012), 233-239.

[2] P. Siffert, E.F. Krimmel, eds. Silicon: Evolution and future of a technology. Berlin,Springer (2004).

[3] Siemens & Halske: BRD Patents 1.102.117 and 1.140.1594 filed 1954, issued 1956

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

[5] E. Ergül, İ. Karakaya, M. Erdoğan, “Electrochemical decomposition of SiO2 pellets to form silicon in molten salts” Journal of Alloys and Compounds, 509 (2011), 899-903.
Bimetallic Electrocatalysts in Li-O2 Battery: How the Componential Proportion Influences the Battery Performance
Authors: Luo Xiangyi , Ge Le , Ma Lu , Kropf Jeremy , Wen Jianguo , Zuo Xiaobin , Ren Yang , Miller Dean , Wu Tianpin , Lu Jun , Amine Khalil
Published: February 2020

In comparison with conventional Li-ion batteries, the superior theoretical energy density makes the lithium-air battery one of the most promising technologies for next-generation energy storage. However, its commercialization is still hindered by several challenges, such as poor cycleability and large overpotential. Particularly, the high charge overpotential not only induces a low Coulombic efficiency and low round-trip efficiency, but also aggravates the whole battery system by increasing the possibility of electrolyte decomposition and byproducts. It is well known that, due to the multiple electron transfer nature, the sluggish kinetics of the OER usually leads to charge overpotential. Hence, various electrocatalysts have been explored to lower the overpotential and to improve the battery performance. However, most of the charge potentials are still too high for practical use of the rechargeable Li-O2 battery.

Over the last few decades, nanostructured bimetallic catalysts have shown extraordinary electronic and chemical catalytic properties for many applications, such as fuel cells, nitrogen production, and biomass-fuel conversion. The greatly enhanced catalytic performance can be ascribed to the formation of the heteroatom bonds on the metal surface and the variation of the local bonding geometry. The former modifies the electronic environment of the surface atoms and their reactivity, while the latter affects the electronic structure of the metal. Therefore, it is possible to tailor the composition and structure of nanostructured bimetallic catalysts to meet requirement for certain applications.

Here, by choosing a right component proportion in Pt-Cu bimetallic electrocatalysts which optimize the electrocatalytic activity on the electrochemical reactions, especially on oxygen evolution reactions, we demonstrated a superior electrochemical behavior with the low charge overpotential of 0.2 V and the cycleability of 50 discharge/charge cycles before the capacity fading. Synchrotron high-energy X-ray diffraction (HE-XRD), X-ray absorption spectroscopy (XAS), and electron microscopy (EM) were employed to study the morphology and component of the electrochemical reaction products. The results of this study have shown that the optimized Pt-Cu bimetallic electrocatalysts significantly reduce the charge overpotential, and furthermore enhance the efficiency, stability, and cycleability of an aprotic Li-O2 battery. It would also serve as a general guide for nanostructured bimetallic catalysts design and optimization.
Transition Metal Sulfides As Cathode Materials for Rechargeable Aluminum Ion Battery
Authors: Geng Linxiao , Guo Juchen
Published: February 2020

Rechargeable aluminum battery system is very intriguing due to the following reasons: First of all, aluminum has high capacity due to its trivalency. And aluminum is very cheap since it is the most abundant metal element in earth’s crust.1 As a result, rechargeable aluminum battery can be very promising in large scale energy storage application. One of the main reasons that hinders the development of rechargeable aluminum battery is the lacking of electrolyte that can enable facile deposition and dissolution of aluminum in the anode side. On the other hand, facile electrochemical deposition and dissolution of aluminum can be achieved in room temperature ionic liquid (molten salt) synthesized by mixing aluminum chloride (AlCl3) with organic salts such as 1-butylpyridinium chloride, 1-ethyl-3-methylimidazolium chloride, etc. at a certain ratio.2,3 In a previous research, our group proposed Chevrel phase Mo6S8 as the first conventional intercalation type cathode material.4 The logic of choosing transition metal sulfide instead of transition metal oxide as cathode material for aluminum ion battery is very important. Due to the strong coulombic effect, the energy barrier of multivalent ions transportation in the crystal structure is very high.5 Thus, a softer anionic framework is needed. Sulfide has a much lower electronegativity than oxide, which makes transition metal sulfide a very promising cathode candidate for rechargeable aluminum ion battery. To further validate this assumption, we synthesized nano sized layered TiS2 and cubic Ti2S4 as well as investigated their electrochemical properties as cathode materials for ionic liquid electrolyte based rechargeable aluminum ion battery at both room temperature and 50 °C. We further confirmed the aluminum intercalation in the TiS2 and Ti2S4 crystal structure using ex-situ XRD and XPS. The proposed titanium sulfide cathode materials showed decent reversible capacity and a higher working potential. In order to further understand the mechanism of Al intercalation into Chevrel Phase Mo6S8, high resolution TEM is used to directly visualize the crystal structure of AlxMo6S8 from different discharged and charged stages. Powder XRD Rietveld refinement is also undertaken to provide support from a theoretical simulation perspective.

1. Li, Q.; Bjerrum, N. J. J. Power Sources 2002, 110, 1.

2. Endres, F. ChemPhysChem 2002, 3, 144.

3. Jiang, T.; Chollier Brym, M. J.; Dube, G.; Lasia, A.; Brisard, G. M. Surf. Coat. Technol. 2006, 201, 1.

4. Geng, L.; Lv, G.; Xing, X. Guo, J. 2015, 27, 4926−4929.

5. Rong, Z.; Malik, R.; Canepa, P.; Sai Gautam, G.; Liu, M.; Jain, A. Persson, K.; Ceder, G. Chem. Mater., 2015, 27 (17), pp 6016–6021.
Optimizing Battery Design for Fast Charging through a Genetic Algorithm Based Multi-Objective Optimization Framework
Authors: Liu Changhong , Liu Lin
Published: February 2020

As the innovation of battery technology, batteries have higher power density than before and electric vehicles can travel longer distance per charge. However, the long charging time of electric vehicles is still one of its limitations. Electric car takes much longer time to fully charge its batteries. Fast charging and super charging are the available solutions but they have a potential of damaging battery with accelerated degradation. It is critical to reduce the charge time without compromise long-term performance. New materials, nanoscale structures, charging strategy have been studies to decrease the charging time. All of these approaches can further benefit from an optimal design of the batter structure for fast charging. We investigate the effect of design variables such as porosity, particle size, and thickness for both anode and cathode electrodes on battery charging and degradation by using a physics-based side-reaction coupled electrochemical model. We develop a computational optimization framework with the Elitist Non-Dominated Sorting Genetic Algorithm (NSGA-II) to find the optimal design variables to improve battery charging and long-term performance. The computational optimization work is computationally efficient of providing a guidance for battery design.
Design Principles of Non-Graphitic Carbon Electrodes for Energy Storage
Authors: Li Zhifei , Bommier Clement , Jian Zelang , Ji Xiulei
Published: February 2020

Energy storage is the missing enabler to facilitate the widespread installation of renewable-but-intermittent solar and wind energy. There are two primary metrics for stationary energy storage: cost and cycling life, where the latter is also about the cost, indeed. It is thus a must to rely on Earth-abundant elements, which rules out lithium-based devices for the stationary purposes, as lithium is rare and its supply is geopolitically challenged. This warrants attention for Na-ion batteries (NIBs) and K-ion batteries (KIBs). For metal-ion batteries, the choice of anode often determines the fate of the battery commercialization, as anode typically determines battery’s cycling life as well as safety features. Considering the cost and performance, non-graphitic carbon anodes are the leading candidates for NIBs and KIBs. To date, much effort has been devoted to preparing such carbons from various unique organic precursors. However, there has been a dearth of knowledge on the basic correlation between the local structures of carbon anodes and their Na (K)-ion storage behavior, where the alkali-metal-cation storage mechanism in hard carbon and soft carbon is still a debated topic. In this talk, I will introduce new insights on storage mechanisms and design principles of hard carbon anodes for NIBs based on the structure-capacity correlation revealed by experimental and theoretical studies. I will also discuss K-ion storage properties of major carbons, including graphite, which proves incorrect an old assumption between graphite and potassium.
An Experimental Analysis on the Impacts of Current Pulsing with Varying Current Amplitudes on Lithium Ion Cells
Authors: Rajagopalan Kannan Dhevathi Rajan , Moss Pedro L. , Weatherspoon Mark H
Published: February 2020

Lithium ion batteries can be charged by different techniques. CCCV (constant current, constant voltage) charging is the conventional method that is predominantly employed for charging the lithium ion batteries. A theoretical analysis of pulse charging using varying current amplitudes with the relaxation periods has shown reduction in the charging time without reaching lithium saturation over the period [1]. It is based on the concept of increasing surface concentration of lithium at initial stages and maintaining the concentration value close to the saturation.

The objective of this work is to experimentally investigate the impacts of varying current pulse amplitudes on the lithium ion battery materials. This method consists of constant width charging, rest period and the applied current is decreased as the charging progress. Implementing the pulsed currents of different amplitudes on cathodic (Lithium Iron Phosphate) and anodic (Graphite and Li 4Ti5O12) half cells separately creates varied impacts on the electrode materials. The results of charging time and overall cycle life are then compared with conventional charging method.

Figures 1 and 2 show the constant current and a portion of pulsed current profile that are used in the analysis. In this experiment, pulsed current profile is controlled by varying the duty cycle, relaxation periods are included in between pulses and current amplitudes are reduced as the charging progress. EIS, SEM and XRD are used in analyzing the impacts of both the charging protocols on the lithium ion cells.

References:

[1] B. K. Purushothaman and U. Landau, “Rapid Charging of Lithium-Ion Batteries Using Pulsed Currents A Theoretical Analysis,” J. Electrochem. Soc., vol. 153, no. 3, pp. A533–A542, Mar. 2006.

Figure 1