Search Results (146)

Solid oxide fuel cells (SOFCs) have been considered as alternative energy conversion devices because of their high energy conversion efficiency, fuel flexibility, and cost efficiency without precious metal catalysts. In current SOFCs, the cermet anode consists of nickel and ion-conducting ceramic materials, and solid oxide electrolytes and ceramic cathodes have been used. SOFCs normally operate at high temperatures because of the lower ion conductivity of ceramic components at low temperatures, and they have weaknesses in terms of mechanical strength and durability against thermal shock originating from the properties of ceramic materials. To solve these problems, metal-supported solid oxide fuel cells (MS-SOFCs) have been designed. SOFCs using metal substrates, such as Ni-based and Cr-based alloys, provide significant advantages, such as a low material cost, ruggedness, and tolerance to rapid thermal cycling. In this article, SOFCs are introduced briefly, and the types of metal substrate used in MS-SOFCs, as well as the advantages and disadvantages of each metal support, are reviewed. Full article

Solid oxide fuel cells (SOFCs) represent a pivotal technology in renewable energy due to their clean and efficient power generation capabilities. Their role in potential carbon mitigation enhances their viability. SOFCs can operate via a variety of alternative fuels, including hydrocarbons, alcohols, solid carbon, and ammonia. However, several solutions have been proposed to overcome various technical issues and to allow for stable operation in dry methane, without coking in the anode layer. To avoid coke formation thermodynamically, methane is typically reformed, contributing to an increased degradation rate through the addition of oxygen-containing gases into the fuel gas to increase the O/C ratio. The performance achieved by reforming catalytic materials, comprising active sites, supports, and electrochemical testing, significantly influences catalyst performance, showing relatively high open-circuit voltages and coking-resistance of the CH₄ reforming catalysts. In the next step, the operating principles and thermodynamics of methane reforming are explored, including their traditional catalyst materials and their accompanying challenges. This work explores the components and functions of SOFCs, particularly focusing on anode materials such as perovskites, Ruddlesden–Popper oxides, and spinels, along with their structure–property relationships, including their ionic and electronic conductivity, thermal expansion coefficients, and acidity/basicity. Mechanistic and kinetic studies of common reforming processes, including steam reforming, partial oxidation, CO₂ reforming, and the mixed steam and dry reforming of methane, are analyzed. Furthermore, this review examines catalyst deactivation mechanisms, specifically carbon and metal sulfide formation, and the performance of methane reforming and partial oxidation catalysts in SOFCs. Single-cell performance, including that of various perovskite and related oxides, activity/stability enhancement by infiltration, and the simulation and modeling of electrochemical performance, is discussed. This review also addresses research challenges in regards to methane reforming and partial oxidation within SOFCs, such as gas composition changes and large thermal gradients in stack systems. Finally, this review investigates the modeling of catalytic and non-catalytic processes using different dimension and segment simulations of steam methane reforming, presenting new engineering designs, material developments, and the latest knowledge to guide the development of and the driving force behind an oxygen concentration gradient through the external circuit to the cathode. Full article

Solid oxide fuel cell (SOFC) systems often employ metallic cathode air pre-heaters (CAPHs), frequently made from alloys with high chromium (Cr) content, to recover thermal energy from exhaust gases and pre-heat incoming air and fuel. Cr evaporation from metallic CAPHs can poison SOFC cathodes, reducing their durability. To mitigate this, we investigated controlled pre-oxidation of a FeCrAl alloy (alloy 318) to form a protective alumina scale by self-growing, assessing its impact on and oxidation resistance and Cr retention capability for CAPH applications. The effects of pre-oxidation were investigated across a temperature range of 800 to 1100 °C and dwelling times of 0.5 to 4 h. The formed oxide scales were characterised using gravimetry in combination with advanced analytic techniques, such as SEM/EDX, STEM/EDX, TEM, and XRD. Subsequently, the pre-oxidised FeCrAl alloys were characterised with respect to the oxidation rate and Cr₂O₃ evaporation in a tubular furnace at 850 °C, with 6.0 L/min air flow and 3 vol% H₂O to simulate the SOFC cathode environment. TEM analysis confirmed that the FeCrAl alloys formed alumina scales with 10 nm and 34 nm thickness after 1 h of pre-oxidation at 900 and 1100 °C, respectively. The corrosion and Cr₂O₃ evaporation rates of the FeCrAl alloy at 850 °C in humidified air were shown to be dramatically decreased by pre-oxidation. It was found that the mechanisms of oxidation and Cr₂O₃ evaporation were found to be controlled by the formation of different alumina phases during the pre-oxidation. Measurements of Cr₂O₃ evaporation and weight gain revealed that the alloy 318 pre-treated at 1100 °C for 1 h will form an α-Al₂O₃ scale, leading to a 98% reduction of the oxidation rate and 90% reduction of Cr₂O₃ evaporation compared to the non-oxidised alloy 318 under simulated SOFC cathode conditions. Full article

In this study, a three-dimensional numerical simulation of a solid oxide fuel cell (SOFC) with dimensions of 6 cm × 6 cm on the anode side and 5 cm × 5 cm on the cathode side (active area) was conducted to determine the performance characteristics of the cell electrodes. The performance characteristics of each SOFC unit cell were investigated through numerical simulations. 3.5a COMSOL Multiphysics software was used to solve the model. The effects of the operating conditions, fuel concentration, and electrode porosity on the electrochemical performance of the SOFC electrodes were examined. In addition, an experiment was conducted to investigate the operating cell performance at 600, 700, and 750 °C. The results indicate that a higher electrode porosity can improve fuel mass transfer, resulting in an almost uniform H₂ concentration at a porosity of 0.75 when the model was investigated with electrode porosities of 0.25, 0.375, 0.55, and 0.75. The simulation results also reveal that the performance of the voltage distribution on electrode surfaces is improved when the input operating temperature of the fuel cell is increased at different temperatures (650, 700, and 750 °C). At the operating temperature of 750 °C, it can be seen from the experimental results that the highest current and voltage of the cell were 587.4 mA·cm⁻² and 1.12 V, respectively. Full article

Solid oxide electrolysis cells (SOECs) are considered one of the most promising technologies for carbon neutralization, as they can efficiently convert CO₂ into CO fuel. Sr₂Fe_1.5Mo_0.5O_6−δ (SFM) double perovskite is a potential cathode material, but its catalytic activity for CO₂ reduction needs further improvement. In this study, Cu ions were introduced to partially replace Mo ions in SFM to adjust the electrochemical performance of the cathode, and the role of the Cu atom was revealed. The results show Cu substitution induced lattice expansion and restrained impurity in the electrode. The particle size of the Sr₂Fe_1.5Mo_0.4Cu_0.1O_6−δ (SFMC0.1) electrode was about 500 nm, and the crystallite size obtained from the Williamson–Hall plot was 75 nm. Moreover, Cu doping increased the concentration of oxygen vacancies, creating abundant electrochemical active sites, and led to a reduction in the oxidation states of Fe and Mo ions. Compared with other electrodes, the SFMC0.1 electrode exhibited the highest current density and the lowest polarization resistance. The current density of SFMC0.1 reached 202.20 mA cm⁻² at 800 °C and 1.8 V, which was 12.8% and 102.8% higher than the SFM electrodes with and without an isolation layer, respectively. Electrochemical impedance spectroscopy (EIS) analysis demonstrated that Cu doping not only promoted CO₂ adsorption, dissociation and diffusion processes, but improved the charge transfer and oxygen ion migration. Theory calculations confirm that Cu doping lowered the surface and lattice oxygen vacancy formation energy of the material, thereby providing more CO₂ active sites and facilitating oxygen ion transfer. Full article

This study analyzes flow uniformity in U-flow pattern and Z-flow pattern solid oxide fuel cell (SOFC) stacks, assessing their performance under different stack heights and rates of fuel/air usage. Both configurations achieved satisfactory flow distribution uniformity in the anode region at the 1 kWe scale, especially with the Z-flow design demonstrating enhanced stability. However, as stack height increased, particularly at 3 kWe, flow uniformity decreased significantly. In the cathode flow region, uniformity was highly sensitive to changes in air utilization rate, with lower air utilization causing more pronounced reductions in flow uniformity for both stack types. Increasing the height of the stack tends to reduce flow uniformity, whereas higher reactant utilization promotes more uniformity. Moreover, flow uniformity strongly correlates with the pressure drop ratio in the core area, where a higher ratio indicates better uniformity. At 75% fuel utilization, the anode flow region of the U-flow pattern 3 kWe stack exhibited excessively high local fuel utilization in the unit cell with the lowest mass flow rate, implying a risk of fuel depletion due to insufficient supply at that height. Overall, the Z-flow pattern stack showed better performance in the anode flow region, particularly at higher capacities, while the U-flow pattern stack performed slightly better in the cathode flow region under low air utilization conditions. These findings indicate that the Z-flow pattern stack is better suited for high-power applications. Full article

Solid oxide fuel cells (SOFCs) have become promising devices for converting chemical energy into electrical energy. Altering the microstructure of cathode materials to enhance the activity and stability of the oxygen reduction reaction is particularly important. Herein, Pr_0.5Ba_0.5Co_1−XNi_XO_3+δ with a tetragonal perovskite structure was synthesized through the sol–gel method. The polarization resistance of the symmetrical half-cell with Pr_0.5Ba_0.5Co_0.9Ni_0.1O_3+δ as the cathode was 0.041 Ω·cm² at 800 °C and 0.118 Ω·cm² lower than that of the symmetrical cell with Pr_0.5Ba_0.5CoO_3+δ as the cathode, indicating that the Pr_0.5Ba_0.5Co_1−XNi_XO_3+δ cathode material had high catalytic activity during the electrochemical reaction. The results of electron paramagnetic resonance revealed that the concentration of oxygen vacancies increased as the Ni doping amount increased to 0.15. As a result of the increase in the Ni doping amount, the thermal expansion coefficient of the Pr_0.5Ba_0.5CoO_3+δ cathode material was effectively reduced, resulting in improved matching between the cathode and electrolyte material. The power density of the single cell increased by 69 mW·cm⁻². Therefore, Pr_0.5Ba_0.5Co_1−XNi_XO_3+δ is a promising candidate cathode material for high-performance SOFCs. Full article

The development of symmetrical solid oxide fuel cells with identical cathode and anode is beneficial for thermal matching and reducing the cost. Herein, proton-conducting electrolyte and novel high catalytic activity electrode material for symmetrical solid oxide fuel cells are proposed. Ni-doping at the B-site of (Sr_0.8Ce_0.2)_0.95FeO_3−δ (SCF) indicates reduced cell edge lengths, cell volume, and a more porous honeycomb structure. The B-site elements in oxide tend to have a high oxidation state via Ni-doping. Simple doping modification in SCF causes better thermal matching between the electrode and electrolyte and form more oxygen vacancies at the operating temperature. At the anode side, Ni-doping improves the stability of the symmetric electrode in reducing the atmosphere. The polarization resistance of symmetrical cells for new electrode material is half of the original both in oxidation and reduction atmosphere, which indicates boosted electrochemical performance for the cathode and anode. At the same time, Ni-doping reduces the impedance activation energy of the anode reaction in symmetric cells. The output performance of the cell is 210.4 mW·cm⁻² at 750 °C and the thickness of the electrolyte is 400 μm, achieving a highly efficient symmetrical electrode in proton ceramic fuel cells. The new finding of materials provides a novel high efficiency symmetrical electrode and proposes guidance for the improvement of solid oxide fuel cells at a reduced temperature. Full article

F-doped PrBa_0.8Sr_0.2Co₂O_5+δ−xF_x (PBSCF_x, x = 0, 0.025, 0.05, 0.075, 0.1) cathode powder was synthesized by the sol–gel method. X-ray diffraction results showed that all the samples doped with F exhibited a typical tetragonal perovskite structure without a heterophase. F doping can effectively reduce the thermal expansion coefficient (TEC) of the cathode materials, which decreased from 25.3699 × 10⁻⁶ K⁻¹ of PBSC to 23.5295 × 10⁻⁶ K⁻¹ of PBSCF_0.1. The area-specific resistance (ASR) of PBSCF_0.05 was 0.0207 Ω·cm² at 800 °C, with a conductivity of 1637.27 S·cm⁻¹ and maximum power density of 856.08 mW·cm⁻². Its performance had slight decay after 100 h at 800 °C. F doping significantly improved the electrochemical performance of this cathode material for solid oxide fuel cells (SOFCs). Full article

Epitaxial layers of water-soluble Sr₃Al₂O₆ were fabricated as sacrificial layers on SrTiO₃ (100) single-crystal substrates using the Pulsed Laser Deposition technique. This approach envisages the possibility of developing a new generation of micro-Solid Oxide Fuel Cells and micro-Solid Oxide Electrochemical Cells for portable energy conversion and storage devices. The sacrificial layer technique offers a pathway to engineering free-standing membranes of electrolytes, cathodes, and anodes with total thicknesses on the order of a few nanometers. Furthermore, the ability to etch the SAO sacrificial layer and transfer ultra-thin oxide films from single-crystal substrates to silicon-based circuits opens possibilities for creating a novel class of mixed electronic and ionic devices with unexplored potential. In this work, we report the growth mechanism and structural characterization of the SAO sacrificial layer. Epitaxial samarium-doped ceria films, grown on SrTiO3 substrates using Sr₃Al₂O₆ as a buffer layer, were successfully transferred onto silicon wafers. This demonstration highlights the potential of the sacrificial layer method for integrating high-quality oxide thin films into advanced device architectures, bridging the gap between oxide materials and silicon-based technologies. Full article

Solid oxide fuel cells (SOFCs) are attracting attention as an eco-friendly power source because they show high power density. However, SOFC requires a high-temperature environment of 800 °C or higher, and accordingly, the problem of thermal stability of the material constituting SOFC has been raised. On the other hand, low-temperature solid oxide fuel cells (LT-SOFCs) research is steadily progressing to improve the electrochemical performance at low temperatures by improving the oxygen reduction reaction of the cathode by applying a cathode interlayer of various materials. In this study, LT-SOFCs were manufactured and electrochemically evaluated using praseodymium oxide (PrO_x) as a cathode interlayer. Scandium Stabilized Zirconia (ScSZ) pellets were used as electrolyte support for LT-SOFC, and PrO_x was deposited by various thicknesses as a cathode interlayer on ScSZ pellets by a sputtering process. Pt and Ni were deposited under the same process conditions for the cathode and anode, respectively. To analyze the thin-film characteristics of the PrO_x cathode interlayer, SEM (Scanning Electron Microscopy), X-ray Diffraction (XRD), and XPS (X-ray Photoelectron Spectroscopy) were analyzed. The electrochemical characteristics of LT-SOFCs were evaluated by electrochemical impedance spectroscopy (EIS). Hydrogen was supplied to the anode at the flow rate of 50 sccm, and the performance of LT-SOFC was evaluated at 500 °C by exposing the cathode to the atmosphere. Full article

Numerical analysis of a U-type solid oxide fuel cell stack was performed using computational fluid dynamics to investigate the effects of stack capacities and fuel/air utilization rates on the internal flow uniformity. The results indicated that increasing the fuel/air utilization rate improved the gas flow uniformity within the stack for the same stack capacity. The uniformity in the anode fluid domain was better than that in the cathode fluid domain. Furthermore, the flow uniformity within the stack was associated with the percentage of pressure drop in the core region of the stack. The larger the percentage of pressure drop in the core region, the more uniform the flow inside the stack. Additionally, under a fuel utilization rate of 75%, the computational results exhibited excessively high fuel utilization rates in the top cell of a 3 kWe stack, indicating a potential risk of fuel depletion during actual stack operation. Full article

Intermediate temperature solid oxide fuel cell (SOFC) operation provides numerous advantages such as high combined heat and power (CHP) efficiency, potentially long-term material stability, and the use of low-cost materials. However, due to the sluggish kinetics of the oxygen reduction reaction at intermediate temperatures (500–700 °C), the cathode of SOFC requires an efficient and stable catalyst. Significant progress in the development of cathode materials has been made over recent years. In this article, multiple strategies for improving the performance of cathode materials have been extensively reviewed such as A- and B-site doping of perovskites, infiltration of catalytic active materials, the use of core-shell composites, etc. Emphasis has been given to intrinsic properties such as chemical and thermal stability and oxygen transport number. Furthermore, to avoid any insulating phase formation at the cathode/electrolyte interface, strategies for interfacial layer modifications have also been extensively reviewed and summarized. Based on major technical challenges, future research directions have been proposed for efficient and stable intermediate temperature solid oxide fuel cell (SOFC) operation. Full article

Double perovskite oxides with mixed ionic and electronic conductors (MIECs) have been widely investigated as cathode materials for solid oxide fuel cells (SOFCs). Classical Fe-based double perovskites, due to their inherent low electronic and oxygen ionic conductivity, usually exhibit poor electrocatalytic activity. The existence of various valence states of B-site ions modifies the material’s catalytic activity, indicating the possibility of the partial substitution of Fe by higher-valence ions. LaBaFe_2−xMo_xO_5+δ (x = 0, 0.03, 0.05, 0.07, 0.1, LBFM_x) is used as intermediate-temperature solid oxide fuel cell (IT-SOFC) cathode materials. At a doping concentration above 0.1, the Mo substitution enhanced the cell volume, and the lattice expansion caused the formation of the impurity phase, BaMoO₄. Compared with the parent material, Mo doping can regulate the oxygen vacancy concentration and accelerate the oxygen reduction reaction process to improve the electrochemical performance, as well as having a suitable coefficient of thermal expansion and excellent electrode stability. LaBaFe_1.9Mo_0.1O_5+δ is a promising cathode material for IT-SOFC, which shows an excellent electrochemical performance, with this being demonstrated by having the lowest polarization resistance value of 0.017 Ω·cm² at 800 °C, and the peak power density (PPD) of anode-supported single-cell LBFM_0.1|CGO|NiO+CGO reaching 599 mW·cm⁻². Full article

In this work, the recent achievements in the application of solid oxides fuel cells (SOFCs) are discussed. This paper summarizes the progress in two major topics: the materials for the electrolytes, anode, and cathode, and the fuels used, such as hydrocarbon, alcohol, and solid carbon fuels. Various aspects related to the development of new materials for the main components of the materials for electrocatalysts and for solid electrolytes (e.g., pure metals, metal alloys, high entropy oxides, cermets, perovskite oxides, Ruddlesden–Popper phase materials, scandia-stabilized-zirconia, perovskite oxides, and ceria-based solid electrolytes) are reported in a coherent and explanatory way. The selection of appropriate material for electrocatalysts and for solid electrolyte is crucial to achieve successful commercialization of the SOFC technology, since enhanced efficiency and increased life span is desirable. Based on the recent advancements, tests were conducted in a biogas-fueled Ni-YSZ/YSZ/GDC/LSC commercial cell, to elucidate the suitability of the LSC as an anode. Results obtained encourage the application of LSC as an anode in actual SOFC and SOFEC systems. Thus, H₂-SOFC demonstrated a satisfying ASR value, while, for biogas-assisted electrolysis, the current values slightly increased compared to the methane-SOFEC, and for a 50/50 biogas mixture of methane and carbon dioxide, the corresponding value presented the higher increase. Full article