bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reducing the Gadolinium Dopant Content by Partial Substitution with Yttrium in a Ce0.9Gd0.1O1.95-based Oxide-Ion Conductor
Authors: Mori Masashi , Sumi Hirofumi , Suda Eisaku 
Published: February 2020

Because of its high oxide-ion conduction and the chemical inactivity, Ce1-xGdxO2-δ fluorites are used as a reaction protection layer between the electrode and the ZrO2 electrolyte and addition materials to electrode elements for intermediate-temperature SOFCs. The rare-earth ores have 17 kinds of rare-earth elements including Sc and Y. However, Gd exists a low mineral content in the ores. Gadolinium element is used as magnetic devices, magnetooptic disk device, and control rod of the nuclear reactor. Under the present conditions, demand for Gd increases.
The conductivity and sintering characteristics are very important as SOFC components and it is well known that two typical compositions, Ce0.9Gd0.1O1.95 and Ce0.8Gd0.2O1.9, have be commercially available. Although many papers for the properties have been reported, the appropriate compositions of Gd are unclear. The reason for this is that the properties are strongly affected by synthesis methods and sintering conditions.
In the present study, the appropriate compositions of Gd-doped cerias with a Gd content of 0 ≤ x ≤ 0.2, which were prepared using the conventional co-precipitation method, have been discussed from the viewpoint of sintering characteristics, electrical conductivity and its long term stability. Sintering characteristics of the doped ceria samples have a tendency to decrease with increasing Gd content. The maximum conductivity of 2.56×10-2 S/cm at 600ºC was observed for the sample with 10 mol% Gd dopant. During the annealing process at 600ºC, the conductivity decreased with annealing time due to the grain-boundary resistance. The synchrotron X-ray diffraction analysis showed to be Gd2O3 phase in the fluorite and the decrease of lattice parameter. These results suggest that the decrease of the conductivity should be related to the segregation of Gd element at the grain-boundary of the Ce0.9Gd0.1O1.95 fluorite.
Fabrication of BaZr1-XYxO3 Powder by Freeze Drying Method
Authors: Kato Tohru , Momma Akihiko , Yoshioka Ayumi , Terayama Takeshi , Tanaka Yohei 
Published: February 2020

BaZr1-xYxO3 is an attractive electrolyte material for low operating temperature SOFCs and SOECs because of its high proton conductivity at temperature less than 600 oC and good chemical stability under CO2 and steam atmospheres. However, its high synthetic temperature more than 1100 oC and the high sintering temperature more than 1,600 oC to get a dense electrolyte membrane cause mismatch of the shrinkage behavior and reaction with other SOFC or SOEC component materials at the fabrication process.
Therefore, in this paper, reducing the synthesizing temperature of BaZr1-xYxO3 powders by freeze dry method has been tried. In the freeze dry process, Ba(NO3)2, ZrO(NO3)2 nH2O, Y(NO3)3 nH2O were chosen as low materials. The hydration numbers of ZrO(NO3)2 nH2O and Y(NO3)3 nH2O were measured by using a differential thermogravimetric analyzer. These nitrates were mixed to produce solution with the molar ratio of metal ions what we desired. The solution was atomized and frozen rapidly by using liquid nitrogen to avoid segregation. The frozen solution was dried under vacuum condition at temperature of about -40 oC. After finishing sublimation, obtained frozen powder was heated and synthesized at the temperatures of 600 to1000 oC. As a result of X-ray diffraction analysis and energy dispersive X-ray spectrometry, it is clarified that BaZr1-xYxO3 can be synthesized at 800 oC which is lower more than 300 oC than conventional synthetic temperature. We are to report the possibility of reducing the sintering temperature of BaZr1-xYxO3 by using obtained powders and properties of the sintered BaZr1-xYxO3 such as the conductivity.
Study of Sr2MgMo0.9Ni0.1O6-δ as SOFC Anode
Authors: Dager Paola Katherine , Mogni Liliana Veronica , Zampieri Guillermo , Caneiro Alberto 
Published: February 2020

The double perovskite Sr2MgMoO6 (SMMO) has attracted the attention to be used as SOFCs-anode because, despite its poor electrical conductivity, it exhibits high electrocatalytic performance for H2-oxidation, sulphur tolerance and thermal stability. This mixed oxide provides multiple positions for doping (Sr, Mg and Mo-sites) and promotes oxygen vacancies formation, which allows to improve its properties such as chemical stability, electrical conductivity, etc. In present work, the Mo-site of SMMO was doped with Ni, in order to gain understanding of the structure, chemical and electrochemical properties of Sr2MgMo0.9Ni0.1O6-δ
(SMMNi). The undoped sample (SMMO) was tested to comparison. The SMMNi and SMMO powders were synthesised by combustion method and thermally treated in air at 1000 and 1100 ºC respectively during 12 h. These materials were characterised by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). XRD patterns for SMMNi powders confirmed the formation of a well-defined double perovskite phase belonging to the space group I-1. TEM micrographs show that SMMNi powders had a mean grain size around 340 nm. The surface analysis of SMMNi and SMMO powders were carried out by XPS on as-synthesised and post-reduced at 800 ºC in 10%H2-Ar for 10 h. Results demonstrated that Mo6+ ions in SMMNi had been reduced to Mo5+after calcined in 10%H2-Ar. Furthermore, XPS spectra exhibited no apparent change in oxidation state of Nickel after subjecting to SMMNi-powders to a reducing atmosphere. The stability studies indicate that SMMNi is more unstable in comparison to SMMO, under 10%H2-Ar. Whereas SMMO remains stable until 1000 ºC, SMMNi decompose above 900 ºC. Additionally, electrochemical impedance spectroscopy (EIS) measurements on symmetrical SMMNi/GDC/SMMNi under reducing atmosphere at 700 ºC allowed seeing the influence of the time and environment conditions (H2 content) in the anode polarisation resistance (Rpa). The aforementioned could be seen in Fig. 1, where the Rpa decreases from 3 to 0.4 Ωcm-2 as pH2 increases from 0.05 to 1 atm. These values are up 5 times higher than those for SMMO in the same conditions.

Figure 1
Metal-Supported Solid Oxide Fuel Cell with High Power Density
Authors: Tucker Michael C 
Published: February 2020

Metal-supported solid oxide fuel cells (mSOFC) display a number of advantages over conventional all-ceramic SOFCs, including low-cost structural materials (e.g. stainless steel), mechanical ruggedness, excellent tolerance to redox cycling, and extremely fast start-up capability. Challenges for mSOFCs include: oxidation of the metal support, especially at 800°C and above; the possibility of the stainless steel exacerbating Cr poisoning of the cathode catalyst; fabrication and materials set restrictions arising from the requirement that stainless steel be sintered in reducing atmosphere; and, only moderate performance and lifetime have been demonstrated to date.
These advantages and challenges suggest that mSOFCs may be well-suited for portable, ruggedized, fast-start, intermittent-fuel, or other unique and innovative applications. Nissan has developed the world’s first light-duty vehicle with a conventional SOFC stack for traction power, fueled by bio-ethanol reformate. Because of the desire for rapid-start capability, developing mSOFC cell and stack technology for this vehicular application is a priority. The small volume allowance for the SOFC stack on-board a small vehicle furthermore demands high power density from the mSOFC. In this work, we seek to maximize mSOFC power density.
This work is an extension of our previous efforts focusing on co-sintered, YSZ-based mSOFCs with porous metal supports on both anode and cathode sides, with catalysts deposited into both electrodes via infiltration. These features provide for a mechanically rugged cell that can be processed with low-cost scalable techniques, and high surface-area catalysts that provide excellent performance by avoiding interdiffusion or coarsening during cell sintering. To support the vehicular traction application, in this work we further develop catalyst infiltration processing for mSOFCs to dramatically increase power density. The goal is to increase cell performance by improving infiltration of conventional catalyst compositions (lanthanum strontium manganite (LSM), Ni, doped ceria) into electrode backbones of conventional yttria-stabilized zirconia (YSZ). Various aspects of the infiltration procedure were optimized, including: precursor composition and dilution with water; catalyst loading; and, crystallization temperature. Figure 1 shows the resulting high performance. Peak power of 1.1 and 1.9 W/cm2 is achieved at 700°C and 800°C, respectively, and the 800°C performance is the highest reported for mSOFCs to date. Cell stability in the operating temperature range 600 to 750°C will also be presented.
Acknowledgements
Funding for this work was provided by Nissan Motor Co., Ltd. This work was funded in part by the U.S. Department of Energy under contract no. DE-AC02-05CH11231.

Figure 1
Effect of YSZ Volume on Polarization Resistance of Anode with Magnetically Aligned Ni
Authors: Nagato Keisuke , Shintani Kodai , Shikazono Naoki , Shimura Takaaki , Nakao Masayuki 
Published: February 2020

In conventional solid oxide fuel cell (SOFC) anodes, yttria-stabilized zirconia (YSZ), Ni and pore phases are randomly distributed, where oxide ion, electron, H2 and H2O gases diffuse. These species electrochemically react at the triple phase boundaries (TPBs). From the viewpoint of tortuosity, aligned YSZ and Ni structure in the thickness direction is desirable, since it can reduce transport resistance. In our previous work [1], it was demonstrated that Ni particles can be aligned by applying the magnetic field during the drying process after screen-printing of Ni/YSZ paste. In this study, the Ni-YSZ volume ratio was varied to investigate the effect of the volume ratio on the polarization resistance of anodes fabricated with and without the magnetic field. In the conventional random structure, volume ratio of Ni and YSZ is generally kept at 50:50 to maintain active TPBs. Here, ionic conductivity of YSZ is much smaller than the electronic conductivity of Ni. Therefore, if Ni alignment can be improved by applying the magnetic field, YSZ volume fraction can possibly be increased, alternatively volume fraction of Ni can be reduced. The trade-off between the decrease in TPB length and the increase in ionic conductivity must be carefully investigated.
The volume ratio of Ni and YSZ was varied as 50:50, 33:67, and 20:80 in the present study. The Ni/YSZ paste was screen-printed on both sides of 200-mm-thick YSZ electrolyte substrate. During the drying process, magnetic field was applied along the thickness direction. After the anodes were sintered at 1400˚C in air, they were reduced in the furnace before the electrochemical measurement. The polarization resistance was measured by electrochemical impedance spectroscopy at 800˚C in 5%H2O, 95%H2 gas. Figure 1 shows the Nyquist plots of the symmetrical cells (a) without and (b) with the magnetic field. Without the magnetic field, the polarization resistance of the cell increased as the Ni volume fraction is reduced, which is reasonable from the percolation theory. On the other hand, with the magnetic field, the polarization resistances remained nearly unchanged. It is considered that the decrease in TPB length cancelled out the increase in ionic conductivity of the YSZ path. On the other hand, it is expected that the reduction of Ni volume fraction will lead to the improvement of durability of the cell, since strengthened YSZ skeleton may supress Ni agglomeration and the mismatch in thermal expansion between electrolyte and anode can be improved.
[1] K. Nagato, N. Shikazono, A. Weber, D. Klotz, M. Nakao, E. Ivers-Tiffée, ECS Trans. 57, 1307-1311 (2013).

Figure 1
Review of Progress in Solid Oxide Fuel Cells at FuelCell Energy
Authors: Ghezel-Ayagh Hossein , Borglum Brian P 
Published: February 2020

Significant progress has been made towards the development of Solid Oxide Fuel Cell (SOFC) at FuelCell Energy Inc. (FCE). The genesis of the advances in the technology is rooted in scale-up of the Company’s anode-support technology made by the TSC (Tape Casting-Screen Printing-Sintering) Process. The anode supported thin electrolyte planar cell platform was adopted for its higher power density at reduced operating temperature (600-800°C). Traditional materials, such as Ni/YSZ anodes, YSZ electrolytes and perovskite cathodes have been utilized in a basic cell structure. Research and development has been successful in developing better electrochemical functional areas at both cathode/electrolyte and anode/electrolyte interfaces. This was achieved through materials advancement, microstructure optimization, and manufacturing process integration. Cell materials development advancements have been made in performance, endurance, cell size (area) scale-up and cost reduction. These advancements led to an enhanced cell performance by reducing cell ASR (Area Specific Resistance) while reducing cell cost through cell design changes and materials reduction. Scaled-up cell size of up to 1000 cm2 have been made and tested with the current baseline cell size of 550 cm2 as the standard unit size for building SOFC stacks. The baseline stack design has been successfully scaled-up from 120-cell 550 cm2 cell area (16 kW nominal) stack. Using standardized manifolds and gas-electrical interconnects, these stacks have been successfully integrated into stack towers and arrays.
FCE recently designed, built, and tested a 50 kW fully automated SOFC system under a Co-operative Agreement with Department of Energy. In a follow-on DOE supported project, currently, FCE is engaged in design and construction of larger 200kW units that utilize baseline factory-built stack blocks representative of the future MW-scale power plants.
Development Progress on the Ceres Power Steel Cell Technology Platform: Further Progress Towards Commercialization
Authors: Leah Robert Timothy , Bone Adam , Hammer Eva , Selcuk Ahmet , Rahman Mahfujur , Clare Andrew , Mukerjee Subhasish , Selby Mark 
Published: February 2020

Ceres Power is continuing to make excellent progress in the development of its low-temperature metal supported SOFC design (the ‘Steel Cell’) based predominantly around the use of ceria. This unique design architecture allows for a robust, low cost, subsidy free fuel cell product, whilst retaining the advantages of fuel flexibility, high efficiency and low degradation.
Over the last year, several significant technological and commercial developments have taken place. The latest generation of SteelCell technology (v4.0) has completed validation and verification testing, and is now the standard version of the technology offered to customers. The v4.0 cell/stack technology has a significantly simplified and lower-cost manufacturing process relative to earlier technology generations, whilst offering improved performance and comparable degradation. v4.0 stacks have been incorporated into natural-gas fuelled Ceres Power SteelGen 700We micro-CHP demonstrators, which have been deployed in several locations in the UK as part of a field trial in association with British Gas funded by the European Ene.field program. In addition to this Ceres is also working with Nissan to evaluate the application of SteelCell technology to an electric vehicle range extender application, taking advantage of the thermal cycle and mechanical robustness of the technology, which is at least an order of magnitude better than published data from any other SOFC stack developer.
In addition to an ongoing joint development agreement with Honda, Ceres has also been granted a US DoE grant working with Cummins on a 5kWe-class stationary power generator for use in data centers. Ceres has also announced a joint development and licensing agreement with another large global OEM to develop a multi-kWe-scale micro CHP system.
A major focus of ongoing technology development is to further improve stack power density, durability and efficiency in line with the technology roadmap for next generation products. Significant progress has been demonstrated at the R&D level on all of these requirements, and the design improvements to achieve them will be incorporated into the next generation of SteelCell technology.
Effect of Infiltrated Transition Metals in Ni/Sm-Doped CeO2 Cermets Anode in Direct NH3-Fueled SOFCs
Authors: Zhang Mengjia , Hashinokuchi Michihiro , Yokochi Ryuji , Doi Takayuki , Inaba Minoru 
Published: February 2020

Ammonia (NH3) has attracted much attention as a fuel for SOFCs. In the case of well-established Ni-based cermets anode, however, the cell performance is poor due to the low catalytic activity for NH3 reforming. In this respect, it is necessary to develop the highly active anode for realizing direct NH3-fueld SOFCs.
Previously, we prepared Ni-M (M : Mo, Ta, W and Nb)/ Sm-doped CeO2(SDC) anodes by infiltration of metal solutions into pre-sintered Ni/SDC cermets and revealed the activity of them as an anode for direct NH3-fueled SOFCs at temperature of 700 to 900 °C [1-2]. From these studies, we have proposed that the synergetic effect of Ni and added metals, which weakly and strongly bind to N atom, enhances the activity of the anodes for NH3 oxidation(NH3 reforming, followed by hydrogen oxidation). In addition, it was found that the enhancement of the activity for NH3 oxidation strongly depended on the added metal. Among them, Mo was the most effective element as an additive. On the other hand, the obvious enhancement of the activity for NH3 oxidation was not observed when Nb, Ta and W were added, which have the larger metal-nitrogen (M-N) binding energy than Mo. The activity of the Ni-M binary anode seemed to be determined by the interaction potential between catalytic surface and N atom, produced by Ni and added metals. Here, we focus chromium(Cr) and vanadium(V) as an additive, because Cr and V have the moderate M-N binding energy (ranked in the order of Mo < Cr < V < W < Nb < Ta) among the metals used in our previous studies.
The addition of Cr and V into the Ni/SDC cermets enhanced the activity of the anode for NH3 oxidation at temperature of 700 to 900 °C. The formation of Ni metal and nitrides (CrN and VN) was confirmed in each anode at 700 °C. This suggests that the synergetic effect of Ni and Cr(V), which has weekly and strongly bind to N atom enhances the activity of the anode for NH3 oxidation. Cr was more effective than Mo as an additive, but V was not. The relationship between the activity of the anode and the M-N binding energy of the added metal are discussed.

Acknowledge

This work was supported by “Kyoto Environmental Nanotechnology Cluster” and “Kyoto Regional Scientific Innovation Hub” from MEXT in Japan.

Reference

[1] M. Hashinokuchi et al., Solid State Ionics, 285, (2016) 222
[2] R. Yokochi et al., ECS Trans. 68(2015) 2745.
Designing the Composite SrVO3-SrTiO3 Anodes for Hydrocarbon-Fueled Solid Oxide Fuel Cells
Authors: Yaremchenko Aleksey , Macias Javier , Frade Jorge 
Published: February 2020

Perovskite-type SrVO3- and SrTiO3-based phases exhibit good resistivity to sulfur poisoning and do not catalyze carbon deposition, and are considered therefore as possible alternative anode materials for hydrocarbon-fueled solid oxide fuel cells. SrVO3 exhibit high electronic conductivity but also a narrow phase stability domain restricted to reducing conditions. On the other hand, SrTiO3 demonstrates remarkable phase and dimensional stability in a wide range of T-p(O2) conditions but rather insufficient electrical conductivity. The present work aimed at the development of SrVO3-SrTiO3 composite anode materials with emphasis on a compromise between dimensional/microstructural stability and electrical properties.
Initial assessment demonstrated that SrVO3 and SrTiO3 form an entire range of solid solutions under reducing conditions. In all cases, exposure to air above 600-700°C resulted in either collapse of perovskite structure (V-rich compositions) or separation of vanadium-containing secondary phases (Ti-rich composition). These phase transformations were accompanied by dimensional changes and were not reversible at temperatures below 1000°C (probably, due to kinetic reasons).
Instability in oxidizing atmospheres complicates the fabrication of anodes in realistic conditions. Therefore, the second approach was to start from oxidized phases and to proceed via in-situ reduction employed for Ni-YSZ cermet anodes. V5+ substituted in titanium sublattice of SrTiO3 acts as donor-type dopant and was found to has a limited solid solubility under reducing conditions (~30-35 at.%). In-situ reduction of oxidized SrTi1-y
V
y
O±δ at 900°C is accompanied however by the reduction of vanadium cations, and the resultant conductivity remains too low (< 0.2 S/cm) being comparable to other acceptor-doped strontium titanates.
The next approach was preparation of composite SrVO3-SrTiO3 anode materials starting from oxidized phases. The precursors with nominal composition SrTi1-y
V
y
O±δ (y = 0.1-0.4) were thermally treated in air at temperatures not exceeding 1100°C to yield equilibrated phase mixtures comprising SrTiO3-based perovskite as a main phase and strontium orthovanadate Sr3(VO4)2 as a second major phase. Transformation of strontium orthovanadate on reduction at 900°C into highly-conductive perovskite-type SrVO3 phase finely distributed in the stable SrTiO3-based matrix resulted in substantial nearly instant increase of electrical conductivity by orders of magnitude reaching 10-30 S/cm for y = 0.3-0.4. Electrochemical activity of composite anodes applied onto yttria-stabilized zirconia solid electrolyte and infiltrated with a fraction of Ce0.9Gd0.1O2-δ electrolyte component was evaluated by electrochemical impedance spectroscopy using symmetrical cell configuration.