bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochemical Performance and Chemical Stability of Architecturally Designed La2-XPrxNiO4+D IT-SOFC Cathodes
Authors: Sharma Rakesh Kumar , Celikbilek Ozden , Burriel Mónica , Dessemond Laurent , Bassat Jean-Marc , Djurado Elisabeth 
Published: February 2020

Solid oxide fuel cells (SOFCs) have attracted widespread attention due to their high energy conversion efficiency and low emissions [1]. The main objective of current research on SOFC is to improve the performance of these devices while operating at Intermediate Temperatures (IT-SOFCs). Both the cathode composition [2] and the microstructural design of the electrode film play an important role in obtaining optimal performances [3, 4]. Porous microstructures with small particle size enhance the catalytic properties by improving the gas distribution and by enlarging the reactive surface area. In this work, architecturally designedLa2-xPrxNiO4+δ films (with x=0.0, 0.5, 1 and 2) have been prepared for the first time by Electrostatic Spray Deposition (ESD) and screen printing (SP). The X-ray diffraction patterns confirm the formation of the pure orthorhombic La2-xPrxNiO4+δ phase in all cases. These novel cathodes consist of an original porous 3D tree-like microstructure sandwiched between a thin dense ESD layer at the electrolyte side and topped by a porous SP layer. The polarization resistance (Rpol) of these La2-xPrxNiO4+δ cathodes was found equal to 0.42, 0.21, 0.11 (Figure 1) and 0.07 W.cm2 at 600°C for x = 0, 0.5, 1 and 2, respectively. These values corresponding to this solid solution are the lowest ones available in the literature to the best of our knowledge. The chemical stability decreases by increasing the Pr content while the Rpol improves. LaPrNiO4+δ is chemically stable up to 30 days at 700°C in air. To conclude, among the La2-xPrxNiO4+δ (0 ≤ x ≤ 2) solid solution, LaPrNiO4+δ shows the best compromise between electrochemical and chemical stability.
Figure 1: Nyquist plot for LaPrNiO4+δ at 600°C in air.
References
[1] D. Ding, X. Li, S. Y. Lai, K. Gerdes, M. Liu, Energy Environ. Sci., 2014, (7), 552.
[2] V. Vibhu, A. Rougier, C. Nicollet, A. Flura, J.C. Grenier, J.M. Bassat,
Solid State Ionics, 2015, (278), 32.
[3] D. Marinha, L. Dessemond, E. Djurado, J. Power Sources, 2012, (197), 80.
[4] R. K. Sharma, M. Burriel E. Djurado, J. Mater. Chem. A, 2015, (3), 23833.

Figure 1
In Situ Raman Studies on Electrochemically Deposited Manganese Oxide on Gold
Authors: Pavlovic Zoran Miroslav , Ranjan Chinmoy , Gao Qiang , Schloegl Robert 
Published: February 2020

Water oxidation is one of the biggest challenges towards establishing a sustainable energy economy based on renewable energy. Non noble metal electrocatalysts can significantly reduce the costs and make usage of electrochemical water splitting on a large scale possible. Those metal oxide catalysts can be an effective replacement even if their electrochemical activities are a fraction of noble metal oxide catalysts. If these catalysts can be developed on such a way that their operational lifetime would become comparable to noble metal materials, problem of electrochemical water splitting would be partially solved.
MnO2-x naturally exists in various polymorphs with various amounts of defects. Each of them has different electrocatalytic performance. Poor electronic conductivity, which is very important for good water splitting catalysts, is also one of the issues with these materials. These catalysts remain a long way from successful implementation within electrolysers, even with enormous potential of usage. It is important that these materials are studied in situ in order to understand performance and limitations under the operando conditions.
In situ Surface Enhanced Raman Spectroscopy is used to track the structural changes of the lattice of hydrous MnOx, while sweeping the potential in the range of 0 - 2.2 V vs RHE. MnOx catalyst is prepared by electrochemical deposition on the surface of roughened gold. It was done by passing an anodic current of 50 mC/cm2 at 1.6 V vs RHE in 0.5 M MnSO4 solution. By following the Mn-O-Mn stretching at various potentials in various electrolytes, the structural conformation of the catalyst was studied. For each electrolyte a unique catalyst structure was finally established. Various electrolytes (alkaline, neutral and acidic) containing alkali metal ions (Li, Na, K, Cs), alkaline earth metal ions (Ca, Sr, Ba) and anions such as borates, phosphates and sulphates were used to study OER under in situ Raman conditions. Catalysts were also studied under conditions of duteration of the electrolytes.

Figure 1
Quantification of Phase Evolution in Praseodymium Nickelates
Authors: Dogdibegovic Emir , Wright Christopher J. , Zhou Xiao-Dong 
Published: February 2020

A new method to quantify the phase evolution in nickelates is developed using sintered metal grids as cathode current collectors. The metal grids not only enable us to carry out phase quantification studies in cathodes, but also retaining the cell’s performance and stability. Moreover, they are chemically compatible with the cathode and allow XRD analysis of the surface and bulk of the cathode after cell operation. Multiple cells were tested to study the reproducibility of measurements. High performance was observed in cells with metal grids, extending the application of this method to cathode durability studies in state-of-the-art SOFCs. Respective advantages and challenges of the method are discussed with an emphasis on phase quantification, and the effects of different noble metals in cells regarding their thermal, electrical, chemical, and mechanical stability. Au was found to be the most suitable current collector due to its low chemical reactivity with the cathode and mechanical compatibility at operating conditions.
Nanostructured Graphene-Supported Pt-NiTiO3 Catalyst for the Oxygen Reduction Reaction for Alkaline Direct Alcohol Fuel Cells Applications
Authors: Hernández Ramírez Anayantzin , Rodriguez-Varela F.J. , Sánchez-Castro Ma. Esther , Kalasapurayil Kunhiraman Aruna , Karthikeyan Palanisamy , Manoharan Ramasamy 
Published: February 2020

The catalytic activity for the ORR of graphene-supported Pt-NiTiO3 (Pt-NiTiO3/G) catalyst was evaluated in 0.5 M KOH. NiTiO3 nanoparticles were synthesized via a wet-chemical method. XRD analysis confirmed the formation of crystalline NiTiO3 nanoparticles with a size of ca. 25 nm. Then, nanostructured 20% Pt-NiTiO3/G catalyst (Pt:NiTiO3 ratio of 1:1) was obtained by the microwave assited polyol method. The titanate-based catalyst showed a high cataytic activity for the ORR in 0.5 M KOH electrolyte. It also showed enhanced tolerance to methanol and ethanol, compared to Pt/C and Pt/Gr catalysts. The results suggest that Pt-NiTiO3/G electrocatalyst is a good candidate for Alkaline Fuel Cells applications.
Agglomeration in Porous Silicon Prepared from Si-Nanowires Structures
Authors: Velez Victor H. , Sundaram Kalpathy B 
Published: February 2020

Silicon nanowires (SiNW’s) arrays prepared by electroless etching method are attractive due to their significant light absorption properties across the visible spectrum [1]. Typical silicon nanowires grown by electroless etching is shown in Figure 1a. Following this preparation of silicon nanowires, these samples are etched in an electrolytic HF and ethanol solution to produce porous silicon quantum confined structures. Mechanical behavior of materials at nanoscale is different due to their quantum confinement effect. When porous silicon nano-structures are prepared from SiNWs obtained through electroless process, they may have a tendency to become thin. Ultimately these nano-structures may collapse and form bunches on the surface [2], as shown in Figure 1b. However, bunched silicon nanowires structures may be desirable in some applications but may not be for some others. In order to avoid bunching of SiNWs, it may be necessary to reduce the surface tension during the growth of nanowires [3].
(a) (b)
Fig 1. Cross-section images of silicon nanowires (a) grown by electroless etching, (b) Porous silicon structures prepared from SiNWs.
SiNW’s were grown by eletroless etching in a solution of hydrofluoric acid (HF) and silver nitrate (AgNO3) at room temperature [4]. The prepared nanowires were then etched in an electrolytic solution containing HF and ethanol to make porous Si quantum confined structures. Reflectance and photoluminescence studies are performed on this structures

Figure 1
Improvement of Quantum Efficiency of the Nanosized Phosphors Using a Flux
Authors: Ha Jungmin , Wang Zhenbin , Novitskaya Ekaterina , Hirata Gustavo , Graeve Olivia A , Ong Shyue Ping , McKittrick Joanna 
Published: February 2020

Micron-sized phosphors have been widely researched for a near UV-LED by the mean of the convenient solid-state method. The phosphors with micron-sized tend to show good quantum efficiency oriented from their large crystallite size, but present high light-scattering and decrease packing density on the LED device, causing low resolution. Therefore, integration of the phosphors for a near-UV LED package has particles size requirements in order to overcome the issue from bulk size phosphors. The scatter effect in visible and UV radiation region will be negligible when the radii of phosphors particles are less than ~400 nm. However, phosphors with nano-size particles have poor quantum efficiency comparing to phosphors with micron sized particles.
In this work, flux effect on quantum efficiency is studied in nano-sized phosphors. Blue colored CaMgSi2O6:Eu2+ phosphors were synthesized by a co-precipitation method and NH4F, NH4Cl, or H3BO3 was added as a flux. Flux is typically used in the solid-state reaction to help diffusion of atoms in the bulk materials, not nano-sized materials. The crystallite size is increased from ~20 nm to ~40 nm, but particles size is unchanged (~ 50 nm) with the addition of a flux in the materials, confirmed by X-ray diffraction, Dynamic Light Scattering analysis, and Scanning Electron Microscopy. The emission wavelength of CaMgSi2O6:Eu2+ is 458 nm under 350 nm as an excitation wavelength. The intensity of emission wavelength is about twice increased when 5wt% NH4F is added as a flux in the phosphors materials comparing to the phosphors without a flux, indicating the improvement of quantum efficiency. This study shows the potential of flux that could improve quantum efficiency in the nano-sized phosphors. This work is supported by the National Science Foundation, Ceramics Program Grant (DMR-1411192).
Magneto-Photoluminescence and Giant Magneto-Resistance in Self-Assembled Vertically-Aligned (ZnO)0.5:(La0.7Sr0.3MnO3)0.5 Nanopillars
Authors: Pan Wei 
Published: February 2020

A great deal of research has been carried out in perovskite rare-earth manganites. Among them, La0.7Sr0.3MnO3 (LSMO) is of particular interest due to its colossal magnetoresistive effect. So far, studies in LSMO have mainly been focused on its bulk magnetic transport properties. Much less work has been carried out in LSMO nanostructures. In fact, to our knowledge, there is no report on exploring low temperature photoluminescence (PL) measurements and the magnetic (B) field dependence in LSMO.
In this talk, I will first report our recent results of magneto-photoluminescence in La0.7Sr0.3MnO3 nanopillars embedded in a self-assembled vertically aligned epitaxial (ZnO)0.5:(La0.7Sr0.3MnO3)0.5 nanocomposite film in the ultra-violet regime at magnetic (B) fields up to 12T. We have observed that at low B fields the PL intensity is nearly constant. As the B field is further increased over a characteristic value, which depends on sample temperature, the PL intensity decreases sharply and eventually quenches at higher magnetic fields. In the second part, I will present our recent results on giant magneto-resistance in LSMO nanopillars.
(Invited) XAFS of Rare Earth Elements in Amorphous Silicon Alloys: What Do We Know about the Local Structure?
Authors: Tessler Leandro R. , Bosco Giacomo Ferreira 
Published: February 2020

X-ray absorption spectroscopy (both XANES, X-ray Absorption Near-Edge Spectroscopy and EXAFS, Extended X-ray Absorption Fine Structure) is a powerful tool to determine the chemical environment of selected elements in solids. It is particularly well suited to study rare earth elements in amorphous silicon alloys. In this paper we review the technique and results obtained for different rare earth elements, especially Er, Eu and Tb.
Whenever possible, the rare earth elements coordinate to any oxygen present in subcoordinated envitronments that vary with the host and can be very distorted. The details of the environment depend on the technique used to prepare the samples. Annealling above 400C makes the coordination evolve towards oxide-like 6-fold environments.
Europium is a special case. It may assume either 2+ or 3+ oxidation states. The X-ray absorption peaks associated with the core electrons binding energy can be used to estimate the relative concentration of each. Annealling in oxidizing atmospheres can modify the Eu3+/Eu2+ ratio, affect the atomic surroundings and change the luminescence spectrum.
In general, efficient luminescence of the 3+ ions is associated with low coordination oxygen environments. This environment does not change significantly at the relatively low annealling temperatures (up to 300C) that maximize the photoluminescence. The reason for the increase of the luminescence intensity with annealling not a modification of the local environment of the rare earth ions.
Calibration of a Circular HV Magnetron Sputtering Source for in-Situ RE Doping of Ecr-PECVD Si-Based Thin Films
Authors: Miller Jeremy William , Wojcik Jacek , Bradley Jonathan D. B. , Mascher Peter 
Published: February 2020

Rare-Earth doped silicon based luminescent materials have become an attractive solution in some key areas of technological development. For instance, in the field of silicon photonics there is a drive to replace electronic on-chip components with photonic counterparts [1-2]. One of the major challenges thus far has been to provide the monolithic integration of an efficient reliable electrically driven light source. Such an element could also be used for solid state lighting, and avoid expensive III-V compounds that cannot be fully integrated into electronic drivers in a CMOS line [3].
In-situ doping of Eu3+ions in silicon oxides and oxynitrides fabricated by electron-cyclotron-resonance plasma enhanced chemical vapour deposition (ECR-PECVD) is performed. Doping is achieved by using a Circular High Vacuum Magnetron sputtering source attached to the ECR-PECVD tool. The doping concentration is varied by varying the distance of the sputtering source to the target. The hot matrix composition is varied through varying oxygen and nitrogen gas flows. The effects on the doping concentrations of the sputtering source distance to target is determined through Rutherford Backscattering Spectrometry and Variable Angle Spectroscopic Ellipsometry. Preliminary luminescence measurements are discussed.
[1] Jalai, B., and Fothpour, S. “Silicon photonics,” Journal of Lightwave Technology 24, 4600-4615(2006)
[2]Liu, A. Jones, R., Liao, L., Samarah-Rubio, Rubin, D., Cohen, O. Nicolaescu, R., and Paniccia, M., “A high-speed silicon optical modulator based on a metaloxide-semiconductor capacitor,” Nature 427, 615-618 (2004)
[3] Ponce, F.A., Bour, D.P., “Nitride-based semiconductors for blue and green light-emitting devices”, Nature 386 (6623), 351-359 (1997)
Impact of Conjugated Mechanical and Electrical Stimuli on Interfacial Adhesion and Electrical Contact
Authors: Zade Vishal , Martini Ashlie , Lee Min Hwan 
Published: February 2020

This work was performed in an effort to fundamentally understand how nanoscale contacts between materials evolve due to coupled stresses, specifically those arising from mechanical and electrical stimuli. To investigate the stress response of contact between these materials, atomic force microscopy (AFM) experiments was performed with the AFM tip-substrate interface subjected to normal mechanical loading and electric current, individually and in combination. Experiments to study the effect of coupled external stresses on metal/metal and metal/graphite interfaces are largely based upon AFM. We chose this experimental tool because the AFM tip mimics the contact of a single nanoscale asperity which provides a means of studying the very complex process by which a contact area evolves with stress. AFM is also advantageous for this study because 1) a predefined force can be applied to the tip-substrate interface enabling measurement of forces down to the pN level; 2) multiple characteristics of an interface can be measured simultaneously under various external stimuli at the nanoscale; and 3) measurements can be made in a non-vacuum environment unlike other nanoscopic equipment. After creating a nanoscale contact by bringing a metal-coated AFM probe or all-metal probe into contact with a sample, coated with either a metal or a graphitic layer, mechanical and/or electrical stresses are applied to the tip-substrate interface. Then the resulting adhesion force and electrical contact resistance are measured. These measurements are used not only to understand how stresses couple to affect the size of nanoscale material interfaces but also to explore limits of continuum contact area expressions for predicting contact evolution and to identify atomic-scale metrics for characterizing nanoscale contacts.
Research supported by the US AFOSR (Grant # FA9550-15-1-0256).
Anodically Grown TiO2 Nanotube Arrays Used As Substrates for Thermal Dewetting of Pt Show Significantly Enhanced Photocatalytic H2 Generation with Minimal Co-Catalyst Amounts
Authors: Nguyen Nhat Truong , Altomare Marco , Schmuki Patrik 
Published: February 2020

TiO2 nanostructures have recently attracted much attention due to their wide range of applications, such as photocatalysis, photovoltaics (dye-sensitized solar cell, photo-electrochemistry) and gas sensing. Particularly, electrochemically formed TiO2 nanotube arrays were shown to exhibit improved photocatalytic activity compared to other TiO2 nanostructures, this being ascribed to their directional electron transport and orthogonal charge carrier separation.1 The advantage of an electrochemical growth of the TiO2 nanotube layers is not only the simplicity of the process, but also the possibility of controlling the tube geometry (length, diameter, wall thickness) by selecting suitable anodization parameters (applied voltage, anodization time, temperature, fluoride concentration). Nevertheless, TiO2 alone is not effective in photocatalytic H2 generation: it requires the presence of noble metal co-catalysts (Pt, Au, Pd).2,3 Among the various noble metals, Pt is the most effective co-catalyst: it enables an efficient electron transfer at the semiconductor interface by providing a favorable solid state junction to TiO2 and it enhances the hydrogen recombination reaction.
There are several well explored methods to decorate Pt onto TiO2 nanotubes, mostly leading to a decoration of the full tube length with nanoparticles (the most frequently used up to date is photodeposition).
With our contribution we show a different approach: we decorate only the outermost surface of anodic TiO2 nanotubes with very thin Pt films (nominally few nm-thick) by using a simple plasma sputtering technique.4 Then, by a controlled thermal treatment, the Pt films are dewetted at the mouth of the tubes into arrays of Pt nanoparticles that are as small as of few nm. This site-selective deposition (only at the tubes top) allows for minimizing the amounts of costly noble metal co-catalyst, while at the same time leads to a significantly enhanced photocatalytic H2 generation compared to tubes that carry along their full length a classic Pt nanoparticle decoration.
[1] K. Lee, A. Mazare, P. Schmuki, Chem. Rev.
2014, 114, 9385–9454.
[2] N. T. Nguyen, J. Yoo, M. Altomare, P. Schmuki, Chem. Commun.
2014, 50, 9653–9656.
[3] N. T. Nguyen, M. Altomare, J. Yoo, P. Schmuki, Adv. Mater.
2015, 27, 3208–3215.
[4] N. T. Nguyen, M. Altomare, J. E. Yoo, N. Taccardi, P. Schmuki, Adv.
Energy Mater.
2015, doi: 10.1002/aenm.201501926.

Figure 1
High-Energy-Density, Long-Life Lithium-Sulfur Batteries
Authors: Manthiram Arumugam 
Published: February 2020

The current lithium-ion technology is based on insertion-compound cathodes and anodes, which limit the charge-storage capacity and energy density. Also, transition-metal ions with multi-electron redox reactions generally encounter a large step in the voltage profile on going from one redox couple to the other. To increase the energy density, much attention is being paid in recent years towards conversion-reaction electrodes, such as sulfur and oxygen as they offer two-electron transfer per sulfur or oxygen atom. However, the Li-S cells suffer from low electrochemical utilization and poor static (high self-discharge) and dynamic (short cycle life) stabilities, arising from the low electronic conductivity of both the end members S8 and Li2S, migration of dissolved polysulfide intermediates from the cathode to the anode, large volume changes during charge/discharge, and poor cycle life and dendrite formation with the lithium-metal anode.
To overcome the above difficulties, this presentation will focus on both novel electrode architectures as well as innovative cell designs. Specifically, the presentation will focus on approaches to enhance the electrochemical utilization of sulfur, suppress the migration of dissolved polysulfides to the anode, stabilize the lithium-metal anode surface, and utilize Li2S as a cathode. For example, novel cell configurations with a microporous carbon paper interlayer between the cathode and the separator, as well as polymeric separators coated with unique carbon architectures to trap and reutilize the migrating ploysulfides and enhance the electrochemical utilization, will be presented. Particularly, attention will be paid to the increase in the sulfur content (wt. %) and sulfur loading (mg/cm2) and the challenges associated with it to make the energy density of lithium-sulfur cells well above that of the currently available lithium-ion cells. In addition, additives to form a stable solid-electrolyte (SEI) layer in situ on a lithium-metal anode will be presented. Also, additives to lower the activation barrier during the first charge of Li2S cathode will be discussed.
Materials Engineering Using Nano-Fibrous and Molecular Cellulose
Authors: Wang Howard 
Published: February 2020

Cellulose is the most abundant natural polymer on earth, and widely used in everyday-life products from building construction to clothing to paper. Fundamental understanding of molecular solutions of cellulose is the key to realize advanced technologies beyond cellulose fibers. It has been previously reported that certain ionic liquid and organic solvent mixtures dissolve cellulose. In this study, the tertiary phase diagram of cotton linter microcrystalline cellulose, 1-Ethyl-3-methylimidazolium acetate (EMIMAc), and dimethylformamide (DMF) mixtures has been determined using primarily optical cloud point method and small angle neutron scattering (SANS). The mechanism of cellulose dissolution in tertiary mixture has been investigated by combining quasielastic and small angle neutron scattering (QENS and SANS). As SANS data show that cellulose chains take Gaussian-like conformations in homogenous solutions, which exhibit characteristics of having an upper critical solution temperature, the dynamic signals predominantly from EMIMAc molecules indicate strong association of EMIMAc with cellulose in the dissolute state. Data indicate that a molar ratio of EMIMAc to cellulose repeating unit greater or equal than 3 is necessary but not sufficient in forming one-phase homogeneous solutions. Clustering of cellulose chains occurs at low EMIMAc/DMF or EMIMAc/cellulose ratio, or at low temperatures. The mechanism of cellulose dissolution in tertiary mixture is discussed, and the potential applications of molecular cellulose are demonstrated.