bluuebunny/crossref_metadata_2025 huggingface dataset:
Flexible and Pixelated Textile Pressure Sensor Fabricated with Weaving Techniques
Authors: Lee Jaehong , Kwon Hyukho , Seo Jungmok , Shin Sera , Kim Dayeong , Lee Taeyoon
Published: February 2020

Recently, electronic textiles (E-textiles) that integrate sensors, actuators and computers into fabrics have attracted considerable attention and several types of textile-based devices have been widely studied. E-textiles have been applied to effectively provide a wide range of information to the people like elderly and patients since they can be worn or embedded in clothing. Among several applications of E-textiles, pressure sensors have significant role to detect a person’s information such as locations, vital signals. In previous studies, textile-based pressure sensors have generally developed by weaving metal wires due to their simple structure and fabrication process, however, it is challenging to apply these pressure sensors on sophisticated devices due to their poor sensing ability.

This research proposes a novel method of fabricating highly sensitive textile-based pressure sensor that can be pixelated through weaving method. We first obtained highly flexible and conductive Kevlar fiber by coating a composite material of Ag nanoparticles and elastomeric polymer. Consequently poly(dimethylsiloxane) (PDMS) was coated on the surface of conductive fiber as a dielectric layer. Through weaving method, the PDMS-coated conductive fibers were woven into fabric to form highly sensitive capacitive pressure sensors located at crossed points of the fibers. The highly sensitive pressure sensor was pixelated in the form of arrays via weaving method. Finally, pressure sensors were applied to monitor detection of small vibration forces from music and impact of a bouncing water droplet on a superhydrophobic surface.
The Influence of Trifluoroacetic Acid on the Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate)
Authors: Du Yi-Chang , Tsai Li-Duan , Fang Jason
Published: February 2020

Poly(3,4-ethylenedioxythiophene) :Poly(styrenesulfonate) (PEDOT:PSS) can disperse in the aqueous solution and shows good processability and exhibits very stable, high conductive and transparent characteristics. Therefore, PEDOT:PSS has replaced ITO glass in some electronic devices, such as anode buffer layer of organic solar cells.

In this study, we explored how the trifluoroacetic acid (TFA) improves the electrical conductivity of the PEDOT:PSS free standing film which was cast and dried from TFA aqueous solution.

To investigate the influence of TFA on the conductivity of the PEDOT:PSS, Raman spectroscope, X-ray photoelectron spectroscope (XPS), and conductive atomic force microscope (C-AFM) were carried out. Besides, the conformation and the phase behaviors of PEDOT:PSS were investigated in this study as well.

According to the results, it was proposed that the improvement of the electrical conductivity of PEDOT:PSS film cast from TFA solution was not caused by the higher doping level with TFA., but caused by changing the conformation of PEDOT chain. As TFA is added into the aqueous dispersions of PEDOT:PSS, it can interact with PEDOT and makes PEDOT with more positive charges and more hydrophilic. The conformation of the PEDOT chains is therefore expanded. As a result, the conductive PEDOT domains construct a continuous conductive network and the electrical conductivity of the PEDOT:PSS film is improved.
Continuous Electrokinetic Separation of Particles Via Wall-Induced Non-Inertial Lift
Authors: Lu Xinyu , Xuan Xiangchun
Published: February 2020

The efficient separation of discrete particle (both synthetic and biological) species is a topic of interest in numerous research fields for its practical application to problems encountered in both academia and industry. We demonstrate in this work a novel continuous-flow method for electrokinetic separation of both a binary mixture and a ternary mixture of colloidal particles based on size. This method utilizes for the first time the wall-induced non-inertial lift force to deflect a sheath flow-focused particle mixture to size-dependent positions in a straight microchannel. A numerical model is also developed to understand this separation and to study the parametric effects on it. The numerical predictions are found to agree reasonably with the experimental observations.
Electrokinetic-Flow Driven Rectification of Ion Current in a Tunable Polymer Nanopore
Authors: Yeh Li-Hsien , Huang Ming-Jiang , Qian Shizhi
Published: February 2020

Ion current rectification (ICR) in a charged nanopore is a diode-like phenomenon, typically showing the distinct behaviors of the nanopore conductance, stemming from an accumulation and a depletion of ionic concentrations, when the voltage polarity is changed. This work experimentally study the importance of the solution properties like pH and salt concentration, and the concentration gradients applied across the nanopore on the ICR phenomenon in a tunable, polymer, conical nanopore. Results obtained show that the degree of ICR becomes significant when the salt concentration is low. In addition, the ICR behavior at the low solution pH is distinctly different from that at the high pH, resulting from the different charge nature of the polymer membrane. In contrast to the previous studies that using a combined organic and aqueous electrolyte solution to generate the ICR in a conical nanopore, we demonstrated that the ICR can be generated through an application of a salt concentration gradient in a pure aqueous solution by the electrokinetic flow (EKF). The ICR behaviors in the nanopore can be controlled by controlling the direction of the EKF in the nanopore.
Molecular Structure and Ion Transport Near Electrode-Electrolyte Interfaces in Lithium-Ion Batteries
Authors: Lordi Vincenzo , Ong Mitchell T. , Verners Osvalds , van Duin Adri C. T. , Draeger Erik W. , Pask John E.
Published: February 2020

The performance of lithium-ion secondary batteries (LIBs) is strongly tied to ionic transport through electrode-electrolyte interfaces. Solvation structure strongly affects ion mobility, and differences in ion solvation near the interface compared to the bulk may affect conductivity. Furthermore, the formation and evolution of solid-electrolyte interphase (SEI) layers, which impede transport between electrode and electrolyte while passivating the interface, are related to molecular interactions at the interface involving solvent molecules, ions, and the electrode surface. In addition, the chemistry of the electrode surface, in particular the edge termination of graphite electrodes, can impact Li ion transport into the electrode and formation of SEI. Understanding these effects is critical to optimizing battery performance.

Here we present molecular dynamics (MD) simulations of typical organic liquid LIB electrolytes in contact with graphite electrodes to understand the relationship between ion solvation structure and transport near the interface. Results for different graphite terminations are presented and the effect of an electric field is explored. Different prototypical organic liquids, including ethylene carbonate and ethyl methyl carbonate, are compared. We observe that anion mobility in an electric field is much greater than that for Li ions, a phenomenon due to the very different solvation structures. In addition, we observe a barrier to Li insertion into graphite when its surface is hydroxyl terminated. Furthermore, we compare the results of ab initio MD with the empirical reactive forcefield ReaxFF and the non-reactive, non-polarizable COMPASS forcefield and note differences in the predictive power of each technique.

Prepared by LLNL under Contract DE-AC52-07NA27344.
In-Situ Observation of Li-O2 Electrochemical Reactions Using Electrochemical AFM
Authors: Byon Hye Ryung , Wen Rui , Hong Misun
Published: February 2020

Despite outstanding gravimetric energy density of a nonaqueous lithium-oxygen (Li–O2) battery in regard to promising future energy storage, a true Li–O2 electrochemical reaction has not been deeply understood. In particular, a little knowledge of dynamic Li–O2 process of formation, growth and decomposition of Li2O2 has been known. Here, we present in–situ imaging of the Li–O2 electrochemical reactions using atomic force microscopy (AFM) coupled with electrochemical tester.[1,2]

A highly oriented pyrolytic graphite (HOPG) and metallic lithium were employed to working and counter/reference electrodes, respectively, which were fully immersed in O2 gas-saturated tetraethylene glycol dimethyl ether (tetraglyme) containing 0.5 M of LiTFSI (LiN(SO2CF3)2). Cyclic voltammetry was carried out at a potential range of 2.0-4.5 V with a scanning of HOPG surface by an insulating AFM tip in an Ar-filled glove box, which offered almost identical condition to the actual Li-O2 cell. In addition, the AFM tip scanning for imaging did not significantly disturb the growth/decomposition process of Li2O2.

Upon the oxygen reduction reaction (ORR), the nucleation of nanoparticle (diameter = 3–10 nm) was observed at the step edge of HOPG. These nanoparticles grew up to a diameter of 200 nm and migrated to the terrace of HOPG. When the potential approached to 2.0 V, new morphology products having rectangular and elongated nanoplates were rapidly formed at the edge of HOPG, which became predominant products for further reduction, thus constructing a thick Li2O2 film, demonstrated by X-ray photoelectron spectroscopy (XPS). Interestingly, the size of Li2O2 nanoplates on the top surface of Li2O2 film was much smaller than the one on the HOPG, which was probably attributed to slow charge transport according to growth of thick Li2O2 film having the poor electronic conductivity. The Li2O2 was decomposed upon oxygen evolution reaction (OER), where the thick and dense Li2O2 film delayed its decomposition and demanded for higher oxidation potential compared to the thin and low density of Li2O2. For control experiments, we replaced the ether-based electrolyte and HOPG electrode with carbonate and nanoporous gold, and also extended the voltammetry cycling number. These conditions provided different morphology of products and chemical identifications, which would be discussed in the presentation.

References

[1] Wen, R.; Hong, M.; Byon, H. R. J. Am. Chem. Soc.
2013, 135, 10870-10876.

[2] Wen, R.; Byon, H. R. Chem. Commun.
2014, 50, 2628-2631.
Investigating Surface and Interface Phenomena in LiFeBO3 Electrodes Using Photoelectron Spectroscopy Depth Profiling
Authors: Maibach Julia , Younesi Reza , Schwarzburger Nele , Gorgoi Mihaela , Fichtner Maximilian , Edström Kristina
Published: February 2020

The formation of surface and interface layers at the electrodes is highly important for the performance and stability of lithium ion batteries. To unravel the surface composition of electrode materials, photoelectron spectroscopy (PES) is highly suitable as it probes chemical surface and interface properties with high surface sensitivity. Additionally, by using synchrotron-generated hard x-rays as excitation source, larger probing depths compared to in-house PES can be achieved. Therefore, the combination of in-house soft x-ray photoelectron spectroscopy and hard x-ray photoelectron spectroscopy (HAXPES) enables reliable and non-destructive depth profiling. Thus, detailed investigation of compositional gradients at electrode surfaces and interfaces from a sub-monolayer to several nanometer length scales can be performed. As this depth region is especially relevant for both electronic and ionic transport processes, the presented combinatorial approach is a very valuable tool in characterizing battery electrodes and their interfaces. We apply this technique to lithium iron borate (LiFeBO3) battery electrodes at different cycling conditions to study the surface and interface layer evolution. Due to its high theoretical capacity (220 mA h g-1) LiFeBO3 is a promising cathode material for lithium ion batteries. However, its application is limited because of significant degradation due to surface reactions upon exposure to moisture and air. Therefore, detailed compositional characterization of LiFeBO3 electrode surfaces is essential to gain further understanding of the degradation processes. To study these properties for the pristine material, the electrode fabrication conditions were carefully controlled to limit contact to air and moisture. The investigation of the iron valence state in dependence of the electrode preparation as well as cycling conditions is presented as higher valence states of iron are most likely involved in the degradation process.
Effect of Different Kind of Binder in a MWCNT/Sulfur Composite Cathodes for Li/S Batteries
Authors: Hernandez-Maya Roberto , Castaneda Homero
Published: February 2020

The Li-S batteries has pronounced as an excellent alternative in Li batteries, mainly due to its high theoretical specific capacity and energy density. However, the practical application of rechargeable Li/S batteries has several problems due to the low utilization of the active material and low efficiency during charge and discharge cycles. This work proposes the use different binder (PVDF, Chitosan and Nafion), with a MWCNT/S composite material, in order to improve the electrochemical behavior, due to the increases on the electronic conductivity between the MWCNT and the S, and avoid the dissolution of polisufides. The MWCNT was previously functionalized to improve the amount of active sites on their surface. The electrochemical characterization was made using EIS (Electrochemical Impedance Spectroscopy) and CV (Cyclic Voltammetry) in organic electrolyte. Also, with techniques of superficial characterization as LEIS (Localized Electrochemical Impedance Spectroscopy) and SECM (Scanning Electrochemical Microscopy), in ionic liquid, we showed the effect of the binder in the surface distribution of active sites in the composite material.
Invited: Solidstate Engineering at Northwestern University
Authors: Razeghi Manijeh , McClintock Ryan
Published: February 2020

III-V semiconductors are playing an increasingly important role in the semiconductor industry as silicon technology slowly researches maturity. A diverse, and expanding, array of III-V semiconductor materials is currently being studied for next generation applications including optoelectronics and power devices. Under the guidance of Professor Manijeh Razeghi, Northwestern University has put itself on the map with a dedicated solidstate engineering faculty and state of the art facilities—all targeted towards training the next generation of solidstate engineers to work with these fundamental semiconductor materials. This is in marked contrast to many universities which focus primarily on the application of power devices, but not the design and construction of these devices.

Northwestern University has a dedicated cleanroom facility with multiple MOCVD and MBE system, and a state of the art toxic gas handling system dedicated to the growth of III-V semiconductor materials. Northwestern also has multiple facilities dedicated to the processing of these semiconductor materials into packaged devices, as well as the expertize and knowledge to test and characterize a wide array of III-V semiconductor devices. These facilities are currently used by undergraduate and graduate students, as well as post-doctoral scholars and research faculty, and support an integrated solid-state engineering curriculum.

The solid state engineering curriculum consists of a core focused on developing a fundamental understanding of theory, design and physics; semiconductor material growth and characterization; and device processing and testing. Three Textbooks have been developed to support this core curriculum:
Fundamentals of Solid State Engineering, 3rd ed.
;
Technology of Quantum Devices
; and
the MOCVD Challenge, 2nd Ed.
This curriculum then branches off into two major thrusts: “electronic transport” and “optoelectronics”. The electronic transport thrust contains classes covering low and high-power electronic devices.

This talk will review the current solidstate educational curriculum at Northwestern and our future plans to expand the coverage of wide-bandgap power devices in order to better educate the next generation of scientists and engineers to work in this important and growing area.
On the Power-Handling Capability of Wide Bandgap (WBG) Semiconductor Power Switching Devices
Authors: Shenai Krishna
Published: February 2020

Power switching devices made using wide bandgap (WBG) semiconductors such as Silicon Carbide (SiC) and Gallium Nitride (GaN) have the potential to make transformative impact on electrical energy generation, transmission, distribution and conditioning [1]. Although SiC power diodes and power MOSFETs are commercially available for voltage ratings up to 1,700 volts, a careful review of the published data suggests that reliability of WBG power devices may be severely compromised compared to identically rated silicon power devices. For example, dv/dt, avalanche, and safe-operating area (SOA) of SiC power diodes and MOSFETs are inferior to silicon power devices with identical ratings. This paper will present a simple physics-based analysis of the power handling capability of WBG power devices and explain the possible causes of lower reliability ratings.

[1] K. Shenai et al, “Current status and emerging trends in wide bandgap (WBG) semiconductor power devices,” ECS J. Solid State Sci. and Tech.
2(8), N3055-N3063, Jul 2013
Wide Bandgap Semiconductor Research Interests at Navy Laboratories
Authors: Hobart Karl D
Published: February 2020

The Navy and other government laboratories have been actively engaged in wide bandgap semiconductor research for power and RF applications for over twenty years. In this presentation I will give brief overview of the scope of research at the Navy labs with emphasis wide bandgap semiconductor power electronics. The research activities are extremely diverse ranging from fundamental wide bandgap materials research to system level deployments. Throughout the talk I will discuss research opportunities within Navy laboratories and the desired skill sets for young scientists and engineers entering the research community.
III-V Nanostructures Grown by Molecular Beam Epitaxy for High Efficiency Solar Cells
Authors: Wu Jiang , Lam Phu , Zhang Yunyan , Tang Mingchu , Hatch Sabina , Liu Huiyun
Published: February 2020

Semiconductor nanostructures have demonstrated great potential in energy harvesting due to their unique optical and electrical properties compared to their bulk counterparts. Particularly, self-assembled semiconductor nanostructures have received much attention in the last decade. For example, zero-dimensional (0D) quantum dots (QDs) with discrete energy levels like atoms have been proposed to realize high efficient photovoltaic devices that employ novel concepts including hot carriers, intermediate band, and multiple exciton generation. In addition, one-dimensional (1D) nanowires (NWs) can not only facilitate effective charge separation but also form nanophotonic structures that enable enhanced light absorption through light trapping. Moreover, the small footprint of NWs has a high tolerance to thermal and lattice mismatch and hence, integration of materials with different structural properties is possible to implement complex device architecture for high efficiency solar cells. In this presentation, we introduce our developments in nanomaterial growth by using solid-state molecular beam epitaxy and the applications of these self-assembled semiconductor nanostructures in photovoltaic applications. Emphasis will be put on design of III-V QDs for intermediate band solar cells as well as growth of III-V NWs on silicon for cost-effective high efficient solar cells.
Heterointegration Technologies for Advanced 3D Neural Interfaces
Authors: Dayeh Shadi A , Chen Renjie
Published: February 2020

Understanding the neurological processes by which humans perceive and act requires development of electro-neural interfaces with resolution that can probe at the single cell or sub-cellular level in a network of a large population of neurons. Si nanowires have been demonstrated as excellent nanoscale neural probes that can penetrate into the neural cell body and measure intracellular action and local field potentials. However, for individual addressability of single Si nanowires in a large scale assembly that is capable of probing neural activity at high spatial and temporal resolution, new integration technologies are required. To accomplish this task, we developed a novel all-solid state wafer bonding technique that allows integration of high-quality Si 3D structures to patterned (electrically isolated) electrode leads on insulating substrates. One key advantage of this technology is that the bonding layers (leads) are conductive, requiring no further processing for electrical addressability. Electrophysiology experiments validated the operation of such probes in high densities. In addition, co-integration and independent multiplexing of microfluidic channels within each nano-electrode is possible. This approach is fab-compatible, easy to manufacture, and allows integration of a variety of sensor and stimulator/inhibitor material elements on arbitrary substrates.
Omnidirectional Broadband Silicon-Based Solar Cells
Authors: He Jr-Hau
Published: February 2020

The relatively high efficiency of solar cells based on silicon (Si) has led them to dominate the solar cell industry for the past few decades. It is of current interest to develop the photon management with nanostructures since the ability to suppress the reflection and light trapping over a broad range of wavelengths and incident angles plays an important role in the performance of optoelectronic devices, such as photodetectors, light-emitting diodes, optical components, or photovoltaic systems. A variety of photon management strategies are developed for more efficient Si photovoltaic devices and are discussed in this talk.
Crystalline Submicrometer Spherical Particles with High Refractive Index for Optical Applications
Authors: Koshizaki Naoto , Ishikawa Yoshie
Published: February 2020

Nanoparticles are generally aggregated in liquid to reduce surface energy, and therefore surface modification of the nanoparticles is important to obtain well dispersed nanoparticles in liquid. Thus the aggregation of nanoparticles should be avoided for practical use of nanoparticles as much as possible.

Recently we found that B4C submicrometer spherical particles by irradiating low-fluence laser onto the B nanoparticles dispersed in organic solvent through the high-temperature carbonization reaction. Furthermore, we also found that similar submicrometer spherical particles were produced for various kinds of materials, such as metals (Au, Ag, etc.), oxides (ZnO, TiO2, etc.) and semiconductors (Si, GaP, etc.) using nanoparticles as raw materials and by unfocused laser beam irradiation.

In these cases, raw nanoparticles are presumably not vaporized nor ablated but melted by nanosecond laser irradiation to form liquid droplets, resulting in spherical particle formation by quenching. Thus, this process “laser melting in liquid” is evidently different from the conventional technique, “laser ablation in liquid” for nanoparticle fabrication using high-fluence laser irradiation in liquid.

More importantly, the particle size increased from nano-size to sub-micrometer size by laser melting in liquid. This is because aggregated nanoparticles melt together by optical absorption and subsequent temperature increase over melting temperature to form larger spherical particles. Thus the aggregation of nanoparticles plays an important role in submicrometer spherical particle formation.

Here we present our recent results on the laser melting in liquid, such as the effect of processing parameters on the products. Especially we discuss the effect of raw particle size by dynamic light scattering and zeta potential on the product morphology and generated particle size. Physicochemical calculation of temperature estimation based on the particle heating-melting-quenching model by laser irradiation is compared with the experimental results. Optical and medical applications of submicrometer spheres is also demonstrated.
Chemically Integrated Hybrid 2-D Materials for Flexible Energy Storage Devices
Authors: Yu Guihua
Published: February 2020

Two-dimensional (2-D) materials have been a promising material platform for making powerful energy devices including highly flexible energy storage devices. Owing to their advantageous features of flexibility, large surface area and open ion transport pathway within 2D layers, highly electroactive 2-D transition-metal oxide and phosphate nanosheets materials show promise in flexible supercapacitors with high power and energy densities. Here I will present our recent progress on chemically integrated hybrid 2-D materials to build ultraflexible, high-performance energy storage devices. One example is the building of integrated hybrid vanadyl phosphate VOPO4/graphene ultrathin-film solid-state pseudocapacitors (1). The other is the development of MnO2/graphene hybrid nanostructures based flexible planar supercapacitors (2).

Rational material and structural design demonstrated in these studies show hybrid structures not only take advantage of excellent electronic conductivity of graphene nanosheets but also introduce more electrochemically active surfaces for absorption/desorption of electrolyte ions, which can greatly facilitate charge transport during electrochemical processes.

References

(1) Wu, C.; Lu, X.; Peng, L.; Xu, K.; Peng, X.; Huang, J.; Yu, G.; Xie, Y. Nature Communications 2013, 4, 2431.

(2) Peng, L.; Peng, X.; Liu, B.; Wu, C.; Xie, Y.; Yu, G. Nano Letters 2013, 13, 2151.
Effects of Morphology on Nanostructured Cobalt Oxides for Oxygen Evolution Reaction
Authors: Cho Sung-Hwa , Roh Gilltae , Park Jun-Young
Published: February 2020

The oxygen evolution reaction (OER) is important process in water-splitting electrochemical devices for oxidation of water to molecular oxygen [1-4]. In particular, OER is the most important reaction process because the overall cell efficiency depends strongly on the reaction rate of the OER. Until now, noble metal catalysts such as iridium, ruthenium, and platinum have shown excellent performances for the OER and even ORR in fuel cell conditions [5]. However, these noble metal catalysts have disadvantage for making commercialization of such electrochemical devices in terms of high cost and limited durability [6, 7].

In order to cope with these issues, in this work, various transition metal oxides such as manganese oxides and cobalt oxides are investigated for replacing expensive noble metals of water-splitting electrochemical cells with enhanced durability [8, 9]. To achieve high efficient electrocatalyst for OER, in addition, various nanostructured metal oxide catalysts are synthesized by the hydrothermal method using nitrate or acetate-based precursors [10].

Synthesized catalysts are physicochemically characterized by X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). For analysis of electrochemical properties, cyclic voltammetry (CV) and OER are measured by rotating disk electrode (RDE) system. A Pt wire and Ag/AgCl electrode are used as a counter electrode and a reference electrode in 0.1 M KOH electrolyte. OER activity is measured by the linear sweep voltammetry (LSV) from 1.2 to 1.7 V at a scan rate of 5 mV s-1
to compare each nanostructured transition metal oxide powders.

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* Corresponding authors: jyoung@sejong.ac.kr (J.-Y. Park).
Enhanced Oxygen Evolution Activity of 3D Nanostructured Cobalt Oxides through Doping with Various Transition Metal Oxides
Authors: Kim Nam-In , So InSeop , Park Jun-Young
Published: February 2020

Photoelectrochemical water-splitting is one of the most renewable and clean ways to produce hydrogen by water electrolysis [1]. However, the oxygen evolution reaction (OER) in anode side of photoelectrochemical water-splitting system shows sluggish kinetics with the high polarization loss due to the 4-electron pathway likewise oxygen reduction reaction (ORR) in fuel cell operating conditions [2-5].

Up to now, noble metals, such as iridium, ruthenium and platinum, have still used as OER catalysts [6]. In comparison with these noble metal catalysts, studies of transition metal oxide catalysts (TMOCs) for photoelectrochemical water-splitting systems have not carried out intensively, although they have similar (or more active) properties about OER [7, 8]. In addition, various state-of-art nanotechnologies for fabricating TMOCs may contribute to improve OER properties significantly for water-splitting [9, 10].

In this work, a variety of nanostructured cobalt oxides (NCOs) are synthesized by the hydrothermal method using urea, hydrogen peroxide and polyvinylpyrrolidone. Then, various transition metal oxides are doped to NCO matrix during hydrothermal reaction. Their physicochemical properties were confirmed by using various analytic techniques such as SEM, TEM, BET, and XRD.

For electrochemical characterizations, a rotating disk electrode system is adopted with an Ag/AgCl reference electrode and a Pt counter electrode in 0.1 M KOH electrolyte. A pretreatment where cyclic voltammetry (CV) post-purging nitrogen gas in the potential range of 0.05 – 1.2 V versus reversible hydrogen electrode (RHE) conducted at a scan rate of 100 mV s-1 for 50 cycles is used for activation of catalyst surface. The OER activity is measured by linear sweep voltammetry (LSV) from 1.2 to 1.7 V at a scan rate of 5 mV s-1 and is compared the oxygen evolution activity at specific current density.

J. Jhang, K. Sasaki, E. Sutter, R. R. Adzic, Science, 315, 220 (2007).

Y. Liang, Y. Li, H. Wang, J. Zhou, J. Wang, T. Regier, H. Dai, Nature Materials, 10, 780 (2011).

J. Suntivich, K. J. May, H. A. Gasteiger, J. B. Goodenough, Y. Shao-Horn, Science, 334, 1383 (2011).

J. Suntivich, H. A. Gasteiger, N. Yabuuchi, Y. Shao-Horn, Nature Chemistry , 3, 546 (2011).

I. C. Man, H. Y. Su, F. C. Vallejo, H. A. Hansen, J. I. Martínez, N. G. Inoglu, J. Kitchin, T. F. Jaramillo, J. K. Nørskov, J. Rossmeisl, ChemCatChem, 3, 1159 (2011)

T. Reier, M. Oezaslan, P.Strasser, ACS Catal., 2, 1765 (2012).

Y. J. Sa, K. Kwon, J. Y. Cheon, F. Kleitz, S. H. Joo, J. Mater. Chem. A, 1, 9992 (2013).

J. Y. Cheon, C. Ahn, D. J. You, C. Pak, S. H. Hur, J. Kim, S. H. Joo, J. Mater. Chem. A, 1, 1270 (2013).

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X. Rui, H. Tan, D. Sim, W. Liu, C. Xu, H. H. Hng, R. Yazami, T. M. Lim, Q. Yan, J. Power Sources, 222, 97 (2013).

* Corresponding authors: jyoung@sejong.ac.kr (J.-Y. Park)
Electrochemical Dechlorination of 2-Chlorophenol on Ti-Ni, Ti-Pd and Ti-Ni-Pd Electrodes
Authors: Arellano Miguel , Texier Anne Claire , González Ignacio
Published: February 2020

Chlorophenols are involved in the manufacture of different compounds as antiseptics, herbicides among others. Unfortunately, the presence of chlorophenols in wastewater of these industries has been detected. Chlorophenols have been listed as priority pollutants by The United State Envionmental Protection Agency (USEPA). Nowadays, the accumulation of chlorinated aromatic compounds in the environment represents an urgent problem to be solved [1].The chlorophenols are resistant physical, chemical or biological treatments and have hazardous impact on living organisms including human beings. Electrochemical dechlorination can be explored as pretreatment of chlorophenol degradation, because it is a promising method for its various advantages: low equipment cost, mild reaction conditions, and produces no pollutants [2]. In this work, nickel-titanium, palladium-titanium and nickel-palladium-titanium alloy cathodes were used for electrochemical dechloration of 2-chlorophenol. The cathodes were prepared by electrodeposition where the experimental conditions were determined from both a thermodynamic study using Predominance Existence and distribution species diagrams, and voltammetric study. The electrodes were characterized by SEM, XRD and XPS. The efficient dechloration of 2-chorophenol was achieved in the electrochemical conditions where the atomic hydrogen adsorption produced for water reduction takes place. The dechloration was performed in a filter press electrochemical reactor FM01-LC. The effluents from electrochemical treatment will be treated in a biological reactor containing denitrifying sludge.

Acknowledgements: Miguel Arellano acknowledges the National Council of Science and Technology (CONACYT) by PhD grant.

References

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Chen, G., Wang, Z. Y., Xia, D. G. Electrochem. Commun. 6, 268. (2004)
Structure and Synthesis of Bi2S3 Nanocrystals for Thermoelectric Device
Authors: Hsiao Yu-Jen , Fang Te-Hua , Wu Cheng-Da , Wang Shi-Hao , Yang Bo-Yi
Published: February 2020

Characteristics and microstructure of bismuth sulfide (Bi2S3) produced by the microwave hydrothermal process are investigated. Bismuth sulfide is a direct band gap material with Eg ~ 1.3 eV and attracts high interest in thermoelectric application. In this work, bismuth sulfide nanostructures can be successfully prepared by a precipitation between bismuth 2-ethylhexanoate and thioacetamide in low-temperature organic solution at about 150 oC by the microwave hydrothermal process. The Bi2S3 products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and absorption spectra. The composite ratio between Bi and S can be adjusted by varying the ratio between two precursors and was determined by using EDS technique. Thermoelectric properties of the Bi2S3will be studied comparatively with those from commercial bulk materials.
Efficient Electrochemical Reduction of CO2 to Formic Acid
Authors: Nath Narayan Chandra Deb , Park Hyunwoong , Choi Seung Yo , Lee Jae-Joon
Published: February 2020

Fossil fuels comprise more than 80% of global energy sources because of their availability, versatility, and high energy density. However, their continued use at this level is accompanied by an unchecked accumulation of atmospheric CO2. An attractive alternative is to develop a scalable synthesis of carbon-containing products (formic acid, methane, methanol, and ethanol) using renewable energy, H2O, and CO2 at room temperature and atmospheric pressure. An efficient catalyst must mediate multiple electron and proton transfers to CO2 for the reduction of CO2 in the presence of H2O, and selectively produce one of many possible products. Researchers over the past three decades have identified several materials (e.g., semiconducting metal oxides) that are capable of reducing CO2 electrochemically in aqueous solutions, but none are efficient and stable enough for practical use due to the large overpotential (>0.7 V) required for CO2 reduction to outcompete H2O reduction. The energy level of the conduction band of semiconducting materials such as Cu2O or CuO cannot contain the sufficient reduction potential of CO2 to formic acid (HCOOH). In this regard, we are going to present our recent progress on the efficient CO2 reduction to formic acid by using bipolar WO3/Cu-CuO nanowires hybrid electrodes with low overpotential.
Mass Transfer in an Anode-Supported Honeycomb Solid Oxide Fuel Cell
Authors: Kotake Shota , Nakajima Hironori , Kitahara Tatsumi
Published: February 2020

An anode-supported honeycomb SOFC can achieve high volumetric power density and improve thermo-mechanical durability at high temperatures. We have so far fabricated the honeycomb cell with a cathode layer of LSM and an electrolyte layer of 8YSZ on a porous anode honeycomb substrate of Ni/8YSZ. The anode-supported honeycomb cell exhibited promising volumetric power densities. Effect of flow channel configurations on the cell performance was investigated in terms of the hydrogen partial pressure distribution in the cell under operation as well[1].

In the present study, current-voltage and current-power density characteristics of the cells having different porous substrate thicknesses and anode/cathode flow channel configurations are studied under different flow rates and partial pressures of fed hydrogen. We also investigate performance changes by forced hydrogen flow through the porous anode substrate taking advantage of valves connected to each outlet of the honeycomb cell.

Reference

S. Kotake, H. Nakajima, and T. Kitahara, “Flow Channel Configurations of an Anode-Supported Honeycomb Solid Oxide Fuel Cell” ECS Trans.,
57(1), B815 (2013).
Cation Intercalation and High Volumetric Capacitance of Two-Dimensional Titanium Carbide
Authors: Lukatskaya Maria R. , Ren Chang E. , Mashtalir Olha , Dall'Agnese Yohan , Barsoum Michel W. , Gogotsi Yury , Simon Patrice
Published: February 2020

We recently produced a new 2-D material, viz. Ti3C2, by selectively etching aluminium from a MAX phase Ti3AlC2 and labelled it MXene. MXenes represents a large family of transition metal carbides and carbonitrides, not just a single phase. MXenes allow a variety of chemical compositions and are establishing themselves as a new class of two-dimensional materials. MXenes possess good in-plane conductivity, which in combination with their rich surface chemistry makes them attractive for electrical energy storage applications. However their use in electrochemical capacitors was only recently demonstrated (Lukatskaya et.al, Science, 2013).

Here, we report on the intercalation of Li+, Na+, Mg2+, K+, NH4
+, and Al3+ ions between the 2D Ti3C2Tx layers. In most cases, the cations intercalated spontaneously. The intercalation of some ions, notably Al3+, can be promoted electrochemically. We also report on intercalation-induced high capacitance of >300 Farads per cubic centimeter (much higher than that of porous carbons) of flexible Ti3C2Tx paper electrodes in aqueous electrolytes. Material showed no degradation of the capacitive properties after more than 10,000 cycles. Several different electrochemical techniques were employed to understand the mechanism of charge storage, such as cyclic voltammetry, electrochemical impedance spectroscopy and EQCM.

Lukatskaya, M.R., et al., Cation Intercalation and High Volumetric Capacitance of Two-Dimensional Titanium Carbide. Science, 2013. 341(6153): p. 1502-1505.
Effects of Stack Stress on Lithium-Ion Cell Degradation
Authors: Cannarella John , Arnold Craig B.
Published: February 2020

Lithium-ion battery cells typically operate under compressive mechanical stress over the entirety of their service lives. This compressive stress is initially applied as a manufacturing stack pressure to maintain intimate contact between the cell components. Here we present results from long term cycling studies of lithium-ion cells in which stack stress is monitored during cycling. These results show that stack stress in lithium-ion cells is a dynamic quantity that fluctuates during charge/discharge due to charging strains and irreversibly increases with cycling due to permanent electrode expansion. Furthermore, we show that higher levels of compressive mechanical stress lead to accelerated rates of capacity fade through lithium consumption by side reactions. We explain the observed coupling between compressive stress and chemical degradation through local transport inhomogeneity that arises from localized separator deformation caused by compressive stress. A post mortem analysis of separators harvested from the aged cells confirms the occurrence of localized pore closure. Experiments of cells constructed with pre-deformed separators show accelerated rates of capacity fade compared to cells constructed with pristine separators, supporting the hypothesis of separator deformation leading to accelerated capacity fade.
The Effect of Etching Temperature upon the Optical Reflactance on Silicon Nanowires Grown By Electroless Etching
Authors: Velez Victor H. , Mertens Robert George , Sundaram Kalpathy B
Published: February 2020

THE EFFECT OF ETCHING TEMPERATURE UPON THE OPTICAL REFLACTANCE ON SILICON NANOWIRES GROWN BY ELECTROLESS ETCHING

The antireflective nature of Silicon nanowires (SiNW’s) revealed by their black color and dull appearances have drawn the attention of researchers [1]. It may eliminate the need for antireflective coating on these nanostructures to reduce energy losses in solar cells [2]. SiNWs arrays prepared by electroless etching method can significantly suppress light reflection across the visible spectrum. Optical reflectance analysis on SiNWs fabricated at different temperatures (Fig. 1) show a significantly decrease in optical reflectivity down to 1.5% at 25°C.

Enhanced optical reflectance may be achieved at lower etching solution temperatures. Low temperatures slow the kinetics reaction that would grew uniform and well aligned SINWs (Fig. 2a) contrary to randomly direction nanowires grow at high temperatures (Fig. 2b). A uniform growing of SiNWs could optimize nanowire spacing that would improve charge collection and enhance optical reflectance [3].

In this experiment a Cary 100 UV-Visible Spectrometer was used for reflectance analysis and silicon (Si) wafers were dipped for 15 minutes at different temperatures (25°C, 35°C, 45°C, 55°C and 70°C) in an electroless solution prepared in a petri dish containing silver nitrate (AgNO3) and hydrofluoric acid (HF) [4].
A Novel Intercalation Cathode Material with 1.7 Li per Transition Metal
Authors: Chen Ruiyong , Ren Shuhua , Cambaz Musa Ali , Hahn Horst , Fichtner Maximilian
Published: February 2020

Vanadium-based materials have received considerable attention for lithium ion batteries due to the facts that vanadium is the fifth most abundant transition metal in the earth’s crust, its relatively low atomic mass, its multiple oxidation states. The redox operating voltage (typically < 4.5 V) of vanadium-based materials is typically within the stability limit of conventional electrolyte, and vanadium oxides have rich crystal structures [1]. The ability of layered V2O5 for Li+ insertion has been well characterized. Intercalation of one Li+ per formula unit corresponds to a specific capacity of 147 mAh g-1. Further Li+ ions (x > 1 in Li
x
V2O5) insertion may cause irreversible structural transformations [2].

In this work, a new high-capacity (> 400 mAh g-1) and high energy density (> 1000 Wh kg-1) cathode material comprising of lithium metal oxyfluoride with a representative composition of Li2VO2F has been synthesized through a mechanical ball-milling method. In comparison with the prior art, several remarkable features of this new compound Li2VO2F are (i) two-electron reaction based on V3+/V5+ is accessible per transition metal, (ii) the initial composition is at lithiated state, (iii) it has a high theoretical specific capacity of 462 mAh g-1. Furthermore, in comparison with the start-of-the-art commercial cathode materials, this new material offers the opportunity to reach higher capacity and energy density.

References:

[1] N. A. Chernova, M. Roppolo, A. C. Dillon, M. S. Whittingham, J. Mater. Chem. 2009, 19, 2526

[2] C. Delmas, H. Cognac-Auradou, J. M. Cocciantelli, M. Ménétrier, J. P. Doumerc, Solid State Ion. 1994, 69, 257.
On the Oxidation State of Manganese in Li-Ion Cells: A New Perspective
Authors: Halalay Ion C. , Ziegelbauer Joseph M. , Li Zicheng
Published: February 2020

It has been long recognized that dissolution of transition metals, particularly Mn, at the positive electrode is the starting point for a major performance degradation mechanism in Li-ion batteries (LIBs).1-4 We present recent X-ray absorption spectroscopy data on components from LixMn2O4 spinel – graphite (LMO-GR) cells with 1M LiPF6in an ethylene carbonate : diethyl carbonate (1:2 v/v) electrolyte, after 20 days of cycling at 50 °C with 100% depth of discharge and C/5 rate.

Results from the Mn K edge (6539 eV) XANES analysis indicate average oxidation states near +3 for Mn cations in the graphite electrodes and separators from cells that were subjected to a 48 hour stand (in either discharged or charged state) subsequent to the high-temperature galvanostatic cycling, see Fig. 1. This suggests that Mn metal or in oxidation state +2 can only be minor fractions of the Mn existing outside the positive electrode of a Li-ion battery. Our results run counter to the prevailing view that Mn2+ cations arising from a disproportionation reaction of two Mn3+cations at the positive electrode, followed by dissolution into and migration through the electrolyte, and ending with deposition at the negative electrode, are widely responsible for the performance degradation observed in graphite-LMO LIBs. We will discuss the possible sources of discrepancy between our results and previously published data, as well as the implications of our results for measures to mitigate the Mn dissolution related LIB performance degradation mechanism, see Fig. 2.

References

1. D. H. Jang, & S. M. Oh, J. Electrochem. Soc.
144, 3342 (1997).

2. Y. Xia, Y. Zhou, & M. Yoshio, J. Electrochem. Soc.144, 2593 (1997).

3. G. Amatucci, C. N. Schmuts, A. Blyr, C. Sigala, A. S. Gozdz, D. Larcher, & J.-M. Tarascon, J. Power Sources
69, 11 (1997).

4. N. Kumagai, S. Komaba, Y. Kataoka, & M. Koyanagi, Chem. Lett.1154 (2000).

Acknowledgements

Use of the National Synchrotron Light Source, Brookhaven National Laboratory, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886. Use of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357.