bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solvothermal Synthesis of Copper Ferrite-Graphene Nanocomposite As a Supercapacitor Electrode Material
Authors: Piao Yuanzhe 
Published: February 2020

In recent years, electrochemical supercapacitors have attracted great attention due to their advantages of short charging times, a long cycle, and high power density. In order to fullfill the market demand for further improved performance, the design of materials with a longer cycling lifetime, higher energy density and economic efficiency is imperative for supercapacitor electrode. Since the performance of electrode materials for supercapacitors is dependent on the accessible specific surface area and the pore structure, the control over structure and morphology of electrode materials is an effective strategy to render them high surface area and efficient paths for ion diffusion. Recently, the applications of graphene based nanocomposites for supercapacitor have attracted much research interest.
Here, a simple method to prepare a uniform sized copper ferrite nanoparticles attached graphene nanosheet is reported. A one-step solvothermal method featuring the reduction of graphene oxide and formation of copper ferrite nanoparticles was efficient, green, and controllable. The composite nanosheet was characterized by using X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy, which demonstrated that the copper ferrite nanoparticles with a diameter of approximately 100 nm were densely and compactly deposited on graphene nanosheet. To investigate the formation mechanism of the copper ferrite nanoparticles attached graphene nanosheet, the effects of a series of experimental parameters, including the concentrations of the precursor, precipitation agent, stabilizer agent, and graphene oxide on the size and morphology of the resulting products were discussed in detail. Furthermore, the electrochemical performances of the copper ferrite nanoparticles attached graphene nanosheet as electrode material for supercapacitor were studied by using cyclic voltammetry and galvanostatic charge-discharge measurements. The nanocomposite showed high electrochemical capacitance of 576.6 F/g at 1 A/g, good rate performance and cycling stability. These results demonstrated that the nanocomposite had a high specific capacitance and good retention. The versatile copper ferrite-graphene nanocomposite held great promise for a wide range of electrochemical fields due to the remarkable synergistic effects between copper ferrite nanoparticles and graphene.
Quantifying Chemical Expansion of Non-Stoichiometric Oxide Thin Films: Challenges and Opportunities
Authors: Swallow Jessica G. , Kim Jae Jin , Chen Di , Bishop Sean R. , Smith James F. , Tuller Harry L. , Van Vliet Krystyn J. 
Published: February 2020

Non-stoichiometric oxides used for the electrodes and electrolytes of solid oxide fuel cells (SOFCs) typically exhibit chemical expansion behavior due to the large defect concentrations required for high ionic conductivity or gas reactivity. Robust SOFC design requires knowledge of how chemical expansion contributes to mechanical strains at interfaces, as such deformation promotes dislocation mobility, delamination, and fracture. Direct measurement of chemical expansion via X-ray diffraction or dilatometry typically requires long time scales (minutes to hours) to allow equilibration of gas atmospheres or bulk samples, or to allow adequate signal detection in the absence of synchrotron access. Here, we describe a new approach to directly and rapidly quantify dynamic chemical expansion of non-stoichiometric oxides in situ at elevated temperatures up to 650ºC, and demonstrate this method for the mixed-ionic-electronic conducting Pr0.10Ce0.90O2-δ (PCO) as a model SOFC electrode. The activity of oxygen is modulated via sinusoidal electrical bias signal, while amplitude and phase lag of film expansion are detected with second-scale temporal resolution and sub-nanometer displacement resolution. These dynamic chemical expansion measurements are coupled with defect models of PCO to advance understanding of defect concentration and mobility under oscillating electrical potential. Extensions of this approach to estimate activation energies, lateral expansion differences, and breathing modes of multilayered electrodes are discussed. This approach provides facile access to dynamic chemical expansion under in operando conditions of SOFC electrodes, facilitating improved design of materials that withstand large chemomechanical changes during SOFC start-up, shut-down, and redox cycling.
Solid Oxide Fuel Cells Using Novel Cathodes in the BaO-Co2O3-Fe2O3 Composited withGDC10
Authors: Hing Peter , Sukleung Montri , Voo Nyuk Yoong , Lim L C , Atkinson Alan 
Published: February 2020

Most current cathodes for SOFCs such as LSM, LSC and LSCF contain lanthanum oxide. The tendency for the lanthanum oxide to absorb moisture and degrade the materials make processing a critical issue. In this study, we have explored the fabrication of cathode materials free from lanthanum oxide. Compositions with high electrical conductivity in BaO-Y2O3-Fe2O3 and BaO-Y2O3-Co2O3-Fe2O3 systems have been obtained. Selected compositions with high electrical conductivities up to 600Scm-1 have been composited with GDC10 solid oxide electrolyte to form composite cathodes with matching thermal expansion to GDC10 for solid oxide fuel cells(SOFCs). Symmetrical cells with GDC10 between the experimental composite cathodes, and small SOFCs with GDC10 as electrolyte, GDC10.NiO as anode and experimental composites as cathodes have been constructed and evaluated up to 800oC. The electrical conductivity, thermal expansion, impedance and power densities have been studied. The power densities between 400oC and 800oC have been measured. The power density obtained at 800oC is found to be about 600mW/cm2. The results are presented and discussed in relation to the processing of the materials, properties, microstructures and performance of the solid oxide fuel cell. Ways to enhance the performance of the SOFCs are highlighted.
Development of a Novel Co-fired SOFC at Murata
Authors: Mori Naoya , Sato Yosuke , Nakai Hideaki , Iha Michiaki , Takada Takahiro , Konoike Takehiro 
Published: February 2020

Murata Manufacturing Co., Ltd. has been developing planar-type solid oxide fuel cells (SOFCs) based on new design concept. The cell is fabricated by a single-step co-firing process and consists of an electrolyte, electrodes, current collectors, gas-separators with manifolds, and gas-flow channels. The membrane electrode assembly (MEA) is sandwiched between ceramic gas-separators with via-hole electrodes providing electrical paths between cells. Murata’s new concept stack achieved volume power density higher than 0.5kW/L. By arranging gas manifolds in the central part of the cell, the temperature distribution in plane of the cell was moderated while keeping high volume power density. As a result, the stack operated stably at high efficiency. A long-term operation has been carried out at 750°C over 8000h under galvanostatic condition. The cell power degradation rate was less than 0.20%/kh after 2000h operation. Cr poisoning in the LSCF cathode after durability test was not observed. That is one reason of high durability of the cell.
Beyond the 3rd Generation of Planar SOFC: Development of Metal Foam Supported Cells with Thin Film Electrolyte
Authors: Han Feng , Semerad Robert , Constantin Guillaume , Dessemond Laurent , Costa Rémi 
Published: February 2020

Manufacturing of thin and gas tight electrolyte is still a challenging issue for metal supported solid oxide fuel cells (SOFCs). In this work, we present a porosity graded multi-layer structure supporting thin film electrolyte. The substrate is made of NiCrAl metal foam impregnated with La-substituted SrTiO3 (LST) ceramic. Furthermore, a 20 µm thick composite anode functional layer with LST and gadolinium doped ceria (GDC) was deposited onto the substrate. The surface of the anode functional layer is later engineered with a suspension of nano-particles with 40 nm average particle size of yttria-stabilized zirconia (YSZ). This results in a mesoporous layer with smooth surface able to support a thin film GDC layers. Finally, a gas-tight GDC electrolyte was deposited by EB-PVD method. The thickness of the thin-film YSZ layer and the gas-tight GDC layer was approximately 1 µm and 2 µm, respectively. Button half cells with size up to 25cm² were successfully produced showing an air leakage rate down to 7.0*10-4 (hPa*dm3)/(s*cm2), satisfying the gas-tightness quality control threshold of the state of the art metal supported SOFCs at DLR. Full cells with LSCF cathodes were then produced and electrochemically tested presenting stable Open Circuit Voltage near to 1V. Results will be presented and discussed in this paper by confronting the performance with the cell microstructure.
Key Words: metal foam, thin-film, electrolyte
The research leading to these results has received funding from the European Union‘s Seventh Framework Programme (FP7/2007-2013) for the Fuel Cells and Hydrogen Joint Technology Initiative under grant agreement n° 303429
Small Scale Power Generation for Road Trucks with Planar SOFC System
Authors: Bossel Ulf 
Published: February 2020

There is increasing interest in small SOFC generators for the conversion of commercial butane/propane fuel into DC electricity. However, with minor modification of the pre-reformer such units can also be used for the conversion of methane, natural gas, biogas or LNG. A consortium of six groups form the UK, Spain, Poland and Switzerland is presently engaged in the development of a small SOFC power source for road trucks powered by LNG. The project “SAFARI” is funded by the FCH-JU Programme of the European Union.
Two different types of SOFC are simultaneously prepared for comparative evaluation. While the project leader “Adelan Ltd.” is optimizing its tubular SOFC design (see separate conference presentation), ALMUS AG is perfecting its planar approach for road truck applications. Stacks of 60 mm x 60 mm foot print are used. They are composed of metal bipolar plates and anode-supported cells. To match the generator output to the power demand, up to four such stacks can be arranged in line, each delivering up to 80 Watts at 24 VDC and 700°C operating temperature. For low heat losses and maximum conversion efficiency, the stack arrangement is surrounded by a 100 mm thick thermal jacket made of the best available insulation material (silica gel). The arrangement is contained in a metal box for safe handling and mounting on the truck platform. A partial oxidation methane reformer is part of the system. Start-up heat is generated by burning small amounts of fuel.
Technical details and first test results will be presented.
Analysis of a Solid Oxide Fuel Cell System with Low Temperature Anode Off-Gas Recirculation
Authors: Engelbracht Maximilian , Peters Roland , Blum Ludger , Stolten Detlef 
Published: February 2020

The daily growing global energy consumption has to be provided in the future by technologies which emit increasingly less greenhouse gases. This requires highly efficient energy systems. Methane fueled SOFC systems are already able to produce electricity with an efficiency up to 60 %. Through the combined use of produced electricity and thermal energy the overall efficiency can be above 90 %.
One possibility for a further improvement of the electrical efficiency is the implementation of an anode off-gas recirculation loop. Challenging is the high anode off-gas temperature of at least 700 °C, which prohibits the use of commercial components. Therefore, the use of ejectors and blowers with or without anode off-gas cooling are discussed in literature. At Forschungszentrum Jülich an anode off-gas recirculation loop operating at temperatures up to 200 °C is favored. To analyze the effect of anode off-gas recirculation, a dynamical model of the system including the recirculation loop was implemented in Matlab/Simulink®. The results show, that the recirculation rate has a huge effect on the electrical efficiency (both positive and negative). In principle, at constant current density high recirculation rates decrease the cell voltage and increase the power consumption of the recirculation blower. Therefore, the highest electrical efficiency can be reached with high systems fuel utilizations, low recirculation rates and in consequence high stack fuel utilizations. On the other hand less amount of steam is available for the reforming reaction at low recirculation rates, therefore the minimum recirculation rate is determined by the formation of carbon. An optimal operation range to avoid carbon formation and to ensure a high electrical efficiency requires recirculation rates between 65 and 70 % and system fuel utilizations above 90 %. This leads to acceptable stack fuel utilizations in the range of 70 to 75 % and electrical efficiencies above 60 %.
Thermodynamic Stability Assessment of MIEC Cathode Materials for Solid Oxide Fuel Cells
Authors: Cetin Deniz , Yu Yang , Luo Heng , Lin Xi , Pal Uday Bhanu , Basu Soumendra Nath , Gopalan Srikanth 
Published: February 2020

Mixed ionic-electronic conductor (MIEC) cathode materials such as La(1-x)SrxCo0.2Fe0.8O3-δ (LSCF,where x=0.2, 0.3, 0.4), Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF 5582), Sr2Fe1.5Mo0.5O6-δ (SFMO), La2NiO4+δ (LNO), GdBaCo2O6-δ (GBCO), and PrBaCo2O6-δ (PBCO) exhibit excellent oxygen transport properties as well as high electronic conductivity at operational temperatures of SOFCs. Their promising electrochemical performance make these materials excellent candidates for potential application as SOFC cathodes. However, their long-term thermodynamic stability in the operating environment of SOFCs, including unexpected and uncommon situations such as CO2-leakage from the anodic side is of concern and should be thoroughly investigated prior to deploying them in cells and stacks.
This study investigates the thermodynamic stability of promising SOFC cathodes under operating conditions, in molten salt media, and through galvanic cell measurements. The cathode materials of interest are La(1-x)SrxCo0.2Fe0.8O3-δ (LSCF, where x=0.2, 0.3, 0.4), Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF 5582), Sr2Fe1.5Mo0.5O6-δ (SFMO), La2NiO4+δ (LNO), GdBaCo2O6-δ (GBCO), and PrBaCo2O6-δ (PBCO). The stability of these materials is studied in air and at various CO2 partial pressures.
Chromium Deposition and Poisoning of LSCF and LSM Oxygen Electrodes of Solid Oxide Electrolysis Cells
Authors: Chen Kongfa , Bo Wei , Hyodo Junji , Ishihara Tatsumi , Jiang San Ping 
Published: February 2020

The degradation of solid oxide electrolysis cells (SOECs) is an issue of both scientific and technical importance. In this study, chromium deposition and poisoning at La0.8Sr0.2MnO3+
d (LSM) and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) oxygen electrodes are studied under SOEC operation conditions. Significant performance degradation was observed for the reaction in the presence of Fe-Cr alloy metallic interconnect, indicating that presence of gaseous Cr species significnatly poisons and degrades the electrocatalytic activity of LSM and LSCF oxygen electrodes. In the case of LSM electrodes, XRD, XPS and SIMS analysis clearly identified the deposition of SrCrO4, CrO2.5 and Cr2O3 phases on the YSZ electrolyte surface and LSM electrode inner surface for the reaction under anodic polarization conditions. In the case of LSCF, Cr deposition occurs in the electrode bulk and on the electrode surface, forming SrCrO4. The results clearly indicate that the Cr deposition is closely related to the increased segregation of SrO species under anodic polarization conditions. The mechanism of the Cr deposition at LSM and LSCF electrodes under SOEC operation conditions is discussed.
Redox-Stable High-Performance Thin-Film Solid Oxide Fuel Cell
Authors: Keuter Thomas , Roehrens Daniel , Menzler Norbert H. , Vaßen Robert 
Published: February 2020

An anode-supported Solid Oxide Fuel Cell (ASC) consists of a mechanically supporting, thick, and highly porous anode substrate, coated on top with thin films of a fine-structured porous anode, a dense electrolyte, and a fine-structured cathode. Both, the anode substrate and the anode are made of a cermet of nickel and yttria-stabilized zirconia (YSZ). An increase of the oxygen partial pressure at the anode side will lead to a reoxidation of the nickel and to microstructural changes. This may result in a macroscopic expansion of the anode substrate and in a complete cell failure, due to cracking of the YSZ electrolyte.
In this work, a redox-stable SOFC with a thin-film sol-gel electrolyte is presented. Using tailored suspensions and polymeric sols of varying target particle size, a 1 µm thick, three layer sol-gel electrolyte is coated on top of a tape cast anode substrate and a screen printed anode by spin-coating and dip-coating techniques. With this sol-gel electrolyte a power output larger than 1.25 W/cm2 at 0.7 V and an operating temperature of 600 °C could be demonstrated. In this study, half cells (anode substrate, anode, and electrolyte) are reoxidized in excess air, in order to test the redox stability of these SOFCs. Afterwards the electrolyte is investigated ex situ using optical microscopy and SEM. No cracks are found in the sol-gel electrolyte after reoxidation for 4 hours at 600 °C and 15 minutes at 800 °C, respectively, whereas a lot of cracks are visible in a standard ASC with a 10 µm thick, screen printed electrolyte for both reoxidation conditions. This means the sol-gel electrolyte can tolerate higher degrees of oxidation (DoO) of the anode substrate than the screen printed electrolyte. The residual compressive stresses of both electrolytes are measured to about 600 MPa using XRD and are therefore not responsible for the higher stability against reoxidation of the sol-gel electrolyte. In contrast, the energy release rate has to be larger than a critical value for the creation of cracks in a thin-film on a thick substrate. Due to the fact, that the energy release rate is proportional to the thickness of the thin-film, a thinner film is more stable against cracking than a thicker film at constant tensile stresses. After reoxidation of 8 hours at 600 °C and 60 minutes at 800 °C, respectively, cracks are also found in the sol-gel electrolyte. However, the SOFC with the thin-film sol-gel electrolyte can be considered as stable against reoxidation, because the long reoxidation time of 4 hours at an operating temperature of 600 °C is unlikely to happen under real conditions.
Coatings for SOFC Interconnects in Fuel Side Environments
Authors: Sachitanand Rakshith , Sattari Mohammad , Svensson Jan-Erik , Froitzheim Jan 
Published: February 2020

Bipolar plates in solid oxide fuel cells operate under a significant oxygen potential gradient (0.2 to 10-18 bar pO2). For air side conditions (pO2 = 0.2 bar), a PVD technique has successfully been used to apply combination reactive element/Co coatings to inhibit the rapid oxidation of and Cr volatilization from Fe-Cr alloys such as Crofer22 APU and Sanergy HT. However, relatively little work has been done on developing similar coating strategies for fuel side conditions.
In this work, the ferritic steel Sanergy HT was coated with single element (Ce,La, Co and Cu) and duplex (Ce/Co, La/Co) coatings of varying thicknesses and exposed at 850°C in Ar-5%H2 charged with 3% H2O in a tubular furnace up to 500 h. Additionally, the effects of a ‘sealing’ step on corrosion mechanisms were also investigated by pre-oxidising the coated steel in air, prior to exposure in the fuel side environment. Chemical analysis on the samples was subsequently performed with SEM/EDX and XRD.
It was established that:
(i) reactive element (Ce and La) coatings brought about a 2-4x reduction in oxidation rate
(ii) Co and Cu coatings negatively affected oxidation performance due to their instability in fuel side conditions.

Figure 1
Sulfur Poisoning of the Reverse Water Gas Shift Reaction (RWGSR) on Anode Supported SOFCs
Authors: Madi Hossein , Singh Vaibhav , Diethelm Stefan , Van herle Jan 
Published: February 2020

SOFCs have the advantage of being able to operate with fuels other than hydrogen due to their high operation temperatures. Among these, biogas from anaerobic digestion is considered to be carbon neutral and highly underused for power generation. Methane-free biogas, which can be produced by inhibition of the methanogenic process, is an alternative high quality fuel, consisting mainly of CO2 (70 to 50%), H2 (30 to 50%) and traces of CO and H2S. The impact of H2S in the ppm range on the performance of anode supported Ni-YSZ SOFC at 750°C is evaluated. An initial voltage drop is observed when the cell is exposed to H2S but the voltage recovers after a few hours of exposure to the impurity. Impedance spectroscopy revealed an increase in the polarization resistance even though the cell voltage was increasing. Furthermore, it was found that this behavior is due to deactivation of the reverse water gas shift reaction (RWGSR); a mathematical model confirmed this conclusion. The poisoning effect is partly reversible under the applied operating conditions.

Figure 1
Results for a New SOFC-Stack Design with Parallel-Connected Cells
Authors: Szepanski Christian , Immisch Christoph , Lindermeir Andreas , Faulstich Martin , Dörrer Lars , Schmidt Ute , Borchardt Günter , Hamje Jens , Wesling Volker 
Published: February 2020

The TU Clausthal and CUTEC institute have teamed up to design, build and test a new stack architecture, based on repeating units with cells connected in parallel. This approach allows the use of electrically conducting seals like brazes and can be realized without any glass sealing.
Unlike conventional (serially connected) stacks, where all cells operate at the same current but individual voltage, in this setup each cell contributes as much current as possible at a common voltage. Thereby accelerated degeneration caused by undervoltage and the associated oxidation of the nickel catalyst can be completely overcome.
The concept uses two cells in electrical parallel connection with the anodes facing each other to form a repeating unit. Two designs have been realized: An all ceramic housing made from 3YSZ, sealed with reactive air brazing (RAB) and a metallic one with a Crofer 22 APU housing, joined by laser beam welding. The housing materials have been chosen with respect to their thermal expansion coefficient (TEC) matching the TEC of the used ESC cells. Special interconnectors have been produced via hydroforming to create an even flow field while providing sufficient contact area.
The paper will focus on the test results of the repeating units under various operation conditions and the analysis of the degradation of components and joints.
Polarization curves for the twincell repeating unit and the individuell cells under H2 and air at 880°C are depicted in figure one.

Figure 1
Evaluation of Ni-YSZ Anode Degradation during Redox Cycling
Authors: Shimura Takaaki , Jiao Zhenjun , Hara Shotaro , Shikazono Naoki 
Published: February 2020

Degradation of SOFC anode under redox cycling was evaluated by microstructure change measurements and overpotential calculations using a Lattice Boltzmann method (LBM). Microstructures were obtained by FIB-SEM reconstruction technique. In the overpotential calculation, exchange current density and YSZ ionic conductivity were considered as degradation factors. Numerical simulation reproduced well the decrease of overpotential just after each of the redox treatments. Then, overpotential increased after subsequent discharge process. This is consistent with the experimental result. However, simulation showed lower overpotential values than the experiment after 10 redox cycles. Decrease of exchange current or YSZ ionic conductivity reduction are considered as the reason for the degradation after redox cycles.