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Special Issue “Emerging Materials and Fabrication Methods for Solid Oxide Fuel Cells (SOFCs)”

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Bahman Amini Horri

Energies 2022, 15(9), 3182; https://doi.org/10.3390/en15093182 - 27 Apr 2022

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Abstract

Nowadays, the ever-growing energy demands, the associated greenhouse gas emissions, and the exhaustible nature of fossil fuels are the biggest challenges of our industrial world [...] Full article

(This article belongs to the Special Issue Emerging Materials and Fabrication Methods for Solid Oxide Fuel Cells (SOFCs))

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Open AccessArticle

Fabrication and Performance of Micro-Tubular Solid Oxide Cells

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Energies 2022, 15(10), 3536; https://doi.org/10.3390/en15103536 - 12 May 2022

Cited by 1 | Viewed by 886

Abstract

Solid Oxide Cells (SOC) are the kind of electrochemical devices that provide reversible, dual mode operation, where electricity is generated in a fuel cell mode and fuel is produced in an electrolysis mode. Our current work encompasses the design, fabrication, and performance analysis [...] Read more.

Solid Oxide Cells (SOC) are the kind of electrochemical devices that provide reversible, dual mode operation, where electricity is generated in a fuel cell mode and fuel is produced in an electrolysis mode. Our current work encompasses the design, fabrication, and performance analysis of a micro-tubular reversible SOC that is prepared through a single dip-coating technique with multiple dips using conventional materials. Electrochemical impedance and current-voltage responses were monitored from 700 to 800 °C. Maximum power densities of the cell achieved at 800, 750, and 700 °C, was 690, 546, and 418 mW cm⁻², respectively. The reversible, dual mode operation of the SOC was evaluated by operating the cell using 50% H₂O/H₂ and ambient air. Accordingly, when the SOC was operated in the electrolysis mode at 1.3 V (the thermo-neutral voltage for steam electrolysis), current densities of −311, −487 and −684 mA cm⁻² at 700, 750 and 800 °C, respectively, were observed. Hydrogen production rate was determined based on the current developed in the cell during the electrolysis operation. The stability of the cell was further evaluated by performing multiple transitions between fuel cell mode and electrolysis mode at 700 °C for a period of 500 h. In the stability test, the cell current decreased from 353 mA cm⁻² to 243 mA cm⁻² in the fuel cell mode operation at 0.7 V, while the same decreased from −250 mA cm⁻² to −115 mA cm⁻² in the electrolysis operation at 1.3 V. Full article

(This article belongs to the Special Issue Emerging Materials and Fabrication Methods for Solid Oxide Fuel Cells (SOFCs))

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Open AccessArticle

Synthesis and Characterization of Gadolinium-Doped Zirconia as a Potential Electrolyte for Solid Oxide Fuel Cells

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Energies 2022, 15(8), 2826; https://doi.org/10.3390/en15082826 - 13 Apr 2022

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Abstract

Zirconia-based composites with high thermochemical stability and electrochemical activity are the most promising solid electrolytes for manufacturing solid oxide fuel cells (SOFCs). In the present work, nanocrystalline composite powders of gadolinium-doped zirconia (GDZ: Gd_2xZr_2(1−x)O_4−x [...] Read more.

Zirconia-based composites with high thermochemical stability and electrochemical activity are the most promising solid electrolytes for manufacturing solid oxide fuel cells (SOFCs). In the present work, nanocrystalline composite powders of gadolinium-doped zirconia (GDZ: Gd_2xZr_2(1−x)O_4−x) with various doping fractions (0.01 ≤ x ≤ 0.16) were synthesized by the Pechini method and applied for the fabrication of several electrolyte pellets to evaluate their physicochemical properties, sinterability, and conductivity. The X-ray diffraction (XRD) patterns and the thermogravimetry/differential thermal analysis (TGA/DTA) of the synthesized powders confirmed the successful formation of nanocrystalline GDZ in the tetragonal phase with complete substitution of gadolinium phase into the zirconia (ZrO₂) lattice. The synthesized gadolinium zirconate powders were then shaped into pellet forms using the tape casting method, followed by sintering at 1300 °C (for 2.5 h). The microstructural analysis of the electrolyte pellets showed suitable grain boundary welding at the surface with an acceptable grain growth at the bulk of the T-phase GDZ samples. The impedance measurements indicated that the T-phase GDZ-8 could provide a comparably higher ionic conductivity (with 7.23 × 10⁻² S/cm in the air at 800 °C) than the other dopant fractions. The results of this work can help better understand the characteristics and electrochemical performance of the T-phase gadolinium zirconate as a potential electrolyte for the fabrication of SOFCs. Full article

(This article belongs to the Special Issue Emerging Materials and Fabrication Methods for Solid Oxide Fuel Cells (SOFCs))

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Open AccessFeature PaperArticle

Pr- and Sm-Substituted Layered Perovskite Oxide Systems for IT-SOFC Cathodes

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Energies 2021, 14(20), 6739; https://doi.org/10.3390/en14206739 - 16 Oct 2021

Cited by 5 | Viewed by 1131

Abstract

In this study, the phase synthesis and electrochemical properties of A^/A^//A^///B₂O_5+d (A^/: Lanthanide, A^//: Ba, and A^//: Sr) layered perovskites in which Pr and Sm were substituted at [...] Read more.

In this study, the phase synthesis and electrochemical properties of A^/A^//A^///B₂O_5+d (A^/: Lanthanide, A^//: Ba, and A^//: Sr) layered perovskites in which Pr and Sm were substituted at the A/-site were investigated for cathode materials of Intermediate Temperature-Operating Solid Oxide Fuel cells (IT-SOFC). In the Pr_xSm_1−xBa_0.5Sr_0.5Co₂O_5+d (x = 0.1–0.9) systems, tetragonal (x < 0.4) and orthorhombic (x ≥ 0.5) crystalline structures were confirmed according to the substitution amount of Pr, which has a relatively large ionic radius, and Sm, which has a small ionic radius. All of the layered perovskite oxide systems utilized in this study presented typical metallic conductivity behavior, with decreasing electrical conductivity as temperature increased. In addition, Pr_0.5Sm_0.5Ba_0.5Sr_0.5Co₂O_5+d (PSBSCO55), showing a tetragonal crystalline structure, had the lowest conductivity values. However, the Area-Specific Resistance (ASR) of PSBSCO55 was found to be 0.10 Ω cm² at 700 °C, which is lower than those of the other compositions. Full article

(This article belongs to the Special Issue Emerging Materials and Fabrication Methods for Solid Oxide Fuel Cells (SOFCs))

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Open AccessArticle

Chemical Degradation of the La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ/Ce_0.8Sm_0.2O_2−δ Interface during Sintering and Cell Operation

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Mélanie François

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Maria Paola Carpanese

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Energies 2021, 14(12), 3674; https://doi.org/10.3390/en14123674 - 20 Jun 2021

Cited by 3 | Viewed by 1453

Abstract

A complete cell consisting of NiO-Ce_0.8Sm_0.2O_3−δ//Ce_0.8Sm_0.2O_3−δ//(La_0.6Sr_0.4)_0.95Co_0.2Fe_0.8O_3−δ elaborated by a co-tape casting and co-sintering process and tested in operating fuel cell [...] Read more.

A complete cell consisting of NiO-Ce_0.8Sm_0.2O_3−δ//Ce_0.8Sm_0.2O_3−δ//(La_0.6Sr_0.4)_0.95Co_0.2Fe_0.8O_3−δ elaborated by a co-tape casting and co-sintering process and tested in operating fuel cell conditions exhibited a strong degradation in performance over time. Study of the cathode–electrolyte interface after cell testing showed, on one hand, the diffusion of lanthanum from (La_0.6Sr_0.4)_0.95Co_0.2Fe_0.8O_3−δ into Sm-doped ceria leading to a La- and Sm-doped ceria phase. On the other hand, Ce and Sm diffused into the perovskite phase of the cathode. The grain boundaries appear to be the preferred pathways of the cation diffusion. Furthermore, a strontium enrichment was clearly observed both in the (La_0.6Sr_0.4)_0.95Co_0.2Fe_0.8O_3−δ layer and at the interface with electrolyte. X-ray photoelectron spectroscopy (XPS) indicates that this Sr-rich phase corresponded to SrCO₃. These different phenomena led to a chemical degradation of materials and interfaces, explaining the decrease in electrochemical performance. Full article

(This article belongs to the Special Issue Emerging Materials and Fabrication Methods for Solid Oxide Fuel Cells (SOFCs))

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Open AccessArticle

Facile Synthesis of Lanthanum Strontium Cobalt Ferrite (LSCF) Nanopowders Employing an Ion-Exchange Promoted Sol-Gel Process

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Sri Rahayu

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Adi Ab Fatah

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Girish M. Kale

Energies 2021, 14(7), 1800; https://doi.org/10.3390/en14071800 - 24 Mar 2021

Cited by 4 | Viewed by 1400

Abstract

The perovskite nanopowders of lanthanum strontium cobalt ferrite (LSCF) have been synthesized using the alginate mediated ion-exchange process. This perovskite-based material is a promising cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs) due to its high electrical conductivity, low polarizability, high catalytic activity [...] Read more.

The perovskite nanopowders of lanthanum strontium cobalt ferrite (LSCF) have been synthesized using the alginate mediated ion-exchange process. This perovskite-based material is a promising cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs) due to its high electrical conductivity, low polarizability, high catalytic activity for oxygen reduction, enhanced chemical stability at an elevated temperature in high oxygen potential environment and high compatibility with the ceria based solid electrolytes. Phase pure LSCF 6428, LSCF 6455, and LSCF 6482 corresponding to La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ, La_0.6Sr_0.4Co_0.5Fe_0.5O_3-δ, and La_0.6Sr_0.4Co_0.8Fe_0.2O_3-δ, respectively were successfully synthesized. The simultaneous thermal analysis (DSC-TGA) and XRD were used to determine the optimum calcination temperature for the dried ion-exchanged beads. Single phase nanopowders of LSCF (6428, 6455, and 6482) have been successfully prepared at a calcination temperature of 700 °C. The TGA analysis showed that every ton of LSCF-ALG dried beads can potentially yield 360 kg of LSCF nanopowders suggesting a potential for scaling-up of the process of manufacturing nanopowders of LSCF. Full article

(This article belongs to the Special Issue Emerging Materials and Fabrication Methods for Solid Oxide Fuel Cells (SOFCs))

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Open AccessArticle

High Channel Density Ceramic Microchannel Reactor for Syngas Production

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Energies 2020, 13(23), 6472; https://doi.org/10.3390/en13236472 - 07 Dec 2020

Cited by 2 | Viewed by 1308

Abstract

Solid oxide fuel cells can operate with carbonaceous fuels, such as syngas, biogas, and methane, using either internal or external reforming, and they represent a more efficient alternative to internal combustion engines. In this work, we explore, for the first time, an alumina [...] Read more.

Solid oxide fuel cells can operate with carbonaceous fuels, such as syngas, biogas, and methane, using either internal or external reforming, and they represent a more efficient alternative to internal combustion engines. In this work, we explore, for the first time, an alumina membrane containing straight, highly packed (461,289 cpsi), parallel channels of a few micrometers (21 µm) in diameter as a microreformer. As a model reaction to test the performance of this membrane, the dry reforming of methane was carried out using nickel metal and a composite nickel/ceria as catalysts. The samples with intact microchannels were more resistant to carbon deposition than those with a powdered sample, highlighting the deactivation mitigation effect of the microchannel structure. The coke content in the microchannel membrane was one order of magnitude lower than in the powder catalyst. Overall, this work is a proof of concept on the use of composite alumina membrane as microchannel reactors for high temperature reactions. Full article

(This article belongs to the Special Issue Emerging Materials and Fabrication Methods for Solid Oxide Fuel Cells (SOFCs))

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Open AccessArticle

The Role of Bi-Polar Plate Design and the Start-Up Protocol in the Spatiotemporal Dynamics during Solid Oxide Fuel Cell Anode Reduction

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Energies 2020, 13(14), 3552; https://doi.org/10.3390/en13143552 - 10 Jul 2020

Cited by 5 | Viewed by 2887

Abstract

Start-up conditions largely dictate the performance longevity for solid oxide fuel cells (SOFCs). The SOFC anode is typically deposited as NiO-ceramic that is reduced to Ni-ceramic during start-up. Effective reduction is imperative to ensuring that the anode is electrochemically active and able to [...] Read more.

Start-up conditions largely dictate the performance longevity for solid oxide fuel cells (SOFCs). The SOFC anode is typically deposited as NiO-ceramic that is reduced to Ni-ceramic during start-up. Effective reduction is imperative to ensuring that the anode is electrochemically active and able to produce electronic and ionic current; the bi-polar plates (BPP) next to the anode allow the transport of current and gases, via land and channels, respectively. This study investigates a commercial SOFC stack that failed following a typical start-up procedure. The BPP design was found to substantially affect the spatiotemporal dynamics of the anode reduction; Raman spectroscopy detected electrochemically inactive NiO on the anode surface below the BPP land-contacts; X-ray computed tomography (CT) and scanning electron microscopy (SEM) identified associated contrasts in the electrode porosity, confirming the extension of heterogeneous features beyond the anode surface, towards the electrolyte-anode interface. Failure studies such as this are important for improving statistical confidence in commercial SOFCs and ultimately their competitiveness within the mass-market. Moreover, the spatiotemporal information presented here may aid in the development of novel BPP design and improved reduction protocol methods that minimize cell and stack strain, and thus maximize cell longevity. Full article

(This article belongs to the Special Issue Emerging Materials and Fabrication Methods for Solid Oxide Fuel Cells (SOFCs))

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Review

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Open AccessReview

Progress in Material Development for Low-Temperature Solid Oxide Fuel Cells: A Review

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Mohsen Fallah Vostakola

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Bahman Amini Horri

Energies 2021, 14(5), 1280; https://doi.org/10.3390/en14051280 - 26 Feb 2021

Cited by 41 | Viewed by 4133

Abstract

Solid oxide fuel cells (SOFCs) have been considered as promising candidates to tackle the need for sustainable and efficient energy conversion devices. However, the current operating temperature of SOFCs poses critical challenges relating to the costs of fabrication and materials selection. To overcome [...] Read more.

Solid oxide fuel cells (SOFCs) have been considered as promising candidates to tackle the need for sustainable and efficient energy conversion devices. However, the current operating temperature of SOFCs poses critical challenges relating to the costs of fabrication and materials selection. To overcome these issues, many attempts have been made by the SOFC research and manufacturing communities for lowering the operating temperature to intermediate ranges (600–800 °C) and even lower temperatures (below 600 °C). Despite the interesting success and technical advantages obtained with the low-temperature SOFC, on the other hand, the cell operation at low temperature could noticeably increase the electrolyte ohmic loss and the polarization losses of the electrode that cause a decrease in the overall cell performance and energy conversion efficiency. In addition, the electrolyte ionic conductivity exponentially decreases with a decrease in operating temperature based on the Arrhenius conduction equation for semiconductors. To address these challenges, a variety of materials and fabrication methods have been developed in the past few years which are the subject of this critical review. Therefore, this paper focuses on the recent advances in the development of new low-temperature SOFCs materials, especially low-temperature electrolytes and electrodes with improved electrochemical properties, as well as summarizing the matching current collectors and sealants for the low-temperature region. Different strategies for improving the cell efficiency, the impact of operating variables on the performance of SOFCs, and the available choice of stack designs, as well as the costing factors, operational limits, and performance prospects, have been briefly summarized in this work. Full article

(This article belongs to the Special Issue Emerging Materials and Fabrication Methods for Solid Oxide Fuel Cells (SOFCs))

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