bluuebunny/crossref_metadata_2025_split huggingface dataset:
eCOs - A Commercial CO2 Electrolysis System Developed by Haldor Topsoe
Authors: Küngas Rainer , Blennow Peter , Heiredal-Clausen Thomas , Holt Tobias , Rass-Hansen Jeppe , Primdahl Søren , Hansen John Bøgild 
Published: February 2020

This paper will cover the technical and commercial features of Haldor Topsoe’s CO from CO2
technology. Haldor Topsoe’s eCOs® is a solid oxide electrolysis cell (SOEC) technology that allows the safe, efficient, and cost-competitive production of carbon monoxide directly at the site of facilities where the gas is needed. The CO-generation device uses feedstock carbon dioxide and electrical power to produce CO in quantities ideal for most operations that today rely on cylinder or tube trailer supply.
An eCOs plant is delivered as a stand-alone unit with power, CO2 and product gas connections. Furthermore, the plant ensures high levels of purity, producing CO at 99.5% assay with minimal contaminants and CO2 as the main contaminant. An eCOs solution can also be customized to produce CO at 99.999% purity. One eCOs plant is able to deliver between 10 and 100 Nm3 CO gas per hour.
The patented eCOs technology ensures security of supply, eliminates the need to transport hazardous gas, and drastically reduce costs related to storage, rentals and connections. In the longer run, this technology opens up for a whole new segment of green and sustainable chemicals from renewable carbon sources.
Field test results from the 12-kW demonstration-unit located in Houston, Texas will be reported, as well as progress towards the 400-kW commercial unit to be delivered in 2018. Results from a 50-kW H2O electrolysis unit located in Foulum, Denmark used for biogas upgrading will also be presented.
Characteristics of New Nickel Porous Alloy for Cathode Current Collector in Solid Oxide Fuel Cells
Authors: Hiraiwa Chihiro , Tawarayama Hiromasa , Higashino Takahiro , Okuno Kazuki , Majima Masatoshi 
Published: February 2020

Introduction

A Nickel (Ni) porous metal is used for anode current collector in solid oxide fuel cells (SOFCs)[1]. However, it is difficult to be applied as cathode current collector due to its large oxidation resistance at high temperature. In this work, we investigated characteristics and applicability of a new Ni-Sn porous alloy as the cathode current collector for SOFCs.

Experimental

The Ni porous alloy was prepared by electroplating process. Sn was deposited continuously by electroplating onto the surface of the Ni porous metal. Then, heat treatment was performed under hydrogen atmosphere to obtain the Ni-Sn porous alloy [2]. Figure 1(A) shows a SEM image of three-dimensional structure of the as-prepared sample.
Oxidation resistances were evaluated by measuring weight increase due to the heat treatment, and the area-specific resistance at high temperature. The crystalline phases of the specimens before and after heat treatment were identified by XRD. Mechanically polished cross-sections of the specimens were observed via SEM-EPMA. Finally, the prototype SOFCs were fabricated using the Ni-Sn porous alloy as the cathode current collector.

Results and Discussion For Ni-Sn porous alloys with various Sn contents, figure 1(B) shows the weight increase due to the heat treatments in air at 800 °C for 1,000 hours and at 600 °C for 3,000 hours. In the case of the heat treatment at 800 °C for 1,000 hours, the weight of Ni-Sn porous alloys increased regardless of the Sn content. And the weight increased more than 1.7 mg/cm2, revealing a noticeable level of oxidation. In contrast, for Ni-Sn porous alloy with Sn content of 5 wt% or more, the oxidation was noticeably retarded in spite of a long-term heat treatment at 600 °C for 3,000 hours. Figure 1(C) shows the distribution of oxygen by using EPMA-EDS to analyze the cross-section area of the Ni-10wt%Sn porous alloy before and after heat treatment at 600 °C in air for 1,000 hours. After heat treatment, one can see a clear existence of oxygen in the depth about 1 μm from the surface, indicating the oxidation of this region.
The IV relationship and the power output characteristics of SOFCs with the cathode current collectors made of Pt mesh or the Ni-10wt%Sn porous alloy. Both the behavior of the IV relationship and the output power of the SOFC with the Ni-10wt%Sn porous alloy were almost equivalent to that using the Pt mesh.
Conclusions
The Ni-Sn porous alloy has relatively low electrical resistance after the heat-treatment in oxygen, and also high electric conductivity at 600 °C. Thus, this new Ni porous alloy has promising perspective to be applied as the cathode current collector for SOFCs operating in an intermediate temperature range. And such demand is expected to grow in near future.
[1] W. Guan, et al., Fuel Cells, 12(2012), 1085-1094
[2] K. Okuno, et al., SEI Technical Review, 75(2012), 137-140

Figure 1
Effect of YSZ Coatings as Diffusion Barrier between Glass Sealing and Steel
Authors: Spotorno Roberto , Fracchia Elisa , Schiller Guenter , Piccardo Paolo 
Published: February 2020

In solid oxide fuel cell (SOFC) stacks the sealing is a critical element which has to ensure gas tightness between different gas streams as well as electrical insulation in several parts of the system depending on its design. It has therefore to establish stable interfaces with different materials such as the ferritic stainless steel (FSS) used for interconnects frame or gas manifolds and the ceramic materials of the cell electrolytes. Therefore, sealants have to be chemically and mechanically stable in contact with such materials at the SOFC working conditions in terms of temperatures, thermal and stress gradients, and exposition to different gas compositions.
Glasses are widely used as sealing material because of their thermal expansion characteristics, mechanical properties, the possibility to obtain gas tight structures and ease of application. However, due to the operating temperatures, reactions and diffusion processes can occur at the interfaces resulting in the formation of undesirable phases that could compromise the glass properties increasing the risk of failures. The application of a barrier layer between the two components is considered as suitable countermeasure avoiding the migration of elements at the interfaces. In this work the barrier properties and compatibility at the interfaces of Yttria-stabilized zirconia (YSZ) has been investigated. YSZ layers have been applied by means of plasma spraying on as-rolled FSS substrates. Several glass compositions, applied on substrates with and without YSZ coating, have been tested at 780°C in static air up to 1000 h to investigate the barrier layer effects, the compatibility of the materials and the stability of the interfaces. Microstructural changes and migration of elements have been characterized post-experiment in cross-section by means of scanning electron microscopy- energy dispersive X-ray analysis.
Reactive-Element-Free, Silver-Based Brazes for SOFC Applications
Authors: Zhou Quan , Bieler Thomas R. , Nicholas Jason D. 
Published: February 2020

The current go-to braze for SOFC applications is the Ag-CuO reactive air braze (RAB). As with other RAB brazes, the ability to use this braze with ceramic materials (such as yttria stabilized zirconia (YSZ) and oxide-protected stainless steel (SS)) is enabled by a braze component (in this case Cu) reacting with the brazing atmosphere to form a surface oxide that facilitates wetting. [1-3]. Although Ag-CuO provides an easy way to join YSZ and SS for SOFC applications, the insufficient ~45° wetting angle of the conventional Ag-4 wt.% Cu braze [1, 2] often leads to braze joint manufacturing defects (Type I pores). Further, the reduction of CuO during dual atmosphere (H2/O2) SOFC operation results in porosity (Type II pores) that: i) mechanically weaken the braze/SS and braze/YSZ interfaces and ii) facilitates H2invasion into the center of the braze, which in turn, hastens the development of gaseous water pockets within the braze (Type III pores) caused by dissolved oxygen and hydrogen meeting.
This poster will present a new method for silver brazing YSZ and SS without the need for reactive air elements. As shown in Figure 1, this procedure (which is performed under SOFC electrode compatible oxygen partial pressures ≥ 1x10-10atm) produces a braze that wets both the YSZ and SS. In addition, this procedure also produces Ag-YSZ bonding which has been shown by Kuhn et. al [4] to have a fracture energy two times higher than conventional Ag-CuO braze joints. It is expected that the elimination of Type I and Type II pores enabled by this new brazing method will increase SOFC braze joint lifetimes.

References

1. Kim, J.Y., J.S. Hardy, and K.S. Weil, Effects of CuO Content on the Wetting Behavior and Mechanical Properties of a Ag-CuO Braze for Ceramic Joining. Journal of the American Ceramic Society, 2005. 88(9): p. 2521-2527.
2. Kim, J.Y., J.S. Hardy, and K.S. Weil, Silver-Copper Oxide Based Reactive Air Braze for Joining Yttria-Stabilized Zirconia. Journal of Materials Research, 2005. 20(3): p. 636-643.
3. Chatzimichail, R., et al., Interfacial properties of (Ag plus CuO) brazes used as sealing materials in SOFC stacks. Journal of Materials Science, 2014. 49(1): p. 300-313.
4. Kuhn, B., et al., Mechanical Performance of Reactive-Air-Brazed (RAB) Ceramic/Metal Joints for Solid Oxide Fuel Cells at Ambient Temperature. Journal of Power Sources, 2009. 193(1): p. 199-202.

Figure 1. Back scattered electron cross-sectional images of a) the entire joint sandwich, b) the SS/braze interface and c) the braze/YSZ interface.

Figure 1
Prediction of Performance Degradation Due to Grain Coarsening Effects in Solid Oxide Fuel Cells
Authors: Mason Jerry Hunter , Celik Ismail Bektas , Lee Shiwoo , Abernathy Harry , Hackett Gregory A 
Published: February 2020

Long term degradation of solid oxide fuel cells is one of the biggest impediments to commercialization. Due to the inordinate amount of time required to properly test degradation experimentally, physics based models which can predict long term degradation can be crucial time and money saving tools. At the cell level, one of the primary modes of degradation comes from grain coarsening and the resulting changes in microstructure properties. In this study a multi-physics model of a single fuel cell is presented which aims to predict performance loss as a function of time caused by coarsening in the electrodes of an LSM/YSZ/Ni SOFC. Microstructural properties are changed as a function of time from their initial values using functional relations derived from data from experiments and phase field models. Specie and charge transport equations are solved using these parameters to predict performance changes with time which result from the aforementioned microstructural changes. The model is first calibrated such that it correctly captures the performance and impedance response of a particular button cell at a given time without any degradation. This same model is run for a duration of 750 hours with performance data being measured for the same cell including impedance measurements being taken intermittently. Performance change over time predicted by the model are compared to experimental data. It is found that the model predicts a slower degradation rate than the rate which occurs experimentally. This is deemed reasonable as other forms of degradation are not being accounted for. The model is then used to make long term predictions of cell performance loss due to grain coarsening. The resulting degradation rate is considered to be the theoretical minimum which occurs when all other modes of degradation are not present. Work is underway to include other forms of degradation in the model so that a complete and robust degradation prediction tool is available for design analysis without the need for costly long term degradation measurements.
Electrochemical Impedance Studies on SOC
Authors: Vinke Izaak C. , Vibhu Vaibhav , Yildiz Saffet , Schiemann Kevin , Eichel Rüdiger- Albert , de Haart L. G. J. 
Published: February 2020

In the institute for fundamental electrochemistry IEK-9 at the Forschungszentrum Jülich GmbH the electrochemical properties of solid oxide cells are electrochemically characterized at a variety of sizes, configurations and operating conditions. In various projects different aspects of the complete cell and the reversible oxygen electrode (ROE) are studies. Both electrode supported cells of 5 x 5 cm² and 20 mm diameter are characterized by galvanostatic DC methods and electrochemical impedance spectroscopy (EIS). Also electrolyte supported symmetric cells are studied using a configuration with reference electrodes to investigate the reversible air electrode in detail. The main focus lies on the use of EIS to try and understand the different fundamental (electrochemical) reactions within the electrode process.
Measurements are conducted on 5 x 5 cm² electrode supported cells comprising a 0.6 mm thick Ni/8YSZ fuel electrode, a 10 µm thick 8YSZ electrolyte, a 10 µm thick GDC diffusion barrier layer and a 50 µm thick LSFC air electrode. The impedance of the cells shows a continuous increase when progressing from fuel cell to electrolysis conditions (see Figure 1A). At high currents densities under both positive and negative current densities an inductive loop appears in the low frequency range. Due to the high currents involved and the use of a power booster during the measurements the EIS data are limited to ~10 kHz in the high frequency range. Therefore the EIS data do not directly show a high frequency intercept with the real axis and the Ohmic resistance has to be determined using a fitting procedure.
Similar measurements were also performed on 20 mm round or button cells of the same composition and microstructure. These cells show similar behavior (see Figure 1B). The overall shape of the impedance spectra is comparable for both cell types although the contributions of the underlying processes seem to vary with the cell size. Here the high frequency intercept can be determined but the measured data have to be corrected for an inductive contribution originating in the measurement setup.
To separate the contribution of the ROE from the total cell resistance, measurements on electrolyte supported cells with symmetrical CGO/LSCF electrodes and a platinum reference electrode are performed. Also here a continuous transformation of the EIS spectra can be observed when going from oxygen reduction in the fuel cell mode to oxygen evolution in the electrolysis mode.
By combining the data of all three different cell geometries an attempt is made to separate contributions from both electrodes and the influence of cell size on the total cell resistance.

Figure 1
Galvanostatic EFM: A New Approach for Testing and Monitoring Fuel Cells
Authors: Moosbauer Dominik Johann , Zhang Xueyuan , Yaffe Max 
Published: February 2020

Electrochemical Frequency Modulation (EFM) is a well-known technique which is mostly used for corrosion studies. It is generally performed in potentiostatic mode and allows calculating the corrosion current as well as Tafel parameters by rearranging the Butler-Volmer equation. It was recently also used for testing fuel cells. However, for electrochemical power systems, galvanostatic control is much more beneficial. Even small potential changes can lead to high currents if a system has a very low internal resistance which can lead to irreversible damages at the cell and safety risks. Nonetheless, no practical and theoretical approach has been published so far for EFM measurement in galvanostatic mode.
This study presents first galvanostatic EFM measurements with fuel cells. The results are compared to other techniques which are typically used for analyzing fuel cells such as polarization experiments, electrochemical impedance spectroscopy (EIS), and current interrupt (CI). Measurements within this study are performed with a small Proton Exchange Membrane (PEM) fuel cell. During galvanostatic EFM experiments, a DC current signal is applied which is superimposed by a perturbation signal consisting of two sine waves with different frequencies (f
1, f
2). The measured voltage answer is more complex due to the non-linear behavior of fuel cells. The voltage signal can be subdivided into its DC response (zero frequency), harmonics (integral multiples of both base frequencies; f = n×f
1/2 where n is an integer > 0), as well as interharmonics (sum and difference of multiple harmonics; f = n×f
1 ± m×f
2 where n, m are integers > 0). In order to determine these terms, a fast Fourier transform (FFT) algorithm is employed on the measured signal. The voltage response can be plotted versus frequency in a so-called intermodulation spectrum. Harmonic and interharmonic amplitudes can be then used to calculate various parameters. As basis for all calculations serves the general equation for the cell voltage V
cellof a fuel cell:

V
cell = E
th - η
act - η
ohm - η
conc

The equation includes three major polarization terms that are responsible for voltage loss. These terms are the activation overpotential η
act, the ohmic overpotential η
ohm, and the concentration overpotential η
conc. E
th is the theoretical thermodynamic potential. The equation can be rearranged by expanding and substituting various terms. Similar to potentiostatic EFM, two causality factors can be extracted which can be used to proof validity of the measured results. Applicability of this method and its calculations are tested under various conditions such as different loads and oxygen concentrations. Finally, the results are compared with other techniques.
Evaluation of Performance and Heat Balance of Dry Reforming SOFC System
Authors: Kushi Takuto , Ohashi Masahumi , Kato Rei , Ito Takuya , Inagaki Shin , Amaha Shinji 
Published: February 2020

SOFCs can achieve high electrical efficiency by utilizing steam reforming because the absorption reformate heat could be supplied from the heat from the stack and the anode off-gas combustor in the hotbox. However, water supply system leads to high manufacturing cost in BOP and may lead to decreased reliability of systems because of sensitive control. On the other hand, partial oxidation (POX) reforming system ensures the simplified system, while POX reforming system leads to lower electrical efficiency than in that of steam reforming because of fuel consumption in reforming.
From the background written above, we are focusing adapting full-scale CO2reforming (dry reforming) to SOFC systems to expand the capability of SOFCs. To reveal the feasibility of the dry reforming SOFC system, we have previously investigated the performance and durability of catalysts (reformer) and a cell stack in simulated dry reforming by comparing with that of steam reforming.
In this study, we investigated the performance of SOFC hotbox adapting dry reforming. The thermally self-supported state was successfully demonstrated in dry reforming operation. Additionally, this study discusses the heat balances of a hotbox under dry and steam reforming conditions. From the obtained results, we will introduce the problem and capability of the dry reforming SOFC system and discuss its feasibility.
Influence of Cell Design on the Performance of Direct Ammonia-Fueled Solid Oxide Fuel Cell: Anode- vs. Electrolyte-Supported Cell
Authors: Singh Vandana , Muroyama Hiroki , Matsui Toshiaki , Eguchi Koichi 
Published: February 2020

In this study, the performance of anode-supported and electrolyte-supported cells was compared under similar operating conditions for direct ammonia-fueled solid oxide fuel cell (SOFC); the cell configuration of both types of cells was as follows, Ni‒YSZ|YSZ|GDC|LSCF. The anode-supported cell showed better performance as compared with that of the electrolyte-supported cell. A power density of ca. 0.358 W cm-2 was achieved for the anode-supported cell at 700 oC, which was higher than that of the electrolyte-supported cell. Furthermore, the ohmic and polarization resistances were lower for anode-supported cell. This is because in the anode-supported cell, the thinner electrolyte layer is responsible for the reduced ohmic resistance and improved cell efficiency.
The effect of humidity on the performance of both types of cells using NH3 and H2 fuels was studied. The experimental results indicated that in the case of ammonia fuel, a small amount of humidity (1.67% H2O) was beneficial for better performance. However, further increase in humidity caused cell performance degradation. The effect of humidity on the cell performance was further analyzed. The anode microstructure of both types of cells was investigated after 10 h of discharge operation at 0.2 A cm-2 at 700 oC using NH3 and H2 fuels under various humidified conditions. For the anode-supported cell, the surface of Ni particles was covered with the small-sized particles after discharge operation; the Ni particles on the anode surface coarsened significantly in the ammonia fuel as compared with the hydrogen fuel. This is because the anode surface is exposed to the gaseous mixture containing large amount of ammonia which may cause the nitridation of Ni particles. On the other hand, at the anode/electrolyte interface the extent of coarsening of Ni particles was almost similar regardless of the fuel. This can be explained by the fact that most of the NH3decomposes catalytically and thermally at the anode surface. Hence, the partial pressure of ammonia will be lower at the anode/electrolyte interface.
In this study, it was found that the anode-supported design is suitable for direct-ammonia fueled SOFCs. In the case of anode-supported cells, the improvement in the performance and the stability can be expected by optimizing the operating conditions, such as the operating temperature and the steam concentration in the inlet gas.

Acknowledgement

This work was supported by Council for Science, Technology and Innovation (CSTI), Cross-ministerial Strategic Innovation Promotion Program (SIP), “energy carrier” (Funding agency: JST).
Microstructure and Electrochemical Properties of La0.8Sr0.2Ga0.8Mg0.2O3 Thin Film Deposited by Vacuum Cold Spray for Solid Oxide Fuel Cells
Authors: Wang Li-Shuang , Li Cheng-Xin , Ma Kai , Zhang Shan-Lin , Yang Guan-Jun , Li Chang-Jiu 
Published: February 2020

Solid oxide fuel cells (SOFC) has attracted considerable attention in recent years as a power conversion system, owing to its high-energy conversion efficiency, fuel flexibility and low pollution emissions as well. Recently, the intermediate temperature-solid oxide fuel cell (IT-SOFC), which operates at lower temperatures (600~800 °C) to reduce cost and to improve efficiency, appears to be an alternative choice for the development of SOFC. La0.8Sr0.2Ga0.8Mg0.2O3 (LSGM), with a perovskite structure, presents a high ionic conductivity at intermediate temperatures. However, the common methods to fabricate the LSGM electrolyte (e.g., solid state method) often lose their advantages owing to the depletion of Ga and the interfacial reaction between the LSGM and electrodes. Vacuum cold spray (VCS), based on the impact adhesion of fine particles to build up ceramic film at room temperature, is a new and promising method to fabricate thin (﹤20 mm) and dense (LSGM) electrolyte membrane. In the present study, the LSGM electrolyte layer with a thickness of ~10 mm is prepared by a home-developed VCS system assisted with in-situ particle heating approach (25~400 °C). The output performance of cells assembled with VCS-LSGM is determined at 500~750 °C. Results show that the OCV value is above 1.0 V, suggesting that the VCS-LSGM electrolyte is dense enough for the application to SOFC. Meanwhile, the ionic conductivities of LSGM coatings prepared by different in-situ particle heating temperatures were determined by an electrochemical impedance spectroscopy system. In addition, the microstructure and phase structure of LSGM coatings was characterized by scanning electron microscopy and X-ray diffraction. Based on this study, it is possible to conclude that the VCS is a promising method to prepare the LSGM electrolyte applied in the IT-SOFC.