bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochemical Analysis of Nano-Infiltrated Solid Oxide Fuel Cell Cathodes
Authors: Call Ann V , Barnett Scott A 
Published: February 2020

Composite solid oxide fuel cell (SOFC) cathodes consisting of ionic conducting scaffolds infiltrated with mixed ionic and electronic conducting (MIEC) nano-particles have exhibited some of the lowest reported polarization resistances in the literature. In this study, symmetric cell cathodes were prepared via wet infiltration of Sr0.5Sm0.5CoO3 (SSC) nano-particles via a nitrate process into porous Ce0.9Gd0.1O1.95 (GDC) scaffolds to be used as a model system to investigate performance under varying infiltration loadings. Detailed analysis of the infiltrated cathodes was carried out using electrochemical impedance spectroscopy (EIS). The results presented show that the infiltrated cathode microstructure has a direct impact on the initial performance of the cell. Small initial particle sizes and high infiltration loadings (up to 30 vol% SSC) improved initial polarization resistance (RP). A simple microstructure-based electrochemical model successfully explained these trends in RP. Further understanding of electrode performance was gleaned from fitting EIS data gathered under varying temperatures and oxygen partial pressures to equivalent circuit models. Both RQ and Gerischer impedance elements provided good fits to the main response in the EIS data, which was associated with a combination of oxygen surface exchange and oxygen diffusion in the electrode. A gas diffusion response was also observed at relatively low pO2.
Stability of Bi2O3-Based Ionic Conductor and Its Application on Composite Cathode
Authors: Tsai Shu-Yi , Fung Kuan-Zong , Ni Chung-Ta , Chang Yu-Fan 
Published: February 2020

In recent years, solid oxide fuel cells(SOFCs) has been considered as desired devices for generating electricity by electrochemical combination of a fuel with an oxidant. Oxygen ion conductors are usually used as the electolytes for SOFCs. Among several types of oxygen ion conductors such as CeO2, stabilized Bi2O3 and ZrO2, Bi2O3with stabilizers exhibit the highest oxygen ion conductivity. Although Bi2O3 tends to be reduced to Bi metal, Bi2O3 incorporated with proper dopants will show enhanced stability against hydrogen. The highest OCV for SOFC using Bi2O3-based electrolyte is around 0.5V which is still too low to be practical. On the other hand, Bi2O3-based system may make a good ionic component for a composite cathode.
In this study, we choose yttria-stabilized bismuth oxides (YSB) as ionic conductor and mixed with s
trontium-doped lanthanum manganite (LSM) for composite cathode. Size effect of LSM on the polarization resistance was investigated by using convertional solid-state reacted and nano-sized LSM.
The electrochemical performances of composite cathodes with different LSM:YSB ratio have been investigated at temperature ranging from 500℃to 650℃ using AC impedance spectroscopy. The polarization resistance measured from a symmetric cell consisting of nano-sized LSM-YSB electrodes on a YSB electrolyte is 50% lower than that of submicron-sized LSM-YSB cathodes by SSR (0.21 ohmcm2) at 650℃.
The polarization of cathode is reduced because of the mixing of high surface area electric conducting materials and ionic conducting materials. The nanostructure of composite cathode is able to extend triple phase boundary(electronic conductor, ionic conductor,and oxygen gas) and provide numerous reaction sites for electrochemical reaction to occur.
Self Healing of Precoated AISI 441 for Solid Oxide Fuel Cell Interconnects
Authors: Berger Robert , Lundberg Mats W , Westlinder Jörgen , Holmberg Håkan 
Published: February 2020

Sandvik Materials Technology develops nanocoatings for SOFC stainless steel interconnects. The self healing properties of cerium cobalt coated AISI441 (EN 1.4509) have been studied. A selectively coated sample was oxidized in air at 800°C for a total of 504 hours. A FIB trench, milled on the uncoated surface, was used as a reference point for the coated border. A second FIB trench, made after oxidation, revealed that the oxide formed on the uncoated part adjacent to the coated area contained both cobalt and cerium. Cerium was detected with EDS in the surface oxide of the uncoated area as far as 10 mm away from the coated edge, cobalt had diffused even further. These findings are encouraging since they suggests that cracks introduce in the coating during stamping and/or forming, which are usually in the 1-3 mm range, are likely to self heal (i.e. become enclosed by an upper Co, Mn, Cr-spinel) upon oxidation.

Figure 1
Effects of Nitride Formation on Anode Catalytic Activity in Ammonia-Fueled SOFCs
Authors: Yokochi Ryuji , Hashinokuchi Michihiro , Doi Takayuki , Inaba Minoru 
Published: February 2020

We have so far developed Ni-Fe and Ni-Mo anodes with high catalytic activity for ammonia(NH3)-fueled SOFCs [1], and have proposed that the performance of NH3 -fueled SOFCs was determined by a balance between NH3 adsorption (Fe, Mo) and nitrogen(N2) desorption (Ni) capability [2]. Furthermore, we also found that both Ni-Fe and Ni-Mo anodes react with NH3 to form metal alloy nitrides (FeNx, γ-Ni2Fe2N and Ni0.2Mo0.8N) and metal Ni under the operation condition, while pure Ni anode does not form nitrides. These results suggested that the nitrides enhance NH3 adsorption at the anode and led to the high anode activity for NH3 oxidation.
In the present study, we prepared three kinds of anodes, Ni-W, Ni-Ta and Ni-Nb and evaluated their performance as anode in NH3-fueled SOFCs to investigate the correlation between the nitride formation and the anode activity. These anodes were synthesized by impregnating W, Ta and Nb precursor solutions into a pre-sintered Ni-SDC anode cermet. The addition of W and Ta enhanced the anode activity for NH3 oxidation, but Nb did not. XRD measurements of metal oxides (WO3, Ta2O5 and Nb2O5) after annealing in NH3 indicated that W and Ta in the anode reacted with NH3 to form nitrides, but Nb did not under the operation condition (i.e. at 973-1173 K in NH3). These results suggest that the easiness of the nitride formation is closely related to the high activity anode for NH3 oxidation.
Acknowledge
This work was supported by the Kyoto Environmental Nanotechnology Cluster from MEXT, Japan.
Reference
[1] W. Akimoto et al., Solid State Ionics, 256, 1–4 (2014).
[2] W. Akimoto et al., ECS Trans., 57 (1), 1639-1645 (2013).
The Influence of Sulfur Poisoning and YSZ Substrate Orientation on Electrochemical Properties of Nickel Pattern Anodes
Authors: Doppler Michael Christoph , Fleig Jürgen , Opitz Alexander Karl 
Published: February 2020

In state of the art solid oxide fuel cells (SOFCs) the anode is usually a ceramic-metal composite consisting of a network of Ni and yttria-stabilized zirconia (YSZ) grains as well as pores allowing for gas transport. This approach, while yielding excellent performance, is rather impractical for kinetic studies of the electrochemical triple phase boundary kinetics of Ni/YSZ since ionic and gaseous transport may also influence the electrode polarization resistance. These interferences make extraction of electrochemical elementary steps as well as mechanistic studies of degradation phenomena (e.g. sulfur poisoning) highly challenging. To circumvent these issues sputter deposited thin film electrodes with well-defined structures can be utilized.
In this study, pattern Ni anodes were investigated in H2/H2O atmosphere by means of electrochemical impedance spectroscopy (EIS). A sample pretreatment method was established to obtain stable values of the polarization resistance (RP) and interface capacitance (C) – i.e. avoiding degradation with time – to allow comparison of different microelectrodes. The effect of different YSZ substrate orientations on Rpand C is statistically evaluated and the correlation between the two properties is discussed.
Based on this knowledge the influence of H2S on Rp and C was investigated. The poisoning influence of sulfur on RP as well as the regeneration behavior was found to be qualitatively consistent with cermet electrodes described in the literature. Interestingly, also the electrode capacitance was affected by H2S: it decreased under sulfur poisoning conditions and regenerated partially after removal. Combined with dependencies of Rp and C on temperature, bias voltage and geometry these findings allow valuable insights into the electrochemical properties of Ni electrodes and their degradation.
Carbon Deposition and Deformation of Ni-YSZ Cermet in Hydrocarbon-Containing Gases
Authors: Ohmura Nobuaki , Nakamura Takashi , Matsuoka Koji , Kudo Takao , Amezawa Koji 
Published: February 2020

For the full-scale commercialization of SOFC systems, the durability and reliability of the cells and stacks should be improved. Carbon deposition and following deformation of the anode and is one of issues to be solved. For SOFC systems, hydrogen-rich gas, which is obtained through the steam reforming of hydrocarbons, is supplied to the anode. In practical SOFC systems, the steam/carbon molar ratio (S/C) is kept high enough to prevent carbon deposition thermodynamically. However, at the start-up/shut-down processes or failures in the reforming system, etc.,hydrocarbon fuel with low S/C may be introduced into the anode. In Ni-YSZ cermet, which is the most common anode material in SOFCs, Ni is highly active for the decomposition of the hydrocarbon gases and carbon formation. If the low-S/C hydrocarbon fuel was supplied to Ni-YSZ cermet, carbon would deposit on Ni. Such carbon deposition causes not only deterioration of conductivity and electrochemical activity but also significant volume expansion of Ni-YSZ cermet.
From the backgrounds mentioned above, in this study, we quantitatively evaluated the carbon deposition and expansion of Ni-YSZ cermet during exposure to 10%CH4-N2, 1%CH4-N2, 1%C2H6-N2 or 1%C3H8-N2with S/C = 0.1 or 1.0 in the temperature range between 973 and 1173 K. The dilatometry and thermogravimetry measurements as well as posterior analyses by SEM/EDX and XRD were performed for blocks of Ni-YSZ cermet.
When S/C was 0.1, significant carbon deposition and expansion were observed during the exposure to hydrocarbon gases. The expansion reached 1% within 5 hours for 1%CH4-N2 and 1 hour for the others. According to SEM/EDX analyses, the amount of deposited carbon was found inside of the specimen after the exposure, although its distribution differed among hydrocarbon gas species. Carbon segregated in the near surface of the specimens for 1%C2H6-N2 and 1%C3H8-N2, while distributed in the whole parts of the specimens for 1% and 10%CH4-N2. The temperature dependency of the expansion was also quite deferent among hydrocarbon gas species. The expansion ratio was smallest at 973 K for 10%CH4-N2 and 1%CH4-N2, while smallest at 1173 K for 1%CH2H6-N2 and 1%C3H8-N2. In the presentation, the expansion mechanism will be discussed based on the obtained results.
Atmospheric Plasma-Sprayed Metal-Supported Solid Oxide Fuel Cells with Varying Cathode Microstructures
Authors: Harris Jeffrey , Kuhn Joel , Kesler Olivera 
Published: February 2020

Metal-supported solid oxide fuel cells (SOFCs) use less expensive materials than traditional anode-supported or electrolyte-supported SOFCs. The active layers of a metal-supported SOFC can be manufactured by plasma spraying without the need for high-temperature sintering. Plasma spraying is a rapid-fabrication process that is scalable for large cell areas and for mass production.
Porous ferritic stainless steel (Sanergy HT, Sandvik, Sweden) supports were manufactured from powders by pressing and sintering pellets. The active cell layers consisted of a composite nickel - yttria-stabilized zirconia (YSZ) anode, a YSZ electrolyte, and a La0.6­Sr0.4Co0.2Fe0.8O3-δ (LSCF) – Ce0.8Sm0.2O1.9 (SDC) cathode.
Plasma spraying produces unique microstructures, as the cell layers are built up by the rapid solidification of molten (or semi-molten) splats. These microstructures were tailored by adjusting the plasma spray process parameters and the ingredients in the feedstock. Dense electrolytes were made using a high-power plasma, a very high torch pass speed (to minimize the plasma heat impulse to the substrate), and a feedstock consisting of YSZ suspended in a mixture of water, ethanol, and ethylene glycol. Cathodes with four different microstructures were produced by varying the plasma spray parameters and mixing carbon or starch-based pore forming agents into the ceramic feedstock powders. Resultant microstructures are shown in Figure 1.
Electrochemical performances of metal-supported button cells with varying cathode microstructures were measured. At 750°C, the cells had open circuit potentials of up to 1.057 V and peak power densities as high as 562 mW/cm². Electrochemical impedance spectra were measured at an operating point of 0.7 V, varying the cathode gas with different air-nitrogen mixtures. With 100% air as the cathode gas, the lowest cell polarization resistance was 0.29 Ωcm² at 750°C. Equivalent circuit modeling was performed to analyse how the cathode microstructure affected the cell performance.

Figure 1
Reactive Force-Field Development for Metal/Ceramic SOFC Anode Modeling
Authors: Saha Leton Chandra , Iskandarov Albert , Nakao Kazuhide , Ishimoto Takayoshi , Umeno Yoshitaka , Koyama Michihisa 
Published: February 2020

A solid oxide fuel cell (SOFC) system anode material is usually composed of a mixture of Ni and other oxide ceramics, such as doped-CeO2, and Sc stabilized ZrO2, due to their high activity and structural stability. Among them the nickel/yttria-stabilized zirconia (Ni/YSZ) cermet is widely used today as an anode material of SOFC due to its good electrocatalytic property against low price.
For SOFC performance, it is essential to improve the stability of the Ni/YSZ cermet anode. Combination of Ni and YSZ has been studied experimentally, but the interaction is not well understood in the boundary between Ni and YSZ. However, there is no evidence about the atomic-scale Ni/YSZ interface dynamics and chemical changes in the structure during the operation of SOFC. Unfortunately, most classical force fields are incapable of describing chemical reactions. To overcome this difficulty, reactive force field (ReaxFF) potential was developed by van Duin and co-workers. Recently, Ni/YSZ/H2 interactions are reported by ReaxFF. But in this interaction Ni/YSZ interface stability is not taken into account. As a first step we developed our own ReaxFF potential to investigate Ni/ZrO2 interface and for determining stable Ni/YSZ interface for modeling of the triple-phase-boundary in SOFCs. Big difference is found between our developed and reported ReaxFF and that is work of separation. Using our ReaxFF potential, work of separation is in excellent agreement with literature. It is found that O around Zr4+cation is reduced in case of bulk and interface regions. Although interface region exhibited less reduction compared to bulk region. More details and Ni/YSZ interface stability through O vacancy may present at conference.
Thermal Gradients in Solid Oxide Fuel Cell Anodes: X-Ray Diffraction, Thermal Imaging and Model Prediction
Authors: Robinson James B. , Engebretsen Erik , Brown Leon D , Clague Ralph , Eastwood David , Reinhard Christina , Lee Peter , Brett Dan J. , Shearing Paul R. 
Published: February 2020

Solid Oxide fuel cells (SOFC) are a widely discussed future power option due to their high energy efficiency and fuel flexibility in addition to low maintenance requirements. However, the long term mechanical stability of the stack can be compromised due to simple operation as a result thermally mismatched materials (1). The commonly used Ni / YSZ anode – electrolyte combination provides a high degree of electrochemical performance; however, the presence of the Ni catalyst which aids the performance of the cell results in a significant mismatch in the coefficient of thermal expansion (CTE) between the anode and electrolyte of cells (2). Issues arising from mismatched CTE can be further exacerbated by the presence of thermal gradients within SOFCs. Thermal gradients which can arise from simple operation, internal reforming and inhomogeneous current distribution amongst other factors (3-5) have been noted to significantly increase the prospect of cell failure (6).
In this study the effect of thermal gradients on SOFC anodes is investigated using both experimental and computational methods. Experiments conducted at Diamond Light Source using combined synchrotron X-ray diffraction and infrared thermal imaging (7) are detailed highlighting the presence of non-uniform thermally derived stresses at operationally relevant temperatures within the Ni phase of the anode of cells. Computationally derived thermal gradients have been generated using finite element method modelling in order to study the effect of cell operation utilising a three dimensional electrochemical model. The results obtained from the model have been coupled with the experimental results in order to investigate the effect of various parameters upon the cell. Operational conditions including cell polarization and fuel flow conditions and configurations are examined to highlight the importance of cell optimisation in minimising stresses within the cell anode to prolong cell lifetime whilst maximising performance.

References

1. S. Majumdar, T. Claar and B. Flandermeyer, J Am Ceram Soc, 69, 628 (1986).
2. W. Z. Zhu and S. C. Deevi, Materials Science and Engineering: A, 362, 228 (2003).
3. H. Apfel, M. Rzepka, H. Tu and U. Stimming, Journal of Power Sources, 154, 370 (2006).
4. H. Severson and M. Assadi, Journal of Fuel Cell Science and Technology, 10, 061001 (2013).
5. R. Clague, A. J. Marquis and N. P. Brandon, Journal of Power Sources, 210, 224 (2012).
6. A. Nakajo, Z. Wuillemin, J. Van herle and D. Favrat, Journal of Power Sources, 193, 203 (2009).
7. J. B. Robinson, L. D. Brown, R. Jervis, O. O. Taiwo, J. Millichamp, T. J. Mason, T. P. Neville, D. S. Eastwood, C. Reinhard, P. D. Lee, D. J. L. Brett and P. R. Shearing, Journal of Synchrotron Radiation, 21 (2014).
Kinetics of Internal Methane Reforming on the Anodes of Low Temperature Ceres Power Steel Cell SOFCs
Authors: Leah Robert Timothy , Lankin Mike , Bone Adam , Mukerjee Subhasish , Selby Mark 
Published: February 2020

Ceres Power has developed a unique low-temperature metal supported SOFC design (the ‘Steel Cell’) based predominantly around the use of ceria. This unique design architecture offers greatly enhanced robustness to real-world operating conditions at a lower cost than conventional SOFC designs, whilst retaining the advantages of fuel flexibility, high efficiency and low degradation.
A widely quoted benefit of SOFCs is the ability to carry out a significant percentage of the reforming of hydrocarbon fuels to syngas within the anode of the cells, simplifying the design of the fuel processing system by comparison with other fuel cell types. In addition performing the endothermic reforming reaction within the stack significantly reduces the requirement for air cooling, which improves the efficiency of a typical SOFC system by reducing the parasitic power demand from the cathode air blower.
It has historically been viewed that a disadvantage of low temperature SOFC operation is that significant levels of internal methane reforming are no longer possible due to poor kinetics and thermodynamically limited methane conversion. The Ceres steel cell technology has been developed to perform relatively high levels (40-60%) of internal methane reforming. In this paper a method for approximately estimating the kinetics of methane reforming on Steel Cell anodes will be described, coupling experimental measurements to a mathematical model.
The Effect of Electrode Morphology on Solid Oxide Fuel Cell Performance
Authors: Pharoah Jon G. , Handl Lisa , Schmidt Volker 
Published: February 2020

The morphology of the active electrode in a solid oxide fuel cell has a strong impact on both the transport properties and the active triple phase boundary length and distribution. The performance of the electrode emerges from the interaction of these two parameters and is impacted strongly by the size and shape of the starting powders used to make the ionically and electronically conducting phases of the electrode as well as by the manufacturing method used and the sintering process post manufacture. This paper presents a numerical study over a range of electrode morphologies chosen to represent different manufacturing processes and presents comparisons of geometric characteristics, transport properties and electrode performance.

Three different morphologies are generated from three different starting powders, spheres representing non aggregated powders, agglomerates of spheres and high aspect ratio cylinders modelling splats formed in plasma sprays. Of particular interest in this study is the effect of anisotropy of the base particles on the resulting electrode.

For each base particle shape multiple stochastic realizations of densely packed particle systems are generated using a collective rearrangement algorithm. The structures are then analysed geometrically with methods from spatial statistics using our own Java-based software, and meshed, solved and analysed with respect to transport and performance using a custom modified version of the open source computational fluid dynamics package, openFOAM. Detailed comparisons are presented in terms of tortuosity of paths through each phase of the material, constrictivity and chord lengths in different directions, directional transport properties in each of the three phases, distribution of the triple phase boundary lines and electrode performance
Effective Conductivity of Solid Oxide Fuel Cell Electrodes
Authors: Zheng Keqing , Ni Meng 
Published: February 2020

Effective conductivity of SOFC electrodes is an important parameter for predicting the ohmic loss in SOFC. This work investigates the effective conductivity of SOFC electrodes via numerical simulation. The microstructures of porous electrodes are reconstructed numerically by packing spherical particles in a computational domain, followed by dilation process to simulate the sintering procedure. The important tortuosity is computed and compared with literature data for model validation. The effects of various parameters on the effective conductivity of the electrodes are investigated, including the particle size, material composition, and porosity. The results are useful for understanding the microstructure properties of SOFC composite electrodes and for subsequent design optimization of SOFC electrodes.