bluuebunny/crossref_metadata_2025 huggingface dataset:
Load Regulation Strategies of Solid Oxide Electrolysis System Coupled with External Heat Sources
Authors: Cui Tonghui , Han Minfang , Ni Meng
Published: September 2023

The asymmetric behavior between the fuel-cell mode and the electrolysis mode of solid oxide cells still needs to be investigated in depth. In this paper, an experimental study was carried out on 10 cm × 10 cm fuel electrode-supported cells. The electrochemical impedance spectra under different DC biases in the two modes were tested, and the resistances were obtained using equivalent circuit model fitting, and then the ohmic overpotential, activation overpotential and concentration overpotential were calculated. The results indicated that the overpotential of the fuel-cell mode and electrolysis mode was asymmetric under the same current in the actual operating current range. The ohmic overpotentials were basically the same, but the activation overpotential and concentration overpotential of the electrolysis mode were higher than those of the fuel-cell mode. The asymmetry between the two modes was negatively correlated with temperature, which was since the asymmetry of activation overpotential decreased with increasing temperature. When the fuel electrode flow rate increased, the asymmetry of both the activation overpotential and concentration overpotential reduced. More importantly, the asymmetry between the two modes increased after a period of operation of the cell. The reason was that the activation overpotential of the electrolysis mode increased sharply due to the deterioration of the fuel electrode charge transfer reaction. That is, for the cell used in this study, the same microstructure changes had a greater impact on the stability of the electrolysis mode. Therefore, the microstructure is more demanding for the electrolysis mode, requiring more careful design and selection.
Degradation Behavior of MK35x Stacks with Chromium-Based Interconnects in Steam Electrolysis Operation
Authors: Riegraf Matthias , Szabo Patric , Lang Michael , Costa Rémi , Rothe Stefan , Megel Stefan , Kusnezoff Mihails
Published: September 2023

The currently ongoing commercialization of high-temperature solid oxide electrolysis (SOEL) requires the understanding of the underlying dominant degradation mechanisms to enable continuous progress in reducing stack degradation rates.

In the present study, the degradation behavior of stacks with chromium-based interconnects (MK35x) and electrolyte-supported cells (ESC) developed at Fraunhofer IKTS is investigated. For this purpose, the initial electrochemical performance of 10-layer stacks was extensively characterized in various operating conditions in both fuel cell and electrolysis mode by electrochemical impedance spectroscopy (EIS). Degradation was evaluated during galvanostatic steady-state steam electrolysis operation over >3000 h in the temperature range of 800-825°C at a current density of -0.6 A cm-2, corresponding to a steam conversion rate of 75%. EIS analysis was used to separate the different loss contributions in the stack and showed that the ohmic resistance increase was the dominating performance degradation phenomenon. Moreover, electrochemical degradation rates in steady-state SOEL mode are compared to the ones in reversible mode with a daily cycling between electrolysis and fuel cell operation.

Post-mortem analysis was carried out with scanning electron microscopy (SEM) to correlate the observed degradation phenomena with microstructural and morphological changes. The observed low degradation rates demonstrate that MK35x are ready for scale-up, and the present work gives guidance for operation strategies and stack design to extend their lifetime even further.
(Invited) DOE EERE Activities in High Temperature Electrolysis and Reversible Fuel Cells
Authors: Gibbons William , Peterson David , Papageorgopoulos Dimitrios
Published: September 2023

Hydrogen and fuel cells are emerging, versatile examples within a portfolio of advanced and sustainable energy options. Dr. William Gibbons will provide an overview of hydrogen and fuel cell research, development, demonstration, and deployment (RDD&D) activities led by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE). The presentation will discuss how EERE’s RDD&D efforts are advancing U.S. commitment to tackling the climate crisis through the DOE Hydrogen Program’s H2@scale vision for clean hydrogen across the economy, and the Hydrogen Energy Earthshot seeking to cut the cost of clean hydrogen to $1 per 1 kilogram in one decade. The presentation will also cover examples of H2@Scale projects demonstrating hydrogen’s emission reduction and economic growth potential in hard to decarbonize sectors such as steel manufacturing and heavy-duty applications, as well workforce development and international collaboration activities.
Effects of Preparation Conditions of Precursor Powders on Sinterability of Green Bodies and Performance of Protonic Ceramic Electrochemical Cells
Authors: Zhang Yuchen , Zhao Zeyu , Sun Quanwen , Wu Wei , Tong Jianhua , Ding Dong
Published: September 2023

As one of promising technologies for hydrogen production and valuable chemical production, protonic ceramic electrochemical cells (PCECs) work at relatively low temperatures (400-600oC), due to high ionic conductivity and low activation energy. However, some undesired structural morphologies and defects presenting in the electrolyte layer during fabrication of PCECs, such as relatively small grain sizes, pinholes, and poor electrolyte/electrode interfaces, presenting detrimental effects on electrochemical performance and durability. PCECs are conventionally fabricated from proton conducting precursor powders, which are usually synthesized by solid state reaction (SSR) method, especially for large quantity fabrication. Thus, the properties and quality of electrolyte precursor powders are crucial for cell performance. Herein, we investigate the influence of fabrication conditions for electrolyte precursors on both manufacturing process and consequential electrochemical performance of PCECs. The present study sheds a light on the discrepancies on the PCEC performance reported in the literature and paves a way for scale-up of PCEC technology.
Sintering of Protonic Ceramics for Tubular Solid Oxide Fuel Cells
Authors: Panthi Dhruba , Du Yanhai
Published: September 2023

Protonic ceramics are considered to be the most promising candidates for intermediate-temperature solid oxide fuel cells (SOFCs) owing to their high proton conductivity and competitive electrochemical performance at intermediate temperatures (typically 500–700 °C). However, the fabrication of proton-conducting SOFCs has been challenging mainly due to the poor sinterability of common proton-conducting electrolyte materials. Significantly high sintering temperatures (1500–1600 °C) and long sintering times (up to 24 h) have been reported for obtaining dense, gas-tight proton-conducting electrolytes. These sintering conditions may lead to undesirable interfacial reactions and dense electrode microstructures, thereby limiting the cell performance. The present work focuses on optimizing the co-sintering temperature of tubular SOFCs with a traditional Ni–yttria-stabilized zirconia (YSZ) anode support and proton-conducting functional layers. BaZr0.3Ce0.5Y0.2O3 (BZCY), Ni–BZCY, and BZCY–BaCo0.4Fe0.4Ce0.1Y0.1O3 were used as the electrolyte, anode functional layer, and cathode, respectively. Various approaches to lowering the co-sintering temperature and resulting cell performances will be discussed. We will also examine the thermal cycling behavior and durability of the fabricated protonic SOFCs.
Co-Electrolysis Performance and Process Analyses for Synthetic Liquid Fuel Production
Authors: Tanaka Yohei , Yamaji Katsuhiko , Ishiyama Tomohiro
Published: September 2023

To achieve carbon neutrality in 2050, carbon recycle technology is attracting much attention coupled with renewable power and electrolyzers to produce “green” fuels such as methane and synthetic oil. We have just started a new NEDO project (FY2020-2024) in Japan for synthetic liquid fuel production using solid oxide electrolysis cells (SOECs) and Fischer-Tropsch (FT) synthesis, which will give higher efficiencies compared to one with water electrolysis at low temperatures. In particular, the project aims at FT oil production from gasoline to diesel fractions (C5-C19) to avoid wax production. We are responsible for R&D of co-electrolysis process for the FT synthesis, cell/stack performance evaluation for the co-electrolysis, and evaluate state-of-the-art commercial single cells and stack that are developed for fuel cell application. Since carbon deposition at higher H2O/CO2 utilization is of concern, material analysis of such cells/stacks will be also carried out to elucidate optimal electrolysis operative conditions and to suggest cell and peripheral components design optimal to syngas production (H2/CO ~ 2.0). In the conference, we will report that developed SOEC performance evaluation methods for co-electrolysis which precisely control steam flowrate, giving cell voltage stability at ± 0.1 mV level. I-V characteristics of commercial cells and 1-2 kW class stack will also be presented at various operative conditions in combination of post-test analysis after the short-term cell/stack evaluation to discuss carbon deposition conditions for syngas production for FT synthesis. Furthermore, numerical process simulation results will be presented to discuss possible energy efficiency of the combined system with SOEC and FT synthesis.
Quantifying Microstructural Degradation in GDC-Infiltrated Fuel Electrodes in Reversible Solid Oxide Cells
Authors: Mulligan Jillian Rix , Ghosh Emily , Lee John In , Akter Ayesha , Gopalan Srikanth , Pal Uday , Basu Soumendra
Published: September 2023

Reversible solid oxide cells (RSOCs) can convert between hydrogen or other fuels and electricity in both directions, offering a promising application as tools for mitigating gaps between renewable energy supply and demand in the electric grid. Many advanced RSOC electrode materials achieve good performance stability during operation—for example, NNO | NNO-NDC50 | GDC10 | YSZ | Ni-YSZ cells have been shown to exhibit excellent performance stability over 500hr testing periods when operated reversibly. However, infiltration of a nanocatalyst species, such as GDC10, into the fuel electrode may further improve electrode performance and stability by mitigating Ni coarsening and offering more resilient paths to active reaction sites. In this study, the microstructural degradation of baseline and GDC10-infiltrated RSOC fuel electrodes are quantitatively compared in the context of in-depth electrochemical characterizations. Scanning electron microscopy (SEM) analysis of cell cross sections elucidates the role of GDC10 in improving and stabilizing electrode performance over long-term operation.
Evaluation of Hydrogen Ions Flowing through Protonic Ceramic Fuel Cell Using Ytterbium-Doped Barium Zirconate as Electrolyte
Authors: Okuyama Yuji , Harada Yoshiaki , Mikami Yuichi , Yamauchi Kosuke , Kuroha Tomohiro , Shimada Hiroyuki , Yamaguchi Yuki , Mizutani Yasunobu
Published: September 2023

Protonic ceramic fuel cells (PCFCs) are clean power generation devices that do not emit carbon dioxide, and generate electricity when protons (hydrogen ions) pass from the fuel electrode through the electrolyte to form water vapor at the air electrode. As a fuel cell, PCFC is expected to be a highly efficient fuel cell because it can operate at medium to low temperatures of around 600°C and no fuel dilution occurs. However, proton-conducting ceramics can conduct not only protons but also a small amount of holes, which can cause electron leakage and lower the power generation efficiency. Therefore, it is very important to understand the ionic and hole conductivity in a fuel cell.

To evaluate the electronic leakage of PCFC, the amount of proton current flowed in PCFC can be measured by an apparatus developed based on the electromotive force of an electrochemical cell using 10 mol% In-doped CaZrO3 (hydrogen sensor) and Y stabilized zirconia (oxygen sensor). Water vapor pressure on cathode was change when hydrogen ion passes thorough PCFC. The current of hydrogen ion can be determined by monitoring water vapor pressure. We measured the current of hydrogen flowing through protonic ceramic fuel cell using ytterbium-doped barium zirconate as electrolyte. Hydrogen ion and hole were found to leak at OCV at 700°C. Then electronic leakage was estimated form the current of hydrogen ion and external current. The electronic leakage was found to be suppressed with increasing electrolyte film thickness. On the other hand, no leakage of hydrogen and holes was observed at 500°C.
Improve the Electrochemical Performance and Long-Term Durability of Protonic Ceramic Electrochemical Cells
Authors: Zhang Weilin , Zhang Qian , Ding Dong
Published: September 2023

Energy and environmental issues have attracted much attention in recent decades. To secure a green and sustainable energy future, we need to redesign current energy systems to move from conventional fossil fuels to renewable energy sources. The potential renewable energy from wind and solar exceeds global energy consumption; however, it is not flexible due to the intermittent nature of sunlight and wind. Thus, a robust, cost-effective, and secure technology is required to efficiently store this renewable energy. Protonic ceramic electrochemical cells (PCECs) are solid-state electrochemical devices that can directly convert between electrical energy and chemical energy (hydrogen and hydrocarbons) by operating in both electrolysis and fuel cell modes. Due to their relatively high operating temperature (~500 °C), PCECs are more favorable in terms of both thermodynamics and kinetics when compared with other similar energy-conversion technologies that are operated at a lower temperature (such as proton-exchange membrane cells). To be commercially competitive, however, several critical challenges related to performance, durability, and the Faradaic Efficiency need to be solved. In this talk, we will present our recent achievements on materials and cell design to solve these challenges. By optimizing the air electrode composition and microstructure, a dramatically enhanced electrochemical performance was achieved on both the fuel cell and the electrolysis cell. The long-term durability was improved via constructing a robust interface between the electrode and the electrolyte. We will also introduce a reliable method to measure the Faradaic Efficiency during the cell operation to the community.
Strontium Free Cu-Doped La2NiO4 Oxides as Promising Oxygen Electrodes for Solid Oxide Electrolysis Cells
Authors: Karki Surendra B , Seymour Lorraine , Le Long , Coyle Christopher , Springer R , Escobar Julian , Meinhardt Kerry , Marina Olga A
Published: September 2023

In this work, strontium-free oxygen electrodes for electrode-supported SOFC/SOEC cells were evaluated. Strontium is known to react with volatile Cr from the metallic interconnect to form Sr-Cr oxides at the surface of the electrode, thus reducing the cell performance. Strontium-free cobalt- or copper-doped nickelates, La2Ni1-xBxO4 (B = Co or Co; x=0.1-0.5) were synthesized using solid state synthesis method. The crystal structures of the oxides were studied by Rietveld refinement analysis of the powder X-ray diffraction data. Similar to the parent compound, the Ruddlesden-Popper (RP) La2NiO4 oxide, the Co- and Cu-doped compositions were confirmed to crystallize with the tetragonal crystal structure with I4/mmm space group.

The electrochemical performance of the La2Ni1-xBxO4 electrodes was studied using 1 inch in diameter button cells in SOEC mode and compared to that of cells with the state-of-the-art (La0.6Sr0.4)0.95Co0. 0.8O3-δ (LSCF)- ceria composite electrodes. The oxide inks were screen printed onto the pre-fired ceria barrier layers on the YSZ electrolytes. Short- and long-term tests were conducted at 650, 750, and 800oC with the Ni-YSZ hydrogen electrode exposed to 50-98% steam in hydrogen. Scanning electron microscopy with electron diffraction spectroscopy (SEM/EDS) was used to analyze the electrode microstructures before and after testing.

In general, the performance of the La2Ni1-xBxO4 electrodes was slightly lower than that of LSCF. However, the electrode microstructures were not optimized, and further improvements could be made. The Co-substituted nickelate performances showed some degradation in in time. Cu-doped nickelates exhibited more performance during the same tests and the degradation rate was insignificant. The composition with 20% Cu appeared to be more active as well as more stable.
Understanding the Mechanical Strength of Protonic Ceramic Electrochemical Cells
Authors: Zhao Zeyu , Yang Haobo , Zhang Yuchen , Wu Wei , Dong Pei , Tong Jianhua , Ding Dong
Published: September 2023

Protonic ceramic electrochemical cells (PCECs) hold the promise for hydrogen production as well as flexible chemical manufacturing by in-situ hydrogen/proton use at intermediate temperatures (400-600oC). As the technology is emerging and fast growing, the manufacturing of PCECs in larger scales, such as 5×5 cm2 and 10×10 cm2, is urgent and necessary for bridging the academic research and the industry application. However, it has been concerned about the mechanical properties of PCECs compared with its counterpart, oxygen-ion conductor based electrochemical cells (OCECs), especially when it is required to be assembled for the stack. Herein, we investigate the mechanical properties of PCECs with various techniques at different scales and under operating conditions. Comparative study is conducted between PCEC and OCEC with corresponding recommendations in both fabrication and operation factors to achieve reliable, repeatable, and durable PCECs for sustainable energy utilization and generation.
Techno-Economic Analysis of Electrochemical Refineries Using Solid Oxide Cells for Oxidative Coupling of Methane
Authors: Rosner Fabian , Tucker Mike C , Hu Boxun , Breunig Hanna
Published: September 2023

With the shift away from fossil resources, there is a need for alternative pathways to carbon-based commodities such as ethylene. The electrochemical oxidative coupling of methane (OCM) enables the synthesis of higher hydrocarbons from simple organic molecules i.e., methane and has the potential to replace conventional ethylene production in the future. However, current solid oxide OCM cell development is still in an early stage and more comprehensive system-level analyses are needed to better understand operating conditions and economics to guide research and development. For this purpose, process models and new integration strategies for the electrochemical OCM process were developed. The integration of the electrochemical OCM unit into the plant revealed to be challenging based on current solid oxide cell designs and will be discussed as part of this presentation. The performance of the OCM plant is benchmarked against current state-of-the-art ethane steam cracker plants. In this context, key performance metrics are efficiency, direct and indirect carbon dioxide emissions, power consumption, plant cost and cost of ethylene. Of particular interest are aspects of hydrogen co-production and carbon dioxide utilization as well as the impact of carbon dioxide emission factors from the grid, which have shown to be of particular importance for electrochemical processes. Moreover, critical aspects of heat integration will be discussed including fuel pre-heating, carbon deposition and thermal cell management. The analysis will provide new insights into economic cost driving factors and the impact of cell cost, current density, overpotentials and Faraday efficiency upon the cost of ethylene. Based upon this information, performance targets will be recommended that will allow electrochemical OCM to become economically competitive in a free market environment.
Development of Direct-Ammonia Solid Oxide Fuel Cells (DA-SOFCs) and the Effect of Incorporating Internal Ammonia Decomposition Catalysts
Authors: Yang Sungeun , Kim Hayoung , Oh Seongkook , Gokbayrak Attila Alkim , Lee JaeHyuck , Oh Min Jun , Ji Ho-il , Yoon Kyung Joong , Son Ji-Won , Lee Jong-Ho
Published: September 2023

Direct-ammonia solid oxide fuel cells (DA-SOFCs) are among the most efficient power sources that use ammonia. The high operating temperature of SOFCs enables ammonia decomposition reaction to proceed inside the anode compartment of SOFCs. Coupling exothermal SOFC operation and endothermal ammonia decomposition reaction increases the efficiency of the device. DA-SOFCs function as well as hydrogen-fueled ones over 750 °C. Recently we have reported that DA-SOFCs suffer significant performance loss under 650 °C, especially the high-performance cells. We discuss a range of phenomena taking place inside the anode compartment of DA-SOFCs: interconnect, current collector, and anode support. Interconnect and current collector have the capability of decomposing significant amounts of ammonia. Nevertheless, incorporating a catalyst is important at low operating temperatures.
Studying the Sulfur Poisoning Mechanism of Solid Oxide Fuel Cells by Means of Patterned Nickel/Yttrium-Stabilized Zirconia Electrodes
Authors: Li Xiaoxiao , Wang Yuqing , Wang Yinan , Shi Yixiang
Published: September 2023

Sulfur causes Ni-based ceramic anode poisoning and thus shortens the life of the cell. Therefore, it is important to clarify the mechanism of sulfur poisoning to improve cell performance and lifetime. However, there is still some controversy about the mechanism of sulfur poisoning. In this work, Ni-patterned electrodes were used for electrochemical experiments to investigate the mechanism of sulfur poisoning under different operating parameters. First, the Ni pattern electrode is operated in H2 fuel containing H2S with the H2S concentration gradually increasing from 5 ppm to 50 ppm. As the concentration of H2S increases, the electrode performance decreases faster. The effect of high oxygen ion flux on the degree of sulfur poisoning was investigated by regulating the operating current of the Ni-patterned electrode SOFC. The results show that the operating current has a large effect on poisoning. This work provides empirical evidence for the mechanism of Ni/YSZ anode sulfur poisoning, and a possible mechanism for Ni/YSZ anode poisoning under sulfur exposure conditions was established.
Optimization of Extrinsic Impact Factors for Improving Performance and Mitigating Performance Degradation of LSCF-SDC/YSZ/Ni-YSZ Cells Under Solid Oxide Electrolysis Operation
Authors: Fan Yueying , Pineault Richard , Abernathy Harry W. , Chen Yun , Song Xueyan , Guan Bo , Liu Jian , Kalapos Thomas
Published: September 2023

Long-term solid oxide electrolysis operation (SOEC) testing was performed to study the performance and performance degradation of LSCF-SDC/YSZ/Ni-YSZ cells under temperatures of 750 oC, 800 oC, and 850 oC, current density of 0.5A/cm2 and 1.0A/cm2, and H2/H2O ratio of 1:1, 1:3, and 2:1. Operational temperature, current density, and H2/H2O ratio played important roles in the cells’ performance and performance degradation. These factors were correlated and should be balanced and/or optimized to maximize overall lifetime performance. LSCF-SDC cells showed better performance and less performance degradation under higher temperature. Electrochemical impedance spectroscopy (EIS) data showed polarization resistance was significantly lower for the cell operated at higher temperature. Therefore, SOEC operation may need relatively higher temperature to be activated. Long-term SOEC testing under different current density showed better performance and less performance degradation at 0.5A/cm2, 850 oC, and 1:1 of H2/H2O ratio. H2/H2O ratio in the functional layer of the cell also played an important role. The cell showed best performance and less performance degradation under 1:1 of H2/H2O ratio. EIS data showed the polarization resistance was significantly lower under 1:1 of H2/H2O ratio. H2/H2O ratio needs to be optimized for different operational temperature and current density. Overdosed steam may react with Ni causing Ni movement in the H2 electrode, adding to cell degradation. Transmission electron microscopy (TEM) studies identified the formation of the (CoFe)Ox along the SDC grain boundaries, which could impact both the SDC conductivity and the LSCF catalytic activity due to the loss of the transition metals in the LSCF. TEM analysis of the H2 electrode identified a large number of NiO clusters relocated into the original pore region, seemingly formed during Ni migration. This NiO formation in the H2 electrode during SOEC operation is another cause of long-term performance degradation.
Root Cause Analysis of Degradation in Protonic Ceramic Electrochemical Cells with Interfacial Electrical Sensors
Authors: Wu Wei , Wang Congjian , Bian Wenjuan , Ding Dong
Published: September 2023

Protonic ceramic electrochemical cells (PCEC), including solid oxide fuel/electrolysis cell, present promising routes to energy harvest and value-added chemical production. Despite tremendous efforts, PCEC still encounters several challenges, including poor thermal/chemical/mechanical compatibility and inferior solid-solid contact at the interfaces between electrolytes and electrodes. In this presentation, we will demonstrate in-line electrochemical characterization of interfacial electrical sensor embedded PCEC that can lead to fast identification of the failure mechanism of electrode supported PCECs. Upon the acquisition of quantitative contributions from different cell components to total degradation, data-driven machine learning is employed to further predict the long-term performance of the full cell up to 3000 hours. This presents novel insights into the degradation mechanism analysis in the solid-state electrochemical units, allowing ones to better modify the electrolyte and electrode materials and the interface between them, and develop more robust PCEC systems. The technology can be appliable to other electrochemical systems, including higher temperature counterpart (e.g., oxygen ion conducting solid oxide electrolysis cells, o-SOEC)
Boosting Water Oxidation on Novel Oxygen Electrode Via Surface Metal Exsolution in Protonic Ceramic Electrochemical Cell
Authors: Zhu Pengxi , Dong Pei , Ding Dong
Published: September 2023

The protonic ceramic electrochemical cell (PCEC) is an emerging and attractive technology that converts energy to hydrogen using solid oxide proton conductors at intermediate temperatures. At this temperature range, the water oxidation reaction (WOR) and oxygen evolution reaction (OER) are dominant for the overall electrode reaction while the development of electrode materials is limited and primarily reply on the knowledge from the conventional oxygen-ion conducting counterpart. Here, we developed a novel Ruddlesden-popper (R-P) electrode that presented excellent electrocatalytic activity and durability, resulted in higher hydrogen production efficiency. The present study could provide a new perspective for materials design and bring more research opportunities in the field.
Impact of Thickness on Direct Ammonia Decomposition in Solid Oxide Fuel Cells, Numerical and Experimental Research
Authors: Machaj Krystian , Skrzypkiewicz Marek , Niemczyk Anna , Kupecki Jakub , Malecha Ziemowit , Chorowski Maciej
Published: September 2023

The growing share of renewable energy sources (RES) in the energy mix and the desire to reduce greenhouse gas and pollutant emissions are driving widespread technological progress. One of the main areas is the development of hydrogen technologies, as manifested, for example, in the emerging hydrogen strategies of countries around the world. However, the widespread use of H2 is limited by the high energy input required for storage. This makes ammonia a promising carbon-free hydrogen carrier. Its application is being considered, e.g. in power systems for deep-sea transportation. Ammonia can be used like a fuel in energy systems, but often requires proper processing or decomposition into hydrogen and nitrogen in the presence of a catalyst. These activities increase financial or technological inputs which can complicate energy systems and reduce their efficiency or energy density. Power plants based on solid-oxide fuel cells (SOFCs) have the ability to process NH3 as fuel whether in external or internal cracking mode. However due to the nickel-based anode and operating temperatures above 600°C, SOFCs can directly use NH3 as a fuel - direct-ammonia SOFCs (DA-SOFCs). Lowering the operating temperature of the cells and reducing their thickness brings with it a wider opportunity for SOFC-based systems e.g. decrease energy density, and reduction of used materials. An additional advantage of direct ammonia conversion in SOFC cells is the endothermic nature of the reaction, allowing for a reduction in the amount of cooling air supplied to the system. In this study, the performance of cells with different anode thickness was compared under similar operating conditions for direct ammonia-fueled solid oxide fuel cells (SOFCs). The experimental results were reproduced in the open source computational fluid dynamics (CFD) software, Open Fuel Cell, in which the source term responsible for internal cracking was introduced. Then calculations were made to determine the distribution of ammonia and temperature in the functional part. It was determined that in the case of counter-current flow of fuel and oxidizer, thinner cells show a smaller temperature gradient. Lowering the operating temperature and cell thickness does not lead to incomplete conversion of ammonia in the cell. Post-mortem analysis of the cells used in the experiment showed no negative effect of ammonia on the functional layers of the cells.
The Coating Effect on Interconnect Materials After >10 Years of Furnace Exposures
Authors: Norrby Niklas , Li Shunyi , Stenström Mikael , Westlinder Jörgen
Published: September 2023

One of the key components in the SOFC stack is the interconnect which requires versatile material properties for a proper functioning, e.g., high temperature corrosion stability, low ASR degradation and low chromium evaporation. At the same time, a high production capacity needs to be reached in order to fulfil the supply demand required for GW levels. The high production capacity is realized through Alleima AB’s production line with coil-coil physical vapor deposition of coated interconnects for SOFC and SOEC applications [1].

More specifically, Sanergy HT 441 is the standard material intended to be used as an SOC interconnect. The substrate is a ferritic stainless steel (ASTM 441) which is coated with thin layers of Ce and Co (<1 µm). The material can be coated on both sides using the same coating or with a different coating. At elevated temperatures the Co coating forms a protective (CoMn)3O4 spinel layer which drastically reduces Cr evaporation while the Ce layer improves the corrosion resistance by reducing the chromia scale growth at the coating/substrate interface and thereby maintaining a low and stable ASR over time.

Since long-term stability is a critical property for interconnects, Alleima has over the years gathered data from furnace samples and can thus present results where some samples have been exposed at elevated temperatures during >10 years. The main results include the effect of Ce thickness or choice of substrate on mass gain and subsequent chromia growth. Selected samples with coating elements different than Co have also been investigated. Samples have been further investigated using scanning electron microscopy for cross-sections, x-ray diffraction for characterization of phases and residual stresses as well as glow discharge optical emission spectroscopy for elemental analysis.

References:

[1] C. Bernuy-Lopez et al., ECS Transactions, 103 (1), (2021).
Highly Active Layered Cobaltite Air-Electrode Materials for Reversible Solid Oxide Cells
Authors: Jo Minkyeong , Hamayun Muhammad Asif , Park Jun-Young
Published: September 2023

The use of fossil fuels, which have increased rapidly since the Industrial Revolution, is causing serious climate change. To overcome this, interest in clean and sustainable energy sources to replace fossil fuels is increasing worldwide. Among alternative energies, the electricity generation from solar and wind resources is difficult to achieve sustainable energy production regardless of the weather and season. Hence, hydrogen is considered as the most promising energy source to replace fossil fuels because of its clean, storable, sustainable, and transportable characteristics.

Recently, reversible fuel cells that can both produce hydrogen with surplus power and generate electricity using the stored hydrogen have attracting attentions as an electrochemical device to promote reliable and economical hydrogen society [1]. Among them, reversible solid oxide cells show high efficiency in a fuel cell mode due to their high operating temperature (700-1000 ℃). However, reversible solid oxide cells exhibit relatively low performance in water-electrolysis cell mode [2]. The main reason of low performance in the solid oxide electrolysis cell mode is the sluggish kinetics of oxygen evolution reactions in air-electrode. Therefore, the electrolysis performance of reversible solid oxide cells can be greatly improved if the air-electrode with high catalytic activity for oxygen evolution reactions is developed.

Among many candidate materials for air-electrodes, cobalt-based layered materials are known to have good electrocatalytic properties in oxygen reduction and oxygen evolution reactions with high electronic conductivity (σ = 100–240 S·cm-1 at 450–650 °C) [3, 4]. Herein, we introduce a novel layered structure material, Ba2Co9O14 (BCO), as air-electrode materials for highly efficient and durable reversible solid oxide cells. In order to further enhance the catalytic property of BCO, Nd and Ca are doped into Ba-site. The Nd0.1Ca0.1Ba1.8Co9O14-cell shows a maximum power density of 2.6 W·cm-2 in fuel cell mode, current density of –4.36 A/cm2 under applied voltage of 1.6 V in electrolysis cell mode, at 800 ℃, surpassing previous reported results of air-electrode catalysts for reversible solid oxide cells.

References

[1] S. E. Hosseini, M. A. Wahid, Renew. Sustain. Energy Rev. 2016, 57, 850.

[2] X. Zhang, L. Liu, Z. Zhao, B. Tu, D. Ou, D. Cui, X. Wei, X. Chen, M. Cheng, Nano Lett. 2015, 15, 1703.

[3] M. Saqib, I. -G. Choi, H. Bae, K. Park, J. -S. Shin, Y. -D. Kim, J. -I. Lee, M. Jo, Y. -C. Kim, K. -S. Lee, S. -J. Song, E. D. Wachsman, J. -Y. Park, Energy Environ. Sci. 2021, 14, 2472.

[4] A. Rolle, N. Preux, G. Ehora, O. Mentré, S. Daviero-Minaud, Solid State Ionics 2011, 184, 31.
Densification of Plasma-Sprayed YSZ Electrolyte by Suction Filtration Using Submicron/Nanoparticle Suspension for Metal-Supported SOFCs
Authors: Gu Xin , Jiang Yidong , Wu Zeyun , Wang Yuqing , Shi Yixiang , Li Shuiqing , Cai Ningsheng
Published: September 2023

Atmospheric plasma spraying (APS) is widely used for the fabrication of metal-supported solid oxide fuel cells (MS-SOFCs) due to its cost-effective and fast process. However, the incomplete melting of partial electrolyte particles in the layer-by-layer deposition process leads to a relatively porous electrolyte layer, which causes severe gas leakage and hinders its implementation on MS-SOFCs. In this study, a simple and efficient two-step method is developed to achieve the densification of a plasma-sprayed YSZ electrolyte layer in a tubular MS-SOFC through suction filtration using a YSZ submicron/nanoparticle suspension. The prepared tubular MS-SOFCs were immersed in the YSZ submicron-particle suspension, and the pressure inside the tubular SOFC was reduced to -20 kPa to drive the YSZ submicron particles to fill the pores in the YSZ electrolyte. After suction filtration for 1 h, the gas permeability of the YSZ electrolyte decreased from 2.57×10-5 to 5.84×10-6 by a factor of 4.4, and the pores in the YSZ electrolyte decreased from the micron scale to the submicron scale. Further densification can be achieved by a second suction filtration treatment in the YSZ nanoparticle suspension so that the pores can be further decreased from the submicron scale to the nanoscale, which ensures gas tightness and can be used as the electrolyte of MS-SOFCs.
Performance and Durability of Metal SOFCs in Alternate Fuels
Authors: Abdul Jabbar Mohammed Hussain , Thompson Dave , Parrondo Javier , Gumeci Cenk , Furuya Yoshihisa , Dale Nilesh , Dewa Martinus , Ha Su , Liu Fan , Duan Chuancheng
Published: September 2023

Electricity generation from solid oxide fuel cells (SOFCs) based power generator are in great demand for both stationary and automotive use. SOFC is considered as one of the best energy conversion devices that is available to demonstrate Nissan’s carbon neutrality goal by 2050. In particular, SOFCs are known for their fuel-flexible operations, for example, SOFCs can operate on renewable fuels such as ethanol, natural gas, jet-fuel, propane. Unlike H2 based polymer fuel cell, the possibility of utilizing liquid fuels directly in SOFCs can pave the way to adopt the existing fuel infrastructure and can limit the greenhouse gas emissions significantly. This abstract presents the potential of using externally supported SOFCs, such as metal based SOFCs (metal-SOFCs) as the highly performing and durable power generator. It is identified that the metal-SOFC technology is a closest viable solution for using SOFCs in stationary and automotive applications.
Study of the Crystallization in a Glass-Ceramic Seal
Authors: Laplace Annabelle , Begos Jean-Gabriel , Vallat Charlène , Regnier Elise , Moles Rémi , Brackx Emmanuelle , Schintu Lilou , Vulliez Karl
Published: September 2023

Sealing is a major issue in high temperature electrolyzers used for hydrogen production. The specifications that seals must meet are particularly demanding. In addition to sealing, the material must have mechanical, thermomechanical and chemical properties, as well as sufficient electrical resistivity. The geometries are complex and the lengths to be sealed are important. These numerous constraints lead to the use of glass powder suspended in organic solvents. This process allows for the installation of the seal by simply depositing the suspension on the areas to be sealed. A heat treatment is then applied to shape the material and ensure the sealing of the system. The use of a composition that tends to crystallize allows, a priori, improving the thermal and mechanical properties.

The reference heat treatment consists of a first temperature rise followed by a crystallization stage. As the temperature rises, the organic solvents evaporate, producing CO2, which causes porosity to appear. Sintering of the glass powder also takes place during this stage. Early surface crystallization can compete with the sintering phenomenon and prevent the maximum densification of the glass ceramic by freezing the structure. The objective of the study is to obtain a seal material with maximum density, thus minimum porosity, by controlling the removal of organic solvents, sintering and crystallization.

This paper will present in particular the study of the material crystallization: phases identification and evolution of crystal morphology as a function of temperature (SEM, XRD) (Figure 1), crystal surface fraction as a function of time and temperature (determined by image analysis). A poikilitic texture phenomenon, particularly important for the crystalline fraction quantification, is also detailed (SEM-EBSD). These data allow to obtain the equilibrium crystalline fraction as a function of temperature, and to further optimize the thermal treatment.

Figure 1
Perovskite-Type Nd1-XBaxCo0.8Fe0.2O3-δ (0 ≤ x ≤ 0.7) Cathodes for Intermediate Temperature Solid Oxide Fuel Cells
Authors: Sikstrom Daniel , Javed Aroosa , Shoaib Muhammad , Thangadurai Venkataraman
Published: September 2023

Perovskite-type metal oxides with a nominal chemical formula of Nd1-xBaxCo0.8Fe0.2O3-δ (NBCF) (0 ≤ x ≤ 0.7)

were prepared by solid-state synthesis method at 1300 °C in air. Powder X-ray diffraction showed that the x =

0.25 member is a single-phase perovskite-type Nd0.75Ba0.25Co0.8Fe0.2O3-δ in the Pnma space group and all other

members were found to be multiphase. All the investigated NBCF compositions show minor reactivity with the

Sr and Mg-co-doped lanthanum gallate (LSGM) when sintered with 30 wt.% LSGM at 1050 °C but maintain

their perovskite-type structure. 4-probe DC chronopotentiometry measurements were performed on the sintered

sample pellets. The x = 0.4 member reaches a maximum conductivity of 1068 S/cm at 300 °C in air. Among the

samples studied, the x = 0.55 member exhibits the lowest area specific polarization resistance (ASR) of 0.026 Ω

cm2 at 750 °C in air.
Interfacial Interaction Between Ni and Oxide in SOFC Anodes
Authors: Matsui Toshiaki , Tsujimoto Hiroaki , Muroyama Hiroki , Eguchi Koichi
Published: September 2023

The interfacial properties of Ni/oxide were quantitatively evaluated by determining the contact angle of nickel particles on oxide substrates at the operating temperature of solid oxide fuel cells (SOFCs). Nickel was coated on 8 mol% Y2O3-ZrO2 (YSZ), 10 mol% Sc2O3-1 mol% CeO2-ZrO2 (ScSZ), and Ce0.9Gd0.1O2-δ (GDC) disks by sputtering. Nickel particles were formed on the substrates by annealing these samples under reducing atmospheres. The wettability of nickel particles was found to be the worst on the YSZ substrates, indicating the lowest bond strength between Ni and YSZ. The contact angle of nickel particles for the samples heat-treated under the humidified atmosphere was smaller than that under the unhumidified atmosphere regardless of the oxide substrate. The presence of water vapor will decrease the surface tension of nickel or increase the surface tension of the oxide substrate.
(Digital Presentation) A Multi-Physics Coupled Single-Cell Numerical Model for Solid Oxide Cells Based on 3D Microstructure Reconstructions
Authors: Su Peng , Jiao Zhenjun
Published: September 2023

A multi-physics coupled numerical model of solid oxide cells (SOCs) is of great significance in understanding the mechanisms of mass transfer and electrochemical reactions in the electrodes. Similar numerical approaches for SOCs have been developed using lattice Boltzmann method and finite element method. However, most of the previous works focuse on the single mode of fuel cell or electrolyser, which limits the scope of the model application. In this work, a novel multi-physics coupled numerical model of SOCs is developed under the environments of MATLAB and COMSOL to accurately predict the cell performances under both fuel cell and electrolyzer modes. The numerical simulation results are then validated using the actual electrochemical measurement results. The accuracy of the numerical model presents great potential in the optimization of microstructure in SOCs.

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(Digital Presentation) Prolonged Operation Strategies For Solid Oxide Fuel Cell Through Barrier Layer-Based Interface Engineering
Authors: Lyu Qiuqiu , Zhu Tenglong , Qu Hongxia , Zhong Qin
Published: September 2023

As one of the current benchmark cathode materials, La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) is in the process of widely commercialization. Normally, a high-density barrier layer, such as doped Ceria (Gd0.1Ce0.9O2-δ, GDC), is essentially introduced in SOFC single cell between Zirconia electrolyte and cathode, in order to prevent chemical incompatibility and elements diffusion. However, in large-scale fabrication, the GDC barrier layer is typically screen-printed onto the as-sintered YSZ electrolyte. Consequently, the post-sintered GDC layer is often porous. Increase GDC barrier layer density can effectively facilitate oxygen ions transfer and inhibit elements diffusion. Therefore, in this study, four YSZ electrolyte supported symmetrical cathode cells with various barrier layers are investigated, i.e. (1) screen printed GDC (named as GDC), (2) screen printed GDC with Cobalt Nitrate sintering aid (GDC-Co), as well as hydrothermal modified cells named as (3) GDC-HY and (4) GDC-Co-HY, respectively. The results show largely decreased Rohm of ~20% when sintering aid are used in GDC barrier layer. Furthermore, both Rohm and Rp values are extremely stable after further hydrothermal modification, with growth rate of 0.014 and 0.03 Ω·cm2/kh for GDC-Co-HY, respectively, which are much lower than 0.22 and 0.248 Ω·cm2/kh for pristine GDC-Co. Current study suggests that increasing the GDC barrier layer density by hydrothermal modification is an effective method to enable better cell performance and more stable long-term operation.

Figure 1 Evolution of (a) Rohm and (b) Rp with aging time in air. Microstructure of the GDC surfaces (c-f) and cell fractures (g-j).

Figure 1
(Digital Presentation) GDC/YSZ Bilayer Electrolyte Fabrication by In-situ Hydrothermal Growth
Authors: He Jianyu , Lyu Qiuqiu , Zhu Tenglong , Zhong Qin
Published: September 2023

GDC (gadolinia-doped ceria) can be used as barrier layer between the high-performance LSCF (La0.6Sr0.4Co0.2Fe0.8O3-δ) cathode and YSZ (8% mol yttria stabilized zirconia) electrolyte, to prevent chemical incompatibility and elements diffusion. However, the GDC layer is difficult to achieve as high density as the YSZ electrolyte, especially under low sintering temperatures. While, increase sintering temperature over ~1200 ℃ could induce the formation of (Ce,Zr)O2 solid solution.

In this work, we report a highly dense bilayer GDC/YSZ electrolyte prepared at low sintering temperature. Specifically, the as-sintered anode supported SOFC half-cell with already-dense YSZ electrolyte was immersed in solution of Gd(NO3)3·6H2O and Ce(NO3)3·6H2O, followed by a hydrothermal treatment at 180 ℃ (accounts for steam pressure of ~1 MPa) for 36 h. This yielded a dense GDC layer growth on YSZ electrolyte with thickness of ~200 nm. Then, the cells were sintered at 1100, 1150 and 1200 ℃, respectively. Afterwards, the hydrothermal treatment was repeated once, to grow an additional GDC layer. This post-grown GDC was then co-sintered with the screen printed LSCF cathode at 1075 ℃.

Results show that, the GDC/YSZ bilayer electrolyte is successfully fabricated under low sintering temperature below 1200 ℃, with overall GDC layer as thick as ~540 nm and ultra-high density as the YSZ electrolyte. The single cell with 1200 ℃ sintered GDC, named as GDC-1200, shows the best output performance, i.e. maximum power density of ~0.96 W/cm2 at 780 ℃. Moreover, the cell runs stably at 720 ℃ for 300 hours, showing decent durability.

Fig. 1 (a) j-V-P curves of bilayer electrolyte SOFCs with varied GDC sintering temperature; (b) operation voltage versus time for GDC-1200 cell under constant current mode; (c) SEM images and (d) EDS mapping of single cell (GDC-1200) fracture

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(Invited) The SOFC Program at the DOE’s Office of Fossil Energy and Carbon Management (FECM) and National Energy Technology Laboratory (NETL)
Authors: Vora Shailesh , Williams Mark
Published: September 2023

The Solid Oxide Fuel Cell (SOFC) Program, managed by the U.S. Department of Energy (DOE) Office of Fossil Energy (FE) and administered by the FE’s National Energy Technology Laboratory (NETL) is currently developing low-cost SOFC power generation systems. SOFC power systems have the potential to achieve greater than 60 percent efficiency. The SOFC’s operating temperature is lower than combustion-based processes and precludes NOx formation. In addition, there are near-zero emissions of CO2, criteria pollutants, and particulates. Furthermore, SOFC power systems require approximately one-third the amount of water relative to conventional combustion-based power systems. The Program includes the testing of SOFC with natural gas in distributed applications, including data centers. In addition to SOFC, there are several projects on various aspects of high temperature solid oxide electrolysis cell (SOEC) for electrolysis of water. The development of efficient systems for hydrogen production is very interesting, especially when supplementary heat is provided from solar or other waste heat sources such as nuclear or coal power plants.