High Volumetric Power Research Articles

Synthesis of P-Doped and NiCo-Hybridized Graphene-Based Fibers for Flexible Asymmetrical Solid-State Micro-Energy Storage Device.

Fiber supercapacitors (FSCs) are promising energy storage devices in portable and wearable smart electronics. Currently, a major challenge for FSCs is simultaneously achieving high volumetric energy and power densities. Herein, the microscale fiber electrode is designed by using carbon fibers as substrates and capillary channels as microreactors to space-confined hydrothermal assembling. As P-doped graphene oxide/carbon fiber (PGO/CF) and NiCo2 O4 -based graphene oxide/carbon fiber (NCGO/CF) electrodes are successfully prepared, their unique hybrid structures exhibit a satisfactory electrochemical performance. An all-solid-state PGO/CF//NCGO/CF flexible asymmetric fiber supercapacitor (AFSC) based on the PGO/CF as the negative electrode, NCGO/CF hybrid electrode as the positive electrode, and poly(vinyl alcohol)/potassium hydroxide as the electrolyte is successfully assembled. The AFSC device delivers a higher volumetric energy density of 36.77 mW h cm-3 at a power density of 142.5 mW cm-3 . In addition, a double reference electrode system is adopted to analyze and reduce the IR drop, as well as effectively matching negative and positive electrodes, which is conducive for the optimization and improvement of energy density. For the AFSC device, its better flexibility and electrochemical properties create a promising potential for high-performance micro-supercapacitors. Furthermore, the introduction of the double reference electrode system provides an interesting method for the study on the electrochemical performances of two-electrode systems.

Physics field distributions within fuel cell stacks with manifolds penetrating through the plane zone and open outlet features

To achieve high volumetric power density, some fuel cell stacks are designed to place fuel/air manifolds within (and penetrate through) the cell plane zone and adopt open outlet manifold. In this paper, a 3D large scale multi-physics model of a whole 18-cell stack with the above two structural features is first completed by carefully coupling momentum, mass, energy and quasi electrochemical equations. Then, the generic distribution regularity of the main physics items, which depends on the above two structural features rather than any specific design and parameters, are reported. The result shows that the air flow rate fed to cell unit monotonously increases with increasing cell number as long as the open outlet of air flow path is adopted. Only 0.41 times the average air flow rate fed to each cell unit can pass through the 1st cell layer; and its value will greatly reduce when the stack scale increases. Placing manifolds within cell plane zone causes complex air/fuel flow distributions over the electrode surface; and adopting cross flow arrangement pattern can relieve the local temperature rising risk. The highest stack temperature appears around the crossing corner of both air and fuel flow exhaust headers in the 1st cell layer.

Plasma Heavily Nitrogen-Doped Vertically Oriented Graphene Nanosheets (N-VOGNs) for High Volumetric Performance On-Chip Supercapacitors in Ionic Liquid

Background: The research of innovative nanostructured materials will be helpful in designing high performance supercapacitor devices in the near future. In this direction, graphenebased structures, such as Vertically Oriented Graphene Nanosheets (VOGNs), have emerged as promising architectures due to their interesting chemical, structural and electrochemical properties. One of the main strategies to enhance the performance of supercapacitive materials consists of the functionalization or modification of their surfaces by means of various approaches focused on doping or the deposition of electroactive material coatings/films among others. Particularly, in this study, the doping effect, by nitrogen plasma, on VOGNs was investigated as innovative electrodes for on-chip supercapacitors. Methods: Nitrogen-doped VOGNs (N-VOGNs) were characterised at morphological (SEM and TEM techniques), structural (XPS and Raman techniques) and electrochemical levels, respectively. Subsequently, the potential of such doped graphene nanostructure was evaluated in a symmetric supercapacitor device using a coin cell configuration. The properties of the supercapacitor were examined in terms of capacitance, energy and power density and lifetime. Results: A maximal N-content of 17% was achieved for VOGNs with a vertical length around 370 nm, through exposure to a N2 microwave-plasma in an electron cyclotron resonance (ECR)-CVD reactor. The deconvolution of N1s spectrum of N-VOGNs reflected the presence of three main peaks corresponding to pyrrolic (400.2 eV), pyridinic (399.0 eV) and graphitic (401.2 eV) nitrogen forms, demonstrating the incorporation of nitrogen into graphene structure. The doping effect reflected an important impact on the morphological (surface defects and reactions, porosity) and structural (conductivity) properties, which allowed to enhance greatly the capacitive properties compared to undoped VOGNs. Conclusion: N-VOGN based supercapacitors have demonstrated excellent capacitive properties such as high volumetric energy (28 mWh cm-3) and power (360 W cm-3) densities as well as an outstanding cycling stability (retention of 80% after 300 000 galvanostatic charge-discharge cycles). These results are very promising compared to the state-of-the art dealing with carbonaceous structurebased supercapacitors. Consequently, this study paves the way to explore the in-depth potential of such nanostructure in the development of innovative high performance supercapacitors. Keywords: Doping, graphene nanosheets, ionic liquid, supercapacitors, vertically oriented graphene, VOGN.

“Carbon‐Glue” Enabled Highly Stable and High‐Rate Fe3O4 Nanorod Anode for Flexible Quasi‐Solid‐State Nickel–Copper//Iron Alkaline Battery

AbstractThe practical application of iron oxide anode in rechargeable alkaline batteries is greatly hampered by the poor electrochemical stability and low rate capability. In addition, flexible solid‐state iron anode‐based rechargeable batteries with distinctive counter electrode coupling are quite lacking. Herein, an interesting “carbon glue” penetration strategy toward Fe3O4 nanorod film anode is proposed. This design not only immobilizes the nanorods and maintains strong adhesion with the current collector but also ensures continuous electrically conductive pathway, resulting in dramatically increased stability (≈99% capacity retention after 1000 cycles) and excellent rate performance (1.2 min charging with ≈70.6% initial capacity kept). By pairing with a new‐type Ni0.49Cu0.51O nanowire array cathode, a unique 1.2 V flexible rechargeable nickel–copper//iron alkaline battery is further assembled, which stores energy based on redox electrochemistry of transition metal ions. It delivers high volumetric energy and power densities (7.21 mWh cm−3; 299.30 mW cm−3), and demonstrates outstanding stability up to 5000 cycles. In particular, with the utilization of quasi‐solid‐state electrolyte, the device still maintains good performance upon substantially bending and twisting. This work presents a new concept to design high stability iron anode‐based alkaline batteries and further pushes forward the development of emerging flexible energy storage systems.

Lignin Laser Lithography: A Direct‐Write Method for Fabricating 3D Graphene Electrodes for Microsupercapacitors

AbstractIn this work, a simple lignin‐based laser lithography technique is developed and used to fabricate on‐chip microsupercapacitors (MSCs) using 3D graphene electrodes. Specifically, lignin films are transformed directly into 3D laser‐scribed graphene (LSG) electrodes by a simple one‐step CO2 laser irradiation. This step is followed by a water lift‐off process to remove unexposed lignin, resulting in 3D graphene with the designed electrode patterns. The resulting LSG electrodes are hierarchically porous, electrically conductive (conductivity is up to 66.2 S cm−1), and have a high specific surface area (338.3 m2 g−1). These characteristics mean that such electrodes can be used directly as MSC electrodes without the need for binders and current collectors. The MSCs fabricated using lignin laser lithography exhibit good electrochemical performances, namely, high areal capacitance (25.1 mF cm−2), high volumetric energy density (≈1 mWh cm−3), and high volumetric power density (≈2 W cm−3). The versatility of lignin laser lithography opens up the opportunity in applications such as on‐chip microsupercapacitors, sensors, and flexible electronics at large‐scale production.

Study on Mechanical Behavior of Metal-Supported Solid Oxide Fuel Cell (MS-SOFC) in Wet Chemical Coating Process

Metal-supported solid oxide fuel cell (MS-SOFC) requires not only high electrochemical performance and durability but also high volumetric and gravimetric power density to be applied to portable and transportation fields. However, reducing the thickness of the metal substrate, which generally occupies the most portion of the volume and mass among components of the MS-SOFC, may cause mechanical deformation during fabrication processes. In this study, mechanical behavior of the MS-SOFC, especially consists of a thin metal substrate (~100 µm) and thin-film electrolyte deposited through wet chemical coating processes, was addressed. First of all, thermal surface stress generated during the wet chemical coating processes and mechanical deformation caused by the thermal surface stress were measured by thermomechanical analysis and surface profiler, respectively. Furthermore, after quantifying the mechanical deformation of the MS-SOFC, a novel method of introducing magnets in the wet chemical coating processes to suppress mechanical deformation was proposed and evaluated. As a result, vertical deformation of the MS-SOFC was successfully suppressed from approximately 160 µm to 30 µm without significant defects of the electrolyte such as cracks, pinholes or residual stresses.

Functionalization of Metal Surfaces Using Hydride Intermediates

Noble metals have important applications in an array of fields including hydrogen storage and sensing, chemical catalysis, and fuel cells. They offer high volumetric power density in metal hydride batteries and pseudocapacitors. However, the kinetics of chemical reactions at their surfaces are often limited by the high stability of surface-bound species. Theoretical[1] and experimental[2],[3] reports suggest that adlayers of other metals can destabilize the surface species, which should increase chemical reaction rates. We have developed a room-temperature electroless atomic layer deposition (ALD) technique in which we grow adlayers of other metals on palladium and platinum substrates.[4] The method contrasts with electrochemical ALD,[3] which requires applying a current to a substrate, and to gas-phase ALD, which requires elevated temperatures that can damage some substrates. Exposing a substrate to dilute hydrogen/nitrogen gas mixtures causes a surface hydride to form. Subsequent addition of a solution containing noble metal salts displaces the surface hydride with the reduced metal in a surface-limited reaction. This process can be repeated, and the thickness of the surface coverage increases, as shown by X-ray photoelectron spectroscopy. We have developed variations of the method that allow a nanoporous layer to be grown in a stepwise manner, and that use aqueous reducing agents to form the hydride instead of hydrogen gas. This technique requires no specialized equipment, and makes use of benign reagents. It is surface-limited in nature, but is not limited to an electrode. This confers important advantages of high scalability and compatibility with complex surface topologies; conductive substrates are not required. We believe that this versatile technique could be widely applied by synthetic chemists to take advantage of enhanced catalytic properties of near-surface alloys. This work was supported by the Laboratory-Directed Research and Development program at Sandia National Laboratories, a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government. SAND2018-3092 A [1] Greeley, J.; Mavrikakis, M. J. Phys. Chem. B 2005, 109, 3460−3471. [2] Bartlett, P. N.; Marwan, J. Phys. Chem. Chem. Phys.2004, 6, 2895−2898. [3] Sheridan, L. B.; Yates, V. M.; Benson, D. M.; Stickney, J. L.; Robinson, D. B. Electrochim. Acta 2014, 128, 400−405. [4] Cappillino, P. J.; Sugar, J. D.; El Gabaly, F.; Cai, T. Y.; Liu, Z.; Stickney, J. L.; Robinson, D. B. Langmuir 2014, 30, 4820−4829.

Modifying Current Collectors to Produce High Volumetric Energy Density and Power Density Storage Devices.

We develop zirconium-templated NiO/NiOOH nanosheets on nickel foam and polypyrrole-embedded in exfoliated carbon fiber cloth as complementary electrodes for an asymmetric battery-type supercapacitor device. We achieve high volumetric energy and power density by the modification of commercially available current collectors (CCs). The modified CCs provide the source of active material, actively participate in the charge storage process, provide a larger surface area for active material loading, need no additional binders or conductive additives, and retain the ability to act as the CC. Nickel foam (NF) CCs are modified by use of a soft-templating/solvothermal treatment to generate NiO/NiOOH nanosheets, where the NF is the source of Ni for the synthesis. Carbon-fiber cloth (CFC) CCs are modified by an electrochemical oxidation/reduction process to generate exfoliated core-shell structures (ECFC). Electropolymerization of pyrrole into the shell structure produces polypyrrole embedded in exfoliated core-shell material (PPy@rECFC). Battery-type supercapacitor devices are produced with NiO/NiOOH@NF and PPy@rECFC as positive and negative electrodes, respectively, to demonstrate the utility of this approach. Volumetric energy densities for the full-cell device are in the range of 2.60-4.12 mWh cm-3 with corresponding power densities in the range of 9.17-425.58 mW cm-3. This is comparable to thin-film lithium-ion batteries (0.3-10 mWh cm-3) and better than some commercial supercapacitors (<1 mWh cm-3).1 The energy and power density is impressive considering that it was calculated using the entire cell volume (active materials, separator, and both CCs). The full-cell device is highly stable, retaining 96% and 88% of capacity after 2000 and 5000 cycles, respectively. These results demonstrate the utility of directly modifying the CCs and suggest a new method to produce high volumetric energy density and power density storage devices.

Conformal Multifunctional Titania Shell on Iron Oxide Nanorod Conversion Electrode Enables High Stability Exceeding 30 000 Cycles in Aqueous Electrolyte

AbstractIron oxide is promising for use in aqueous energy storage devices due to the high capacity, but one of the most challenging problems is cycling instability within the large potential window that results from the complete quasi‐conversion reaction. Herein, a conformal surface coating strategy toward iron oxide via atomic layer deposition (ALD) is presented and an Fe3O4@TiO2 core–shell nanorod array anode is reported that exhibits remarkable cycling performance exceeding 30 000 times within a wide potential window in neutral lithium salt electrolyte. ALD offers a uniform and precisely controllable TiO2 shell that not only buffers the inner volume expansion of Fe3O4, but also contributes extra capacity through Li+ intercalation/de‐intercalation and helps to alleviate the water electrolysis. Furthermore, by pairing with a pseduocapacitive cathode of V2O3@carbon and using a hydrogel electrolyte of PVA‐LiCl, a unique flexible quasi‐solid‐state hybrid supercapacitor can be assembled. With a high voltage of 2.0 V, the device delivers high volumetric energy and power densities (2.23 mWh cm−3, 1090 mW cm−3), surpassing many recently reported flexible supercapacitors. This work highlights the importance of ALD conformal multifunctional shell to instable nanoarray electrodes in aqueous electrolytes and brings new opportunities to design advanced aqueous hybrid energy storage devices.

Ultrathin all-solid-state supercapacitor devices based on chitosan activated carbon electrodes and polymer electrolytes

Two of the most promising current trends in supercapacitor research, (i) the development of biomass based carbon electrodes, and (ii) the transition to solid thin flexible form factors via polymer electrolytes are combined and investigated. A high surface area (3312 m2 g−1) mesoporous activated carbon was synthesized from chitosan biomass and showed excellent capacitive behaviour in a range of acidic, neutral, and alkaline liquid electrolytes. The performance in the neutral Li2SO4 electrolyte system was particularly promising with the chitosan AC electrodes showing a high capacitance (264 F g−1) similar to the values in acidic and alkaline electrolytes but with a much larger 1.8 V potential window. The chitosan AC also proved compatible with a series of solid polymer electrolytes through a detailed comparison in which solid-state chitosan supercapacitor devices were shown to closely mimic the capacitance and high rate performance of their liquid counterparts. This is an important finding as it demonstrates that high surface area, intricately porous activated carbon networks can still be readily accessible to solid electrolytes. Combining the chitosan AC with a Li2SO4-polyacrylamide (PAM) solid electrolyte enabled the fabrication of ultra-thin (<0.38 mm) supercapacitor devices which demonstrated a capacitance close to 3 times greater than analogues prepared with a commercially available microporous AC (YP-50). These chitosan devices also demonstrated high volumetric energy density (1.6 mWh cm−3) and power density (0.8 W cm−1) comparable to state-of-the-art SC devices utilizing much more expensive materials. This material system represents a simple and cost effective approach for the design of next-generation solid thin, flexible energy storage devices.

Amphiphilic ligand exchange reaction-induced supercapacitor electrodes with high volumetric and scalable areal capacitances

We introduce high-performance supercapacitor electrodes with ternary components prepared from consecutive amphiphilic ligand-exchange-based layer-by-layer (LbL) assembly among amine-functionalized multi-walled carbon nanotubes (NH2-MWCNTs) in alcohol, oleic acid-stabilized Fe3O4 nanoparticles (OA-Fe3O4 NPs) in toluene, and semiconducting polymers (PEDOT:PSS) in water. The periodic insertion of semiconducting polymers within the (OA-Fe3O4 NP/NH2-MWCNT)n multilayer-coated indium tin oxide (ITO) electrode enhanced the volumetric and areal capacitances up to 408 ± 4 F cm−3 and 8.79 ± 0.06 mF cm−2 at 5 mV s−1, respectively, allowing excellent cycling stability (98.8% of the initial capacitance after 5000 cycles) and good rate capability. These values were higher than those of the OA-Fe3O4 NP/NH2-MWCNT multilayered electrode without semiconducting polymer linkers (volumetric capacitance ∼241 ± 4 F cm−3 and areal capacitance ∼1.95 ± 0.03 mF cm−2) at the same scan rate. Furthermore, when the asymmetric supercapacitor cells (ASCs) were prepared using OA-Fe3O4 NP- and OA-MnO NP-based ternary component electrodes, they displayed high volumetric energy (0.36 mW h cm−3) and power densities (820 mW cm−3).

Dense graphene papers: Toward stable and recoverable Al-ion battery cathodes with high volumetric and areal energy and power density

Since Al ion batteries (AIBs) are known to be a novel energy storage prototype of more safe and higher energy density, challenges are still in the currently explored carbon cathodes, specifically in balancing the rapid ion transport channels and volumetric/areal energy storage capability at a dense fashion. In this contribution, exceptional graphene nanosheet (GN) papers that are well stacked by conductive graphene nanosheets have been demonstrated as an electrochemically stable host for fast AlCl4- ion transport/storage along with high volumetric/areal energy storage at a dense state (1.6~1.8gcm−3). Owing to the exclusive morphological and chemical advantages, the as-assembled AIBs with the binder-free GN paper cathode enables to deliver considerably high specific capacity 100mAhg−1 at the current density 50mAg−1 (approaching the theoretic value of carbon AIB cathodes), coupled with much enhanced volumetric capacity, areal energy density and power density compared to the reported carbon AIB cathodes. Particularly, the term of tortuosity has been employed to understand the fundamental relationship between volumetric energy performance and microscopic structures, which suggests a unique platform for developing advanced practical AIBs.

A rationally assembled graphene nanoribbon/graphene framework for high volumetric energy and power density Li-ion batteries.

High volumetric energy and power densities are crucial for Li-ion batteries, which are however hindered by the loose structure and/or insufficient conductivity of conventional electrode laminates. Herein, an efficiently conductive framework of graphene nanoribbons (GNRs) and graphene (G) is rationally constructed to wrap LiFePO4 (LFP) into a binder-free dense electrode by a coupling technique of spray deposition and vacuum filtration. The spray ensures a uniform mixing of LFP, G and GNRs, meanwhile the vacuum filtration leads to a dense packing of the mixture. With only 2 wt% of G and GNRs, the LFP/GNR/G electrode delivers a high rate capability and a stable (dis)charge cycling performance under high LFP loading conditions. Moreover, the dense LFP/GNR/G electrode exhibits superior volumetric properties among all the reported LFP electrodes on the basis of the entire electrode volume, including a Li storage capacity of 318 A h L-1, an energy density of 1020 W h L-1 and a power density of 5.1 kW L-1 at 5C rate. This unique assembly strategy and the electrode structure pave a new way for high-volumetric-performance batteries.

Three-dimensional flow channel arrangements in an anode-supported honeycomb solid oxide fuel cell

An anode-supported honeycomb SOFC can achieve high volumetric power density and improve thermo-mechanical durability at high temperatures. We have so far fabricated a honeycomb cell with a cathode layer made of La0.7Sr0.3MnO3 (LSM) and an electrolyte layer of 8YSZ on a porous anode support in the honeycomb form of Ni/8YSZ. In the present study, current-voltage and volumetric power density characteristics of the cells having different anode/cathode flow channel arrangements are measured under different flow rates of fed hydrogen to show the effect of three-dimensional fuel transport and distribution in the porous anode support on the cell performance. Ohmic resistances of the cells varying with current is also evaluated to clarify the nickel re-oxidation of the anode support by fuel depletion depending on the anode flow channel arrangements. We thereby discuss the difference of the advantage between the flow channel arrangements depending on the flow rate of the fed fuel to choose more suitable operation mode.

Improved flexible Li-ion hybrid capacitors: Techniques for superior stability

Flexible power devices play an increasingly crucial role in emerging flexible electronics. To improve the electrochemical performance of flexible power devices, novel electrode structures and new energy-storage systems should be designed. Herein, a novel flexible Li-ion hybrid capacitor (LIC) is designed based on an anode comprising Li4Ti5O12 nanoplate arrays coated on carbon textile (LTO/CT) and a cathode comprising a flexible N-doped graphene/carbon-nanotube composite (NGC) film. The LTO/CT anode is fabricated by directly growing Li4Ti5O12 nanoplates on CT with robust adhesion using a simple one-pot hydrothermal reaction. Considering the volume of a real-device flexible LIC, the NGC//LTO/CT configuration delivers high volumetric energy and power densities of 2 mWh·cm−3 and 185 mW·cm−3, respectively. Furthermore, the flexible LIC shows excellent flexibility and electrochemical stability, with extremely small capacity fluctuation under different bending states. This work demonstrates a scalable route to assemble flexible LICs as high-performance power devices.

Geometric Design of Anode-Supported Micro-Tubular Solid Oxide Fuel Cells by Multiphysics Simulations

High volumetric power density (VPD) is the basis for the commercial success of micro-tubular solid oxide fuel cells (mtSOFCs). To find maximal VPD (MVPD) for anode-supported mtSOFC (as-mtSOFC), the effects of geometric parameters on VPD are analyzed and the anode thickness, tan, and the cathode length, lca, are identified as the key design parameters. Thermo-fluid electrochemical models were built to examine the dependence of the electrical output on the cell parameters. The multiphysics model is validated by reproducing the experimental I-V curves with no adjustable parameters. The optimal lca and the corresponding MVPDs are then determined by the multiphysics model for 20 combinations of rin, the inner tube radius, and tan. And all these optimization are made at 1073.15 K. The results show that: (i) significant performance improvement may be achieved by geometry optimization, (ii) the seemingly high MVPD of 11 and 14 W/cm3 can be easily realized for as-mtSOFC with single- and double-terminal anode current collection, respectively. Moreover, the variation of the area specific power density with lca∈(2 mm, 40 mm) is determined for three representative (rin, tan) combinations. Besides, it is demonstrated that the current output of mtSOFC with proper geometric parameters is comparable to that of planar SOFC.

Highly compact and robust hollow fiber solid oxide cells for flexible power generation and gas production

The future clean energy deployment in our contemporary society needs the innovative use of emerging technologies in the coal industry, like the integrated gasification combined cycle (IGCC) integrated with solid oxide cell technology for flexible electricity generation and chemical production. For this purpose, a cell design with a high volumetric power density and a compact size for gas production is an important consideration for cheaper and simpler integration. In this study, robust and compact hollow fiber solid oxide cells with an integrated electrolyte and cathode structure were designed. The peak power density achieved was up to 516mWcm−2 at 850°C, using hydrogen as the fuel and air as the oxidant. In the Solid Oxide Electrolysis Cell (SOEC) mode, the steam electrolysis can be carried out at high applied voltage, up to 2.0V, and operated at 850°C to achieve high electrolysis efficiencies. A stable hydrogen and oxygen production rate with the respective flux rates of 14.5 and 6.5mLmin−1cm−2 are achieved. Successful development of strategies for the synthesis of robust hollow fiber solid oxide cells would be a great step moving forward towards the large scale commercial application in future advanced energy technologies.

Multi-functional Flexible Aqueous Sodium-Ion Batteries with High Safety

Summary Flexible energy storage devices are attracting extensive attention, but most of the reported flexible batteries and supercapacitors use either strong acid or base or toxic flammable organic solutions as electrolytes, which pose potential safety issues when worn by humans or implanted into the body. Here, we present a highly safe family of flexible sodium-ion batteries (SIBs) based on a Na 0.44 MnO 2 cathode, a nano-sized NaTi 2 (PO 4 ) 3 @C anode, and various aqueous electrolytes containing Na + . The resulting belt- and fiber-shaped aqueous SIBs exhibit high volumetric energy and power density, high flexibility, and long life and thus can be safely applied in wearable electronic devices. When normal saline or cell-culture medium is used as the electrolyte, these SIBs can still work well, indicating potential application in implantable electronic devices. The fiber-shaped electrodes in Na + -containing aqueous electrolytes exhibit an electrochemical deoxygenation function, which could be applied in biological and medical fields.

Three-Dimensional Modelling of a Microtubular SOFC: A Multiphysics Approach

There is an increasing interest in the use of Microtubular Solid Oxide Fuel Cells (µ-SOFC) for a broad spectrum of applications with power demands ranging from a few watts to several hundred watts. µ-SOFC’s possess inherently favourable characteristics over alternate configurations such as high thermo-mechanical stability, high volumetric power density and rapid start-up times. The use of computational modelling at the design level is essential for minimising cost and maximising productivity, giving critical insight into the complex phenomena occurring during SOFC operation and their interrelationships. To date, models have been limited by oversimplified geometries, often failing to account for cathode air supply complexities, gas distribution within pores and radiative heating effects[1-3]. In this study, a three-dimensional Computational Fluid Dynamics (CFD) model of an anode, electrolyte, cathode, current collectors, fuel inlet/outlet and furnace temperature effects is considered. The model has been validated with a mirroring experimental setup, varying fuel compositions, operating temperature and interconnect configuration. COMSOL Multiphysics is used to simulate the physics, describing the distribution of temperature, current density, electrical potential, pressure and gas concentrations throughout the cell. Results show good correlation with experimental data and the model is reliable for prediction of fuel cell performance as a function of operating conditions within these set parameters.

A Novel Method to Fabricate Inert Substrate-Supported Microtubular Solid Oxide Fuel Cells by Selective Leaching

Microtubular solid oxide fuel cells (mT-SOFCs) are promising electrochemical energy conversion devices due to their high volumetric power density, capability of bearing high thermal stresses, and rapid start up. The inert substrate-supported mT-SOFCs have an additional advantage of high reduction–oxidation (redox) cycling stability. In this study, a novel method is suggested to fabricate inert substrate-supported mT-SOFC by leaching out the nickel from an anode supported mT-SOFC that has an anode functional layer. The anode supported mT-SOFCs were prepared by a sequential dip coating and co-firing process. The manufactured inert substrate-supported mT-SOFCs possess the configuration of yttria-stabilized zirconia (YSZ) support/Ni–Scandia stabilized zirconedia (ScSZ) anode/ScSZ electrolyte/strontium-doped lanthanum manganite (LSM)-ScSZ cathode/LSM cathode current collector. Selective leaching of the nickel from the Ni-YSZ composite was used in conjunction with the burn out of microcrystalline cellulose pore-former for the proper tuning of porosity and facilitating the gas diffusion through the inert support. The effectiveness of this approach on enhancing the fuel cell performance will be discussed. Figure 1