bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Numerical Simulation of Sintering Process in Solid Oxide Fuel Cell Anode
Authors: Shikazono Naoki , Hara Shotaro 
Published: February 2020

Solid oxide fuel cell (SOFC) is expected as a promising energy conversion device because of its high efficiency and fuel flexibility. It is widely known that electrode microstructures are of great importance for attaining high performance as well as high reliability of SOFCs. In the SOFC fabrication processes, sintering of sub-micron scale ceramic and metallic powders is one of the most important step to achieve efficient and reliable electrodes. In addition, microstructural changes in SOFC anodes associated with particle sintering during high temperature operation may lead to severe performance degradation. Thus, in order to develop more reliable electrodes of SOFC, a method that can offer quantitative information of sintering behavior at the sub-micron scale is highly demanded.
Accurate prediction of microstructure evolution during sintering, even in single-phase systems, is still very challenging. This is because sintering behavior is deeply affected by the three-dimensional (3D) complex geometries of the powder compacts, such as grain and pore size distributions, their shapes, relative density and coordination number, etc. Among many types of numerical approaches, a mesoscale kinetic Potts Monte Carlo (KMC) method has the potential to overcome this difficulty [1]. This method is capable of capturing three dimensional microstructural evolution from the initial to the final stages of solid-state sintering. However, the underlying kinetics at the sub-micron scale are not yet completely understood. Validation of the results using quantitative 3D microstructure data is indispensable to develop a numerical simulation tool which can reproduce proper sintering trajectory of real powder sintering.
In the present study, KMC simulations of nickel (Ni) and nickel oxide - yttria stabilized zirconia (NiO-YSZ) composite are carried out starting from the green powder microstructure obtained using focused ion beam - scanning electron microscopy (FIB–SEM). Quantitative topological changes during sintering of real powder compacts are obtained by FIB–SEM. This technique offers a great advantage because of its high resolution, which is sufficient to capture the 3D geometric nature of sub-micron-sized powder compacts (typically < 1/10 of the powder size). The simulated temporal trajectories of microstructural parameters are compared with the experimental data from FIB-SEM to verify the numerical modeling results.
[1] Hara, S., Ohi, A. and Shikazono, N., Sintering Analysis of Sub-Micron-Sized Nickel Powders: Kinetic Monte Carlo Simulation Verified by FIB-SEM Reconstruction, J. Power Sources, 276, pp. 105-112 (2015).
(Invited) The Stability of Solid Oxide Fuel Cells: Insights through in Situ X-Ray Tomography
Authors: Kennouche David , Chen-Wiegart Yu-chen Karen , Yakal-Kremski Kyle J , Wang Jun , Gibbs John , Barnett Scott A , Voorhees Peter W 
Published: February 2020

With the advent of high energy x-ray sources it is now possible to follow microstructural evolution in three dimensions and as a function of time. The ability to observe and quantify the the evolution processes provides fundamentally new insights into factors controlling the microstructure of materials. We illustrate this through observation of the high-temperature microstructural evolution of a solid oxide fuel cell Ni-Yttria-stabilized zirconia (Ni-YSZ) anode. Unlike prior studies that compared microstructural differences between different anodes, this three-dimensional measurement directly shows the changes occurring in the same region of an anode, enabling a new understanding of evolutionary processes. High-temperature ageing for 48 h at 1050 °C yielded substantial structural changes in the Ni, YSZ and pore networks, including coalescence of Ni particles, leading to a three-fold decrease in three-phase boundary length. The implications for long-term degradation of fuel cells will be discussed, as well as time resolved x-ray tomography.
(Invited) Single Step Direct Electrocatalytic Reduction of CO2 towards CO and Hydrocarbons
Authors: Schmid Guenter , Reller Christian , Krause Ralf Karl , Schmid Bernhard , Neubauer Sebastian Stefan , Fleischer Maximilian 
Published: February 2020

Switching from fossil based to renewable power generation requires the installation of large overcapacities of wind and solar due to their intermittency. Storage or conversion possibilities are essential due the volatility of electricity. Economic feasibility is difficult when considering the low fossil energy carrier prices and the physical efficiency limitations of the processes. Therefore, we choose to focus on high volume chemical feedstock such as Ethylene or CO, where the chemical value exceeds by far its pure heating value.

Electrocatalyts facilitate the conversion of CO2 to valuable base chemical feedstocks – for selectivity improvements substantial advances in electrode design are required. Depending on the electro catalytic system, CO2 can be electrochemically reduced to carbon monoxide (CO), methane (CH4), ethylene (C2H4) and various other hydrocarbons even in aqueous media. CO could be obtained with faradic efficiencies over 90% at current densities exceeding the industrial necessary level of 100 mA/cm² with a total energy efficiency approaching 50%. Ethylene is more challenging due the highly complex reduction process involving 12 electrons and 8 protons. Faradic efficiencies up to 57% for ethylene at current densities above 150 mA/cm² could be obtained using in-situ-deposited nano-structured copper based electrocatalysts. In many experiments we observed a large gap in the sum of the current efficiencies of gaseous products to 100% FE. It is well known, that the electro-reduction of CO2 also yields liquid products. This gap could be fully closed by detailed analysis of the electrolyte revealing a strongly pronounced formation of ethanol (> 20% FE) accompanied by wide range of C1-C3 alcohols, carboxylates and ketones in yields up to ~ 5%. To the best of our knowledge, the here reported faradaic efficiencies for ethanol above 20% in a current density regime above 150mA/cm2 have been unpresent in the literature so far. In addition time resolved parallel analysis of the gaseous and liquid product distribution revealed striking relationships between different species i.e. the parallel formation of ethylene and ethanol.

Figure 1
(Invited) In Operando Optical Studies of Solid Oxide Electrochemical Cells
Authors: Owrutsky Jeffrey C , Kirtley John D. , Qadri Syed Noorullah , Steinhurst Daniel A , Eichhorn Bryan W. , Walker Robert A 
Published: February 2020

Solid oxide fuels cells (SOFCs) are promising devices for fuel flexible and efficient power generation. The high temperatures (>700 oC) required enable operation on hydrocarbon fuels but avoiding degradation by carbon deposition remains a challenge. In operando optical methods, including Raman and Fourier Transform infrared emission spectroscopy (FTIRES) and near infrared thermal imaging (NIRTI), have been developed to characterize and understand molecular and material processes in SOFCs in order to improve their performance and durability. Recent results include studies of SOFCs on methane operating under various reforming conditions. Dry reforming, using carbon dioxide, which is also simulated biogas, reveals a high degree of anode activity based on substantial cooling of the anode but also reduced carbon formation compared to unreformed methane. An intermediate amount of anode cooling and carbon formation is observed with steam reforming. Related studies have been carried out to assess the effectiveness of carbon removal by steam and carbon dioxide using a new, duplex method in which NIRTI and FTIRES are performed simultaneously. Also, NIRTI has been used in conjunction with near ambient pressure X-ray photoelectron spectroscopy (APXPS) to identify spatially resolved regions where the emission intensity changes are observed due to ceria reduction during water electrolysis. The results are consistent with the APXPS results and interpretation for the reaction. The observations also provide an example of emissivity rather than temperature changes observed with high temperature thermal imaging in solid oxide electrochemical cells.
The Effect of Precusor Gel Desiccation, Ceria Oxide Pre-Infiltration, and Precursor Solution Additives on Infiltrated Lanthanum Strontium Ferrite-Lanthanum Strontium Cobaltite Solid Solution Nano-Particles
Authors: Burye Theodore E. , Tang Hongjie , Nicholas Jason D. 
Published: February 2020

Abstract

Here, average La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) nano-particle sizes were controllably modulated from 48 to 24 nm by desiccating La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) precursor nitrate solutions or infiltrating La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) precursor nitrate solutions into Ce0.9Gd0.1O1.95 (GDC) scaffolds pre-infiltrated with a large amount of GDC nano-particles. Scanning electron microscopy, thermo-gravimetric analysis, and x-ray diffraction experiments conducted on decomposed/decomposing precursor gels within, and outside of, porous GDC scaffolds showed that desiccation and pre-infiltrated nano-GDC resulted in reduced nitrate decomposition temperatures and reduced La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) average particle sizes. GDC scaffolds infiltrated with La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) precursor gels, desiccated with CaCl2, and subsequently fired at 700oC, contained high-phase purity La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) nano-particles with average particle sizes ranging from 31-27 nm. GDC scaffolds pre-infiltrated with nano-GDC infiltrated particles, infiltrated with La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) precursor gels and subsequently fired at 700oC, contained high-phase purity La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) nano-particles with average particle sizes ranging from 29-24 nm. In contrast to comparable, standard nano-composite cathodes (NCC’s) containing 48 nm average-sized La0.6Sr0.4CoxFe1-xO3-δ (0≤x≤1) particles and achieving polarization resistances of 0.10 Ωcm2 at 640°C, the best CaCl2-dessicated NCC’s achieved 0.10 Ωcm2 at 600°C, while the best pre-infiltrated nano-GDC NCC’s achieved 0.10 Ωcm2 at 540°C.

Acknowledgements

This work was supported by National Science Foundation award number CBET-1254453.

Figure 1.

Scanning electron micrographs for La0.6Sr0.4CoxFe1-xO3-δ nano-particles produced inside a GDC scaffold at 700°C for citric acid-containing precursor gels that were standard (a-e) desiccated (f-j) and pre-infiltrated nano-GDC oxide particles (k-o). Note, LSF = La0.6Sr0.4FeO3-x, LSFC = La0.6Sr0.4Fe0.8Co0.2O3-x, LSCF55 = La0.6Sr0.4Fe0.5Co0.5O3-x, LSCF = La0.6Sr0.4Co0.8Fe0.2O3-x, and LSC = La0.6Sr0.4CoO3-x. All scale bars are 50 nm in width.

Figure 1
Fuel Cell Performance of (Cyanamide + Polyaniline)-Iron-Carbon Cathode Catalyst
Authors: Chung Hoon T , Yin Xi , Purdy Geraldine M , Martinez Ulises , Cullen David A. , Mukundan Rangachary , More Karren L. , Zelenay Piotr 
Published: February 2020

Polymer electrolyte fuel cells (PEFCs) are a green alternative to the internal combustion engine, particularly in the transportation sector. Currently platinum (Pt) is a state-of-the-art catalyst for both anode and cathode. As the oxygen reduction reaction (ORR) is inherently six orders of magnitude slower than the anodic hydrogen oxidation, there is a significantly higher Pt loading requirement for the cathode. Volatile pricing and geopolitical instabilities of the precious-metal market have thus enthused the development of entirely non-platinum group metal (non-PGM) cathode catalysts for PEFCs.
With the recently realized highly active non-PGM catalyst development,1-5 implementing these catalysts into PEFCs and demonstrating high fuel cell performance (i.e., competitive with state-of-the-art Pt catalysts) is becoming increasingly needed. Up until now, a majority of non-PGM catalysts have been tested under H2-O2 conditions, which tend to mask the true effects of mass transport likely encountered under practical automotive applications conditions (H2-air).
Recently, we introduced a new non-PGM ORR catalysts derived from two nitrogen precursors, cyanamide and polyaniline, both exhibiting high H2-air fuel cell performances.6 To understand the fuel cell performance of these catalysts more deeply under H2-air condition, we have tested/characterized theses catalysts using diverse H2-air fuel cell test conditions and characterization methods: H2-helox fuel cell testing, impedance characterization, as well as carbon dioxide and fluoride emissions detection. These results promise to provide a better insight into the performance of the dual nitrogen precursor catalysts under the conditions approaching those of an automotive fuel cell power system.

Acknowledgement

Financial support for this research by DOE-EERE through Fuel Cell Technologies Office is gratefully acknowledged. Microscopy research supported through a user project at ORNL’s Center for Nanomaterials Sciences, which is an Office of Science User Facility.

References

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A. Serov, K. Artyushkova and P. Atanassov, Adv. Energy Mater., 4, 1301735 (2014).

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H. Chung, D. Higgins, D-H. Kim, G. Wu, U. Tylus, K. L. More, D. Cullen, P. Zelenay, 227th ECS Meeting, Chicago, IL, USA (2015).
Electrochemical Deposition of PGM Based Fuel Cell Electro Catalysts
Authors: Mathe Mkhulu K. , Modibedi Remegia Mmalewane , Khotseng Lindiwe Eudora , Nonjola Patrick thabo , Ozoemena Kenneth I. 
Published: February 2020

The talk will focus on the applications of electrochemistry and nanotechnology for the synthesis and characterisation of electro-catalysts used in fuel cells. Electrochemical methods such as, Electrochemical Atomic Layer Epitaxy (EC-ALE) and Electrochemical Atomic Layer Deposition (EC-ALD) are being explored for synthesis as other potential techniques used in the improvement of PGM based electro-catalysts for proton electrolyte membrane fuel cells (PEMFCs). Synthesis and characterisation of these electro-catalysts (nanostructured/ nanomaterials), including their proposed application in fuel cells, will be discussed as part of the talk. The connection of the electro-catalysis work to alkaline direct alcohol fuel cells (DAFCs) with focus on micro fuel cells and anionic membrane development will also be highlighted.

ACKNOWLEDGEMENT

The author wish to acknowledge the DST, NRF and CSIR for funding.
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Comparison of TiO2 and SnO2 Electron Transport Layers in Planar Perovskite Solar Cells
Authors: McCarthy Melissa , Walsh Adrian , Ryan Louise , Kegel Jan , Pemble Martyn E , O'Brien S , Povey Ian M 
Published: February 2020

Over the past few years single junction perovskite solar cells have been extensively studied with reported power conversion efficiencies approaching 20% [1-3]. Despite such advances, high efficiency combined with low fabrication cost, parasitic absorptions and long term stability have remained issues. One approach to curtail some of these obstacles has been the investigation of planar architectures where the mesoporous TiO2/Al2O3 is removed from the cell and the electron transport layer (ETL) is reduced to a nanometre scale compact charge blocking layer [4]. Typically this layer has been TiO2 but more recently band gap engineering studies have shown that SnO2 has significant potential in removing TiO2 hysteresis effects whilst maintaining efficiencies [5]
In this study we examined planar stacks comprising glass/FTO/ETL/perovskite/spiro MeOTAD hole transport layer/contacts with an aim to further optimize the metal oxide ETL. The metal oxides studied in this work were atomic layer deposition grown SnO2, nominally undoped TiO2 and doped TiO2, all grown at temperatures below 180°C to align with the requirements of silicon-perovskite heterojunction cells [6]. The influence of the ALD growth parameters and composition of the ETL on the subsequent perovskite deposition, as well as the resultant cell performance are highlighted and discussed in terms of efficiency and hysteresis.

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Investigations of the Electrochemical Behavior of Hydrocarbons in Adiponitrile
Authors: Cheek Graham T. 
Published: February 2020

Introduction
Recent investigations from this laboratory have shown that adiponitrile (NCCH2CH2CH2CH2CN) / tetraethylammonium tetrafluoroborate (TEABF4) is a versatile solvent system for organic electrochemistry (1,2). The extraordinarily wide eight volt potential window noted in earlier work (3) has been confirmed and applied to the measurement of water (1) and electrodeposition of metals (4). The positive limit at +5 V vs Ag/AgCl opens up another 2 V for study, compared to that of most other solvents. The present paper addresses the usefulness of the positive potential region for oxidation of hydrocarbons.
Experimental
Adiponitrile was obtained from Sigma-Aldrich, and tetraethylammonium tetrafluoroborate was purchased from Southwestern Analytical Chemicals. Cyclic voltammograms were obtained on a PAR 283 potentiostat using PowerSuite software. Potentials are referenced against a Ag/AgCl reference electrode (1).
Results and Discussion
A cyclic voltammogram of 15 mM naphthalene in adiponitrile / 0.2 M TEABF4 is shown in the attached figure. The reversible reduction of naphthalene is observed at -2.5 V, followed by an irreversible oxidation process at +1.74 V. Scan reversal at +2.00 V shows no reduction current associated with the oxidation process at 100 mV/s. If the potential scan is continued to +5.0 V, considerable filming is observed, and the peak currents for the redox processes at -2.5 V are considerably lessened. Similar behavior for naphthalene oxidation has been observed in acetonitrile (5), and the irreversible nature of the oxidation was ascribed to rapid coupling of naphthalene radical cations. These results show that the entire positive potential range in adiponitrile is available for study of the representative aromatic hydrocarbon naphthalene.
References

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Figure 1
Electroreductive Free Radical Coupling from Xanthates Derived from Acetophenones, New Route to 1,4-Dicarbonyl Compounds
Authors: Frontana-Uribe Bernardo A. , Lopez-Lopez Ernesto Emmanuel , Miranda-Gutierrez Luis Demetrio 
Published: February 2020

In this contribution it is shown the synthesis of 1,4 dicarbonyl compounds from the electrochemical reduction of xanthates via a free radical coupling reaction. These starting materials are cheap and accessible. Electrosynthesis reaction is carried out in green chemistry conditions with excellent yields, which let to propose the route to be used as building blocks of more complex molecules or materials.
Acknowledgements: Funding by DGAPA UNAM project IN202011 is recognized

Figure 1
Electrochemical Generation of Stabilized Halogen Cation Pools
Authors: Yoshida Jun-ichi , Horiuchi Shun , Hayashi Ryutaro , Ashikari Yosuke , Shimizu Akihiro 
Published: February 2020

Halogen cations such as I+ and Br+ are highly unstable species, although some of them are identified in the gas phase. The electrochemical oxidation provides a powerful method for generating and accumulating highly reactive cationic species in the solution, whereas the chemical methods are not effective because of reversibility of cation generation. We have already reported that some carbocations and onium ions can be generated and accumulated as cation pools at low temperatures (the “cation pool” method). However, halogen cations are very difficult to accumulate in the solution as “cation pools” because they are too unstable.
We envisioned that the use of a stabilizing agent that coordinates the cation being generated would solve the problem. Coordination of a neutral molecule gives a positively charged species and coordination of an anionic species gives a neutral species, although the halogen is the +1 oxidation state in both cases. Some stabilizing agents have already been reported. For example, Miller and co-workers reported the generation and accumulation of “I+” cation in acetonitrile (CH3CN), and later we reported the detection of CH3CN−I+ and (CH3CN)2I+ by cold-spray-ionization mass spectroscopy. Shono and co-workers reported that “I+” could be accumulated in trimethyl orthoformate (TMOF).
In this paper we report that dimethyl sulfoxide (DMSO) serves as a neutral stabilizing agent and that TfO− anion serves as a negatively charged stabilizing agent in the electrochemical generation and accumulation of halogen cations such as I+ and Br+. We also report their reactions with organic molecules to give the corresponding halogen-containing products, which serve as useful transformations in organic synthesis.