bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoelectrochemical Properties of InGaN Thin Film Grown By Plasma Assisted Molecular Beam Epitaxy
Authors: Shen Yu-Min , Ganguly Abhijit , Chen Li-Chyong , Chen Kuei-Hsien 
Published: February 2020

In this work, high quality epitaxial InxGa(1-x)N films were synthesized on Si (111) substrate using plasma assisted molecular beam epitaxy (PAMBE) and applied for photoelectrochemical (PEC) application. The study demonstrated that a proper tuning of composition via controlling the In/Ga ratio the PEC performance of InGaN can be optimized. X-ray diffraction study confirmed the controllable formation of c-axis InxGa(1-x)N with different compositions. Photoluminescence results indicated the variation of band gap energy within 2.4~2.8 eV depending on In/Ga ratio. Transmission electron microscopic study confirmed the epitaxial growth of InGaN films, without observable evidence of phase separation at ~0.88% lattice mismatch between InGaN and Si substrate. From the PEC study, performed in hydrochloric acid solution (1M), an optimum efficiency of 1.31% was achieved with 15.5% In content in the InGaN. Detailed electrochemical and optical studies were carried out to address the factors that might influence the PEC performance, such as the crystallinity, carrier concentration, band gap energy, energy level position, and protons diffusion length. We believe that this study could lead to a better insight into the issue of InGaN for PEC application.
Keywords: plasma assisted molecular beam epitaxy, InGaN, water splitting, carrier concentration

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(Invited) Emerging Oxide Nanowires: Creation Concept and Their Promises for Novel Nanoscale Devices
Authors: Yanagida Takeshi 
Published: February 2020

Self-assembled one-dimensional “
Nanowires
” have attracted much attention due to not only the fundamental interests in nanoscale-confided physical properties but also novel nano-device applications, where existing nanomaterials have not been applicable. Nanowires are attracting the interests of researchers from diverse research communities ranged from physics, chemistry, material science, electrical engineering, chemical engineering and others. Group VI and III-V compounds nanowires have demonstrated their great promises for exploring fundamental physical properties at nanoscale and also the feasibility of diverse nano-device applications. Although metal oxides exhibit their rich variety of physical properties including photo catalysts, ferroelectric, ferromagnetic, high-Tc superconducting, memristive switching, which are hardly attainable to other materials, compared with group VI and III-V compounds nanowires, the feasibility of functional oxide nanowires has been strongly limited due to the absence of fabrication method for various transition metal oxide nanowires.
Here we demonstrate i) “Creation Concept” for well-defined oxide nanowires via vapor-liquid-solid (VLS) mechanisms, and ii) the memristive switching phenomena within a single oxide nanowire down to 10 nm scale.We have succeeded to fabricate a well-defined single crystalline metal oxide nanowire by controlling precisely formation environments. When comparing with MD simulations as to VLS growth, the importance of material transport via the metal catalysts has been found. Especially, we have found that the difference between LS interface and VS interface on the critical nucleation size essentially allows us to perform VLS nanowire growth. This knowledge can be expanded to discover novel metal oxide nanowires via VLS mechanisms. Next, we have constructed highly stable RS junctions comprised of Pt/single oxide nanowire /Pt. The nanowire memristor exhibited the endurance up to 108 by utilizing self-assembled nanowires and well-defined nano-gap electrodes. In addition, information as to the memristive switching including the carrier type for memristive switching and the spatial switching location, have been extracted by the present nanowire memristor, which had been buried in conventional memristors. We believe that the presented approaches by utilizing self-assembled oxide nanowire/metal junctions offer an important system and platform for investigating not only nanoscale confined physical properties of transition metal oxides but also exploring exciting novel nano-devices with other electric materials, which had not been possible.
Transition Metal Sulfides As Conductive Additives for Sulfur Electrode in Li-S Battery
Authors: Sun Ke , Su Dong , Zhang Qing , Bock David C , Marschilok Amy C , Takeuchi Esther S , Gan Hong 
Published: February 2020

Lithium-Sulfur (Li-S) battery has been a hot research topic currently due to its potential of combining high energy density and low cost together. In this work, we have investigated various transition metal sulfides (CuS, FeS2, TiS2, CoS2) as conductive additive to sulfur electrode in lithium-sulfur (Li-S) battery. We found that all metal sulfides additives enhanced the utilization of sulfur cathode at high rate discharge when compared with a sulfur-carbon composite electrode with equivalent sulfur volumetric loading. Systematic study suggests the reason for the enhancement is the activation of the polysulfide to Li2S2/Li2S conversion process that constitutes the second plateau in Li-S battery discharge. Besides, the results also indicate that the high electronic conductivity of transition metal sulfides could not fully account for the second plateau activation. Instead, it is found that the interaction between polysulfide and metal sulfides is actually helping the nucleation process of Li2S2/Li2S nucleation and deposition, and the level of this interaction also has profound influence on the cycle life and columbic efficiency of sulfur electrodes with transition metal sulfide additives. The results of this study will help to direct the design of non-carbon based conductive fillers for sulfur electrodes and enable the development of high power Li-S batteries.
UCSD ECS Student Chapter: A Burgeoning Local Community in San Diego
Authors: Parikh Pritesh , Liu Haodong , Alvarado Judith , Nguyen Han , Meng Ying Shirley 
Published: February 2020

The ECS student chapter at the University of California, San Diego (UCSD) represents a myriad group of students across various disciplines and education level that are involved in promoting electrochemistry science and technology.
With over 24,000 undergraduate students, 4000 graduate students and 1000 full time faculty, UCSD has a large community that is interested topics ranging from energy storage and conversion to nanocarbons to photonic devices and even energy efficient building systems. The recent announcement of the multi-disciplinary SPEC (Sustainable Power and Energy Conversion) Center and a student run Energy Club provides our ECS local chapter with a unique opportunity to collaborate and educate students about electrochemistry.
With the support of our faculty advisor, Prof. Shirley Meng and the ECS community at large, we have successfully hosted seminars from both academic and industry connections. Students associated with the UCSD ECS chapter have also had an opportunity to attend and present their work at annual symposium gatherings. A successful first year of the student chapter, in 2014, enabled us to be featured in the ECS interface magazine. Following into our second year of operations, we are geared for another series of exciting seminars and demonstrations.
We are very happy to share with you some of previous efforts, ongoing activities and future plans for our local student chapter.

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Electroplating Titanium on Conductive and Non-Conductive Substrates
Authors: Parker Margaret 
Published: February 2020

Crista Chemical Company LLC’s (3C) goal was to develop a novel, low-cost, industrial method of plating titanium on metallic and nonmetallic materials. Crista Chemical Company achieved this goal by developing an innovative technology of titanium electroplating and receiving a patent for the achievement U.S. Patent No. 9,023,187, and soon to be published ASTM B999-15. The innovation was ground breaking as before the discovery, titanium electroplating was considered impossible.
Crista Chemical Company’s revolutionary innovation electrodeposits coatings of Titanium and Titanium-zirconium alloys on conductive and non-conductive substrates coated with low, medium, or high phosphate electroless nickel. Two methods of titanium deposition were designed and optimized. One was a conventional electroplating method—which used constant current—and another one was a nanocrystalline electrodeposition (we refer to as the “turbo method”), which uses pulse plating. In both methods electrodeposition of the titanium alloys proceeded from the sulfuric acid solution.
The advantages of the method of plating titanium include a) low cost, b) relatively low number of process steps, thus posing minimal effect on the environment (safer and zero discharge process) and c) very broad application. Moreover, Produced materials are characterized by a) light weight, b) high corrosion resistance c) high yield strength, d) wear resistance, e) high resilience, stiffness at room temperature as well as at elevated temperature (e.g. up to 200C). This makes the titanium coating an attractive technology for a variety of industries including: high efficiency batteries, medical applications, biotechnology, aerospace, defense, sports and automotive.
Electrochemical Mechanism Insights from Mott-Schottky Measurements: Application to Europium in Molten Oxide
Authors: Caldwell Andrew Harvey , Allanore Antoine 
Published: February 2020

Electrochemical impedance measurements are commonly conducted at a constant direct current (DC) potential while sweeping the frequency of the perturbation. The mainstream plots used to discuss data are then Nyquist and Bode plots, on which fitting curves for the postulated equivalent circuit are represented.
Unfortunately for high temperature electrochemists interested in faradaic reactions in molten electrolytes with a high concentration of electroactive species [1] or a very high conductivity [2], this method rarely provides meaningful results due to data that are often noisy and difficult to interpret at potentials away from the open-circuit potential (OCP).
Methods employing a dynamic sweep of the DC potential at a fixed frequency of perturbation experimentally provide more reliable insight into electrochemical impedance phenomena in molten electrolytes. The archetypical example is alternating current (AC) voltammetry in its various forms, such as sine- or square-wave voltammetry [3][4]. However, most modern potentiostats offer only one means of conducting DC potential sweep impedance measurements, the so-called Mott-Schottky (MS) method. This method is not truly dynamic from a DC potential perspective, and is traditionally used for capacitance measurements and characterization of semi-conductor electrodes.
The present work shows a procedure to extract faradaic data from MS data, inspired from the background subtraction method previously proposed for AC-polarography [5]. Nyquist-type representations are derived from the MS data, enabling a connection to mainstream impedance analysis methods. An example of this procedure, an investigation of the electrochemistry of europium ions in molten oxide, is provided.
[1] A. Kisza, Polish J. Chem., 67 [1993] 885-894
[2] B. Savova-Stoynov and Z.B. Stoynov, Journal of Applied Electrochemistry, 17 [1987] 1150-1158
[3] A.M. Bond et al., Anal. Chem., 77 (9) [2005] 186-195
[4] C. Montel, C. Russel and E. Freude E, Glastech Ber, 61, [1988], 59–63
[5] A.M. Bond et al., J. Electroanal. Chem., 222 (1) [1987] 35-44.
An Active Li-Mn-O Compound for High Energy Density Li-Ion Batteries
Authors: Freire Melanie , Kosova Nina V. , Jordy Christian , Chateigner Daniel , Lebedev Oleg , Maignan Antoine , Pralong Valerie 
Published: February 2020

Due to their low weight, high energy densities and long cycle life, the battery scientific community is still trying to develop new high capacity cathodes materials in order to increase the energy density of storage devices [1].
After a composition screening, a new material family has been discovered in the Li-Mn-O system and has been investigated as potential new material for Li-ion batteries to replace conventional NMC materials (LiNi1/3Mn1/3Co1/3O2) [2]. In this study, we report for the first time the synthesis, structural and electrochemical characterizations of a new non-lamellar oxide with the highest capacity observed ever before in the Li-Mn-O system. This new patented [3] material with the composition of Li4Mn2O5 shows a discharge capacity of 300 mAh/g. It is a rock-salt type nanostructured material, prepared by a direct mechanochemical synthesis. The typical crystallite size is about 5-10nm (from Transmission electron microscopy TEM and electron diffraction ED). The ring ED pattern of this individual phase can be indexed on the cubic Fm-3m structure, with a rock-salt cell parameter of a=4.16Å, according to Rietveld refinement.
The electrochemical performances were performed at a C/20 rate, and show a reversible discharge capacity about 300 mAh/g. A gradual increase in the cut-off voltage up to 4.8V activates the material and prevents the electrolyte degradations. During cycling, the derivative curves indicate at least 2 active redox couples [4]: Mn3+/ Mn4+ (around 3.3V), Mn4+/ Mn5+ and/or O2-/ O- (around 4.1V). In order to have a better insight of lithium deinsertion process, we used magnetic measurements at various charge states. We will show that magnetic measurements are perfect tools to access to the oxidation level of the material, and in agreement with the values obtained after iodometric redox titrations. We will namely show that this material is oxidized up to Mn5+oxidation state with a competition of the oxygen oxidation [4].
In short, in this work are reported the first results of a new electrochemically active compound as positive electrode for Li-ion batteries, with the active participation of both redox centers: Manganese and Oxygen [5].
[1] B.L. Ellis, et al., Chem. Mater., 2010, 22, 691
[2] H. Koga, et al., J. Electrochem. Soc., 2013, 160, A786
[3] Patent FR1258625
[4] M. Sathiya, et al., Nature Mat., 2013 , 12, 827
[5] M. Freire et al., Nature Mat. Letters, 2015, 14, DOI : 10.1038/NMAT4479
Positive and Negative Potassium-Ion Electrodes' Behavior in Non-Aqueous Electrolytes
Authors: Vaalma Christoph , Buchholz Daniel , Passerini Stefano 
Published: February 2020

Recent concerns about the availability of raw materials for lithium-ion batteries (LIBs) have led to an increased interest in alternative secondary battery technologies. Recently, from about 2010 on, researchers’ attention shifted back to sodium-ion batteries (NIBs) as they offer advantages like the replacement of the copper current collector of the anode by aluminum and low cost and abundant Na-reserves instead of relatively high cost and poorly distributed Li-reserves. These advantages are considerable, since NIBs show a comparable electrochemical performance to LIBs.1

A significant advantage of potassium-ion batteries (KIBs), if compared with NIBs, is the lower potential of K/K+ related to the standard hydrogen electrode (SHE). The standard potentials are reported as −2.71 V for Na/Na+, −2.94 V for K/K+ and −3.04 V for Li/Li+.2 Therefore, in theory, KIBs should deliver cell voltages similar to LIBs and higher than NIBs. Nevertheless, it needs to be considered that the higher radius and increased mass of K-ions result in decreased gravimetric and volumetric energy densities (76 pm and 6.941 g mol-1 for Li+; 100 pm and 22.990 g mol-1 for Na+; 140 pm and 39.098 g mol-1 for K+).2,3 Taking these aspects into account, KIBs could potentially show a combination of the advantages of LIBs and NIBs without suffering of their drawbacks.
With this work we demonstrate as positive and negative K-ion materials, including a K-ion full cell, may show interesting electrochemical performances which are worth to be investigated in greater detail by a wider scientific community.

References

1. N. Yabuuchi, K. Kubota, M. Dahbi, and S. Komaba, Chemical Reviews, 114, 11636–11682 (2014).
2. S. Komaba, T. Hasegawa, M. Dahbi, and K. Kubota, Electrochemistry Communications, 60, 172–175 (2015).
3. M. E. Wieser et al., Pure and Applied Chemistry, 85, 2013 (2013).
The Development of High Capacity V-Based BCC Electrodes for Aqueous Metal Hydride Air Systems
Authors: Weadock Nicholas , Yang Heng , Tan Hongjin , Fultz Brent , Bugga Ratnakumar V 
Published: February 2020

The energy density of traditional Ni-MH batteries could be dramatically increased by developing a higher capacity metal hydride alloy. An even larger increase in energy density for MH-type electrochemical cells would be seen by pairing the high capacity metal hydride with an air cathode to create an MH-air battery. Vanadium based BCC alloys are a promising choice for high capacity anode materials, and discharge capacities of greater than 450 mAh/g have been reported in the literature for TiV2.1-xCrxNi0.3 alloys.1 The kinetics and power density of these alloys are further improved by reducing the microstructure via rapid solidification.2

Pure vanadium metal forms a dihydride with a total hydrogen content of 4 wt.% or a theoretical electrochemical capacity of 1068 mAh/g. Practical cycling capacity is limited by the fact that the VH and VH2 phase transitions differ by several orders of magnitude in pressure.3 The plateau pressures of these phase transitions are strongly affected by the composition and lattice parameter of host metal alloy, and the kinetics depend on microstructure and electrode design. We initially identified a ternary TiVNi alloy4 that delivers close to the theoretical capacity of about 1100 mAh/g by accessing both the monohydride and dihydride phase transitions. The transitions manifest as two voltage plateaus in the charge/discharge profile of the metal hydride electrode, as seen in the accompanying figure. The difference in voltage plateaus is directly related to the difference in gas phase plateau pressures via the Nernst equation. From the figure we see a difference of ~120mV, corresponding to a 4 – 5 order of magnitude difference in plateau pressure. This alloy has poor cycle life, so Cr is added to prevent corrosion resistance. We will present results on the effect of composition on the capacity and cycle life of the alloy, and the role that microstructural reduction through rapid solidification and ball milling play on improving the kinetics.
1. H. Inoue, S. Koyama, and E. Higuchi, Electrochimica Acta, 59, 23–31 (2012).
2. H. Tan, N. Weadock, B. Fultz, and R. V. Bugga, Meet. Abstr., MA2015-01, 19–19 (2015).
3. M. Tsukahara et al., J. Alloys Compd., 224, 162–167 (1995).
4. C. Iwakura, W.-K. Choi, R. Miyauchi, and H. Inoue, J. Electrochem. Soc., 147, 2503–2506 (2000).

Figure 1
(Invited) Carbon Nanotubes: Towards an Advanced Material for Energy and Electronic Applications
Authors: Flavel Benjamin S 
Published: February 2020

Ever since their discovery, carbon nanotubes (CNTs) have been touted as a material of the future and a lengthy list of possible applications are often cited in the literature. However, the realization of these applications have so far been hindered by exactly the property which made CNTs so attractive in the first place, namely their varying optical and electronic properties. In order to become a true advanced material of the future it is necessary to develop techniques to prepare CNTs with defined length, wall number, diameter, electronic and optical property on the large scale. Furthermore, in addition to simply having large quantities, it is important that strategies for their incorporation into large-area devices are developed.
In our work we address these issues with the use of aqueous gel based sorting techniques to routinely prepare milligram quantities of metallic and semiconducting, single chirality and even double walled carbon nanotubes with defined outer-wall electronic type. This ‘toolbox’ of available CNTs is then used for the realization of CNT based devices with applications to energy. For example CNT:Fullerene solar cells, CNT:Si solar cells and CNT based light sensitive elements. In addition to being of fundamental scientific interest these applications also provide us the opportunity to address the challenges of controlling this 1 D nanomaterial on the macro-scale. To this end we prepare inks from sorted CNT material and look at strategies to align them in thin films over large areas.
[1] K. E. Moore, M. Pfohl, D. D. Tune, F. Hennrich, S. Dehm, V. S. K. Chakradhanula, C. Kuebel, R. Krupke, B. S. Flavel, ACS Nano 9 (2015) 3849-3857.
[2] D. D. Tune, A. J. Blanch, C. J. Shearer, K. E. Moore, M. Pfohl, J. G. Shapter, B. S Flavel, Applied Materials & Interfaces (2015) 10.1021/acsami.5b08212.
[3] M. Pfohl, K. Glaser, J. Ludwig, D. D. Tune, S. Dehm, C. Kayser, A. Colsmann, R. Krupke, B. S Flavel, Advanced Energy Materials (2015) 10.1022/aemn.201501345.
[4] B. S. Flavel, K. E. Moore, M. Pfohl, M. M. Kappes, F. Hennrich, ACS Nano 8 (2014) 1817-1826.
(Invited) Growth of Single-Walled Carbon Nanotubes with Specific Structure
Authors: Li Yan , Yang Feng 
Published: February 2020

Single-walled carbon nanotubes (SWNTs) present unique structure-dependent properties and the controlled preparation of chemically and structurally pristine SWNTs is a crucial issue for their advanced applications (e.g. nanoelectronics) and has been a great challenge.Epitaxial growth of SWNTs from well-defined seeds has shown to be a promising strategy to control the structure of SWNTs. Inspired by the specificity of enzyme-catalyzed reactions, we realized that only catalysts with unique crystal structure and desired atomic arrangements can act as the structural templates for chirality specific growth of SWNTs, relying on the high selectivity in geometry match between catalysts and SWNTs. We developed a new family of catalysts, tungsten-based intermetallic compounds, which have high melting point and very special crystal structure, to synthesize SWNTs with designed chirality. Using W6Co7 catalysts, (12, 6) SWNTs was directly grown with the purity higher than 92%. The selective growth of (12, 6) tubes is due to a good structural match between the carbon atom arrangement around the nanotube circumference and the metal atom arrangement of (0 0 12) planes in the catalyst. Similarly, (16, 0) SWNT exhibits good structural match to (1 1 6) plane of Co7W6 catalyst. By manipulating the chemical vapor deposition (CVD) conditions, zigzag (16, 0) SWNTs, which are generally known as a kinetically unfavorable species in CVD growth, were obtained at the purity of ~80%. The chirality-specific growth of SWNTs is realized by the cooperation of two factors: the structural match between SWNTs and the catalysts makes the growth of SWNTs with specific chirality thermodynamically favorable; and further manipulation of CVD conditions obtains optimized growth kinetics for SWNTs with this designed chirality. This idea has also been proved to be valid for SWNTs with other chiralities and intermetallic catalysts.
References
1. Yang, F.; Wang, X.; Zhang, D.; Yang, J.; Da, L.; Xu, Z.; Wei, J.; Wang, J.-Q.; Xu, Z.; Peng, F.; Li, X.; Li, R.; Li, Y.; Li, M.; Bai, X.; Ding, F.; Li, Y., Nature
2014, 510, 522-524.
2. Yang, F.; Wang, X.; Zhang, D.; Qi, K.; Yang, J.; Xu, Z.; Li, M.; Zhao, X.; Bai, X.; Li, Y., J. Am. Chem. Soc.
2015, 137, 8688-8691.