bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Imprinted Functional Nano-Structures for Highly Efficient Photonic Devices
Authors: Lee Heon
Published: February 2020

Recently, nanoimprint lithography (NIL) has gained great attention as an effective patterning technology in the fields of light emitting diodes (LEDs), solar cells, and other optical devices, because of its simplicity and cost effectiveness.  The aim of this research is the development of NIL based direct printing process with an imprint resist containing dispersed various metal oxide (ZnO, TiO2, and ATO) nano-particles.  A functional nano pattern can be easily fabricated by this direct printing of functional materials.  The properties of substrates, such as transmittance, diffraction, refractive index, and hydrophobicity, was successfully controlled by forming the functional nano-patterns.  Finally, the efficiency of optoelectronic devices, such as solar cell and light-emitting diodes was drastically enhanced.
(Invited) Mesoporous Anatase Single Crystals for Efficienct Co(2+/3+) Based Dye-Sensitized Solar Cell
Authors: Kim Jung Ho
Published: February 2020

Highly crystalline mesoporous architectures are very promising for a number of applications due to their uniqute properties arising from their excellent electronic conductivity, structural coherence, mass-trasport-efficienct channels, and large surface area/pore volume. Herein, we report a facile synthesis approach to mesoporous anatase single crystals with special polydedral pores (approximately 7 nm). This achitecture is employed to contruct MK-2 sensitized solar cells using a cobalt redox shuttle, with a maximum efficiency of 8.7 % achieved, which is significantly higher than for analogous devices based on commercial Dysol TiO2 paste (6.3%).
A Controllable and Widely Applicable Electrochemical Anodization Process to Fabricate Porous Anodic Aluminum Oxide Membrane
Authors: Lin Yuanjing , Lin Qingfeng , Liu Xue , Gao Yuan , Fan Zhiyong
Published: February 2020

Inspired by the versatile applications of porous alumina nanostructures on solar cells, supercapacitors, biosensors, and so forth, research on fabrication of anodized aluminum oxide (AAO) with nanopore structure has achieved substantial advancements. Porous AAO membrane with nanostructures has become one of the most popular template materials for synthesis of a broad range of functional nanostructures such as nanowires, nanopillars, nanotubes, etc. While fabrication of highly ordered nanoporous AAO with tunable geometric features has been widely reported, its growth rate can be easily affected by the fluctuation of parameters such as acid concentration and temperature during the electrochemical anodization process. In order to meet the demand of fabricating AAO with various surface parameters and precise target pore depth control for scientific research and commercial applications, a controllable fabrication process is essential. Here, we developed a method which can implement precise pore depth control of AAO layer during the electrochemical anodization process, via monitoring the integrated charge. This method is applicable in a large voltage range and can be widely applied in fabrication of nanostructure with material such as TiO2and so on.
(Invited) New Electrochemiluminescent Materials for Bioanalysis
Authors: Xu Guobao , Qi Wenjing , Zhang Ling , Liu Xiaoqing , Hu Lianzhe
Published: February 2020

Electrochemiluminescence (ECL), or electrogenerated chemiluminescence, is light-emitting phenomenon from electrochemical reactions. It has broad applications, such as immunoassays, DNA probe assays, aptasensors, biological study, drug screening, medicine determination, and light-emitting devices. Various ECL systems, such as ruthenium complex, luminol, semiconductor nanocrystals, graphene oxide, and nanoclusters, have been reported. Generally, ECL reactions involve in luminophores, coreactants, and electrode. Electrocatalysts and/or additives are also frequently used. The performance of ECL depends significantly on these materials used [1-2].

We have recently developed various materials to improve ECL performance, such as new coreactants, new luminophores, noble metal nanocrystals, silica nanomaterials, new electrodes. The possible mechanism for enhanced properties are discussed. The analytical applications of some materials were demonstrated. The use of these materials extends applications, improve ECL sensitivity and simplify detection. [3-7].

 

Acknowledgements

This project was supported by the National Natural Science Foundation of China (No. 21475123 and 21175126).

References

   [1]  Z. Y. Liu, W. J. Qi, G. B. Xu, Chem. Soc. Rev., 2015, DOI: 10.1039/c5cs00086f.

   [2]  L. Zhang, W. X. Niu, G. B. Xu, Nano Today, 2012, 7, 586-605.

   [3]  X. Q. Liu, L. H. Shi, W. X. Niu, H. J. Li, G. B. Xu,  Angew. Chem. Int. Ed., 2007, 46, 421-424.

   [4]  W. J. Qi, Z. Y. Liu, J. P. Lai, W. Y. Gao, X. Y. Liu, M. Xu, G. B. Xu, Chem. Commun., 2014, 50, 8163-8166.

   [5]  L.Z. Hu, Z. Bian, H. J. Li, S. Han, Y. L. Yuan, L. X. Gao, G. B. Xu, Anal. Chem., 2009, 81, 9807-9811

   [6]  W. J. Qi, D. Wu, J. M. Zhao, Z. Y. Liu, W. Zhang, L. Zhang, G. B. Xu, Anal. Chem., 2013, 85, 3207.

   [7]  L. Zhang, W. X. Niu, W. Y. Gao, L. M. Qi, J. P. Lai, J. M. Zhao, G. B. Xu, ACS Nano 2014, 8, 5953–5958.
Cultivation of Rat Nerve Cells on Nanoimprinted Microstructures on Polydimethylsiloxane Sheets
Authors: Koshinuma Eiki , Maenosono Hirotaka , Endo Daisuke , Nishioka Yasushiro
Published: February 2020

Regenerative medical research has attracted remarkable attention after the development of induced pluripotent stem (iPS) cells [1]. Current focus in this field of research aims at restoring the function of the nervous system after trauma. The transplantation of neural stem cell suspension into an injured area has proven to be an effective treatment method. Several reports related to possible treatments of extensively injured areas and extension of remedy time have been published [2]. However, the shortcoming of this research is mainly associated with the limited ability of the nerve cells to regenerate. Other interesting areas of regenerative medicine are related to the artificial fabrication of the lost human functions such as the nervous system in a laboratory setting [3].

Polydimethylsiloxane (PDMS) films are very flexible and stretchable films and various kinds of micro patterns have been fabricated onto these using microelectromechanical system (MEMS) techniques such as nanoimprinting [4]. Here we report the cultivation of nerve cells on PDMS culture sheets with micro trench structures on a PDMS substrate fabricated using nanoimprinting.　We fabricated micro trench structures with varying widths of 15 and 150 μm and depths of 30 and 60 μm using the nanoimprint technique on a 100 μm thick polydimethylsiloxane culture sheet used as a biocompatible polymer culture sheet. Rat neurons were observed to grow after 3 days selectively within those micro trenches with widths larger than 15 μm, and they were coated with polylysine. Accumulation of glial cells was also observed in the trenches.

References

[1] K. Takahashi and S. Yamanaka, Cell, 126 (2006) 663.

[2] P. Brundin, J. Karlsson, M. Emgård, G. S. Schierle, O. Hansson, A. Petersén, and R. F. Castilho, Cell Transplant., 9 (2000) 179.

[3] R Singhvi, A. Kumar, G. P. Lopez, G. N. Stephanopoulos, D. I. Wang, G. M. Whitesides, and D. E. Ingber. Science, 264 (1994) 696.

[4] M. N. De Silva, R. Desai, and D. J. Odde. Biomed. Microdevices, 6 (2004) 219.
Plasma Assisted Low Temperature Synthesis of WSe2
Authors: Medina Henry , Chen Yu-Ze , Su Teng-Yu , Li Jiang-Kuang , Chueh Yu-Lun
Published: February 2020

The two-dimensional layered structure of transition metal dichalcogenides (TMDs) materials has attracted much attention due to their particular structure. The electrical properties show large differences depending on the choice of the metal employed. These TMD layered materials may exhibit metallic, superconducting, or semiconducting properties. Particularly, tungsten disulphide (WSe2) shows a semiconducting electronic structure that varies with their thickness. Previous studies using exfoliated WSe2, have demonstrated a particular ambipolar behavior with large on/off ration and large mobilities. Despite the exceptional electrical and optical properties of WSe2 reliable synthesis methods on large area are still in early stages. The use of large processing temperatures (over 800°C) restricts the use of substrates used for synthesis, which are able to bear high temperature. Furthermore, the films have to be transferred to an additional substrate due to the damage caused to the original substrate used for synthesis. In this work, we present a method to synthesize WSe2 from the reduction and later selenization of WO3. The oxygen atoms are replaced selenium in a plasma assisted chemical vapor deposition (CVD) system. By controlling the plasma power the process temperature can be further lowered from 800°C to 250°C. The thickness can be defined by precisely controlling the thickness of predeposited WO3. The plasma assisted synthesis of WSe2 develops a new approach that can be extended to other TMD layered materials; and due to the low temperature does not requires further transfer and is compatible with current silicon semiconductor processes (300°C)
Characterization of Compound Semiconductors using Aberration-Corrected Electron Microscopy
Authors: Smith David
Published: February 2020

Epitaxial growth of semiconductor materials presents many obvious challenges. In addition to preparation of the substrate surface and careful attention to the growth conditions, there are several additional obstacles for heterovalent structures based on two (or more) dissimilar materials. As well as lattice mismatch, which inevitably leads to strain and likely defect formation, valence mismatch and differences in thermal expansion, are further factors that can seriously impact the eventual epilayer quality. The transmission electron microscope has a wide range of imaging, diffraction and analytical techniques that can provide invaluable information about the often-competing effects of growth conditions and compositional differences. The development of aberration correction has enabled electron microscope information limits to be extended beyond the 1-Å resolution barrier, and makes it (almost) routine to achieve atomic-resolution imaging from many different types of materials. For elemental and compound semiconductors it is even possible to resolve the projections of individual atomic columns, often referred to as dumbbells, in the common <110> projection. Composition profiles across heterovalent interfaces, as well as bonding information at the atomic level, can also be achieved when using the probe-corrected configuration. The challenge for the electron microscopist is to utilize these enhanced capabilities to provide useful constructive feedback to the growers responsible for materials growth. In this talk, recent studies of II-VI/III-V, IV-IV, and III-nitride heterostructures using aberration-corrected electron microscopy will be described.
Bridging the Gap - Rediscovering Black Phosphorus As an Anisotropic Layered Material for Electronics and Optoelectronics
Authors: Wang Han
Published: February 2020

In this talk, I will discuss our recent work in introducing black phosphorus (BP) to the layered-material family as a novel anisotropic 2D material for electronic and optoelectronic applications [1] [2]. Narrow gap BP thin film (0.3 eV in bulk) serendipitously fill the energy space between zero-gap graphene and large-gap TMDCs, making it an promising material for near and mid-infrared optoelectronics [3]. BP thin films show high mobility above 650 cm2/V.s at room temperature along the light effective mass (x) direction, implying its promising potential for high frequency, thin-film electronics. Furthermore, its anisotropic nature within the plane of the layers may allow for the realization of conceptually new electronic and photonic devices impossible in other 2D materials. In the talk, I will also present our work in demonstrating 20 GHz black phosphorus radio-frequency transistors [4]. Our recent progress in characterizing the optical properties of monolayer BP [5] and in achieving large-area synthesis of black phosphorus thin film will also be discussed. I will conclude with remarks on promising future directions of black phosphorus research and how this new material is expected to benefit the next-generation electronics and photonics technologies.

References

[1] X. Ling, H. Wang*, S. Huang, F. Xia, M. Dresselhaus* “The Renaissance of Black Phosphorus” Proceedings of the National Academy of Sciences (PNAS), 112, 15, 4523-4530, 2015. doi: 10.1073/pnas.1416581112.

[2] F. Xia*, H. Wang*, Y. Jia “Rediscovering Black Phosphorus as an Anisotropic Layered Material for Optoelectronics and Electronics” Nature Communications, 5:4458 doi: 10.1038/ncomms5458, 2014.

[4] F. Xia, H. Wang, D. Xiao, M. Dubey, A. Ramasubramaniam “Two-Dimensional Material Nanophotonics” Nature Photonics, 8 (12), 899-907.

[3] H. Wang*, X. Wang, F. Xia*, L, Wang, H. Jiang, Q. Xia, M. Chin, M. Dubey, S.-J. Han “Black Phosphorus Radio Frequency Transistors” Nano Lett., 14 (11), 6424-6429, 2014.

[5] X. Wang, A. M. Jones, K. L. Seyler, V. Tran, Y. Jia, H. Zhao, H. Wang, L. Yang, X. Xu, F. Xia "Highly Anisotropic and Robust Excitons in Monolayer Black Phosphorus" Nature Nanotechnology, published on line,  2015. doi:10.1038/nnano.2015.71.
Inductively Coupled BCl3/Cl2/Ar Plasma Etching of High Al Content AlGaN
Authors: Douglas Erica , Sanchez Carlos , Baca Albert G. , Allerman Andrew , Kaplar Robert J.
Published: February 2020

III-nitride materials are researched extensively for high power electronics as well as for UV and visible optoelectronics. One of the many attractive qualities of III-nitride materials is their chemical stability. However, this quality can make material processing and device fabrication challenging. Though significant research has been carried out on processing III-nitride materials, comparatively few studies on high aluminum content AlGaN have been reported.

Al and Ga chlorides are volatile, making the gas chemistries of BCl3 and Cl2 attractive for use in dry etching. However, obtaining a smooth surface of AlGaN with a dry etch can be difficult due to two compounding effects: AlClx has a lower volatility than GaClx and the bond energy of Ga-N is lower than that of Al-N. This exploratory work aims to document some of the etch characteristics during inductively coupled plasma reactive ion etching (ICP-RIE) of high aluminum content AlGaN with a BCl3/Cl2/Ar plasma. Etch rate and surface morphology were investigated for Al0.85Ga0.15N. Etch rate lends insight into chemical tendencies of AlGaN alloys, while surface morphology is of interest in structures requiring subsequent processing steps such as gate recessing.

Our results show that lowering rf bias and increasing ICP power leads to smoother surfaces while maintaining an attractive etch rate. Also, the ratio of BCl3 to Cl2 significantly affects the surface roughness. In addition, we show significant improvement of surface roughness, even under sub-optimal etch conditions, by implementing a 1min BCl3/Ar plasma pre-treatment dry etch step prior to introducing Cl2 to the main etch using a BCl3/Cl2/Ar plasma.

This work was supported by the Laboratory Directed Research and Development (LDRD) program at Sandia. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Figure 1
Rotating Disk Electrode System for ORR Measurements at Elevated (>100 C) Temperature and Pressure Conditions
Authors: Fleige Michael J , Wiberg Gustav K H , Arenz Matthias
Published: February 2020

Rotating disk electrodes (RDE) are widely used for mimicking conditions in polymer electrolyte fuel cells (PEMFCs), for example for ex situ measurements of the catalytic activity of fuel cell catalysts. However, using RDE current densities are much lower compared to fuel cells, as in liquid electrolyte mass transport of dissolved reactant gases is limited by orders of magnitude lower concentrations and diffusion coefficients compared to gas phase. Furthermore, owing greatly reduced gas solubility by increasing vapor pressure of water at elevated temperatures, RDE studies in open systems have been limited to about 60 C.1 Employing RDE at elevated pressure would allow increasing reactant gas solubility and raising the boiling point of water. In addition, conc. phosphoric acid (PA), which is typically not considered in RDE studies due its even lower gas solubility, could be used for RDE measurements at sufficient gas concentration.

This presentation will discuss a developed RDE system that was integrated in an elevated pressure and temperature electrochemical cell setup reported earlier.2
,3 The RDE system is based on a magnet coupled drive, avoiding use of a rotary seal autoclave feed-through as proposed previously.4

We tested the magnet coupled RDE up to 100 bar pressure by studying the ORR on polycrystalline Pt as a test reaction in 0.5 M H2SO4 as well as conc. PA electrolyte. By increasing the pressure of oxygen in the closed cell, the diffusion limited current densities can be increased by almost two orders of magnitude in dilute electrolyte and RDE measurements in conc. PA are enabled. The RDE system also was successfully tested at elevated temperatures up to 140 C. Kinetic measurements of the ORR under elevated pressure conditions are currently in preparation.

1 U. Paulus, T.J. Schmidt, H. Gasteiger, and R.J. Behm, J. Electroanal. Chem. 495, 134 (2001).

2 G.K.H. Wiberg, M.J. Fleige, and M. Arenz, Rev. Sci. Instrum. 85, 085105 (2014).

3 M.J. Fleige, G.K.H. Wiberg,  and M. Arenz, under Review.

4 J. McBreen, W.E. O’Grady, and R. Richter, J. Electrochem. Soc. 131, 1215 (1984).
In Operando Vibrational Raman Studies of Chlorine Contamination in Solid Oxide Fuel Cells
Authors: Reeping Kyle Wyatt , Walker Robert A
Published: February 2020

Vibrational Raman spectroscopy coupled with voltammetry and impedance measurements was used to explore the effects of chlorine on solid oxide fuel cell (SOFC) performance and durability. Experiments described in this talk use newly developed vibrational Raman methods to acquire vibrational spectra from SOFC anodes exposed to CH3Cl and CH4.
 SOFC anodes were exposed to 110 ppm dry CH3Cl at 650°C for up to four hours while intermittently exposing the cell to methane for ten minute intervals. In these experiments Raman spectroscopy was used to monitor carbon accumulation kinetics and using a new optically accessible apparatus designed to fit on the stage of the Raman microscope. Electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) measurements performed under CH4 following 1 hour of exposure to CH­3Cl showed marked degradation.  This degradation was less apparent when the SOFC was operated with H2 following exposure to CH3Cl.  Under methane peak power reduced at a rate of 13.8% per hour in the presence of CH3Cl. EIS with CH4 following exposure to CH3Cl showed a small increase of bulk resistance yet consistent polarization resistance (Rpol) until the end of the final exposure, when Rpol increased dramatically. Observable carbon accumulation during CH3Cl exposure became less pronounced over time and eventually stopped accumulating at all suggesting that the primary effect of the Cl contaminant was deactivation of the Ni catalyst. Interestingly, these effects of Cl on SOFC performance with methane proved largely reversible as performance and carbon accumulation behavior recovered upon removal of the CH3Cl.
Reliable Determination of Surface Exchange and Bulk Diffusion Coefficients of La2NiO4+Î Cathode Materials for SOFC
Authors: Li Wenyuan , Guan Bo , Liu Xingbo
Published: February 2020

Accurate assessment of the electrode candidates for solid oxide fuel cell (SOFC) is crucial in understanding the underlying mechanisms of the performance, and in focusing our effort to the most promising ones. The evaluation of those materials can be divided into individual criterion so that unambiguous conclusions can be made on different aspects of the materials, such as the bulk diffusion (D) and surface exchange (k) coefficients. In this study, k of lanthanum nickelates La2NiO4+δ is characterized by electrochemical impedance spectroscopy (EIS) on dense electrode symmetric cells, and by electrical conductivity relaxation (ECR) on GDC-supported thin layer samples. Surface-dominant situation is confirmed in both approaches. k derived from polarization resistance is ~8.6×10-7 cm/s at 700oC in air, in comparison to ~1.6×10-5 cm/s fitted from ECR testing. The correlation between those two values is discussed based on the definitions and exchange mechanisms. To determine D accurately, pellet samples with D or D&k co-control are measured with ECR. The pre-known k values from the thin layer samples facilitate reliable fitting on D by reducing k variable in the equation. Such ECR strategy of avoiding D&k interplay successfully yields electrochemical parameters in good accuracy.
Potential of Knudsen Effusion Mass Spectrometry (KEMS) for Thermo Chemical Studies in Materials Science
Authors: Markus Torsten
Published: February 2020

The determination of valuable thermodynamic data for materials at elevated temperatures is a very important issue in Materials Science. This can be achieved by the elucidation of vaporization processes with high temperature mass spectrometry.

Knudsen Effusion Mass Spectrometry provides the identification of gaseous species present above condensed phases and permits the determination of their partial pressures up to a total pressure of 200 Pa.

The key for establishing model calculations using DG minimization tools like FactSage, Pandat or Thermocalc is the knowledge of the thermodynamic data of molecules and compounds. This includes the partial pressures of gaseous species, the standard enthalpies and entropies of formation of gaseous and condensed phases as well as their enthalpies and entropies of mixing and the knowledge of phases and chemical compounds which are formed upon reactions.

The method will be described and examples and an insight will be given how basic thermodynamic data are derived with the above mentioned method for the incorporation into thermodynamic databases. Examples of investigations carried out in our lab will be given.
Oxidation Behaviors of Ash Free Coals in a Coin Type Direct Carbon Fuel Cell
Authors: Lee Sang-Woo , Kim Tae-Kyun , Kim Yoo-Jeong , Lee Choong-Gon
Published: February 2020

Ash free coals (AFCs) extracted from bituminous, sub-bituminous, lignite, and anthracite coals were served as fuel in a direct carbon fuel cell (DCFC) and their oxidation behavior were investigated with electrochemical method of steady state polarization. AFCs were produced by a micro-wave method with a polar solvent of NMP. The electrochemical oxidation behaviors of AFCs were investigated in a coin type DCFC. The extraction yields are bituminous > sub-bituminous > lignite > anthracite. However, the open circuit voltages and voltages at a polarization state were similar among the AFCs. Regardless of the raw coal species the AFC has similar oxidation behavior in a direct carbon fuel cell.
Mass Transport in Oxide Thin Films - Visualization and Control
Authors: Kim Jae Jin , Chen Di , Bishop Sean R. , Cook Stuart N. , Tuller Harry L.
Published: February 2020

Device miniaturization has long stimulated great interest in the development of thin films and means for the characterization of their properties.  This trend has more recently been directed towards solid state ionic devices, stimulated by the growing interest in micro-batteries, -fuel cells and –sensors.  Mass transport is likewise believed to control the operation of one of the latest memory technologies based on the so-called memristive effect. 

Whether in bulk or thin film form, a fundamental understanding of oxygen defect equilibria and transport kinetics is essential for achieving enhanced performance and longevity in many oxide-based device applications. The ability to diagnose a material’s behavior under operating conditions in situ, is therefore of importance.  Achieving this in thin films is often more challenging given their low mass and support-film interactions.  Here we present experimental results obtained by a novel experimental technique developed in our laboratory capable of simultaneously performing in situ optical absorption and electrochemical impedance spectroscopy (EIS) measurements over a wide range of temperatures and controlled atmospheres.  We show, when applied to model materials systems such as PrxCe1-xO2-δ
(PCO), that these techniques are capable of deriving a detailed picture of the defect equilibria and transport properties of such materials and determining whether and to what degree they differ from bulk properties. We also show how monitoring time and spatially dependent changes in optical absorption can be used to study oxygen exchange and diffusion kinetics and discuss the impact of surface chemistry and metal current collector on the reaction kinetics. Finally, we report on recent color front migration studies in PCO films designed to extract oxygen diffusivities.
Vertical-Aligned Nanocomposites Oxide Thin Films with Enhanced Ionic Conductivity
Authors: Su Qing , Zhang Wenrui , Jacob Clement , Yoon Daeil , Manthiram Arumugam , Wang Haiyan
Published: February 2020

Oxide thin films with high ionic conductivity are crucial for the satisfactory operation of sustainable energy production systems (e.g. fuel cells) that provide efficient and environmental-friendly electricity for human beings. Key materials science efforts associated with developing oxides with high ionic conductivity will be reviewed. Of particular importance for developing thin film oxide materials is high performance and good stability in the operation temperature range. A vertical-aligned nanocomposites (VAN) approach will be reviewed in this talk. It creates vertical interface of two oxide materials and provides a new design paradigm to tune/manipulate functionalities that cannot be obtained in individual constituents.

Within recent extraordinary results in VAN field, two major examples corresponding to ionic conducting oxide thin film will be presented: (1) to design vertical-aligned electrolyte/electrolyte nanocomposites with superior vertical ionic conductivity, and (2) to use vertical-aligned electrode/electrolyte nanocomposites as an interlayer to increase the catalytic reaction probability. Opportunities of tuning/controlling functionality of such VAN systems will be introduced.
Electrochemical Characterization of Columnar Anodic Thin Films Deposited By Pulsed Laser Deposition
Authors: Cavazos Sepulveda Adrian Cesar , Bi Lei , Traversa Enrico
Published: February 2020

(La0.75Sr0.25)0.95Cr0.5Mn0.5O3-∂ (LSCM) is a promising redox-stable material for solid oxide fuel cell (SOFC) anodes with hydrocarbon fuels. LSCM requires additional catalysts to boost the anodic performance due to a relatively low electrochemical activity for hydrocarbon oxidation. Nickel, which is usually employed as the catalyst, provokes coking and degrades with sulphur. Therefore, an alternative approach to reduce the area specific resistance (ASR) needs to be devised, such as to significantly increase the density of the triple phase boundary (TPB) sites.  

A solution can be to create an anode with vertically aligned columns with submicron diameter. To reach this goal, thin films of vertically aligned LSCM columns were deposited by pulsed laser deposition (PLD). Initially, LSCM was deposited on Si wafers to optimize the columnar morphology. Then LSCM anodes were deposited on Sm0.2Ce0.8O2-∂ (SDC) pellets and were subjected to heat treatments under ambient and reducing atmospheres. The morphology of the samples was characterized using scanning electron microscopy (SEM). Electrochemical impedance spectroscopy measurements were performed to investigate the anode performance under H2 and CH4 environments.
Let`s Design the Structural-Defect Twists in Solid State Ionic Films: Strained Architectures for Novel Electronics and Energy Conversion Devices
Authors: Rupp Jennifer L. M.
Published: February 2020

The next generation of energy conversion and storage devices, information memories and neuromorphic computer logics in electronics rely largely on solving fundamental questions of mass and charge transport of oxygen ionic defects in materials and their structures. Here, understanding the defect kinetics in the solid state material building blocks and their interfaces with respect to lattice and interfacial strains are the prerequisite to design new material properties beyond classic doping. Through this presentation basic theory and model experiments for solid state electro-chemo-mechanics and lattice strain modulations is being discussed as a new route for tuning material and properties in ionic conducting oxide film structures up to new device prototypes. Central are the making and manipulation of the mechanics in solid state ionic conducting heterostructures, in-situ spectroscopic and microscopic techniques coupled with electrochemical micro-measurements to probe near order structural bond strength changes relative to ionic and electronic diffusion kinetics and the materials integration to new optimized device architectures and operation schemes.

We will discuss basic fundamentals of oxygen ionic transport under strain for heterostructures and exemplify their impact on novel classes of electrochemical devices such as for energy harvesting: "Micro-Energy Conversion Membranes under Tuned Strain Fields", and for innovative types of ionically-operated data storage and logics: "Strained Memristor micro-Dots for Information Storage" or "Oxygen-Ionic Controlled Non-Binary Transfer Logics to replace Electronically Operated Transistors".

1) The Effect of Mechanical Twisting on Oxygen Ionic Transport in Solid State Energy Conversion Membranes

Y. Shi, A.H. Bork, S. Schweiger and J.L.M. Rupp

Nature Materials, accepted  (2015)

2) A Micro-Dot Multilayer Oxide Device: Let’s Tune the Strain-Ionic Transport Interaction

S. Schweiger, M. Kubicek, F. Messerschmitt, C. Murer and J.L.M. Rupp

ACS Nano, 8, 5, 5032 (2014)

3) Memristor Kinetics and Diffusion Characteristics for Mixed Anionic-Electronic SrTiO3-δ: The Memristor-based Cottrell Analysis Connecting Material to Device Performance

F. Messerschmitt, M. Kubicek, S. Schweiger and J.L.M. Rupp

Advanced Functional Materials, 24, 47, 7448 (2014)
Proton Conducting Micro-Solid Oxide Fuel Cells with Nanoscale Palladium Interlayers
Authors: Adam Suhare , Ramanathan Shriram
Published: February 2020

We will consider solid oxide fuel cells with electrolyte membranes whose dimensions approach the tunneling limit. Suspended oxide membranes allow exploring ionic and electronic conduction in quasi-2D structures without interference from the substrate at temperatures below 600C. One can consider minority carrier transport mechanisms at such lengthscales to design solid electrolytes wherein dc ionic conductivity alone may not be the critical factor. The thermo-mechanical stabilty of such membranes are in turn closely related to the electroneutrality conditions under the operating environment. Cation valence change driven lattice distortions can profundly modify the strain states and dictate material selection. At the same time, oxide heterostructures can be fabricated in freestanding manner to explore the possibility of local energy storage in an electrode at such low temperatures. We will consider opportunities with Mott insulators for the same wherein the onset of correlated metallic state is closely linked to disorder. Representative examples of fuel cells operating directly in methane will be presented.
Study of the Effect of Calcination Temperature on the Morphology and Activity of Iridium Oxide Electrocatalyst Supported on Antimony Tin Oxide (ATO) for PEM Electrolyser Technology
Authors: Karimi Fatemeh , Peppley Brant A. , Bazylak Aimy
Published: February 2020

Iridium oxide nanoparticles supported on Antimony Tin oxide (ATO) have been used for oxygen evolution reaction in polymer electrolyte membrane (PEM) electrolysis. The morphology, crystallinity, catalyst-support interaction and electrocatalyst oxygen evolution reaction (OER) activity of the catalyst Iridium oxide supported on ATO at various calcination temperatures have been studied. The supported catalyst was synthesized using the modified Polyol method. The synthesized electrocatalyst was physically characterized by Differential Scanning Calorimetry, Thermogravimetric Analysis, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Brunauer, Emmett and Teller BET surface area measurements. The catalyst was electrochemically characterized by cyclic voltammetry and polarization measurements in a typical three electrode system. The main focus of this work is to study the effect of calcination temperatures of 200, 350, 500 and 700 ⁰C. Iridium oxide phases formed as a function of temperature, degree of crystallization as well as the interaction of Iridium oxide nanoparticles with the ATO nanoparticles support will be presented.
Solvent-Engineering of High-Performance Non-Precious Metal Catalysts
Authors: Martinez Ulises , Dumont Joseph H , Chung Hoon T , Artyushkova Kateryna , Mohite Aditya , Gupta Gautam , Zelenay Piotr
Published: February 2020

Non-precious metal catalysts (NPMCs) with high volumetric activity and low H2O2 yield are being considered as potential replacement for Pt-based oxygen reduction reaction (ORR) catalysts in the PEFC cathode. State-of-the-art NPMCs are typically synthesized from highly heterogeneous precursors and amorphous carbon materials [1-2], which complicate the understanding and development of new materials with improved activities. Recent efforts have been focused on developing carbon nanostructures with superior structural and functional properties from less complex systems, such as graphene oxide (GO). Catalysts derived from GO are more homogeneous and possess several highly desirable properties, such as good chemical stability and excellent conductivity. More importantly, they can be functionalized in a controlled manner [3]. Our efforts have demonstrated the importance of the effective removal of intercalated water on the structure, and consequently, the ORR activity of GO-based NPMCs [4].

In this study, we report the synthesis of solvent-engineered NPMCs with improved performance based on our findings from the more homogenous GO-based systems (Fig. 1). Despite the widely known presence of residual water in GO and more complex carbon systems, no report exists about the effective removal of water to improve the catalyst activity. In this presentation, we focus on the effect of solvent-engineered pretreatments on the structure and function of the ORR catalysts.

References

Wu, G., More, K. L., Johnston, C. M., Zelenay, P., Science, 332, 443-447 (2011).

Bashyam, R., Zelenay, P., Nature, 443, 63-66 (2006).

Qu, L., Liu, Y., Baek, J.-B., Dai, L., ACS Nano,
4, 1321-1326 (2010).

Gupta, G et al, Highly Tunable and Ordered Graphene-Oxide-Based Materials for Energy Applications, 2014 ECS and SMEQ Joint International Meeting (October, 2014).

Figure 1
Pore Network Modeling of Gas Diffusion Layer As a Support to Better Understand Water Management in Proton Exchange Membrane Fuel Cells
Authors: Pauchet Joel , Prat Marc , Belgacem Najib , Agaesse Tristan , Straubhaar Benjamin
Published: February 2020

PEMFC (Proton Exchange Membrane Fuel Cells) is considered as a promising solution for producing clean energy. To increase its industrial development for automotive application, performance and durability are still to be improved and cost needs to be reduced.

Water management is one of the most important remaining bottlenecks to increase performance and durability of PEMFC. Nevertheless, despite numerous studies, many questions remain open and for instance it is not possible yet to propose reliable optimization of the porous layers (Gas Diffusion Layer, Active Layer…) to optimize transfers (and especially water management) in the MEA and thus increase performance and durability. One main reason is that water transfers in the MEA, and also the link between structural properties of these layers and performance, are not correctly described and understood. For instance, classical modeling used in PEMFC do not account for these structural properties despite the fact that they have a huge influence on performance.

More descriptive modeling approaches have been proposed in the last years to better understand the link between structural properties of these layers and transfers in the MEA. Amongst those, Pore Network Modeling (PNM) is more and more applied to GDL. This approach, classically used for soil application, allows simulating two-phase flows in porous media taking into account local properties (Pore/Throat Size Distribution, local structure, local wettability…) which is an important progress compared to classical PEMFC modeling based on Darcy approach.

This keynote lecture focuses on PNM and its application to GDL to better understand (gas and liquid) transfers in the MEA and to try and link local structural properties of GDL to the performance of PEMFC. Experimental results are presented all along the discussion either to validate the main hypothesis or to validate the PNM simulations.

After a description of the PNM approach, two-phase transfers inside GDL are discussed: influence of wettability, thickness, local structure…; study of GDL degradation; role of the Micro Porous Layer (MPL); validity of classical Darçy “laws”… The two classical scenarii of water transfers in the GDL (liquid injection and/or condensation) are also discussed. The coupling between PNM and performance model, which is a step towards upscaling of PNM, is introduced by the analysis of performance loss of PEMFC as a function of hydrophobicity loss of GDL. Advanced results comparing two-phase PNM based on real 3D images of GDL and X-Ray tomography of liquid pattern inside the GDL are also presented as a step towards even more representative PNM modeling of MEA components.

Finally it is shown how PNM can be extended to the Active Layers by coupling two-phase transfers to charge transfers by electrochemistry.
Surface Characterization and Platinum-like Electrocatalytic Activity of Nano-Scale Platinum Deposited on Transition Metal Carbide Nanotubes via Atomic Layer Deposition
Authors: Saha Shibely R. , Witters Zachary Everett , Leonard Brian M. , Li Dongmei
Published: February 2020

Due to the similar electronic and geometric structures between transition metal carbides (TMC) and Platinum (Pt), Pt supported on TMC surfaces (a.k.a., Pt/TMC) has been the focus of significant research interest. This presentation focuses on a new class of electrocatalyst fabrication in which high purity β-molybdenum carbide (referred to as Mo2C hereafter) was synthesized into hollow nanotubes and subsequently modified with nanoscale platinum particles (1-5 nm) deposited via rotary Atomic Layer Deposition (ALD) (referred to as Pt/Mo2C).  X-Ray diffraction (XRD) measurements of Mo2C and Pt/Mo2C showed no molybdenum peaks and a very small amount of unreacted multi-wall carbon nanotubes (MWCNT) in the Mo2C samples, indicating that Pt was primarily supported on Mo2C nanotubes. Strong interaction between Pt nanoparticles and the Mo2C nanotube support was observed in lattice spacing changes from high resolution transmission electron microscopy (HRTEM) images, in addition to Pt binding energies from x-ray photoelectron spectroscopy (XPS) results of Pt/Mo2C.  Atomic adsorption spectroscopy (AAS) measurements of Pt mass in Pt/Mo2C samples showed an average of 2.4% Pt loading in Pt/Mo2C nanoparticles. The electochemically active surface area (ECSA) of the 2.4% Pt/Mo2C was found to be 70% higher than commercial 20% Pt/C, indicating an increased number of electrochemically active sites, possibly resulting from the interaction between ALD-deposited Pt nanoparticles and Mo2C nanotube support. 

Cyclic voltammograms of the 2.4% Pt/Mo2C catalyst showed higher hydrogen oxidation reaction (HOR)  activity than commercial 20% Pt/C, while bare Mo2C did not demonstrate any significant HOR activity. For the hydrogen evolution reaction (HER), the 2.4% Pt/Mo2C showed similar activity to the 20% Pt/C, while bare Mo2C nanotube showing noticeable, but not significant HER activity.  Another focus of this talk is to present the 2.4% Pt/Mo2C catalyst performance in a PEMFC anode (HOR), which outperformed the commercial 20% Pt/C with up to a 403% increase in peak power density and 448% increase in current density. Consequently, the reported Pt/Mo2C validates a new fabrication approach for practical nanoscale electrocatalysts where the supported catalyst is deposited via atomic layer deposition onto high purity transition metal carbide nanotubes. Ongoing work in our group focuses upon long-term stability, the corrosion mechanism, and ORR activity of the Pt/Mo2C catalyst.  Furthermore, we are conducting systematic investigations on how the number of ALD cycles affects the size and distribution of Pt on Mo2C nanotube and subsequent HER, ORR activity and PEMFC performance of resultant catalysts.
Materials and Cell Designs for Bipolar Fuel Cells
Authors: Ahlfield John M. , Deshpande N. A. , Liu Lisha , Huang Wenjiao , Chu Deryn , Kohl Paul A
Published: February 2020

Bipolar membranes fuel cells utilizing both anion and cation conductive materials have several advantages compared to their purely acidic or alkaline counterparts due to improved water management and electrode kinetics. Material transport properties play an important role in determining viability of membrane and ionomer materials. Additionally, the material at the cation/anion junction is critical to device performance, as it must conduct ions to the interface in addition to mechanically binding the membranes. A series of devices using different interfacial materials has been fabricated for use in direct methanol and hydrogen fuel cells. These fuel cells were characterized by performance metrics and electrochemical impedance spectroscopy to determine specific areas for improvement in the bipolar devices. Operation under varying humidity was studied in order to understand water management necessary for bipolar fuel cells. This work will drive the future optimization of bipolar devices.

Financial support from US Office of the Deputy Assistant Secretary of the Army for Defense Exports and Cooperation (DASA-DE&C) is gratefully acknowledged.
Platinum Dissolution from Carbon Supported Nanoparticles
Authors: Wang Zhongqi , Tada Eiji , Nishikata Atsushi
Published: February 2020

Platinum (Pt) dissolution concerns the instability of Pt-based cathode catalysts for polymer electrolyte fuel cells (PEFCs). Studies on unsupported Pt, polycrystalline plates or electroplated films, suggest that Pt dissolution relates to Pt oxide formation and reduction. Pt dissolution from the carbon supported nanoparticles, however, is rarely discussed. In this study, we investigated Pt dissolution using commercial carbon supported nanoparticles (Pt/C). We prepared Nafion-free inks by mixing Pt/C samples with H2O and isopropyl alcohol (IPA). We evaluated the amount of Pt dissolution over potential cycling tests using inductively-coupled plasma-mass spectrometry (ICP-MS). We also scrutinized the Pt dissolution behaviors from the Pt/C in a single cycle using a channel flow double electrode (CFDE)1.

The Pt/C samples we used were produced by Tanaka Kikinzoku Kogyo (TKK); the Pt particle size distributions before test were characterized by TEM. For each Pt/C sample, we mixed about 10 ~ 15 mg Pt/C with 3.8 ml H2O and 1.2 ml IPA, and sonicated the mixture in an ice bath for 60 mins. We loaded an appropriate amount of ink on a glassy carbon (GC) substrate. The Pt/C electrode was then dried under an ambient atmosphere for 120 mins. The Pt/C electrode was cycled 30 or more times between 0.05 and 1.4 V (vs. SHE) in 0.5 M H2SO4 to remove organic adsorbents and to obtain a reproducible electrochemical surface area (ECSA). The ECSA was used for normalization of Pt dissolution.

First, we conducted 300 cycles of potentials cycling in 0.5 M H2SO4 in a stationary cell. The geometric surface area of the GC was ca. 0.25 cm2 and we loaded about 2 µl ink on it. Two upper potential limits (E
U) of 1.0 and 1.4 V were used with a same lower potential limit (EL

) of 0.4 V. The testing solutions were analyzed by ICP-MS.

Second, we tested Pt dissolution from the Pt/Cs using a CFDE in argon-deaerated 0.5 M H2SO4. The CFDE consisted of a GC working electrode (WE) and a gold (Au) collector electrode (CE). The geometric surface area of the GC was ca. 0.05 cm2 and we loaded about 0.6 µl ink on it. The CV of a 46wt% Pt/C obtained in the CFDE at 25oC shows that the Pt/C is relatively stable without Nafion. Pt dissolution from the Pt/C-WE was monitored by the CE. The CE collected 30% of dissolved Ptn+. We set the CE at 1.4 V for detecting Pt2+, and at 0.7 V for Pt4+. We also set the CE at 0.3 V for collection of both Pt species.

The ICP-MS data evaluate the overall amount of Pt dissolution and CFDE data provide details of the dissolution behaviors against potential. Using both data, we discuss the mechanism of Pt dissolutions from the Pt/Cs with respect to temperature, E
U, and Pt particle size.

Reference

1. Z. Wang, E. Tada, and A. Nishikata, J. Electrochem. Soc., 161 (4), F380 (2014).

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