Micro-tubular Solid Oxide Research Articles

The role of pore former type on the performance of anode functional layer in microtubular solid oxide fuel cells

The role of pore former type on the performance of anode functional layer in microtubular solid oxide fuel cells

Numerical Modeling of a Polymer Electrolyte Membrane Fuel Cell for Electric Aircraft Propulsion

Electrified propulsion systems with hydrogen-fueled fuel cells can potentially reduce carbon dioxide emissions from aircraft. However, achieving a substantial increase in the gravimetric/volumetric power density of fuel cell systems poses a considerable challenge. In this study, we focus on polymer electrolyte membrane fuel cells (PEMFCs) working between 100 and 200°C. To design an optimized PEMFC structure for an electric aircraft, we have developed a numerical model that employs the finite element method (FEM) (COMSOL Multiphysics) to couple electrochemistry, gas diffusive and convective transports, and heat transfer in fuel cell components such as separators, gas flow channels, gas diffusion layers, catalyst layers, and a PEM1)2). We thereby three-dimensionally visualized the current, hydrogen, oxygen, and water vapor concentration distributions, as well as the temperature distributions, assuming conditions in aircraft operations. Moreover, we developed a machine learning model from the data outputs of the FEM model, which serves as training data, to reduce the computational costs for the fuel cell stack design incorporated in a system-level numerical model.AcknowledgementThis study is based on results obtained from a project, JPNP14004, commissioned by the New Energy and Industrial Technology Development (NEDO). We are indepted to Boeing Research & Technology, Boeing Japan for their support and discussions. We are also grateful to Professor Motoaki Kawase of Kyoto University for his fruitful suggestions. Thanks are offered to Professor Kohei Ito and Associate Professor Tatsumi Kitahara of Kyushu University for their valuable discussions.References1) Ö. Aydın, T. Ochiai, H. Nakajima, T. Kitahara, K. Ito, Y. Ogura, J. Shimano, Mass transport limitation in inlet periphery of fuel cells: Studied on a planar Solid Oxide Fuel Cell, Int. J. Hydrogen Energy, 43 (2018) 17420–17430. https://doi.org/10.1016/j.ijhydene.2018.07.0302) X. Wang, H. Nakajima, Y. Iwanaga, K. Ito, Numerical and experimental investigation of a cathode-supported microtubular solid oxide electrolysis cell from current and temperature variations in-situ assessed with electrode-segmentation method, J. Energy Storage, 72 (2023) 108459. https://doi.org/10.1016/j.est.2023.108459

Investigation of a sacrificial template material suitable for fabrication of anode support microtubes in microtubular solid oxide fuel cells

This study investigates the use of various sacrificial template materials in the form of a solid rod, including wood, carbon fiber, polyamide, resin and polylactic acid (PLA), for fabricating anode supports in microtubular solid oxide fuel cells (SOFCs) via tape casting and isostatic pressing. Anode support strips, produced via tape casting, are wound around these sacrificial rods. The rods are then burnout through co-sintering to yield microtubular anode supports. The results highlight PLA as a particularly promising material due to its balance of cost and performance. A novel rod design involving hollow PLA pipe is then explored to enhance the fabrication process. The anode support tape length or the wall thickness of anode support microtube is also considered. Microtubular cells are fabricated on the anode supports by dip coating other cell layers, and electrochemical and microstructural investigations are carried out. The final cell provides 0.365 W/cm2 maximum power density at 800 °C under 0.3 NL/min hydrogen flow and stationary air. Moreover, a patterned microtubular anode support is successfully fabricated using a 3D printed PLA tube featuring an array of dimples. The overall findings indicate that the proposed methodology not only simplifies the manufacturing process but also supports the feasibility of producing high-performance microtubular SOFCs with enhanced electrolyte-electrode interfaces through patterned anode designs.

Performance and stability of microtubular solid oxide cell with LNO-SDC air electrode operating in fuel cell and electrolysis modes

Microtubular (MT) geometry of solid oxide cells have a number of distinctive properties, such as high volumetric power density, thermocycling stability and fast start-up capability. In this study, we evaluate the performance of the MT cell with LNO-SDC as air electrode under both fuel cell and electrolysis cell mode operation. While working in the fuel cell mode, the maximum power densities of MT cell reached 533, 740 and 792 mW cm−2 at 750, 800 and 850 °C, respectively. Moreover, the MT cell exhibit excellent long-term stability with no critical performance degradation operating at 750 °C. In the electrolysis mode, current density at 800 °C reached value of 780 mA cm−2 under applied voltage of 1.3 V with fuel gas containing 30 % H2O. The results on CO2 electrolysis indicate remarkable efficiency of studied MT cell with current density of 854 mA cm−2 at an applied voltage of 1.5 V.

Effect of Continuous Electrolysis on the Power Generation Performance of a Microtubular Oxide Fuel Cell Using Intermediate Ring‐Shaped Collector

An anode‐support microtubular solid oxide fuel cell (MTSOFC) using an intermediate ring‐shaped electrode collector is simulated using COMSOL Multiphysics software to investigate current density distribution and mass transfer in both power generation and electrolysis modes. The cell is converted to power generation mode during continuous electrolysis, and the electrochemical performance of MTSOFC is tested to study the effect of electrolysis on the power generation performance. The power density output of the MTSOFC decreases from 250 to 150 mW cm−2 after only 40 h of continuous electrolysis. The microstructural changes in different regions during operation are observed through posttest analysis conducted on the fuel inlet, electrochemical reaction concentration region, and fuel outlet of the microtubular cell. The local agglomeration of nickel occurs in the concentrated region of the electrochemical reaction, while the coarsening of nickel oxidation mainly takes place at the fuel inlet and outlet.

Co-extruded triple-layer micro-tubular solid oxide fuel cell: The influence of cathode extrusion rate on the fuel cell properties and performance

Micro-tubular solid oxide fuel cells (MT-SPFC) have emerged as a potential alternative for efficient energy generation. This study investigates the impact of cathode extrusion rates (ranging from 3 to 6 mL min−1) on the triple layer anode/electrolyte/cathode MT-SOFC fabricated via a simplified phase inversion-based co-extrusion/co-sintering technique. Higher cathode extrusion rates (6 mL min−1) indirectly thin the electrolyte layer, improving ion hopping efficiency between the cathode and anode. Moreover, increasing the extrusion rate enhances anode thickness, providing ample electrode reaction sites and thereby enhancing the gas diffusion process. The C6 sample attains a peak power density of 1.46 W cm−2 with 1.08 V OCV at an optimum 800 °C operating temperature, which is high for MT-SOFCs in high-temperature applications. There was a 71.8 % increase in power density for C6 when the temperature changed from 750 °C to 800 °C. The composite cathode material fulfilled both the electronic and ionic conductivity requirements. The optimal cathode extrusion rate for this simplified MT-SOFC fabrication was found to be 6 mL min−1.

3D printing of porous zirconia support for solid oxide fuel cells with high cell performance

This work reports the preparation and characterization of a 3D-printed porous 3 mol% yttria-stabilized zirconia (3YSZ) inert-supported micro-tubular solid oxide fuel cell (MT-SOFC) with high cell performance. For the first time, the impacts of pore-former particle size and mass fraction on the microstructure of 3D-printed porous 3YSZ, along with the influences of debinding atmosphere and pre-sintering temperature on the flexural strength and the shrinkage rate, were comprehensively explored. Optimal results were achieved using a particle size of 3 μm and a mass fraction of 30 wt%, facilitating the preparation of a printable 3YSZ photocurable slurry with a relatively low apparent viscosity of 4.2 Pa s at a shear rate of 30 s−1. Notably, 3D-printed porous 3YSZ debound in nitrogen and sintered in air at 1400 °C exhibited the highest flexural strength of ∼80.2 MPa compared to debinding in air or vacuum. Based on flexural strength and shrinkage rate considerations, the 3D-printed porous 3YSZ debound in nitrogen and pre-sintered at 1150 °C was deemed suitable as an inert support for SOFC. Cells prepared using this optimized approach demonstrated exceptional performance, achieving a maximum power density of 876.8 mW cm−2 at 850 °C, surpassing inert-supported MT-SOFCs fabricated using traditional methods. The outstanding cell performance underscores the successful application of 3D printing technology in preparing porous 3YSZ inert supports for SOFCs, offering an attractive approach for cell preparation and porous ceramics.

One-click startup operation of a micro-tubular solid oxide fuel cells using propane/air/steam

The design and performance of a tubular solid oxide fuel cell (SOFC) integrated with a one-click startup thermal self-sustaining reformer is presented, allowing the tubular SOFC to operate without any external heat source by using propane/air/steam. Double conductive Ni-pads (DCNPs) are utilized as anode current collector in μT-SOFC. The reformer consists of a combustion chamber for initial heating and a reforming chamber for syngas production for the SOFC. The thermal energy generated by complete propane combustion is adequate to achieve thermally self-sustaining operation and efficiently raise the cell temperature above 700 °C. Operating at 700 °C with pure H2, a cell with a length of 12 cm achieves a maximum power density of 138 mW cm−2, which decreases by 13 %–120 mW cm−2 when using syngas produced by steam-propane reforming. The syngas composition from steam-propane reforming reaches 7.6 % CO and 61.7 % H2. COMSOL Multiphysics software is used to simulate the multi-physical field of a single cell exposed to various syngas compositions, showing that syngas produced by steam-propane reforming exhibits excellent electrochemical performance in tubular SOFCs compared to catalyst partial oxidation (CPOX).

Effects of tape thickness on the fabrication and performance of microtubular solid oxide fuel cells manufactured by tape casting

The role of tape thickness in the fabrication of microtubular anode supports for solid oxide fuel cells (SOFCs) by tape casting and isostatic pressing is investigated in this study. The anode support slurry of the same formulation is tape cast by varying the doctor blade gap (DBG) from 100 μm to 700 μm and the obtained tapes are wrapped at different lengths on a metal pin of 5 mm in diameter, while the appropriate tape length for each DBG is decided by considering anode support microtubes with a similar geometry for a reasonable comparison. The analyses reveal that the microstructure of the anode support microtube varies depending on DBG and in general delamination and crack formations occur in the supports at high DBGs. The resultant porosity and pore/grain sizes are also found to be different depending on DBG. Therefore, the supports and the cells with these supports show different mechanical and electrochemical performances. In this regard, DBG of 300 μm provides microtubular anode supports without any microstructural problems. The microtubular cell built on this support also exhibits the highest peak performance of 0.313 Wcm−2 at an operating temperature of 800 °C under 300 sccm hydrogen flow and open cathode condition.

Optimization of the BSCFM5-Based Cathode Layer in the Microtubular Solid-Oxide Fuel Cells and the Study of Its Effect on the Power Characteristics

Optimization of the BSCFM5-Based Cathode Layer in the Microtubular Solid-Oxide Fuel Cells and the Study of Its Effect on the Power Characteristics

Microtubular solid oxide fuel cells decorated with gadolinium doped ceria nanoparticles

A simple and feasible method is proposed in this study for the infiltration of gadolinium doped ceria (GDC) into both anode and cathode electrodes of microtubular solid oxide fuel cells (SOFCs) to improve the cell performance. Some crucial infiltration parameters are also systematically optimized according to electrochemical and microstructural investigations along with short-term lifetime tests. The results reveal that the cell performance can be significantly enhanced with nanoparticle GDC decoration. While the reference cell provides only 252.7 mW/cm2 peak power density under hydrogen fuel at 800 °C, the infiltrated cell with the optimized parameters shows 523.0 mW/cm2 maximum power density under the same testing conditions. The noteworthy improvement in the cell performance is found to be as a result of reduced electrode resistances due to increased number of active electrochemical reaction sites resulting from high surface area of nano GDC particles infiltrated as well as GDC being mixed conductor with high ionic conductivity.

Microtubular solid oxide fuel cells with a two-layer LSCF/BSCFM5 cathode

In this study, we present the development of microtubular solid oxide fuel cells (MT-SOFC) with a two-layer cathode: a composite cathode functional layer (CFL) adjacent to the buffer layer (BL) and a cathode current-collecting layer (CCCL). CFL consists of a mixture of BL material Ce0.9Sm0.2O1.95 (SDC) and perovskite Ba0.5Sr0.5Co0.75Fe0.2Mo0.05O3-δ (BSCFM5), which has a high exchange rate with oxygen. The widely used cathode material La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) with high electrical conductivity was used as the CCCL. A significant increase in the peak power density of the MT-SOFC to 1.2 W/cm2 at 850 °C was achieved using the proposed two-layer cathode.

Double Conductive Ni-pads for a kW-class micro-tubular solid oxide fuel cell stack

Double Conductive Ni-pads (DCNPs) are prepared for the anode collector of micro-tubular solid oxide fuel cells (MTSOFCs) to fabricate a kW-class MTSOFC stack. The dimensions of the pad, in terms of width and length, are approximately 3.1 mm and 11.3 mm respectively. COMSOL Multiphysics software is utilized to simulate the multi-physical field of a single cell and SOFC stack to study anodic DCNPs current distribution and mass transfer operated at various voltages. A 160-cell stack consists of eight 20-cell sub-stacks exhibits a maximum power output exceeding 1 kW at an operating temperature of 700 °C. Furthermore, long-term operation tests under constant current or constant voltage conditions are conducted on both the 20-cell sub-stack and the 80-cell stack, demonstrating excellent performance and stability when utilizing DCNPs as anode collectors. The application potential for DCNPs as anode collectors in micro-tubular solid oxide fuel cells extends to various fields including auxiliary power units or high-power stacks, thereby introducing new possibilities for MTSOFC technology.

Ni‐phase erosion losses at a Ni‐pore interface of microtubular solid oxide fuel cells during 5218 h of operation

AbstractA microtubular solid oxide fuel cell (μT‐SOFC) with an anode buffer layer in the inner wall of the anode is successfully fabricated. The anode buffer layer comprises nickel (Ni), gadolinium‐doped ceria, and ruthenium (Ru), of which Ru exhibits excellent stability in mixed impurity gases. At 700°C, the maximum power density of the μT‐SOFC reaches around 0.76 W/cm2 under a hydrogen flow rate of 10 sccm. After 5218 h of operation at a constant current density of 0.2 A/cm2 at 650°C, there is almost no degradation (0.093%/kh) in area‐specific resistance after 2000 h of operation under the protection of the anode buffer layer. The aggregation and migration of nanoscale Ni particles are observed at the Ni particle boundary near the triple‐phase boundary (TPB), with gradual corrosion of the Ni particles. Ni migration and loss in the TPB are determined as reasons for the decay of the fuel cells during their long‐term operation. Moreover, Ni in an amorphous state is also observed on the periphery of the Ni particles, indicating that during the corrosion process of Ni, transformation to the amorphous state occurred, which impairs the catalytic activity and electronic conductivity of Ni, resulting in a deterioration in its performance.

Experimental Study on High-Efficiency Microtubular Solid Oxide Fuel Cell Stacks Using Various Fuels

: Microtubular solid oxide fuel cells (mtSOFCs) are a clean and low carbon emission power generation technology that has great prospects in the field of portable power generation. Improving the power generating efficiency and broadening the variety of fuels available can significantly improve the performance of portable power generation devices based on mtSOFCs. In this study, mtSOFC stacks assembled by mounting modular substacks in an array on a designed fuel/air distribution base were tested. By changing the connection of the substacks’ current collection nodes, the influence of circuit connection modes on the overall output performance of the stack was studied. At a temperature of 700℃ and a fuel feed of hydrogen, the mtSOFC stack composed of 6 substacks in series can achieve a maximum power of 296 W. Fuel cascade utilization was realized by transferring the spent fuel gas from the upstream substacks to the downstream substacks. A maximum power generation efficiency of 45.7% was achieved in the two-cascade stack. The feasibility of using liquified fuel gas (ammonia, propane and diesel) as fuel for the mtSOFC stack has also been experimentally verified. A total continuous discharge time of more than 100 h was achieved at an average power ≥ 180 W under different fuel conditions.Key words: Microtubular SOFC; Substack array; Fuel cascade utilization; Liquified fuel gas; Ammonia

Design and Fabrication of an Easily Assembled Anode Supported Microtubular SOFC Stack

Microtubular solid oxide fuel cells have shown many advantages that make them suitable for mobile and portable applications. In this study, a microtubular SOFC stack consisting of 8 cells was designed and fabricated using a metallic current collector and interconnect, enabling a pluggable modular design pattern. To avoid the difficulty of high-temperature sealing, the cold sealing method was adopted, where the temperature at the sealing position was under 130°C when the stack was operated at 700°C. The open circuit voltage (OCV) reached over 4 V while the power output reached over 20 W with a 2 (in series)×4 (in parallel) array. The stack module can be further connected in series or in parallel to satisfy larger power requirements.

Numerical and experimental investigation of a cathode-supported microtubular solid oxide electrolysis cell from current and temperature variations in-situ assessed with electrode-segmentation method

The electrode segmentation method has been applied to experimentally assess the current and temperature distributions in a cathode-supported microtubular solid oxide electrolysis cell (mt-SOEC). A detailed three-dimensional SOEC model considering the mass/momentum/charge/energy transfer is also developed to explain the in-situ working mechanism with spatial current and temperature variations considering the electrochemical performance and degradation. Both the experimental and numerical results reveal that the electrode-segmentation method exhibits notable nonuniform current and temperature distributions among the segments (up-, mid-, and downstream). Reactant starvation in the mid- and downstream regions leads to spatial current and temperature variations, with the largest temperature gradient observed and predicted between the up- and midstream regions. Further analysis of the temperature variations indicates that endothermic electrochemical Peltier heat in the air (oxygen) electrode (anode) is the primary cause of temperature decrease from 1.0 V to 1.3 V, while heat production with the overpotentials in the fuel (hydrogen) electrode (cathode) dominates temperature increase above 1.3 V.

Design and Fabrication of an Easily Assembled Anode Supported Microtubular SOFC Stack

Anode-supported micro-tubular solid oxide fuel cell has shown many advantages which make it suitable for portable devices. In this study, we developed a micro-tubular SOFC stack and module using a metallic current collector and interconnector which enabling pluggable modular design pattern. In order to ensure the sealing performance, we adopted the low-temperature sealing method and the temperature at the sealing position is under 130℃ while the stack is operated at 750℃.The stack was made of 8 micro-tubular cells, which were connected in series and parallel, in a 2×4 array. The open circuit voltage (OCV) was above 4.22V, thus the single cell’s OCV value could reach about 1.06V. The stack module can be further connected in series or in parallel to satisfy larger power requirements.

Experimental Study on High-Efficiency Microtubular Solid Oxide Fuel Cell Stacks Using Various Fuels

Microtubular solid oxide fuel cell (mTSOFC) is a clean and low carbon emission power generation technology that has great prospects in the field of portable power generation. Improving the efficiency and broadening the variety of available fuels can significantly improve the performance of portable power generation devices based on mTSOFC. In this study, mTSOFC stack assembled by mounting modular sub-stacks in an array on a designed fuel/air distribution base were tested. By changing the connection of the current collection nodes, the influence of circuit connection modes on the overall output performance of the stack was studied. At a temperature of 700℃ and a fuel feed of hydrogen, the mTSOFC stack composed of 6 sub-stacks can achieve a maximum power of 353W. Fuel cascade utilization was realized by transferring the spent fuel gas from the upstream sub-stacks to the downstream sub-stacks. A maximum power generation efficiency of 45.67% was achieved in the two-cascade stack. The feasibility of using hydrogen, ammonia, propane and diesel as fuel for the mTSOFC stack has also been experimentally verified. A total continuous discharge time of 21h was achieved at an average power ≥ 190W under ammonia feeding conditions.

Correction to: Characterization of anode supported micro-tubular solid oxide fuel cells prepared by successive non-aqueous electrophoretic deposition

Correction to: Characterization of anode supported micro-tubular solid oxide fuel cells prepared by successive non-aqueous electrophoretic deposition