bluuebunny/crossref_metadata_2025_split huggingface dataset:
First-Principles Analysis of Oxygen Incorporation into Sr(Ti1-xFex)O3-D : Using External Dopants to Tune the Incorporation Mechanism
Authors: Kim Namhoon , Ertekin Elif 
Published: February 2020

Although solid oxide fuel cells have been under intensive investigation for several decades, their practical development is hindered still by several fundamental challenges. One in particular is related to the kinetics of the electrode reactions, especially with respect to oxygen exchange at the cathode. Oxygen exchange requires chemisorption, dissociation, and incorporation, and can involve a complicated set of competing processes: for example, it may occur through directly via gas phase oxygen interaction with a surface vacancy through an active site-mediated mechanism, or it may occur directly onto a pristine surface with vacancies in the interior serving only as the final sink for the incorporated oxygen species. Often, resolving the rates of the relevant processes is challenging.
The material Sr(Ti1-xFex)O3-
d(STF) is a model system for the study of oxygen exchange mechanisms on electrodes of solid oxide electrodes. The perovskite material is stable in a wide range of oxygen partial pressures, and exhibits a flexible defect chemistry and electronic structure. The B-site substitution of Ti for Fe results in fast oxygen exchange kinetics. Even so, there remain several questions about the rate limiting steps to oxygen exchange in these materials, with contradictory suggestions that oxygen incorporation is limited by either electron transfer to the adsorbed molecules at the electrode surface or by the vacancy concentration at the surface.
In this work, we will present the results of our first-principles calculations to provide some clues to the nature of oxygen incorporation in STF. We use density functional theory to consider several incorporation mechanisms under different environmental conditions. In particular, we consider how the presence of external dopants (eg A-site doping with La) might allow access to different ranges of oxygen vacancy concentrations and carrier concentrations in the material. We will show (i) the results of a defect chemistry equilibrium model to calculate the equilibrium defect concentrations and carrier concentrations in different chemical environments and under different degrees of extrinsic doping, and (ii) the reaction mechanism for oxygen molecule adsorption at the surface for different degrees of doping. The defect chemistry model shows that the concentration of oxygen vacancies and the Fermi level of the material can be tuned by the incorporation of external dopants. Further, according to our simulations, we predict that the most favorable pathway for oxygen incorporation can be controllably changed from an active-site mediated mechanism to a direct adsorption mechanism by appropriately tuning the dopant concentration.
Synthesis and Evaluation of Ni/BaCe0.5Zr0.3Y0.2O3-d Hydrogen electrode for Proton Conducting Soecs
Authors: Nishikawa Ryosuke , Nishino Hanako , Kakinuma Katsuyoshi , Brito Manuel E. , Uchida Hiroyuki 
Published: February 2020

Solid oxide electrolysis cells (SOECs) are promising candidates for highly efficient hydrogen generation. In particular, proton-conducting SOECs have the advantage of producing high-purity dry hydrogen. For the practical application of proton-conducting SOECs, the development of highly efficient hydrogen electrodes with gas diffusion pathways and proton-electron mixed conducting pathways is required. In this research, we propose a new design concept of a current collecting / catalyst double layer (CCL/CL) hydrogen electrode using a proton-electron mixed conductor, BaCe0.8-xZrxY0.2O3-δ (BCZY), with a unique fused-aggregate network structure (Fig. 1) for proton-conducting SOECs. We also evaluated the performance of the hydrogen electrode as a function of the Ni loading amount.
The proton-electron mixed conductor (BCZY (x = 0.3)) powder was synthesized by the flame oxide-synthesis method. The BCZY (x = 0.7) electrolyte was prepared by solid state reaction. The BCZY (x = 0.3) scaffold was synthesized on the BCZY (x = 0.7) electrolyte by sintering at 1000°C for 4 h in air. The CCL of Ni-BCZY (x = 0.3) composite was formed on the BCZY (x = 0.3) scaffold at 1050°C after 4 h. The Ni nanoparticle catalysts were loaded on the BCZY (x = 0.3) scaffold by an infiltration method to obtain the CL. The counter electrode was a Pt-BCZY (x = 0.3) composite. The crystal phases were characterized by XRD, ICP-MS and STEM-EDX. The performance of the double-layer electrode was evaluated under hydrogen flow at 700°C.
The XRD patterns for BCZY (x = 0.3) and BCZY (x = 0.7) were consistent with a single perovskite phase. BCZY (x = 0.3) had a unique microstructure, with a fused-aggregated network structure, which was able to provide a gas diffusion pathways and proton-electron mixed conducting pathways while maintaining the high surface area (Fig. 2(a)). The STEM-EDX image of a cross-section of the CL showed that the Ni nanoparticles (diameter 70 ± 12 nm) were highly dispersed on the fused-aggregated BCZY (x = 0.3) scaffold (Fig. 2(b)). The polarization curves of the double-layer electrode showed that the electrode performance improved with increasing Ni loading amount up to 20 vol.%. The Ni particles maintained a highly dispersed state on the BCZY (x = 0.3) scaffold, indicating that the increased effective reaction zone (ERZ) was able to enhance the performance of the double-layer electrode. At Ni content ≥ 20 vol.%, the electrode performance decreased significantly. This was ascribed with certainty to a decrease in the extent of the ERZ, because the aggregation of Ni particles was observed by STEM.

Reference

K. Katahira, Y. Kohchi, T. Shimura and H. Iwahara Solid State Ionics,
138, 91 (2000).

Figure 1
Feasibility of (Ni-GDC/GDC half-cell) Manufactured By Tape Casting and Reactive Magnetron Sputtering Processes
Authors: Hernandez Londono Carlos , Combemale Lionel , Gao Fei , Billard Alain , Briois Pascal 
Published: February 2020

Nickel Oxide and Gadolinium Doped Ceria (10% Gd) powders, with -40 mesh and -100 mesh particle size respectively, were mechanically milled in a Turbular-(System Schatz Willy a Bachofeng) up to 24 to 48 hours. Half-cells, 28 mm of diameter, Ni-GDC composite anodes have been fabricated by slurry based tape casting (Elcometer4340 Automatic Film Applicator) method for anode supported solid oxide fuel cell [1]. The chosen ceramic powders in suspension was prepared with the mass ratio of 65:35 for NiO to GDC10 maintained constant. The microstructural evolution of powders (crystallite size) was followed by means of X-ray diffraction (XRD) and Scanning electron microscopy (SEM). The anode porosity was examined by Archimedes method [2]. The pre-sintered anode green tape were coated with a GDC electrolyte film by reactive magnetron sputtering using PEM techniques [3]. An Alcatel SCM650 sputtering chamber was used for synthesizing the dense GDC layers. A Ce-Gd metallic target (90-10% at) was powered by a pinnacle + pulsed current generator from Advanced Energy. The structural, microstructural and morphological features of the half-cells were determined by XRD, SEM and 3D profilometry as deposited and after different annealing treatments. Finally, the EIS measurements were performed on Ni-GDC/GDC half-cells under 60 sccm nitrogen by the means of a Solartron SI 1260 impedance / gain analyzer from 20 MHz to 0.1 Hz with 11 points per decade.
References
[1] Fabrication and characterization of Ni-SSZ gradient anodes/SSZ electrolyte for anode-supported SOFCs by tape casting and co-sintering technique. Chao Jin, Yachun Mao, Naiqing Zhang, Kening Sun. Harbin, China. Institutional Journal of Hydrogen Energy.
[2] Manufacturing and Characterization of Single cell Intermediate-Temperature Solid Oxide Fuel Cells for APU in transportation application. Visweshwar Sivasankaran. Dijon France. 2ICB- Département I.RM. Université de Bourgogne-CNRS
[3] F. Perry, A. Billard, C. Frantz, Surface Coatings Technology 94-95 681 (1997).
Nanocomposite YSZ-NiO Particles with Tailored Structure Synthesized in a Two-Stage Continuous Hydrothermal Flow Reactor
Authors: Zielke Philipp , Xu Yu , Kiebach Wolff-Ragnar , Simonsen Søren Bredmose , Norby Poul , Hendriksen Peter Vang 
Published: February 2020

The increasing amount of fluctuating electricity generation from renewable sources requires a flexible energy system and storage technologies to ensure that energy services can be covered in a stable and affordable manner. In order to become truly independent from fossil fuels, increasing the performance of energy storage and conversion devices such as fuel cells, electrolyzers and batteries is important. One promising approach to further improve these devices is the use of carefully structured nanosized materials. Nano-composite particles combining different materials in advanced geometries like core-shell structures or surface decorated particles could exhibit better performance compared with single phase materials. To obtain such advanced structures is the aim of the ProEco project (www.proeco.dk). In this project, a two-stage continuous reactor is built and used to synthesize such nano-composites.
Here we report on the design of the two-stage continuous hydrothermal flow synthesis reactor and first results on obtaining structured nano-composite consisting of yttria-stabilized zirconia (YSZ) and NiO materials. These materials are commonly applied in the fuel electrodes of today’s state-of-the-art solid oxide fuel and electrolysis cells. The prepared particles were characterized by X-ray powder diffraction, (high resolution) transmission electron microscopy, scanning tunnel transmission microscopy and Raman spectroscopy in order to determine crystal structure, particle size, surface morphology and element distribution.
Understanding the Conductivity Degradation Mechanism of Er2O3-Stabilized Bi2O3
Authors: Yun Byung-Hyun , Lee Kang Taek 
Published: February 2020

Rare earth stabilized bismuth oxides have attracted much attention due to their high oxygen ionic conductivity. Among singly-doped stabilized bismuth oxides, the Er2O3-stabilized Bi2O3, which is generally abbreviated to ESB, is particularly known for its superior ionic conductivity to even other stabilized Bi2O3s, not to mention conventional oxygen ion conductors such as doped ceria and stabilized zirconia[1]. In spite of its remarkable ionic conductivity (≈ 0.3S/cm at 700℃), ESB has not been practically employed as a SOFC electrolyte. This is not only because ESB has thermodynamic instability under reduction conditions, but also because it experiences time-dependent conductivity degradation on extended annealing below 600℃.
In this study, the crystallographic structure and conductivity of ESB were analyzed using X-ray diffraction and electrochemical impedance spectroscopy, respectively, during its prolonged annealing at 600℃ over 400h in order to investigate the mechanism of the time-dependent conductivity degradation of ESB. It was found that the initial cubic phase of ESB was mostly transformed to the rhombohedral phase within first 100h. At the same time, the discrepancy in time constant of the phase transformation(65h) and the conductivity degradation(52h) was observed. In order to elucidate this time constant discrepancy, the activation energies of low temperature domain before and after annealing were evaluated. The activation energy of as-sintered ESB was approximately 1.2eV, whereas that of the annealed ESB was approximately 1.01eV. Such a decrease in the activation energy can be attributed to order-disorder transition of the oxygen sub-lattice in ESB[2]. Therefore, the conductivity degradation of ESB is probably the combined effect of the phase transformation from cubic to rhombohedral as well as the order-disorder transition.

Acknolwdge

This research was supported by (1) Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2014R1A1A2057681), (2) the DGIST R&D Program of the Ministry of Science, ICT and Future Planning of Korea (1501- HRLA-01) and (3) the Global Frontier R&D on Center for Multiscale Energy System funded by the National Research Foundation under the Ministry of Science, ICT & Future Planning, Korea (2014M3A6A7074784).

References

[1] M.J. Verkerk et al., J. Appl. Electrochem., 1980, 10, 81.
[2] E.D. Wachsman, J. Eur. Ceram. SOC., 2004, 24, 1281

Figure 1
Electron-Ion Mixed Conduction of Nd0.6Sr0.4FeO3 Cathode Electrode Thin Film for Solid Oxide Fuel Cell
Authors: Namiki Wataru , Tsuchiya Takashi , Minohara Makoto , Kobayashi Masaki , Horiba Koji , Kumigashira Hiroshi , Higuchi Tohru 
Published: February 2020

Ln1-x
Sr
x
FeO3 (Ln=La, Nd) bulk crystal exhibits various electrical and magnetic properties by Ln substitution. In particular, Ln1-xSrxFeO3 has been extensively studied in the bulk and thin film forms due to electrochemical application of cathode electrode for Solid Oxide Fuel Cell (SOFC). However, La1-x
Sr
x
FeO3 thin film as electrode is not practical material since the mixed conduction is low. Therefore, new cathode material with high mixed conduction and durability is necessary for realization a practical SOFC device. In this study, we have prepared the Nd0.6Sr0.4FeO3 thin film on Al2O3 substrate by RF magnetron sputtering and characterized its electrical conductivity.
The Nd0.6Sr0.4FeO3 (NSFO) thin film was deposited on Al2O3 (0001) substrates by RF magnetron sputtering using a ceramics target. The NSFO ceramics target for sputtering was prepared by the solid-state reaction method. The flow rate of Ar gas, the deposition pressure , and substrate temperature were set at 0.67 sccm , 8.0×10-3 Torr and 700 ˚C, respectively. The film thickness was changed between ~42 and ~160 nm. The structural properties of the NSFO thin films were characterized by powder X-ray diffraction (XRD) analysis.
The electrical conductivity was measured by the AC impedance method in dry atmosphere in a temperature region from 300 to 700 ˚C. The measurement frequency region was from 0.1 Hz to 32 MHz. In order to probe conducting carriers, the conductivity was measured by changing oxygen gas partial pressure (PO2).
The electronic structure was characterized by photoemission spectroscopy (PES) and X-ray absorption spectroscopy (XAS). The energy resolutions of PES and XAS were 100 and 60 meV, respectively, at hν=1010 eV.
The lattice constant of the (112)-oriented thin film increases with increasing film thickness due to relaxation of lattice distortion. The chemical composition of the thin film was confirmed by PES. The electrical conductivity depends on film thickness. The conductivity increases with film thickness in 40~112 nm and decreases in 156 nm. This result is closely related to the lattice constant. The 112 nm thick film exhibits high conductivity and low activation energy (EA) of 0.45 eV. The EA is in a good agreement with the band gap obtained by PES and XAS, indicating the electron conduction. Furthermore, the conductivity above 500 ˚C does not depend on oxygen gas partial pressure, which corresponds to ionic conduction. The above results indicate that the Nd0.6Sr0.4FeO3 thin film has the oxygen ion-electron mixed conduction.
Oxygen Activity in a-Site Ordered Perovskites through in-Situ Neutron and Synchrotron X-Ray Diffraction
Authors: Taylor Daniel D. , Levitas Benjamin D. , Rodriguez Efrain E. 
Published: February 2020

A-site ordered perovskites have been investigated for a number of solid-state oxide conducting applications including oxygen storage, solid oxide fuel cells, and solid oxide electrolysis cells. By combining a large divalent cation (e.g. Ba2+) with a smaller trivalent cation (e.g. Y3+), it is possible to form 2 dimensional layers of highly mobile oxide anions. This stems from the smaller coordination number typically stable around the trivalent cation than is present in the prototypical perovskite structure – the A-site ordered structure is provided in Figure 1. Within these layers, oxygen is able to quickly and topochemically be inserted or extracted in the case of oxygen storage materials, or transported in the case of solid oxide fuel and electrolysis cells.
Despite this link between these materials’ layered structures and their high oxygen activity, fundamental questions remain as to which structural features are key in determining their performance. Furthering this understanding will help in the future design of oxygen conducting and storing materials.
To this end, we used in-situ neutron and synchrotron X-ray diffraction to study the structure of BaYM2O5+δ for M = Mn, Fe, and Co, under operating conditions - both oxidizing and reducing conditions at elevated temperatures. With an aim to link the local coordination around the redox active transition metals to the materials performance, we were able to track how the structure of the materials change with oxygen content and temperature. A number of different phase transitions were observed for each material potentially affecting the oxygen mobility within these materials. These insights into how the chemical environment of oxygen changes under operation conditions will aid in the future design of materials with high oxygen mobility.

Figure 1
Controlled SOFC Anode Porosity Using Aligned Sacrificial Fibers
Authors: Hays Thomas H , Wachsman Eric D 
Published: February 2020

Solid oxide fuel cell anode supports serve a multipurpose role. This layer must be both the mechanical backbone of the cell and an active electrode. While high porosity is desired to maximize reaction sites, it negatively impacts strength. Therefore, efforts should be made to design anode microstructure for high strength while maintaining electrochemical performance.
Currently, solid oxide fuel cell anodes are fabricated such that there is little control over the final microstructure. A new technique for creating porous anode support layers in solid oxide fuel cells was developed. Using sacrificial, high aspect ratio pore formers, anode support layers with non-random porosity networks were created utilizing dielectrophoresis. Variation in applied voltage and frequency during dielectrophoretic treatment allowed control over the resulting structure. Microstructure analysis and electrochemical testing of novel anode support layers was performed and compared to results of standard SOFC designs.
Novel Thin Film Solid State Ionic Device with Electrochemically Tunable Resistance Based on Lithium Plating/Stripping
Authors: Oukassi Sami , Berr Bruce , Poncet Séverine , Secouard Christophe , Amiran Johnny , Poulet Sylvain , Salot Raphaël 
Published: February 2020

Electrochemically induced property tuning has recently emerged as a promising pathway to achieve accordable devices and reconfigurable circuits, in most cases making use of the change of one or several material properties with ion exchange or the local electroformation of conducting structures in an insulating material [1–3]. In the present work we report on the electrochemical tuning of a solid state ionic device impedance using lithium ion plating and stripping at a current collector/solid electrolyte interface [4,5].
The device presented a design with two actuation vertical metal electrodes separating a Cu/LiPON/Li multilayer, and two measurement interdigitated electrodes embedded in the LiPON layer. The measurement electrodes were isolated from the bottom actuation electrode by an Al2O3 dielectric layer (Fig1). The devices were microfabricated on silicon substrates with varied architectures including lithium plating surfaces ranging between 1µm² and 3000µm² (Fig.2).
Upon chrono-potentiometric stimuli, lithium was plated between the measurement electrodes, thus changing significantly the impedance, and more particulary the electrical resistance. Fully reversible variation of the real part of the impedance (Re Z) over a range of more than 3 decades was observed by electrochemical impedance spectroscopy upon the formation and dissolution of nanometric lithium layer (Fig.3). Particular attention was put on the investigation of the influence of the current density during plating/stripping (plated lithium morphology), and the architecture (interdigitated electrodes design, plating surface) on the device performance.
References
[1] X. Meng, F. Quenneville, F. Venne, E. Di Mauro, D. Işlk, M. Barbosa, et al., Electrolyte-Gated WO3 Transistors: Electrochemistry, Structure, and Device Performance, J. Phys. Chem. C. 119 (2015) 21732–21738. doi:10.1021/acs.jpcc.5b06777.
[2] I. Valov, R. Waser, J.R. Jameson, M.N. Kozicki, Electrochemical metallization memories--fundamentals, applications, prospects., Nanotechnology. 22 (2011) 254003. doi:10.1088/0957-4484/22/28/289502.
[3] F. Xiong, H. Wang, X. Liu, J. Sun, M. Brongersma, E. Pop, et al., Li Intercalation in MoS2: In Situ Observation of Its Dynamics and Tuning Optical and Electrical Properties, Nano Lett. 15 (2015) 6777–6784. doi:10.1021/acs.nanolett.5b02619.
[4] M. Motoyama, M. Ejiri, Y. Iriyama, Modeling the Nucleation and Growth of Li at Metal Current Collector/LiPON Interfaces, J. Electrochem. Soc. 162 (2015) A7067–A7071. doi:10.1149/2.0051513jes.
[5] M. Motoyama, M. Ejiri, Y. Iriyama, In-Situ Electron Microscope Observations of Electrochemical Li Deposition/Dissolution with a LiPON Electrolyte, Electrochemistry. (2014) 3–7. doi:10.5796/electrochemistry.82.364.

Figure 1
(Invited) Electrochemical Properties of Graphite Electrode in Propylene Carbonate-Based Electrolyte Solution Containing Mg Salt
Authors: Abe Takeshi , Takeuchi Saya , Song Heeyoub , Kokumai Ryohei , Miyazaki Kohei , Fukutsuka Tomokazu 
Published: February 2020

It is well-known that charge-discharge reactions of graphite electrode cannot take place in propylene carbonate (PC) based electrolyte solutions. Since the melting point of PC is much lower than that of ethylene carbonate (EC), PC-based electrolyte solutions are preferable when lithium-ion batteries are operated in the lower temperature regions.
Vast work has been done on graphite electrodes in PC-based electrolyte solutions. One of our colleagues, Jeong found that concentrated salt PC solutions enabled charge-discharge reactions at graphite electrodes [1]. This was the first approach for use of concentrated salt electrolyte solutions. The concept of the concentrated electrolyte solutions was the change of the solvation states of lithium-ion.
We also found that the addition of divalent cations such as calcium ion and magnesium ion in the PC-based electrolyte solutions also made graphite electrode active for the intercalation/de-intercalation of lithium-ion [2,3]. Since the Lewis acidities of Mg2+ and Ca2+ are higher than that of Li+, PC should preferentially solvate with the divalent cations. This will result in the change of solvation states of lithium-ion. Then, charge-discharge reactions could take place at graphite electrode.
Further, we used “in situ” atomic force microscopy (AFM) for the understanding of the formation of solid electrolyte interface (SEI) on graphite electrode in PC-based electrolyte solutions containing Mg2+. As a result, we found the co-intercalation of lithium-ion and solvent was suppressed by the addition of Mg2+. The detail will be reported in the conference.
References
[1] S. K. Jeong, Electrochem. Solid State Lett. 6, A13 (2003)
[2] S. Takeuchi et al., Electrochim. Acta, 56 (2011) 10450.
[3] S. Takeuchi et al., submitted.
Acknowledgement
This work was partially supported by CREST, JST and JSPS KAKENHI Grant Number 16H04216.