bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Probe Electrode to Investigate Condition of Concrete By EIS
Authors: Okamoto Tatsuki , Tokieda Hiroyuki , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki
Published: February 2020

An electrochemical technique to obtain real-time information related to the condition of reinforced concrete is essential for assessing durability and safety. Dawson et al. [1] investigated the condition of reinforcing steel in concrete by an electrochemical impedance spectroscopy (EIS). They [1] emphasized that the EIS can be employed for the evaluation of the corrosion rate of rebar in concrete. Nòvoa [2] reported an application of EIS to investigate the microstructure of cementitious cover, transport of chlorides in concrete, and the steel-concrete interface.

In the present study, we developed a new method to determine the degradation of concrete using the cylindrical steel probes by EIS. Figure 1 shows the cylindrical steel probes developed in the present study. These probes have 10 mm diameter and 8 mm thick. These probes are embedded in concreate and the electrochemical impedance is monitored. We expect that the degradation of concreate can be determined by monitoring of the electrochemical impedance of the cylindrical steel probes. In order to establish the proposed monitoring method, the electrochemical impedance of the cylindrical steel probes embedded in concreate was measured. The size of concrete specimen was 100 mm × 100 mm × 200 mm. The two holes were drilled on the concrete surface of 100 mm × 200 mm. The diameter of each hole was 10 mm. The distance between both probes was 50 mm. The probes were embedded in these holes and fixed by the epoxy resin. The depth of the probes embedded in concrete specimen was 2.0 mm, 5.0 mm and 10 mm. The concrete specimen was immersed in 10 % sodium chloride aqueous solution. Figure 2 shows a schematic diagram of the measurement system. The air was continuously provided by pump during the immersion of the concrete. The electrochemical impedance was automatically monitored at 10 kHz and 10 mHz using a corrosion monitor (Corp. i-pec, CEM-100A) by two electrode system. The potential amplitude was 10 mV.

The charge transfer resistance R
ct was estimated from the impedance of the cylindrical steel probes measured at 10 kHz and 10 mHz. The degradation of concreate was discussed based on the changes of values of R
ct with time.

Reference

[1]　J. L. Dawson, L. M. Callow, K. Hladky and J. A. Richardson, Corrosion/78, No-125 (1978).

[2]　X. R. Nòvoa, J Solid State Electrochem, 20, (2016) 2113-2125.

Figure 1
Mass Transfer Mechanisms in Solid Electro Deposition
Authors: Narui Yuka , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki , Yanagimoto Hiroshi , Hiraoka Motoki , Iisaka Hirofumi
Published: February 2020

Copper plating is generally used for the fabrication of printed circuit boards of electronic devices. The patterning is carried out by masking with insulator for the partial plating on the substrate. It is desirable to develop a new alternative technology that takes environmental issues into consideration because the partial plating with a mask involves very complicated processes and wastewater treatment. Solid Electro Deposition (SED) method with the solid electrolyte membrane was reported by Yanagimoto et al.1) as the way to resolve the problem. The SED can be performed by a simple electrochemical cell in which the solid electrolyte membrane is sandwiched by counter and working electrodes. Imposition of voltage between two electrodes enables electrodeposition on the working electrode. The advantages of SED are written as follows.

・The electrochemical cell is very simple because the electrolyte is solid.

・The post-processing is also simple．

・It can be high-rate plating because the driving force of mass transfer of reactant is migration.

Among these advantages, the principle for high-rate plating by SED is explained below. Figure 1 shows the conceptual diagrams of mass transfer of cupric ions on electrode surface in two electrolytes. The charge transfer rate increases depending on the overvoltage in the case of plating in liquid electrolyte. However, the concentration polarization occurs on the electrode surface when the charge transfer rate is higher than the mass transfer rate of reactant. In this case, the driving force of mass transfer in electrolyte is normally diffusion. On the other hand, the mass transfer of reactant is dominated by migration in the SED if the transport ratio of metal ions in the solid electrolyte is unity. In this condition, the charge transfer rate becomes equal to the migration rate and the concentration polarization of reactant in the vicinity of the electrode does not occur, even if the charge transfer rate is increased. Therefore, it is possible to realize high-rate plating because diffusion is not rate-limiting process. We report the relationship between mass transfer mechanisms in solid electrolyte membrane and potential-current curves and establish the theory of high-rate copper plating by the SED. Reference:

1) K. Akamatsu, Y. Fukumoto, T. Taniyama, T. Tsuruoka, H. Yanagimoto, H. Nawafune, Langumuir, 27, 11761-11766 (2011).

Figure 1
(Invited) Flexible and Stretchable Thermoelectric Generators
Authors: Hussain Muhammad M. , Rojas Jhonathan P. , Singh Devendra N. , Torres Sevilla Galo A. , Fahad Hossain M. , Inayat Salman B.
Published: February 2020

Thermoelectricity can be an interesting source of power from otherwise wasted heat. Therefore, for many decades discovery and optimization of new thermoelectric materials has shown important leap toward thermoelectric generator applications. However, from an engineering perspective, structural modifications at the device level can play an important role to maximize the power output. We base our study on device architecture reconfiguration by adopting various in-plane and out-of-plane fractal design to develop flexible and stretchable thermoelectric generator. Physical flexibility allows the devices to be conforming to asymmetric surfaces and mechanical stretching allows to dynamically controlling the distance between the hot and cold end in a thermoelectric generator. This way, one can tune the distance, maximize the temperature difference and maintain a high temperature difference which directly relates to efficiency of a thermoelectric generator. Adopting low cost materials like paper and Off-Stoichiometry Thiol-Enes (OSTE) as structural materials we demonstrate the integration strategy to rationally design materials, processes and devices for flexible and stretchable thermoelectric generators.
Thermoelectric Properties & Characterizations of Surmof Thin Films
Authors: Chen Xin , Hassan Zeinab Mohamed , Redel Engelbert , Baumgart Helmut
Published: February 2020

A new class of thermoelectric materials termed surface-anchored (metal-organic frameworks and coordination network compounds) SURMOFs thin films materials will be introduced. SURMOFs thin films demonstrates promising application potential of organic porous thin films in future thermoelectric and electronic devices working highly efficient in the RT (Room Temperature) region. In our first studies we have characterized the Seebeck coefficient of polycrystalline and highly-ordered SURMOF thin films.1,2

Since SURMOFs are highly porous and the size of their pores are highly adjustable, they can be further functionalized and tailored due to their electrical and thermal conductivity properties. SURMOFs can be therefore regarded as tailorable organic Thermoelectric Material of the future. An outlook will be given on their further electronic characterization, Hall measurements and thermal conductivity as well as on first ZT Chip measurements.

References:

1) X. Chen, Z. Wang, P. Lin, K. Zhang, H. Baumgart, E. Redel, C. Wӧll, ECS Trans.,75, 119-126 (2016)

2) X. Chen, Z. Wang, Z. M. Hassan, P. Lin, K. Zhang, H. Baumgart, E. Redel, ECS Journal of Solid State Science and Technology, 6, P150-P153 (2017).

Figure 1
Lithium-Ion Battery Precursor Chemistry: Understanding the Role of Solution Conditions on Composition and Structure of Transition Metal Oxalates
Authors: Dong Hongxu , Koenig Gary , Wang Anny , Barron Alexandra
Published: February 2020

Coprecipitation is a popular approach to synthesize precursors for transition metal oxide cathode materials used in lithium-ion batteries. Many papers in the literature have reported tuning the particle morphology using careful control of reaction conditions, and the morphology of the precursor particles can also be retained after calcination to obtain final active materials of tunable size and shape. Oxalate coprecipitation provides a route to substitute the more common hydroxide and carbonate coprecipitation; and oxalate provides an advantage where most transition metal ions form stable oxalate precipitates in aqueous solutions exposed to air. Different oxalate polymorphs may occur; however, depending on the detailed reaction conditions. In this talk, we will present studies of pure and blend oxalate coprecipitations using manganese and nickel, and will discuss the impact of feed conditions on the precipitate composition and structure. We will also demonstrate a method to determine the rate of loss of individual transition metals from solution to the solid phase.
Ion and Solvent Effects on Aquivion Perflourosulfonic Acid Ionomer Infrared Spectra with Respect to State-of-Solvation
Authors: O'Hagan Ryan , Loupe Neili , Doan Jonathan , Smotkin Eugene S.
Published: February 2020

The impact of solvent polarity and ion exchange on Aquivion perfluorosulfonic acid ionomer (PFSI) infrared spectra were probed as a function of sorbed solvent content. Aquivion membranes were exchanged with lithium or sodium ions, dehydrated, and then solvated in methanol or ethanol. These samples were installed in a controlled temperature/pressure IR sample compartment that enabled acquisition of time dependent spectra as the membranes were desolvated. In all cases, the local symmetry of the ionomer exchange site retained a 3-fold axis of symmetry during desolvation. The spectra were interpreted in terms of local symmetry based IR band assignments. The bandwidths of peaks directly associated with the exchange site functional group progressively increase (solvated PFSI-H < solvated PFSI-Li < solvated PFSI-Na). FWHM trends are explained in terms of electric field induced exchange site polarization. The smaller Stokes Einstein radius of solvated Na+ enables closer proximity to the exchange site and thus greater induced band broadening as compared to Li+ and H+.
Iron Phosphate Polyanion Compounds As Anodes for Aqueous Lithium Ion Batteries
Authors: Paharik Ethan , Koenig Gary
Published: February 2020

The widespread adoption of wind and solar energy generation is limited by the lack of cheap, efficient, stable, and safe energy storage systems. Aqueous lithium-ion batteries, combining the high efficiency and cycling stability of intercalation materials with the low cost and flammability of aqueous electrolytes, are potentially an excellent solution to the stationary energy storage problem. In this work, four iron based phosphate polyanion compounds were evaluated as anode materials for an aqueous lithium-ion battery. Constant current cycling of these materials in deoxygenated aqueous electrolyte closely matched organic half-cell cycling data and previous literature results, indicating the stability of the aqueous electrolyte and the materials under these conditions. When dissolved oxygen was present in the aqueous electrolyte, all four iron phosphate materials had low coulombic efficiency which was attributed to a parasitic oxygen reduction in the electrolyte. Of the novel iron phosphate/LMO full cell pairings, deoxygenated aqueous Li3Fe2(PO4)3/LiMn2O4 cells achieved good capacity retention over 100 cycles while maintaining excellent round trip energy efficiency.
(Invited) Increasing the Bandwidth of Semiconductor Photodetectors through Hot Carrier Generation in Nanometer-Scale Optical Coatings
Authors: Krayer Lisa J , Munday Jeremy N
Published: February 2020

Nanometer scale optical coatings have recently been developed with tunable, high absorption through excitation of zeroth order Fabry-Perot (FP) modes. Such optical coatings have primarily increased above bandgap absorption in ultrathin semiconductor films with applications in thin film photodetection, photovoltaics and photocatalysis. We propose the use of zeroth order FP modes for expanding the bandwidth of semiconductor devices through sub-bandgap absorption in nanoscale metal contacts to semiconductors such as silicon. The absorption in the metal generates hot carriers that are injected into the semiconductor, enabling photocurrent generation from light with energy below the semiconductor bandgap energy. However, for efficient photocurrent injection, the metal must be highly absorptive at long wavelengths and ultra-thin in order for the hot carriers to reach the Schottky interface with enough energy to traverse the barrier. We show that by selecting materials with optical properties that satisfy a zeroth order FP mode (n ~ k for m = n + ik), it is possible to obtain ~80% absorption in materials as thin as 10-15 nm.
(Invited) Welding of Nickel Nanowires By Ions Beam Irradiation: From Small to Large Scale
Authors: Honey Shehla , Ahmad Ishaq , Naseem Shahzad , Malik Maaza , John Kennedy
Published: February 2020

In order to replace conventional transparent conducting electrodes, metal nanowires (MNWs) networks have long been act as promising contenders due to their high mechanical flexibility. However, nanowire-nanowire contact resistance is main technical obstruction in terms of improvement in their performance. To reduce nanowire-nanowire contact resistance, welding of nanowires (NWs) is essential.

In this work, MeV proton and argon ions beam irradiation induced nanoscale welding technique to fabricate X-, Y-, II- and T-shaped molecular junctions between nickel nanowires (Ni-NWs) is presented. Ni-NWs are irradiated by 2.75 MeV proton ions and 3.5 MeV argon ions at doses 1x1016ions/cm2 and 5x1015 respectively while temperature is kept constant. Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and x-ray diffraction (XRD) results reveal that Ni-NWs are welded without losing stability in crystal structures of NWs. Afterward, a two-dimensional large scale random network of Ni-NWs is fabricated by 3 MeV proton ions beam irradiation induced nanoscale welding of Ni-NWs at crossing positions. Proton ion beam induced large scale network fabrication is confirmed by TEM and SEM techniques. Moreover, these networks are characterized optically using UV-VIS spectroscopy. It is observed that at a beam fluence of 5x1015 ions/cm2, perfect molecular junctions between Ni-NWs in X-, II-, and V-shapes are achieved and a large scale welded network of Ni-NWs is obtained without distorting the morphology of NWs. Moreover, structure of Ni-NWs remains stable under 3MeV proton ions beam irradiation and networks are found to be optically transparent. The results exhibit that fabrication of Ni-NWs network precede through three steps:

i- High energy ions beam irradiation induced heat spikes lead to locally heat and fuse Ni-NWs,

ii- Formation of molecular junctions on small scale,

iii- Formation of large scale network

Ions beam irradiation induced welding of Ni-NWs can improve performance of NWs networks by reducing contact resistance between NWs for application as transparent conducting electrodes. These high quality welded MNWs networks may potentially be applied as transparent conducting electrodes in optoelectronic devices.
Nickel Metal Alloy’s As PGM-Free Catalysts for Hydrogen Oxidation Reaction in Anion Exchange Membrane Fuel Cells
Authors: Roy Aaron Joseph , Atanassov Plamen , Artyushkova Kateryna , Serov Alexey , Zulevi Barr , Rezaei Talarposhti Morteza
Published: February 2020

Anion exchange membrane fuel cells (AEMFCs) offer considerable advantages over proton exchange membrane fuel cells (PEMFCs) in that the kinetics for oxygen reduction reaction (ORR) are greatly improved in alkaline media [1]. The improved kinetics of ORR in alkaline media thus allows for the use of PGM-Free catalysts in AEMFCs. Though there have been many efforts to develop PGM-Free cathode catalysts for AEMFCs, PGM-Free anode catalysts, with catalytic activity for HOR comparable to Pt, are still in the early stages of development [2]. The slow development of these AEMFC anode catalysts is largely due to the lack of compatible ionomers for anion exchange. However, recent development of anion exchange ionomers show great improvements over PEMFC ionomers, such as NAFION, in AEMFCs [3].

Carbon supported nickel has been shown to have high activity for HOR in AEMFCs, however the susceptibility of Ni to electrochemical oxidation, as well as the less than optimal hydrogen binding energy to the Ni active site, suggest there is further room for optimization of the Ni/C system [1]. Here, we have proposed to address these issues through alloying Ni with transition metals to tune the electronic environment of Ni, as well as to improve the corrosion resistance of Ni in alkaline media.

 

For this project, catalysts are prepared by an incipient wetness method using the metal nitrates as catalyst precursors and KetjenblackÒ, DENKA BLACKÒ, graphene oxide (GO) and reduced graphene oxide (rGO) as support materials. GO and rGO have been prepared from Hummers’ method. In some cases, a sacrificial support method is also used to control the primary particle size of the NiM materials.

Figure 1 shows the open circuit and close circuit polarization curves for NiMo/C with peak power density observed for HOR of ~ 120 mW/cm2, which is an encouraging result though not competitive with Pt or Pd. Therefore, our aim is to explore the role of the alloying metal (M = Mo, W, Cr, Co, Cu) as well as to investigate the role of the carbon support (ex: GO, rGO, N-doped rGO) on the kinetics of HOR in alkaline media on these NiM/C catalysts.

References:

[1] Zhuang, Z.; Giles, S. A.; Zheng, J.; Jenness, G. R.; Caratzoulas, S.; Vlachos, D. G.; Yan, Y. Nature Communications 2016, 7, 10141.

[2] Serov, A.; Kwak, C. Applied Catalysis B: Environmental 2009, 90 (3-4), 313–320.

[3] Kreuer, K.-D. Fuel cells: selected entries from the Encyclopedia of Sustainability Science and Technology; Springer: New York, 2013.

Figure 1
Structural and Chemical Evolution of Li-Rich Li2IrO3 during Electrochemical Cycling
Authors: Li Liang , Castro Fernando , Park Joong Sun , Lee Eungje , Freeland John W , Yao Zhenpeng , Fister Timothy T , Vinson John , Shirley Eric , Wolverton Christopher , Dravid Vinayak , Thackeray Michael M. , Chan Maria K. Y.
Published: February 2020

In the pursuit of novel cathode materials with high Li capacities, the Li-rich oxides with Li/TM (transition metal) ratio larger than 1 have recently gained increased interest. For instance, the active role of oxygen ions in the charge compensation has been reported in layered rocksalt Li2IrO3,1 which serve as a model system to understand the structural response of Li-rich cathodes to Li extraction, as well the role of oxygen in compensating Li+ loss.

In this study, we employed various experimental techniques as well as first-principles density functional theory (DFT) to investigate the structural and electronic evolution of Li2IrO3 upon electrochemical cycling. It is found that Li2IrO3 undergoes phase transition and slight capacity fading at each cycle. All the thermodynamically stable phases of Li2-xIrO3 (0≤x<2) are identified through a complete structural screening based on electrostatic energy and DFT calculations. Electron Energy Loss Spectroscopy (EELS) and X-ray Absorption Near Edge Spectroscopy (XANES) are adopted to probe the changes in the oxygen electronic structure at various (de)lithiation stages, and corresponding O K-edge spectra are simulated based on first-principles calculations. The cationic/anionic charge compensation mechanism of Li2IrO3 upon delithiation is discussed based on the spectroscopic observations.

1. E. McCalla et al., Science, 350, 1516–1521 (2015)
Molybdenum Substituted Vanadyl Phosphate ε-VOPO4 for Lithium-Ion Batteries
Authors: Siu Carrie , Lee Krystal , Omenya Fredrick , Chernova Natasha , Whittingham M. Stanley , Lin Yuh-Chieh , Ong Shyue Ping
Published: February 2020

Maintaining the structural reversibility of multiple electron transfer cathodes is a challenge one has to address in order to increase the energy density of current lithium-ion batteries. ε-VOPO4 is a promising cathode material with two redox transitions of V3+/V4+ and V4+/V5+ at about 2.5 and 4 V, respectively. However, the reversibility and cycling stability is compromised with more than one lithium cycling. The goal of this work is to investigate if the substitution of molybdenum can enhance the electrochemical performance of ε-VOPO4. We have focused on molybdenum because it is predicted by the first-principle calculations to display multiple redox potentials in useful voltage window and to form relatively stable substituted ε-VOPO4 phases. We have refined the synthesis method, where by changing a solvent we can control morphology and obtain either loose uniform 100 nm particles, or make those particles form secondary micron-sized spheres. Combing the analysis of X-ray diffraction, and inductively coupled plasma mass spectrometry, we have determined the limits of molybdenum substitution in the structure. The effects of the substitution and morphology on the electrochemical performance will be discussed. This research is supported as part of the NorthEast Center for Chemical Energy Storage (NECCES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0012583. CS gratefully acknowledges the financial support from Graduate Assistance in Areas of National Need (GAANN) Fellowship and Binghamton University Provost's Doctoral Summer Fellowship.
Mechanisms of Degradation and Necessity of ALD Coatings for High Voltage NMC532, NMC622, and NMC811 Li-Ion Cells
Authors: Dahlberg Kevin , Trevey James E , King David M , David Lamuel , Ruther Rose Emily , Wood David L , Stevenson Lisa , Townsend Dennis
Published: February 2020

Lithium-ion battery-based energy storage is widely regarded as the best technology to realize affordable electrification of automobiles (hybrids and EVs), buses, and ships. However strategies to realize higher energy density and lower cost come at the expense of cell lifetime and safety. For example, 10-20% higher energy density can be achieved by charging cells with layered cathodes (e.g., NMC and NCA) to voltages higher than 4.2V, however this is well known to accelerate capacity fade, resistance growth, SEI growth, and gas evolution. Although studies increasingly show the sites of degradation are active material particle surfaces and the active material-electrolyte interface, the specific mechanisms of these phenomena remain unclear and difficult to quantify. Without clear understanding of the specific degradation mechanisms that dominate cell failure during higher voltage cycling, solutions to enable high voltage operation will have limited success. We have isolated key mechanisms occurring at higher voltages in NMC532, NMC622, and NMC811 cells including positive electrode resistance growth (Rct) as measured by Electrochemical Impedance Spectroscopy (EIS), and Mn dissolution as measured by Inductively Coupled Plasma (ICP) of cycled negative electrodes, and shown the correspondence to cycle life of 95mm x 64mm pouch cells using graphite anodes. Foremost, we have found that Al2O3 ALD coatings dramatically diminish these degradation mechanisms and enable significantly better cycling performance in pouch cells when charged to higher voltage.
Role of Solution Chemistry in Composition of Lithium-Ion Battery Precursors
Authors: Koenig Gary , Dong Hongxu , Barron Alexandra , Wang Anny
Published: February 2020

Coprecipitation is a popular method to synthesize precursors for lithium-ion battery active materials because it is easy to implement in the lab, fast, scalable, and adaptable to a variety of transition metal compositions. In addition, coprecipitation provides routes to control and modify precursor and resulting final active material particle morphology, resulting in battery materials with tunable size, shape, and polydispersity. In many cases, especially under conditions where morphology control or tunability is desirable, the coprecipitation is run under conditions of either low transition metal concentration in solution and/or conditions where significant fractions of the transition metals stay soluble in the solution. Within these solution environments the composition of the resulting battery precursor particles can deviate from the solution feed conditions, a consequence not often designed for or reported in the battery material synthesis literature but which can significantly influence the resulting composition and thus electrochemical properties of the final active material. In this talk, efforts will be described in our lab to understand the solution environment during coprecipitation of battery particles with the final goal of explicit control over the composition of the resulting precursor particles both with regards to composition and structure. Insights from probing the rate at which transition metals are deposited onto the precipitate particles will also be presented.
Ag@TiO2-TiO2 NF As a Visible Light Photoanode in Photocatalytic Fuel Cells
Authors: Lui Gregory , Jiang Gaopeng , Fowler Michael , Yu Aiping , Chen Zhongwei
Published: February 2020

An Ag@TiO2-TiO2 flower composite is used as a photoanode in a photoelectrochemical cell. The photoanode shows exceptional performance in the simultaneous photodegradation of organic compounds and photogeneration of electrical power. The TiO2 flower composite provides a hierarchical morphology that greatly improves the electronic properties of the anode. The addition of small quantities of Ag@TiO2 immediately improves the short-circuit current of a methanol photocatalytic fuel cell, and the optimal addition of Ag@TiO2 enhances the maximum power output of the cell under solar simulated light. Compared to commercial TiO2 material, the Ag@TiO2-TiO2 flower composite improves the short-circuit current of the photocatalytic fuel cell by 97% (1.7 mA cm-2) and the maximum power by 131% (0.6 mW cm-2) under solar simulated light.
Novel Nanomaterials and Systems for Solar Fuel and Chemical Production
Authors: Mubeen Syed
Published: February 2020

Becoming more energy sustainable is a major current societal goal, which, of necessity, involves greater use of sunlight as a primary source of energy. However, if solar energy is ever to displace fossil fuels as our main energy source, it could only do so if we solve the energy storage problem. The first portion of the talk will introduce our research efforts to develop novel fault tolerant semiconductor nanostructured architectures for solar fuel production. Focus, would be on single nanowire photoelectrochemistry to understand carrier transport pathways across multiple interfaces. The second part of the talk will focus on exploring hot electrons from plasmonically active metals to drive important fuel and chemical producing reactions such as water splitting and CO2 reduction reaction.
Visible-Light Active Thin-Film WO3 Photocatalyst Crystallized By Post-Annealing in Air
Authors: Oka Nobuto , Takashima Junya , Murata Akiyo , Jia Junjun , Shigesato Yuzo
Published: February 2020

Photocatalysts with visible light activity have been widely studied in recent years. We have reported on WO3 films as the high-performance visible-light active photocatalyst [1,2]. These films were deposited by dc magnetron sputtering on heated fused silica substrates at 800 oC. It must be preferable for the industrial application that the substrate temperature during the deposition should be lower for the window coatings for automobiles and architectures. In this study, the effect of post-annealing in air and total gas pressure during the deposition were studied. In addition, the loading effects of Pt nanoparticles on the WO3 film surface were also studied for the improvement of the photocatalytic activity.

The WO3 thin films were deposited on unheated fused silica glass substrates by dc magnetron reactive sputtering using a W metal target, and with Ar and O2 as the sputtering and reactive gases, respectively. Post-annealing temperature was varied from 300 to 800 oC for the films sputter deposited at total gas pressure of 5.0 Pa. Furthermore, total gas pressure during the deposition was varied from 1.0 to 9.0 Pa. After the post-annealing at 400 or 600 oC, Pt nanoparticles were deposited on the WO3 film surface also by sputtering for 0, 7 or 40 sec. The surface coverage of Pt on the WO3 films were estimated by X-ray photoelectron spectroscopy. The Photocatalytic decomposition of acetaldehyde (CH3CHO) on the Pt/WO3 films was evaluated by the decrease in the concentration in the quartz cell. The visible light source was a Xe lamp with a 410-500 nm band pass filter (1.0 mW/cm2 at the film surface).

Figure shows the photocatalytic decomposition for the WO3 films loaded by the Pt nanoparticles under visible light irradiation. It was found that the potocatalytic activities of the films crystallized by post-annealing（400 oC）was superior to the films deposited on the heating substrate at 800 oC, which was enhanced by the Pt loadings.

[1] M. Kikuchi, Y. Shigesato, et al., Abstract of the 21st IUPAC SYMPOSIUM (2006) 496.

[2] M. Imai, N. Oka, Y. Shigesato, et al., J. Vac. Sci. Technol. A 30, 031503-1-031503-5 (2012).

[3] N. Oka, Y. Shigesato, et al., APL Materials 3, 104407-1-104407-6 (2015).

[4] N. Oka, Y. Shigesato, et al., Jpn. J. Appl. Phys. 51, 055501-1-055501-5 (2012).

Figure 1
Effects of Ionic Liquids on Biofilm Formation in a Loop-Type Laboratory Biofilm Reactor
Authors: Kanematsu Hideyuki , Saito Tatsuki , Hirai Nobumitsu , Kogo Takeshi , Ogawa Akiko , Tsunashima Katsuhiko
Published: February 2020

Biofouling and biofilm formation on inside walls of pipes where various liquids flow have caused varoius netagive industrial problems so far, since it would lead to corrosion, slimes and scales to deteriorate the functions such as heat exhcnage capability and materials qualities/characteristics themselves. As the countermeasure, various biocides and chemical cleaners have been used to control liquid qualities and to prevent those negative industrial problems. Various acids, alkaline agents, surfactants etc. have been used conventionally so far. At this point, hypoochlorous acid and some organic agents seem to be excellent chemical cleaners. However, the former might induce corrosoin on the substrate walls. On the other hand, the latter might evaoprate during the use, evne though any of them might show higher performances. In this experiment, we focused on some ionic liquids. They might be able to overdome those defencts mentioned above. When we come to think about the applicability of ionic liquids to practical industrial purposes, the price and the environmental friendliness may be serious problems in the futuure. In those cases, it will be key points how we could minimize the amount of use for the purpose. Therefore, we tried in this experiment to confirm how very small amounts of some ionic liquids could control biofilm formation. To produce biofilms articially with good reproducibility, we used a loop-type laboratory biofilm reactor which we designed and produced in our laboratory. Two kinds of ionic liquids were used for the experiments. 1-Butyl-3-methylimidazolium Tetrafluoroborate(BMImBF4) and Tributhylocthylphosphonium chloride(P4448Cl). Small amount of them were added into LBR filled with tap water. The liquids including ionic liquids were circulated by a pump and biofilms formed on specimens placed with a stick-type jig, being parallel to the flow direction. After a couple of days passed, the specimens were talken out from the system and the material surfaces were observed. Some types of liquids without ionic liquids were used as control and all of these specimens after exposures in the LBR were analyzed by optical micrscopes, staining by crystal violets and Raman spectroscopy and discussed. The effect of ionic liquds were obviously recognized during the initial stage of biofilm formations. However, ionic liquids also had the difficulty to disolve the solidified biofilms contained lots of calcium carbonate produced at the second half of biofilm formation process.
Elucidating the Correlation between Morphology and Ion Dynamics in Polymerized Ionic Liquids
Authors: Heres Maximilian Ferdinand , Cosby James Tyler , Strehmel Veronika , Benson Roberto , Sangoro Joshua R
Published: February 2020

The impact of chemical structure on ion dynamics and morphology in ammonium and imidazolium based polymerized ionic liquids (polyIL) are investigated using broadband dielectric spectroscopy and wide angle X-ray scattering (WAXS). Increasing the alkyl chain length results in longer backbone-to-backbone spacing of the adjacent polymer chains. In the ammonium-based systems this increase correlates with the Tg-independent ionic conductivity and activation energies associated with ion hopping below Tg. In contrast, imidazolium systems show weak dependence of ion dynamics on alkyl chain lengths. In addition, we find that the Tg-independent ionic conductivity of the acrylate-derived ammonium systems and the vinyl-derived imidazolium polymers does not depend upon the placement of the ion within the polymer structure, but rather the chemical structure of the cation, volume of the counterion and the morphology. The implications of these results on the design of novel polymerized ionic liquids for electrochemical energy applications will be discussed.
Theoretical Investigation of Vanadium Crossover Phenomena through Different Types of Membrane in Vanadium Redox Flow Battery
Authors: Jeong Daein , Jung Seunghun
Published: February 2020

Redox flow batteries (RFBs) as enery storage system are getting much public attention because their power and capacity can be configured independently with relatively low capital investment compared to other types of batteries. All vanadium redox flow battery (VRFB) has an additional advantage of low maintenance cost. In detail, becasue positve and negative electrode of a VRFB share the same active material (vanadium), contaminated electrolyte due to vanadium crossover through membrane can be recycled by rebalancing process. Electrolyte contamination in a VRFB is mainly caused by the amount of vanadium and water crossover through the membrane, which causes capacity decay and power loss accompanied by additional maintenance cost during VRFB operation.

The vanadium crossover is controlled by diffusion, migration, and convection across the membrane. It was reported that the following side reactions occur when vanadium ions move to the counter electrode side (1):

It is also known that the water transfer through the membrane is controlled by three mechanisms as follows (2):

1) Water molecules are transferred along with a vanadium ion that moves to the counter electrode

2) Water molecules are transferred along with a proton to satisfy electro-neutrality

3) Water molecules are transferred by osmosis phenomenon due to vanadium concentration difference between two electrolytes

The above vanadium and water transfer through membrane strongly denpends on the physico-chemical properties of the membrane. In this study, we aim to elucidate crossover phenomenon and its consequence in a VRFB by taking computational apporach with a physics-based multi-dimensional VRFB model that has capability of simulating complex species transfer mechanisms. Further, we analyze the cause and effect of each crossover mechanism according to the different types of membranes such as anion exchange membrane, cation exchange membrane, and micro-porous separator. We conclude our study by suggesting electrolyte rebalancing strategies for each type of membrane.

References

[1] K. W. Knehr, Ertan Agar, C. R. Dennison, A. R. Kalidindi, and E. C. Kumbur, J. Electrochemical Society 159(2012) A1446-A1459

[2] Chenxi Sun, Jian Chen, Huamin Zhang, Xi Han, Qingtao Luo, J. Power souces 195 (2010) 890-897

Figure 1
MXenes As Candidate Cathodes for Non-Aqueous Lithium-Oxygen Batteries
Authors: Lee Andrew , Krishnamurthy Dilip , Viswanathan Venkatasubramanian
Published: February 2020

Nonaqueous lithium-oxygen (Li-O2) batteries have emerged as possible high energy density alternatives to Li-ion batteries that could address the limited driving range issues faced by electric vehicles. This battery chemistry allows for high energy densities and an exceptionally high theoretical efficiency. Carbon, the current cathode catalyst, exhibits low stability against oxidation and reacts with the products formed during the discharging phase of the battery. In addition, due to other undesired side-reactions while charging the battery, all the reactants are not recovered leading to a poor rechargeability of a few cycles. A good cathode that can mitigate these issues requires careful screening and can help improve cycle life, increase capacity and help mitigate electrolyte decomposition. In this work, we focus on identifying possible cathodes from a family of intriguing two-dimensional (2D) materials known as MXenes, for lithium-oxygen batteries. MXenes have a general formula of Mn+1Xn, where M is an early transition metal and X is nitrogen or carbon, and being 2D layered materials, they have a large surface area [1]. MXenes are possible cathode candidates for lithium-air batteries owing to two considerations: (i) high electronic conductivity and (ii) high stability. We explore MXene carbides and nitrides of various transition metals as potential cathodes with low nucleation overpotentials.

We use density functional theory (DFT) calculations to investigate the stability and activity of various terminated and non-terminated nitride and carbide MXenes of transition metals. We begin by exploring the MXenes of titanium and scandium such as Ti4N3, Ti4C3, Sc4N3, Sc4C3and their variants with the F, O and OH terminated groups. We observe that the nitrides are more stable than the carbides, and this trend holds also for the terminated compounds. Between the scandium and titanium MXenes, the titanium carbides are more stable than their scandium carbide equivalents; however, this observed trend is reversed for the nitride MXenes, with the scandium nitrides being more stable than titanium nitrides.

The nucleation overpotential for Li-O2 batteries is determined by the adsorption free energy of the intermediate LiO2 [3]. We identify active MXene catalysts by computing the adsorption free energy through DFT calculations and we find that the non-terminated carbides and nitrides are stronger binding than the optimal binding strength. The transition metal and the termination group in the MXene are two tuning variables to weaken the binding in order achieve optimal binding strength. We will report on the activity and coverage effects of various transition metal carbide and nitride MXenes to identify promising cathodes for the Li-O2batteries.

 

 

 

 

 

 

References

[1] Naguib, M. et.al. Adv. Mater., 2014, 26, 992-1005.

[2] Urbankowski, P. et.al. Nanoscale, 2016, 8, 11385-11391

[3] Krishnamurthy, D. ACS Energy Lett. 2016, 1, 162-168

 

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Electrochemical Synthesis of Well-Ordered Macroporous Structures of Nickel – Ruthenium Alloys with Low Overpotential on Hydrogen Evolution Reaction
Authors: Kutyla Dawid , Kolczyk Karolina , Kowalik Remigiusz , Zabinski Piotr
Published: February 2020

This work presents the results concerning electrochemical deposition of Ni-Ru alloys from aqueous acidic solutions. The Ni-Ru coatings were obtained by the potentiostatic electrodeposition on copper porous substrates and polystyrene matrix. The influence of applied potential and concentration of electroactive species on the composition and the quality of obtained coatings was determined. The elemental composition was determined with the XRF method. X-Ray analysis has been use to determine phase composition of obtained alloys. The surface morphology was investigated with the use of scanning electron microscopy. Electrochemical measurement as a linear and cyclic voltammetry was used to perform comparative examination of catalytic properties of the obtained 3-D structures in aqueous NaOH solutions.

Acknowledgment

The authors would like to thank Polish National Science Centre for the financial support provided by the grants: No UMO-2016/21/N/ST8/00222.
Characterization of Perfluorinated Sulfonic Acid Proton Exchange Membranes with Heteropolyacid Functionalized Fluoroelastomer
Authors: Hoffman Jessica , Herring Andrew M , Motz Andrew R , Kuo Mei-Chen , Pandey Tara P
Published: February 2020

Perfluorinated sulfonic acid (PFSA) membranes have long been the standard for proton exchange membranes (PEMs), despite many efforts to improve upon their chemistry. The saturated conductivity of these PFSAs is impressive, but a need still exists for a membrane with similar proton conductivity at low relative humidities.1 The motivation of this study was to optimize the loading of heteropolyacid (HPA) covalently bonded to the fluoroelastomer in order to increase low humidity conductivity while maintaining chemical and mechanical stability. HPAs are known to be strong Brønsted acids as well as strong oxidants and have high thermal stability in the solid state.2 These qualities should serve to effect enhanced proton conductivity and chemical durability at high temperature ranges (80 - 120 ºC) and lower humidity ranges (less than saturated conditions). Specifically, a Keggin-type silica tungstic HPA was used for its comparative stability to hydrolysis in aqueous solutions.3

In order to classify membrane behavior as a function of weight percent polyHPA (reference figure 1), membranes were synthesized in 0 wt%, 25 wt%, 50 wt%, 75 wt%, and 100 wt% polyHPA and the balance PFSA. Electrochemical impedance spectroscopy (EIS) was used to characterize conductivity of the membranes at 80 ºC with a relative humidity sweep (50 - 90 %RH). Additionally, small-angle x-ray scattering (SAXS) was performed at 80 °C with a relative humidity sweep from 0 - 95 %RH, and FTIR was performed at 80 °C at 0 %RH and 100 %RH. These conditions were chosen specifically for the typical operating region for PEMFC applications. In this blend study, the addition of polyHPA was found to categorically decrease performance (conductivity) of standard 3M© 825EW PFSA membrane. Though improvement of the PFSA membrane was not achieved, this research will provide valuable information regarding the morphology of blended membranes, particularly in membranes exhibiting two-phase behavior; furthermore, results will provide some insight into choosing other viable additives for improved conductivity of PEMFCs.

Figure 1. Chemical structure of polyHPA, 60 wt% HPA (K8SiW11O39)

References

Ramani, V., H.R. Kunz, and J.M. Fenton. "Investigation Of Nafion®/HPA Composite Membranes For High Temperature/Low Relative Humidity PEMFC Operation". Doi.org. N.p., 2017. Web. 24 Apr. 2017.

Kozhevnikov, I.V., and K.I. Matveev. "Homogeneous Catalysts Based On Heteropoly Acids (Review)". Applied Catalysis 5.2 (1983): 135-150. Web.

Tsigdinos, G.A., and G.H. Moh. "Aspects Of Molybdenum And Related Chemistry". Materials Chemistry 4.1 (1979): 111-112. Web.

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The Influence of Various Fluencies of Copper Ions (Cu+) on Optical and Electrical Properties of Silver Nanowires (Ag-NWs) Thin Films for Photovoltaic Applications
Authors: Honey Shehla , Ahmad Ishaq , Khan Shakeel , Z. Naveed , Naseem Shahzad , Maaza Malik
Published: February 2020

The effect of copper ions (Cu+) of various fluencies on optical and electrical properties of silver nanowires (Ag-NWs) thin films is investigated. It is found that electrical conductivity and optical transmittance rises with increase in fluencies of copper ions. At 3x1015 ions/cm2, optical transmittance of Ag-NWs thin films increased upto 80 % in the visible (Vis) region and 55% in ultraviolet (UV) region in comparison with pristine Ag-NWs thin films. At the same beam fluence of Cu+ ions, electrical conductivity is raised thrice to that of pristine value. The increase in optical transmittance is attributed to Cu+ ion beam irradiation-induced localize heating effect cause melting and slicing of Ag-NWs, whereas Cu+ ion beam induced fusion of Ag-NWs at contact points is the main reason to enhance electrical conductivity. This study offers a technical base for designing of transparent conducting electrodes (TCEs) based on Ag-NWs thin films for multiple photovoltaic applications. Besides, this investigation is also helpful for application of photovoltaic devices based on MNWs thin films in radiations containing environment such as upper space.
Fabrication and Electrochemical Properties of Hydrogenated TiO2 Nanotube Arrays
Authors: Zhang Qi , Du Kang , Liu Guohua , Yang Changping , Wang Kaiying
Published: February 2020

Nowadays, the requirement for energy and environment are a great challenge for our research society. Energy application and storage become the main issues. As a new energy-storage device with high power density, long cycle life and good application prospect, supercapacitors have attracted growing interest in recent years. The electrode materials for supercapacitors play an important role in the field of electrochemical capacitors. [1-5]

In this paper, we report two easy and novel approaches to improve the conductivity of titanium dioxide nanotubes as electrochemical supercapacitor electrodes: first, increase the thickness of the TiO2 nanotube arrays (TNTAs), second, the synthesis of hydrogenated TiO2 NTAs. We fabricated TiO2 for 6 h,12 h and 16 h by anodization respectively(the thicknesses of each TNTAs are 4, 9, 40 micrometer when anodization time increases), and then hydrogenated each of them by electrochemical doping for 5s at the same condition. The H- TiO2 NTAs show great improvement of capacitance. For the 4 um H-TiO2, the hydrogenation improved the capacitance up to 7.83 mFcm-2 from CV calculation at a scan rate of 100mvs-1, which is 11 times higher than the capacitance obtained from TiO2 by air-annealed at the same condition. The largest capacitance we obtained is 25.14 mFcm-2 at a scan rate of 100 mvs-1 for 40 um H-TiO2.Hydrogenation produces reactive oxygen vacancies within the lattice by changing to which increase the host material by acting as a donor. The increase of the thickness provides longer tubular channel path and more active surface sites for ion diffusion and charge transfer. This work provide an suitable route for increasing the electrochemical capacitance of supercapacitors.

Reference

M. Salari, S.H. Aboutalebi, K. Konstantinov and H.K. Liu, Phys. Chem. Chem. Phys. 13, 5038–41 (2011).

J. Wang, J. L. Polleux, J. Lim, B. J. Dunn, Phys. Chem., 111, 14925−14931 (2007).

Z.K. Zheng, B.B. Huang, X.Y. Qin, X.Y. Zhang, Y. Dai and M.H. Whangbo, J. Mater. Chem. 21: 9079–87 (2011)

X. Chen and S.S. Mao, Chem. Rev. 107, 2891–959(2007)

X.H. Lu, G.M. Wang, T. Zhai, M.H. Yu, J.Y. Gan, Y.X. Tong and Y. Li Nano Lett., 12:1690–6 (2012)

Figure 1