bluuebunny/crossref_metadata_2025 huggingface dataset:
Pt Current Collectors Artificially Boosting Ceria Oxygen Surface Exchange Coefficients
Authors: Ma Yuxi , Burye Theodore E. , Nicholas Jason
Published: September 2023

The SOFC/SOEC community has an oxygen surface exchange measurement reproducibility crisis. This is exemplified by a >1,000 times variation in the literature-reported chemical oxygen surface exchange coefficient (k
chem) values of Pr0.1Ce0.9O2−x
(PCO) at 700 °C in air, a >10,000 times variation in the literature-reported k
chem values of La0.6Sr0.4FeO3-x (LSF) at 650 °C in air, and a >100,000 times variation in the literature-reported k
chem values of Ba0.6Sr0.4Co0.8Fe0.2O3-x (BSCF) at 500 °C in air. Many of these k
chem values have been determined electrically (often via Electrochemical Impedance Spectroscopy or Electrical Conductivity Relaxation) using precious metal current collectors. Unfortunately, the Time-of-Flight Secondary Ion Mass Spectroscopy and Curvature Relaxation k
chem measurements performed here on Pulsed Laser Deposited Pr0.1Ce0.9O2−x
(PCO) thin films show that unpolarized Pt current collectors can dramatically improve PCO k
chem values (by up to 2 orders of magnitude) through i) a reduction in the PCO surface Si concentration, and/or ii) Pt diffusion into the underlying PCO lattice. Further, this phenomenon can occur in PCO thin films only exposed to mild temperatures of 500 °C. Hence, it seems likely that precious metal current collectors may be responsible for at least some of the large k
chem variation reported in the literature for “identical” materials tested under “identical” conditions.

Reference: Ma Y, Burye TE, Nicholas JD. Pt Current Collectors Artificially Boosting Praseodymium Doped Ceria Oxygen Surface Exchange Coefficients. Journal of Materials Chemistry A. 2021; 9: 24406.
Numerical Simulation of the Carbon Deposition Mechanism of Solid Oxide Fuel Cells Based on Total Harmonic Distortion Analysis
Authors: Wang Yinan , Zhang Ruiyu , Li Xiaoxiao , Wang Yuqing , Shi Yixiang
Published: September 2023

Identifying the corresponding degradation mechanisms at the early stage of operation is important for the long-term stable operation of solid oxide fuel cells (SOFCs). This paper uses total harmonic distortion analysis (THDA) to identify the anode carbon deposition mechanism in the early stage of SOFC operation with carbon-containing fuels. An accelerated calculation model for the electrochemical impedance spectrum (EIS) and a total harmonic distortion calculation model were constructed to study the carbon deposition mechanism and carbon removal strategy of SOFC anodes based on a one-dimensional transient elementary reaction kinetic model of an SOFC fueled by a CH4/H2O mixture. It is shown that the THDA calculation model can identify the primary stages of carbon deposition on SOFC anodes at specific frequencies. The THDA profiles at frequencies greater than 2 kHz contain essentially the same key information as at lower frequencies, suggesting that THDA can significantly reduce the test time for identifying performance degradation in the early stages of SOFC operation compared to EIS. Using a mixture of hydrogen and water vapor to remove the solid carbon generated by the cell anode and restore it to its initial performance, the THDA computational model can successfully respond to this process.
Integration of Reversible Solid Oxide Electrolysis (rSOC) to Wastewater Treatment Plants for Sustainable Green Gas Production and Balancing of Green Power
Authors: Weiss Robert , Rautanen Markus , Saarinen Ville , Kiviaho Jari , Pennanen Jari , Himanen Olli
Published: September 2023

Biogas produced from anaerobic digestion (AD) of sewage sludge and organic wastes at wastewater treatment plants (WWTPs) can present an important energy contribution to a sustainable society. This raw biogas contains typically 50-65 molar% methane (CH4) and 50-35 molar% carbon dioxide (CO2). The raw AD biogas can be further upgraded to biomethane (with over 98 molar% CH4). This is a sustainably produced gas of biological origin which has same usability and energetic properties as fossil natural gas. Either by use as biofuel in transportation, local combined heat and power (CHP) or directly fed into the gas grid, biomethane has become a vital non-fossil energy source in Europe but also other parts of the world.

During the CO2 separation step of biomethane upgrading, substantial amounts of CO2 are emitted to the atmosphere. A methanation unit can convert this CO2 into sustainable Synthetic Natural Gas (SNG), with a strong potential to be used as additional biomethane (SNG-Biomethane). The methanation unit can replace the conventional carbon dioxide (CO2) separation unit for biomethane upgrading, but needs addition of hydrogen from water electrolysis, e.g. high performance Solid Oxide Electrolysis (SOE). Such SOE can also be built as a novel high-performance reversible Solid Oxide Electrolysis (rSOC), as demonstrated in the European H2020 project BALANCE. Besides the SOE mode, such rSOC can operate also in the opposite fuel cell direction (SOFC): In times when power demands exceed sustainable supply, the SOFC mode of the rSOC can convert raw AD biogas directly to electricity. In this way, WWTPs can act as energy storage solutions to buffer temporal electrical energy surplus and produce domestic sustainable SNG to the transport sector or the gas grid. At the same time, the rSOC provides a concept of zero-emission power production. To highlight the zero-emission potential of the rSOC, this paper emphasizes author’s earlier results from the European H2020 project DEMOSOFC, which demonstrated zero-local emission SOFC using raw biogas from WWTP sewage sludge and organic wastes.

In this paper, profitability estimations for optimal rSOC and methanation investment and operation strategies at a modern city level WWTP in Finland, Europe, are presented. Power used in rSOC electrolysis mode (SOEC) origins from intermittent green power sources such as wind power, while power produced in rSOC fuel cell mode (SOFC) uses raw AD biogas. For the assessment, we utilize a dedicated Power-to-X optimization model which combines optimally power market operations, dimensions of renewable power sources, plant dimensions and operational scheduling strategies. The assessment showed high profitability using European gas crisis power market data 2021-2022, resulting in sustainable biomethane net production costs of 30-70 €/MWh.
Spatially Heterogeneous Chemistry Observed using NIRTI on SOFC Anodes
Authors: Pomeroy Elias D , Steinhurst Daniel , Tsoi Stanislav , Kirtley John David , Eigenbrodt Bryan , Owrutsky Jeffrey , Maza William A , Walker Robert A.
Published: September 2023

Carbon formation remains the primary degradation mechanism for solid oxide fuel cells (SOFCs) operating on carbonaceous fuels. The mechanisms for the remediation of carbon (C) induced degradation via electrochemical gasification and reforming using O2(g) and H2O(g) was studied using Near Infrared Thermal Imaging (NIRTI), Fourier Transform Infrared Emission Spectroscopy (FTIRES), chronoamperometry/chronopotentiometry (CA/CP), and mass spectrometry (MS). Carbon removal follows a stepwise mechanism, first oxidizing surface carbon to CO(g), and subsequently to CO2(g). CO(g) oxidation requires a catalytic surface to form CO2 which plays a key role in removing C via the reverse Boudouard chemistry. NIRTI reveals spatially heterogenous chemistry and suggests a specific role of surface oxygen species. These species form from dissociative adsorption and non-faradaic oxide flux through the electrolyte, as well as O2 transport limited processes occurring due to high O2 utilization. C removal from electrochemical oxidation and steam spatially homogeneous compared to O2, due in part to the respective active surface species, and their respective transport limitations. Under O2 C removal is appears incomplete, despite electrochemical results. These experiments clarify the mechanisms responsible for remediation of C on SOFC anodes and highlight the need of spatially resolved techniques to study SOFCs under operating conditions.
Degradation Analysis of SOFC Performance for Long-Term Operation with High Fuel Utilization (2)
Authors: Asano Koichi , Imabayashi Takumi , Ido Akifumi , Morita Hiroshi , Yamamoto Tohru , Mugikura Yoshihiro
Published: September 2023

Solid oxide fuel cells (SOFCs) are a power generation technology with its high efficiency and low environmental impact, and the most important issue for SOFC for practical use is to improve reliability as well as high efficiency. A national project on SOFC development in Japan, “Development of advanced evaluation and analysis technologies for the durability of Solid Oxide Fuel Cells stacks (2020-),” has been initiated as a NEDO project in order to clarify their long-term durability and find dominant degradation factor for each SOFC stacks. Central Research Institute of Electric Power Industry (CRIEPI) has operated three kinds of different SOFC cell/stacks (flat-tubular and two kinds of planer) for durability under NEDO’s project, which have been developed by KYOCERA, MORIMURA SOFC Technology, and DENSO.

Long-term durability tests of 20,000 hours have been conducted under high fuel utilization of 80% and 85%, which is close to the operating limit of each SOFC cell/stack for high efficiency, to evaluate the effects on the performance and degradation behavior of the cell/stack. In previous projects, we have developed an electrode polarization model that can accurately represent SOFC performance, including cell voltage and each overvoltage, under a variety of conditions. The degradation factors for durability of each SOFC cell/stack have been analyzed by using this model. The analysis revealed that the dominant degradation factors were increased cathode overvoltage and IR loss, similar to the SOFC cell/stacks that were modified from the previous project to improve their long-term durability. On the other hand, the degradation rate of cell voltage was higher at 85% than at 80% fuel utilization in one cell/stack, and the performance degradation factor analysis revealed that this difference was due to an increase in anode overvoltage at 85% than at 80% fuel utilization, where anode overvoltage was not the primary degradation factor.

This work has been carried out under the projects (JPNP13001 and JPNP20003) of the New Energy and Industrial Technology Development Organization (NEDO), Japan as contract research. We would like to express our gratitude to NEDO, many SOFC developers, as well as to university partners and National Institute of Advanced Industrial Science and Technology (AIST).
Rapidly Direct Laser 3D Printing of High-Performance Protonic Ceramic Fuel Cells
Authors: Tong Jianhua
Published: September 2023

Fuel cells with a dense ionic conducting electrolyte layer sandwiched between two porous electrode layers are one of the most efficient fuel-to-electricity energy conversion devices. Their reversible operation can also efficiently electrolyze water to hydrogen, reduce carbon dioxide to fuels, synthesize ammonia, upgrade fuels, and store energy on large scales. Compared with the popular low-temperature (~80 oC) proton exchange/polymer electrolyte membrane fuel cells and the high-temperature (700-1000 oC) oxygen ion-conducting solid oxide fuel cells (SOFCs), initially used in electric vehicles, auxiliary powers, power plants, and hydrogen electrolyzers, the rising star of protonic ceramic fuel cells (PCFCs) based on proton conducting oxide electrolytes offers excellent suitability for operating at 400-700 oC, the optimum temperature range for electrochemical energy devices, enabling extensive superiorities (high efficiency and performance, long thermal and chemical stabilities, flexible fuels, and cost-effective compatible materials) compared to their counterparts. In recent ten years, many high-performance PCFCs have been reported. However, most performances were achieved using small-area button cells (<0.5cm2) fabricated using spin coating, drop coating, manual brushing, and screen printing of electrolytes on the dry-pressed anode supports, followed by co-firing. There are challenges to transferring the excellent microstructures and materials chemistries/properties obtained from small-area cells to large-area cells and stacks. Furthermore, the decrease in cell component layer thickness for high volumetric cell performance and the requirement for more efficient, faster, and more cost-effective manufacturing motivated the advanced manufacturing of PCFCs.

This work will focus on the direct laser 3D printing (DL3DP) of PCFCs performed at Clemson University. The DL3DP integrated 3D printing (microextrusion and ultrasonic spraying) and laser processing (drying, sintering, and machining), allowing for manufacturing PCFC components, single cells, and stacks with the desired microstructures and geometries irrelevant to the area. The DL3DP could rapidly and cost-effectively manufacture PCFCs without conventional long-term furnace processing. The processing speed could be 2 orders of magnitude faster than the conventional tape-casting and furnace co-firing method. The achieved cells and stacks showed excellent fuel cell performance and less dependence on the effective area. The cells showed peak power densities 1.6-2.6 times that of the conventionally processed samples. The stacks demonstrated a peak power of 7 W and constant power outputs of 0.5-3.1 W for 110-260 hours. This DL3DP can be expanded to manufacturing other heterogeneous ceramics for energy conversion and storage devices.

Figure 1
Machine Learning-Assisted Discovery of High-Performance Perovskite Electrolytes for Intermediate-Temperature Protonic Ceramic Electrochemical Cells
Authors: Zhai Ximei , Han Xiaoyan , Ding Fei , Zou Minda , Han Liang , Kitamura Ryo , Luo Feng , Tong Jianhua
Published: September 2023

Solid oxide electrochemical cells (SOECs) have attracted intensive attention because of their high efficiency and low environmental impact. Much effort has been made to decrease the operating temperature of SOECs down to the intermediate-temperature range. The electrolyte materials with high ionic conductivity are the crucial factor in deciding the operating temperature of SOECs among all components. Proton-conducting perovskite oxides are one of the most promising electrolyte materials for intermediate-temperature SOECs due to their excellent ionic conductivity, usually called protonic ceramic electrochemical cells (PCECs). The most common method to discover the new potential proton-conducting perovskite electrolytes is that the introduced aliovalent dopants facilitate the creation of oxygen vacancy to maintain electroneutrality and give rise to protonic defects when exposed to a reduced atmosphere. In addition to the dopant elements and the dopant content, the total conductivities of doped perovskite electrolytes also depend on the synthesis conditions, the measurement condition and so on. Therefore, the investigation of potential perovskite electrolytes for the intermediate-temperature range should not only be based on the search for the most promising compositions but also requires a detailed study of the influences of its microstructure and processing conditions on the total conductivities. The traditional models of trial-and-error experimental processes limit the development of promising electrolyte materials. Machine learning has emerged as a powerful tool to gain hidden rules from extensive data. By focusing on the investigation of the potential perovskite electrolytes, we collected 400 training data and defined 34 desirable features. Features related to basic elemental properties, crystal structure, microstructure, synthesis conditions, and measurement conditions have been included. Based on these data from the published literature, machine learning models are utilized to predict the total conductivity of perovskite compositions at targeted conditions. Thereafter, feature importance is evaluated to establish a guideline for the rapid and accurate screening of potential perovskite electrolytes in the intermediate-temperature range. Consequently, the screened compositions with high total conductivity from the trained model are prepared, and the experimental results are consistent with the predicted results. This study establishes a new avenue to discover perovskite electrolytes with high total conductivity for intermediate-temperature PCECs.

Keywords: Perovskite electrolyte, Proton conducting, Protonic ceramic cells, Machine learning.

Figure 1
Micro Tubular Solid Oxide Reversible Cell Using LaGaO3 Electrolyte Film Prepared on Channel Size Controlled NiO-YSZ Substrate
Authors: Ishihara Tatsumi , Liu Bin , Song Jun Tae , Watanabe Motonori
Published: September 2023

Reversible operation of SOFC is now important subjects from energy storage of renewable electric power from solar or wind power. At present, planer type cell design is widely used for this purpose, however, because of tight gas sealing, tubular type cell design is more suitable. In this study, micro tubular solid oxide cell using La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) thin electrolyte film was prepared by dip-coating and co-sintering process.

NiO-YSZ porous substrate with 10 mm diameter and 30 mm length was used for preparation of the cell. LaGaO3 based oxide film was deposited with dip coating method. Two kinds of NiO and YSZ particles with different particle size (0.91 and 0.65 mm for NiO and 0.62 and 0.25 mm for YSZ) were mixed and extruded for tubular substrate. 4 types of NiO-YSZ anode porous substrate were Average porosity of each 4 tubular substrate was ca. 70% after reduction. However, from SEM observation, channel size in NiO-YSZ substrate was changed and NiO-YSZ using larger NiO and YSZ particles shows larger channel diameter.

Power generation property of 4 tubular cell using different NiO and YSZ particle size for substrate. It was found that the cell deposited on NiO-YSZ using larger particles shows lager power density, in particular, the cell using both NiO and YSZ larger particles shows the largest power density (0.37 W/cm2 at 873 K), which is reasonably large power density. On the other hand, in case of electrolysis, channel size is also strongly influenced on the electrolysis current. As similar manner with fuel cell operation, the LSGM cell prepared on larger particles size of NiO and YSZ shows larger steam electrolysis current. Impedance analysis suggests that the effects of particle size of NiO and YSZ was explained by small concentration overpotential, and so larger channel size is effective for improving the initial performance of the SORC performance. Long term stability of the steam electrolysis was performed and it was found that the LSGM tubular cell prepared on NiO-YSZ with larger particles shows the reasonable stable electrolysis performance in long term stability (-4%/1000h average degradation rate). The main reason for degradation was assigned to the increased IR loss however overpotential was hardly changed over 600 h and so it seems most likely that the reoxidation of NiO or aggregation of NiO is the main reason for degradation of the cell.

This study reveals that the control of channel size in NiO-YSZ porous substrate is highly important for initial performance and long-term stability of SORC.
Life Testing and Redox Cycling of Ni- and Ru-Doped Strontium Iron Titanate Exsolution Fuel Electrodes in Electrolyte-Supported Solid Oxide Cells
Authors: Zhang Yubo , Horlick Samuel A , Dogdibegovic Emir , Barnett Scott A
Published: September 2023

Recently perovskite materials have gained much attention as potential candidates for solid oxide cell (SOC) fuel electrodes due to their advantages of redox stability, coking resistance and sulfur resistance over their cermet counterparts. Enhanced electrochemical performance has also been observed for some of these perovskite materials resulting from exsolution, where nano-sized metal particles are formed on the material surface under reducing conditions. However, the degradation mechanism of these perovskite fuel electrodes has yet to be fully understood and the relationship between their long-term stability and operating envrionments (fuel-cell/electrolysis, fuel compositions, redox cycles, operating pressure, etc.) has not been fully investigated.

Here, life tests were conducted in open-circuit and reversible operation at 850oC on electrolyte-supported symmetric and full cells with Ni and Ru-doped strontium iron titanate (Sr0.95Ti0.3Fe0.63Ni0.07O3 and Sr0.95Ti0.03Fe0.63Ru0.07O3) as fuel electrodes (SrTi0.3Fe0.6Co0.1O3 used as the air electrode in the full cells). For both materials, higher degradation rate was observed when operated with 97% H2 + 3% H2O compared with 50% H2 + 50% H2O as fuel; an increase in ohmic resistance and gas adsorption/desorption resistance contributed to most of the degradation observed. STFN also showed higher degradation rates than STFRu in both fuel compositions. Exsolution from both compositions was confirmed by scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) with both fuel compositions and in situ X-ray Diffraction (XRD) showed the simultaneous perovskite to Ruddlesden-Popper (RP) phase transformation. The faster perovskite-RP phase transformation is believed to be responsible for the higher degradation rates observed for cells using fuel electrode materials with less stable perovskite structure (STFN over STFRu) and tested in more reducing fuel compositions (97% H2 over 50% H2). Moreover, redox cycles were introduced for STFN and STFRu during life tests and partial performance recovery was observed; in situ XRD and SEM microstructural analysis suggests that the recovery resulted from a transformation from RP back to perovskite for both materials. Finally full cell reversible operation durability tests (6 hrs each in fuel cell and electrolysis modes at 0.8 A/cm2) conducted at 850oC with 50% H2 + 50% H2O as fuel at 1 atm showed reasonably good stability over 1000 h. Initial reversible life testing at 3 atm operating pressure showed higher degradation rates, and the possible reasons for this will be discussed.
La0.5Ce0.5O1.75-Catalytic Layer for Methane Conversion into C2 Products Using Solid Oxide Fuel Cell
Authors: Vilela Vanessa Bezerra , Thyssen Vivian Vazquez , Fournet Fayard Franck , Massim Laurance , de Florio Daniel Zanetti , Ferlauto Andre Santarosa , Steil Marlu Cesar , Fonseca Fabio Coral
Published: September 2023

Methane (CH4), the major constituent of natural gas and biogas, is an abundant source to obtain value-added hydrocarbons. The oxidative coupling of methane (OCM) is a direct catalytic route to convert CH4 towards C2 hydrocarbons, ethane (C2H6) and ethylene (C2H4). Using a solid oxide fuel cell (SOFC) is a strategy to overcome some challenges of fixed-bed catalytic reactors. In this context, we have studied the La0.5Ce0.5O1.75 (LCO) oxide as a catalytic layer in a SOFC for methane conversion to ethylene. Single phase LCO was synthesized by the combustion method. X-ray diffraction (XRD) showed that LCO solid solution has a disordered fluorite crystalline structure. Raman spectroscopy data evidenced the presence of surface oxygen vacancies, which may benefit the OCM reaction. SEM images evidenced a microstructure composed of porous agglomerated particles with an irregular shape, expected from the combustion synthesis. Impedance spectroscopy (IS) measurements of sintered LCO pellets were performed in a wide range of both temperature and oxygen partial pressure (pO2). Thermally activated behavior of the total electrical conductivity revealed that LCO is predominantly an ionic conductor at 10-6 < pO2 < 0.21 atm, whereas at pO2 ~ 10-21 atm, n-type electronic conductivity leads to a mixed ionic electronic conductor behavior, due to the Ce4+/3+ reduction. The catalytic properties of LCO and the optimized OCM reaction conditions were investigated a fixed-bed reactor. The desired products were obtained (C2H6 and C2H4), as well the parallel products (COx, and traces of C3H8 and C4H10). The higher rates of CH4 conversion (22 %), C2 selectivity (54 %) and yield (12 %) were reached for the reaction developed with 4CH4:1O2 at 750 ºC. Electrolyte-supported single cells were prepared using a YSZ disk (diameter ~ 19 mm, thickness ~ 0.4 mm) as the electrolyte. The cathode (LSM) and anode (NiO/YSZ) layers were both deposited by screen-printing on each side of the YSZ disk. For the catalytic layer, LCO was deposited, using the spray-coating technique, on the anodic side. The electrochemical properties of such fuel cell tests were characterized under 10 % H2 between 750 – 800 ºC, and then, the fuel was switched to 10 % CH4, both using Helium as a carrier gas. The anode outlet gas was monitored by an online gas analyzer setup that showed formation of C2H4, C2H6 and COx, indicating the effectiveness of the catalytic layer.
Degradation Evaluation of LaCrO3-Based Interconnect on the Basis of Oxygen Permeation Measurements
Authors: Yamaguchi Takuya , Ishiyama Tomohiro , Yamaji Katsuhiko
Published: September 2023

Degradation of LaCrO3-based Interconnect was evaluated by comparing the oxygen permeation flux for flat tube SOFC cell before and after long term operation (20,000 hours). Oxygen permeation flux was estimated based on the amount of water vapor, which was generated as a result of oxygen permeation from the hydrogen side to the air side. The estimated oxygen permeation flux for the SOFC cell before long term operation was found to be in the range of 0.02~0.06 mL cm−2 min−1 at 750 °C. For the cell after long term operation, the oxygen permeation flux was determined to be 0.049 mL cm−2 min−1, which was almost similar with that for the cell before long term operation. This suggested that degradation of LaCrO3-based Interconnect, i.e., increase in oxygen permeation, is quite small.
Computational and Experimental Study on the Combined Sulfur and Chromium Poisoning Mechanism of LSM, LSCF and LNO Cathodes
Authors: Wang Rui , Parent Lucas R , Gopalan Srikanth , Zhong Yu
Published: September 2023

Prevovskite (La,Sr)MnO3 (LSM), (La,Sr)(Co,Fe)O3 (LSCF) and Ruddlesden-Popper (RP) type La2NiO4 (LNO) phase, as solid oxide fuel cell (SOFC) cathodes, has been used due to its high efficiency and low emissions. To further understand the long-term degradation mechanism of the LSM, LSCF, and LNO phase in SO2 and Cr vapor gas impurities, they were prepared, sintered, and heat-treated at 800, 900, and 1000 ℃ in the sulfur, chromium, and water vapor-containing atmospheres, respectively. Later, XRD, SEM and TEM techniques were applied to the samples and corresponding simulations were made by the CALPHAD approach based on the same experimental conditions to verify the formation of the detrimental secondary phases. Results showed good agreement among the predictions and experiments. More importantly, extensive simulations were also conducted under different conditions (temperature, the partial pressure of oxygen and impurities) to understand the long-term degradation mechanism and optimize the operating conditions.
Operando Characterizations of Proton Exchange in Proton Conducting Solid Oxide Electrolysis Cells (p-SOECs)
Authors: Meng Yuqing , Zhang Qian , Zhao Haiyan , Ding Dong
Published: September 2023

The proton conducting solid oxide electrolysis cell (p-SOEC) has attracted tremendous attention for its fast hydrogen production at intermediate temperatures. This work characterizes transport and hydration properties of the state-of-the-art electrolyte materials using in situ Diffuse reflectance infrared Fourier transform infrared spectroscopy (DRIFTS) together with electrochemical impedance spectroscopy (EIS). The adsorption of water molecules and formation of surface hydroxyl groups on the electrolyte surface as a function of temperature, steam concentration, and electrical potential were systematically investigated by DRIFTS under operando conditions. The quantitative information on the concentration of hydroxyl species on the electrolyte materials before and after exposure to steam were obtained. The determination of OH intensity leads to the direct determination of the proton exchange coefficient k, at different steam concentrations and biases. Thermalgravimetric analysis (TGA) was used to reveal bulk hydration behaviors. The results are unique and should be able to provide valuable insights into the mechanisms of proton formation, migration, and evolution under various operating conditions, which is critical to design better electrolyte compositions and optimize the operation conditions for next-generation p-SOECs.
Long-Term Tests and Advanced Post-Test Characterizations of the Oxygen Electrode in Solid Oxide Electrolysis Cells
Authors: Celikbilek Ozden , Sassone Giuseppe , Prioux Manon , Ferreira Sanchez Dario , Benayad Anass , Hubert Maxime , Morel Bertrand , Vulliet Julien , Léon Aline , Laurencin Jérôme
Published: September 2023

Solid Oxide cells (SOCs) are promising high-temperature electrochemical energy-conversion devices, which enable a fossil-free sustainable development. Nevertheless, performance degradation is still a bottleneck for the large-scale commercialization. The most commonly employed material for the air electrode is La1-xSrxCoy-1FeyO3-δ. The chemical decomposition of this material is known to considerably impact the cell performance [1,2].

The studied cells are composed of a La0.6Sr0.4Co0.2Fe0.8O3
-δ (LSCF) current collecting layer (CCL) and a LSCF-Ce0.8Gd0.2O2
-δ (LSCF-GDC) composite for the air electrode, GDC for the barrier layer, (Y2O3)0.08(ZrO2)0.92 (YSZ) for the electrolyte and Ni-YSZ for the functional layer and the support layer of the fuel electrode. The present study aims to investigate the degradation occurring in the air electrode of a complete cell aged at 750°C for 2000 h in electrolysis mode. The cell degradation is assessed by electrochemical measurements, such as polarization curves and electrochemical impedance spectroscopy (EIS), and post-mortem characterizations of the air electrode using high resolution multimodal chemical imaging based on synchrotron X-ray diffraction (µ-XRD) in Paul Scherrer Institut (PSI, microXAS), complemented by X-ray photoelectron spectroscopy (XPS).

The electrochemical characterizations performed at the beginning of the test and after ageing showed a decrease in the cell performance. Notably, a significant evolution at the high frequency region was observed in the impedance spectrum. However, the medium frequency region of the EIS, mainly ascribed to the air electrode using a physically-based multiscale model [3], did not show any particular evolution. Post-mortem characterizations using synchrotron µ-XRD technique showed an inter-diffusion layer (IDL) in between the GDC and YSZ layers, for both pristine and aged samples (Fig. 1). In addition, a slight increase in the LSCF unit cell volume was observed after ageing. Nevertheless, XPS results did not highlight any significant evolution in the Sr segregation after operation. According to the impedance spectra and the post-mortem analyses, the ageing of the air electrode seems to have a limited impact on the cell performance loss in these operating conditions.

References

[1] J. Laurencin, M. Hubert, D.F. Sanchez, S. Pylypko, M. Morales, A. Morata, B. Morel, D. Montinaro, F. Lefebvre-Joud, E. Siebert, Electrochimica Acta. 241 (2017) 459–476.

[2] M. Kim, H. Muroyama, T. Matsui, K. Eguchi, J. Electrochem. Soc. 166 (2019) F1269.

[3] G. Sassone, E. Da Rosa Silva, M. Prioux, M. Hubert, B. Morel, J. Laurencin. Under preparation.

Figure 1
A Sr2CoNbO6-δ@Sm0.2Ce0.8O2-
δ nanofiber composite as cathode accelerates oxygen reduction reaction for IT-SOFC
Authors: Dhongde Vicky , Velpandian Muthuraja , Haider Mohammad Ali , Basu Suddhasatwa
Published: September 2023

Boosting the lower oxygen reduction reaction (ORR) activity of perovskite cathode material is essential for the development and widespread use of IT-SOFC. Oxygen ion migration at the cathode-electrolyte interface can enhance by introducing structural modifications consisting of high grain boundary density and heterointerfaces [1]. Herein, we fabricated Sr2CoNbO6-
δ @Sm0.2Ce0.8O1.9 (SCNO@SDC) nanofiber composite using an electrospinning technique and examined the electrochemical impedance for the symmetric cell in air atmosphere. The distinct phases of SCNO and SDC were observed from XRD and FESEM-EDAX analysis. The ionic conductivity was analysed to monitor the electrochemical activity of synthesised material, and the results illustrated that the activation energy for the nanofiber was 0.51 eV lower than conventional composites’ 0.73 eV. The thermal expansion coefficient showed improvement as the value of 14.3 Х 10-6 K-1 for nanofiber composite than the 17.6 Х 10-6 K-1 of SCNO-SDC [2]. The symmetric SCNO|SDC|SCNO cell electrodes from nanofiber were fabricated, and electrochemical performance was compared with 20% SDC-SCNO composite in an air atmosphere with varying temperatures from 500oC to 700oC. Figure 1. compares polarisation resistance with increased temperature for nanofiber and conventional electrodes. The polarization resistance significantly decreased from 2.76 Ω cm2 to 0.69 Ω cm2 for the nanofiber composite than the conventional electrode 5.2 Ω cm2 to 2.1 Ω cm2 [3]. The sluggish ORR activity improved due to unique microstructure, high porosity, and specific surface area, which provides extensive triple phase boundaries and a continuous path for charge transfer [4]. Therefore, SCNO@SDC nanofiber composite offers an alternative approach for attaining efficient performance of IT-SOFC.

References

Choi, Y., Cho, H. J., Kim, J., Kang, J. Y., Seo, J., Kim, J. H., & Jung, W. (2022). Nanofiber Composites as Highly Active and Robust Anodes for Direct-Hydrocarbon Solid Oxide Fuel Cells. ACS nano, 16(9), 14517-14526.

Li, Z., Peng, M., Zhao, Y., Li, J., & Sun, Y. (2021). Minimized thermal expansion mismatch of cobalt-based perovskite air electrodes for solid oxide cells. Nanoscale, 13(47), 20299-20308.

Kumari, N., Tiwari, P. K., Haider, M. A., & Basu, S. (2017). Electrochemical performance of infiltrated Cu-GDC and Cu-PDC cathode for CO2 electrolysis in a solid oxide cell. ECS Transactions, 78(1), 3329.

Zhao, B., Zhang, L., Zhen, D., Yoo, S., Ding, Y., Chen, D., & Liu, M. (2017). A tailored double perovskite nanofiber catalyst enables ultrafast oxygen evolution. Nature communications, 8(1), 1-9.

Figure 1
Zirconia Overcoats and Ceria Nanoparticles Do Not Improve the 650oC Stability of LSCF-Infiltrated Solid Oxide Cell Electrodes More When Used Together
Authors: Zhang Yubo , Wen Yeting , Huang Kevin , Nicholas Jason
Published: September 2023

Nano-composite electrodes fabricated by introducing nano-sized mixed ionic and electronic conducting (MIEC) catalysts into partially-sintered micro-sized ionic conducting backbones have been used by many researchers to improve the electrochemical performance, and/or reduce the operating temperature, of Solid Oxide Cells (SOCs).1 Unfortunately, these infiltrated electrodes have often possessed poor electrochemical performance stability.2

This presentation will review recent results showing how pre-infiltrated ceria nano-particles3 or atomic layer deposited zirconia overcoats4 can be used as on-board Sr getters to increase the long-term stability of La0.6Sr0.4Co0.8Fe0.2O3-x (LSCF)-infiltrated Ce0.9Gd0.1O1.95-x (GDC) SOC electrodes, without compromising initial performance. This talk will also present results showing that when combined, these surface modification techniques result in LSCF-GDC performance degradation rates that are no better than those obtained from each technique used separately. Lastly, this talk will present GDC pre-infiltration results supporting a newly-emerging consensus that Sr does not surface segregate in Sm0.5Sr0.5CoO3-x (SSC) like it does in LSCF.

References

D. Ding, X. X. Li, S. Y. Lai, K. Gerdes and M. L. Liu, Energy Environ. Sci., 7, 552 (2014).

M. Shah, P. W. Voorhees and S. A. Barnett, Solid State Ionics, 187, 64 (2011).

Y. Zhang and J. D. Nicholas, Journal of the Electrochemical Society, 168, 024522 (2021).

Y. Zhang, Y. Wen, K. Huang and J. D. Nicholas, ACS Applied Energy Materials, 3, 4057 (2020).
Solid Oxide Electrolysis Cells Fabrication: From Single Cells to Batch Production
Authors: Ureña Torres Violeta , Ruiz Kandela , Ciaurriz Paula , Judez Xabier , Aguado Mónica , Garbayo Iñigo
Published: September 2023

Energy transition towards a net-zero emission scenario requires, primarily, a significant increase on the renewable energy production capabilities. However, the inherent intermittency of most common renewable sources, added to the limitations of full electrification in some important hard-to-abate sectors (heavy-duty transport, aviation, steel industry...), implies also the need of developing reliable solutions for energy conversion and storage. Here, hydrogen is gaining more and more popularity in the recent years as an effective solution as energy carrier, mostly for the decarbonization of the key industries and transport. Among the different technologies under development for power-to-hydrogen conversion, solid oxide electrolysis (SOE) outstands due to its high conversion efficiency, fuel flexibility (e.g. CO2 electrolysis) and possibility of working in reversible mode (the same device both as electrolyser and fuel cell).

Currently behind competing low temperature electrolysis technologies (AEL, PEMEL) in terms of technology readiness, main challenges of SOE today relate to long-term degradation, heat management and design and reliable fabrication of large stacks and systems. Although many projects are lately flourishing in this line, the number of players able to demonstrate an upscaled fabrication of SOE stacks and systems is still limited. The work presented here represents the first step carried out at CENER for the future demonstration of a pilot fabrication line of SOE stacks, from the optimization of functional materials and inks to the fabrication of single cells and building of 2-10 kW stacks.

In this study, a fabrication route for SOE planar cells (5x5 cm2) is proposed, including the optimization of every single step of the process: raw material pre-treatment, ink/slurry development, functional printing and sintering. Particular emphasis is placed on ensuring a reliable upscaling for batch production of cells and thus materials are processed in large quantities (~1 L/batch). In terms of functional materials, standard electrode and electrolytes are chosen in a first approach, viz. Ni-YSZ as hydrogen electrode, YSZ as electrolyte and LSM-YSZ as air electrode. For film deposition, tape casting and screen printing techniques are combined. The electrochemical characterization of the fabricated cells will be presented and compared with commercial ones, including degradation analysis.
Effect of Fabrication Processes on Electrochemical Performance of Metal-Supported Solid Oxide Fuel Cells
Authors: Yamaguchi Yuki , Sumi Hirofumi , Takahashi Hiroaki , Aso Shinobu , Tanabe Shigeyuki , Shimizu Hiroshi
Published: September 2023

Metal supported solid oxide fuel cells (MSCs) which have the robust porous metal substrate are expected for the use in some mobilities. MSCs are prepared by various fabrication processes such as sputtering and screen printing. When the electrolyte layer is fabricated by the wet processes, the electrolyte must be sintered with metal substrate at a high temperature. However, it is difficult to obtain the dense electrolyte on porous metal substrate because sintering temperatures of an electrolyte ceramic and a metal material used in substrates are different. In this study, MSCs were fabricated on the sintered porous metal substrates by screen printing and spin coating with high-temperature sintering in reduced atmosphere. The electrochemical performance of MSCs strongly depended on the process conditions.

MSCs were prepared by the process which is similar to the process for anode supported cell fabrication. Anode paste including nickel oxide and scandia stabilized zirconia with a weight ratio of 60/40 was coated on the green compact of substrate by screen printing. After drying, the electrolyte layer is coated on it by same procedure. Samples were heat-treated around 400 ºC for 1 h to degrease the organic compounds included in cells. These are finally sintered at 1100 – 1250 ºC in reduced atmosphere. The relationship between the electrochemical performance and the structural property were investigated.

In order to obtain dense electrolyte, the shrinkage behavior of porous metal substrates is quite important. Large shrink of substrate can assist the densification of electrolyte in the sintering process. It was found that the degrease temperature affected the shrinkage behavior in sintering process. It was considered that the oxidation of metal particles in substrate affected on the shrinkage. When the sintering temperature were high to obtain the dense electrolyte, Fe and Cr diffused from the substrate to the anode layer. This metal elements diffusion strongly deteriorated the performance of the anode. Additionally, gas atmosphere also affected the metal elements diffusion. When the MSCs are prepared by wet process with high temperature sintering, controlling the sintering behavior of all components by adjusting the process parameter was quite important to low polarization resistance.
(Invited) The Status of SOFC and SOEC R&D in the Clean Hydrogen Partnership
Authors: Atanasiu Mirela , Aguilo-Rullan Antonio , Dirmiki Dimitra , Tsimis Dionysios , Kontonasiou Eleni
Published: September 2023

The Clean Hydrogen Partnership—the successor of the Fuel Cells and Hydrogen Joint Undertaking (FCH JU)—aims to accelerate the development and improvement of advanced clean hydrogen technologies. It builds on 13 years of cooperation between public and private sectors through the FCH JU to help innovative technologies graduate from the experimental phases to be exploited by industry, businesses, and consumers for the benefit of Europe. The three members of the partnership are the European Commission, fuel cell and hydrogen industries represented by Hydrogen Europe and the research community represented by Hydrogen Europe Research. Supported topics cover all fuel cell technologies, SOFC being mostly developed for the stationary heat and power applications, while SOEC technologies are considered for the hydrogen production applications.

There are different groups working in Europe on the SOFC/SOEC technologies and supported partially by the Clean Hydrogen partnership. So far, around €262 million have been allocated to support 71 projects, which address specifically SOFC or SOEC technologies. Largely thanks to this support, the EU is now a world leader on SOFC and SOEC technology with a well-established supply and value chain. In addition, several EU companies have commenced their efforts to increase their manufacturing capabilities with views to introduce their products beyond Europe. The mentioned figures do not include all projects of the first Call for Proposals 2022 of the Clean Hydrogen Partnership as some are still pending signature at the moment of writing. The Clean Hydrogen Partnership presentation will cover the status of R&D in Solid Oxide technologies in Europe including an overview of the European competitiveness in this sector.
Multiphase Porous Electrode Theory for the Next Generation of SOFC/SOEC Electrodes
Authors: Williams Nicholas J , Leah Robert , Mukerjee Subhasish , Zhuang Debbie , Bazant Martin Z. , Skinner Stephen J
Published: September 2023

The mixed-ionic electronic conduction (MIEC) of gadolinium doped ceria (CGO) under reduced oxygen conditions makes it an excellent fuel electrode material for SOFC/SOEC applications. As part of a composite electrode (Ni/CGO), the nickel phase offers a fast electronic conduction pathway to the current collector and may act as an electrocatalyst at the three-phase boundary. Although the Ni/CGO cermet provides superior electrochemical performance compared with older technologies such as Ni/YSZ, the models used to study MIEC materials do not capture the unique transport and kinetic physics which makes them an excellent choice for the next generation of fuel electrodes. Within the framework of multiphase porous electrode theory, this work provides a novel set of differential-algebraic equations which captures the effects of the activation overpotential on electronic defect concentration, electrostatic surface potential and ionic transport to accurately predict the current-voltage behaviour of the Ni/CGO electrode. Moreover, through concerted electron and proton tunnelling events, we unify the theory of the electrostatic surface potential with proton-coupled electron transfer kinetics.
Improved DRT Determination Through a Modified Sparse Spike Deconvolution
Authors: Bergmann Tobias , Schlüter Nicolas
Published: September 2023

Impedance spectroscopy is a powerful characterization method to evaluate the performance of electrochemical systems. However, overlapping signals in the resulting impedance spectra oftentimes cause misinterpretation of the data. The distribution of relaxation times (DRT) method overcomes this problem by transferring the impedance data from the frequency domain into the time domain, which yields DRT spectra with an increased resolution. Unfortunately, the determination of the DRT is an ill-posed problem, and appropriate mathematical regularizations become inevitable to find suitable solutions. [1]

The Tikhonov algorithm is a widespread algorithm for the determination of the DRT
g
and is given by [2]

min

g

(||
Z
- A ⋅
g
|| + λ ⋅ ||L ⋅
g
||)

where the regularization parameter λ scales the penalty term. Unfortunately, this leads to unlikely spectra due to necessary boundaries. The sparse spike deconvolution is using the known positive distribution function for a ZARC-element. Thus this deconvolution leads to more natural spectra for the determination of the DRT. However, the sparse spike deconvolution has a very limited scope by using one single regularization parameter. Consequently, we replaced the scalar regularization parameter with a vector
P
and added a new regularization parameter k for the simultaneous minimization of the vector and the norm of the residuals. The minimization function of this method is given by [3]

min

P

(||
Z
- A ⋅ G(
P
) ⋅
c
|| ⋅ k + ||ln(1 -
P
)||)

Herein the G is a matrix with multiple impulse functions.

Literature:

[1] Ivers-Tiffée, E., & Weber, A., J.Ceram. Soc. Jpn. 2017, 125, 4.

[2] Gavrilyuk, A. L., Osinkin, D. A., & Bronin, D. I., Russ. J. Electrochem., 2017, 53, 6.

[3] Bergmann, T. G., & Schlüter, N., ChemPhysChem, 2022
Phase Segmentation of Ni/YSZ Anode for Solid Oxide Fuel Cells by Deep Learning
Authors: Wang Yige , Matsui Yodai , Hosomizo Akihito , Kishimoto Masashi , Han Minfang , Iwai Hiroshi
Published: September 2023

With the collection and analysis of the large dataset of sequential microstructure images by focused ion beam-scanning electron microscopy (FIB-SEM), 3D electrode microstructure can be reconstructed and quantitatively analyzed, which is important for understanding the performance and stability of the solid oxide fuel cell (SOFC). Even though great efforts have been made on the developments for FIB-SEM imagining, reliable segmentation of the composing phases requires adequate image processing techniques. The conventional method for segmentation requires manual operation based on commercial software. The processing time is often in the range of weeks for a single dataset. In this work, an automated segmentation method with the deep learning network was proposed and tested, which was useful in shortening the image processing time by almost two orders of magnitude. Besides, the influences of various data augmentation operations for the training set on prediction accuracy were investigated, and the guidelines for selecting data augmentation operations for training sets of different sizes and structures were given. The feasibility of transfer learning between different microstructures was also tested. It was found that the prediction accuracy was significantly improved if 1/6 of the data included in the training set came from the same samples as the test set. For a Ni/YSZ anode of SOFC, the segmented images obtained by the conventional manual method (which could be regarded as ground truth) and the deep learning network were compared. The mean intersection over union (mIoU) score reached 93.63%, and the area fraction calculated from the ground truth and deep learning data showed good agreement.