Film Solid Oxide Fuel Cells Research Articles

Effect of Electrolyte Thickness of Thin Film Solid Oxide Fuel Cell on Nanostructure and Performance

Effect of Electrolyte Thickness of Thin Film Solid Oxide Fuel Cell on Nanostructure and Performance

Simulation of a Thin Film Solid Oxide Fuel Cell System Equipped with an Internal Fuel Reforming Unit

Simulation of a Thin Film Solid Oxide Fuel Cell System Equipped with an Internal Fuel Reforming Unit

Geometrical scale dependency of thin film solid oxide fuel cells

To study the geometrical scale dependency of thin film solid oxide fuel cells (SOFCs), we fabricated three thin films SOFCs which have the same cross-sectional structure but different electrode areas of 1 mm2, 4 mm2 and 9 mm2. Since the activation and ohmic losses of SOFCs depend on their active region, we examined the variations of the power density of the cells with a Pt/YSZ/Pt structure and simulated the power density variations using the COMSOL software package.

Experimental Analysis of Performance Variation on Thin Film Solid Oxide Fuel Cell with Different Cathode Area Sizes

To study the geometrical scale dependency of thin film solid oxide fuel cells (SOFCs), we fabricated three thin films SOFCs with the same cross-sectional structure but with different electrode areas of 1, 4 and 9 ㎟. Since the activation and ohmic losses of SOFCs depend on their active region, we examined the variations of the power density of the cells with a Pt (anode)/sputtered YSZ/Pt (cathode) structure. We found that a cathode electrode with a low aspect ratio may suffer from high ohmic and activation losses because of the geometrical scale dependency.

Effects of Nanoscale PEALD YSZ Interlayer for AAO Based Thin Film Solid Oxide Fuel Cells

Performance of thin film solid oxide fuel cells (TF-SOFCs) were improved by inserting plasma enhanced atomic layer deposition (PEALD) of yttira-stabilized zirconia (YSZ) interlayers. By controlling the ratio between Y2O3 and ZrO2 in YSZ deposition supercycles, Y2O3 mol.% in YSZ films were changed. High Y2O3 contained PEALD YSZ interlayered cell showed higher maximum power density (123.6 mW/cm2 at 500 °C, 286.1 mW/cm2 at 550 °C) and smaller polarization resistance compared with reference Y2O3 concentrated PEALD YSZ interlayer cell. (108.5 mW/cm2 at 500 °C, 181.1 mW/cm2 at 550 °C) Exchange current densities of TF-SOFCs at 500 °C also improved ~ 59.3% at high Y2O3 concentrated PEALD YSZ interlayer cells. These phenomena caused by high density of oxygen vacancies in high Y2O3 concentrated PEALD YSZ interlayer, which helps oxygen incorporation reactions at cathode-interlayer interface. Therefore, cathodic polarization loss related with oxygen reduction reactions was decreased, and then, performance and exchange current density were improved. Results of this study imply that insertion of simple PEALD YSZ interlayer at cathode-electrolyte interface efficiently improves performance and electrochemical characteristics of TF-SOFCs.

Au-Coated Lanthanum Strontium Cobalt Ferrite Cathode for Lowering Sheet Resistance of a Solid Oxide Fuel Cell

In this paper, we fabricate a thin film solid oxide fuel cell (SOFC) with a lanthanum strontium cobalt ferrite (LSCF) cathode which is coated with an Au layer by sputtering. The fabricated thin film SOFC has a 370-nm-thick Ni anode/880-nm-thick YSZ electrolyte/440-nm-thick LSCF cathode/130-nm-thick Au layer. The electrochemical performances of the thin film SOFC with the LSCF cathode coated with a 130-nm-thick Au layer and another SOFC without an Au layer are measured at the operating temperature of 600 °C. Since the LSCF cathode coated with a 130-nm-thick Au layer significantly lowers the sheet resistance (in-plane direction resistance), the peak power densities of the thin film SOFC with the LSCF cathode coated with a 130-nm-thick Au layer and the thin film SOFC with the LSCF cathode without a 130-nm-thick Au layer are 500 mW/cm2 and 49 mW/cm2, respectively. Due to the LSCF cathode coated with a 130-nm-thick Au layer, the peak power density of the thin film SOFC with the Au-coated LSCF cathode is 10 times higher than that of the LSCF cathode without Au layer.

Thin Film Solid Oxide Fuel Cells Operating Below 600°C: A Review

Thin film solid oxide fuel cells (TF-SOFCs) are one of the promising portable power sources in terms of rapid on/off, compact system volume, and high power density. This paper reviews fabrications, and designs of TF-SOFCs operating the temperature range of 300-500°C. The fabricating processes of both the electrolyte and the electrode via chemical vapor depositions and physical vapor depositions are discussed. The two platforms for designing TF-SOFCs are described: porous substrate and free-standing structures.

3D Porous Nickel Anode for Low Temperature Thin Solid Oxide Fuel Cell Applications

AbstractA simple fabrication process for a 3D porous nickel anode for a thin film solid oxide fuel cell (SOFC) is developed. The 3D porous nickel anode is fabricated using a metal/proppant mixing method followed by pressing and heat treatment. The anode bulk possesses a high porosity which is required for efficient delivery of fuel to the cell. Following fabrication, the anode's surface is processed by means of mechanical, chemical, and ion etching to minimize surface roughness and reduce the surface pore size allowing for the deposition of a high quality, pore‐free, thin electrolyte. Yttria‐stabilized zirconia is used for the thin film electrolyte layer followed by deposition of a thin film La0.6Sr0.4Co0.2Fe0.8O3−d cathode layer to complete the thin film SOFC. The fabricated cell performs with a very stable output power of 130 mW cm−2 at temperatures of the order of 450 °C. This anode is not only easy to shape, weld, and recycle but is also very economic.

State-of-the-Art La0.6Sr0.4Co0.2Fe0.8O3-δ Cathode for SOFC: Microstructural and Electrochemical Properties

Solid Oxide Fuel Cells (SOFCs) have drawn much attention because they convert chemical energy into electrical energy efficiently in eco-friendly way. The performance of a SOFC depends on several combined factors in each cell compartments (i.e. anode, cathode and electrolyte). Especially the polarization resistance of the cathode becomes significant for intermediate temperature operations (500 – 700 °C). For this reason, the cathode reaction kinetics and influence of microstructure of state-of-the-art cathode materials have been extensively researched through comparative experimental studies and numerical simulations in the literature. Porous cathodes comprising mixed ionic-electronic conductors (MIEC) are commonly preferred in these energy conversion devices operating at intermediate temperature. They grabbed particular attention since the oxygen reduction reaction (ORR) is extended at the electrode/electrolyte interface, beyond the triple phase boundary (TPB) points. Earlier in our group, reaction kinetics of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) deposited by electrostatic spray deposition (ESD) technique was studied in two different microstructures, i.e; the coral and columnar-types [1-3]. Thanks to nanostructured microstructure features, one of the lowest polarization resistance (Rpol) values compared to literature was achieved. The present study concerns the influence of the thickness of columnar LSCF films on the area specific polarization resistance (ASR) of the cathode. Symmetrical cells of LSCF were deposited on dense Ce0.9Gd0.1O2-δ (CGO) electrolyte. The cathodes were consisted of double layer films of LSCF deposited sequentially by ESD technique as cathode functional layer (CFL) and by screen printing (SP) technique as current collecting layer (CCL) as shown in Figure 1. The thickness of CFL was varied between 0.5 and 18 μm by controlling the time of ESD deposition from 20᾿, 40᾿, 1h, 1h45᾿, 3h and 4h30’. Thickness of CCL was varied by SP from 20 to 50 μm. The resulting electrode thicknesses and microstructures were investigated by scanning electron microscope and microstructural parameters (porosity, specific surface area) were calculated by 3D reconstruction of the images obtained by FIB/SEM tomography. The electrode performance in terms of ASR as well as current constriction effects were monitored by electrochemical impedance spectroscopy (EIS). The results are discussed in terms of microstructure, adherence at the electrode/electrolyte interface, conductivity and optimized cathode performance. The hierarchical porous character of CFL is highlighted with macro porosity separating the columns and nano porosity within the columns [4]. The CCL provides a flatter surface than the CFL, thus improving the current collection by increasing the contact points between the surface and current collecting grid. We have shown that the electrochemically active layer in LSCF nanostructured columnar cathodes deposited by ESD concentrates on only a couple hundred nanometers away from the electrode/electrolyte interface [4]. One can conclude that the optimized films require at least 4-5 µm CFL thickness and 36 µm total thickness (CFL-CCL). In this geometry, the optimized ASR value of 0.065 Ω cm2 at 600 °C was achieved for double layer cathode characterized by a porosity amount of approximately 22 % and a specific surface area of 19 μm-1 with a columnar-type microstructure [4]. This ASR value is still amongst the highest specific surface area values achieved for SOFC cathodes. D. Marinha, C. Rossignol, E. Djurado, Influence of electrospraying parameters on the microstructure of La0.6Sr0.4Co.2Fe.8O3- d films for SOFCs, Journal of Solid State Chemistry 182 (2009) 1742–1748.D. Marinha, L. Dessemond, J.S. Cronin, J.R. Wilson, S.A. Barnett, E. Djurado, Microstructural 3D reconstruction and performance evaluation of LSCF cathodes obtained by electrostatic spray deposition, Chem. Mater. 23 (2011) 5340-5348.D. Marinha, J. Hayd, L. Dessemond, E. Ivers-Tiffée, E. Djurado, Performance of (La,Sr)(Co,Fe)O3−x double-layer cathode films for intermediate temperature solid oxide fuel cell, J. Power Sources. 196 (2011) 5084–5090.Celikbilek O., Jauffres D., Siebert, E., Dessemond L., Burriel M., Martin C.L., Djurado E., Rational Design of Hierarchically Nanostructured Electrodes for Solid Oxide Fuel Cells, J. Power Sources. 333 (2016) 72–82. Figure 1

A Silicon-Based Nanothin Film Solid Oxide Fuel Cell Array with Edge Reinforced Support for Enhanced Thermal Mechanical Stability.

A silicon-based micro-solid oxide fuel cell (μ-SOFC) with electrolyte membrane array embedded in a thin silicon supporting membrane, featuring a unique edge reinforcement structure, was demonstrated by utilizing simple silicon micromachining processes. The square silicon supporting membrane, fabricated by combining deep reactive ion etching and through-wafer wet etching processes, has thicker edges and corners than the center portion of the membrane, which effectively improved the mechanical stability of the entire fuel cell array during cell fabrication and cell operation. The 20 μm thick single crystalline silicon membrane supports a large number of 80 nm thick free-standing yttria-stabilized zirconia (YSZ) electrolytes. The fuel cell array was stably maintained at the open circuit voltage (OCV) of 1.04 V for more than 30 h of operation at 350 °C. A high peak power density of 317 mW/cm(2) was obtained at 400 °C. During a rigorous in situ thermal cycling between 150 and 400 °C at a fast cooling and heating rate of 25 °C/min, the OCV of the μ-SOFC recovered to its high value of 1.07 V without any drop caused by membrane failure, which justifies the superior thermal stability of this novel cell architecture.

Ultra-Thin Film Solid-Oxide Fuel Cell Technology Development: Status, Challenges, and Opportunities

Solid oxide fuel cell (SOFC) is one of the cleanest ways to convert chemical energy stored in fossil fuel into electricity. SOFC offers over 50 % electrical efficiency with low pollutant emission and low noise, and it can be utilized in various applications including portable electronics, remote power, and combined heat and power unit for homes. However, the technology has been under development for many decades, but not yet seen large scale commercialization due to issues in cost and durability. SiEnergy Systems is developing low temperature ultra-thin solid oxide fuel cell that potentially offer major cost reduction and reliability improvement. The use of ultra-thin films reduces the amount of materials required in creating fuel cells, including rare-earth materials, therefore significantly reducing the material cost of the fuel cell. Additionally, the reduced thickness leads to the enhanced ionic conductance across the electrolyte, and enables SOFC operation at 350-550 °C, which is substantially lower than operating temperature of conventional SOFCs that is at 750 °C or above. SOFC operating at this temperature range avoids the disadvantages of conventional SOFCs, such as slow start-up time, costly materials and bulky thermal insulation, while potentially taking advantages of high energy conversion efficiency. In this talk, recent advancement in thin film solid oxide fuel cell research and development will be reviewed with particular emphasis on electrode materials development and large-area cell demonstration.

Characterization of a Cu‐La0.75Sr0.25Cr0.5Mn0.5O3 ‐CeO2/La0.75Sr0.25Cr0.5Mn0.5O3‐YSZ/Ni‐ScSZ Three‐Layer Structure Anode in Thin Film Solid Oxide Fuel Cell Running on Methane Fuel

AbstractAnodes for Solid Oxide Fuel Cell that is capable of directly using hydrocarbon without external reforming have been of great interest recently. In this paper, a three‐layer structure anode running on methane is fabricated by tape casting and screen printing method. The slurry of catalyst layer Cu‐LSCM‐CeO2 (with weight ratios of 1.5:7.0:1.5, 2.0:7.0:1.0, 2.15:7.0:0.85 and 2.25:7.0:0.75, weight ratios of Cu/CeO2 is 1:1, 2:1, 2.5:1 and 3:1, respectively) is screen‐printed on LSCM‐YSZ support layer and Ni‐ScSZ active layer. Thus, LSCM‐YSZ/Ni‐ScSZ anodes with Cu‐LSCM‐CeO2 catalyst layer (denoted as LSCM‐YSZ1010, LSCM‐YSZ2010, LSCM‐YSZ2510 and LSCM‐YSZ3010, respectively) are obtained. Single cells with three‐layer structure anode are also fabricated and measured, of which the maximum power density reaches 491 and 670 mW cm−2 for the cell with LSCM‐YSZ2510 anode running on methane at 750 °C and 800 °C, respectively. No significant degradation in performance has been observed after 240h of cell testing when LSCM‐YSZ2510 anode is exposed to methane at 750 °C. Very little carbon deposition is detected on the anode, suggesting that carbon deposition is limited during cell operation. Consequently, Cu‐LSCM‐CeO2 catalyst layer on the surface of LSCM‐YSZ support layer makes it possible to have good stability for long‐term operation in methane due to very little carbon deposition.

Characteristics of Thin Film Yttria-Stabilized Zirconia Electrolyte by Atomic Layer Deposition for Thin Film Solid Oxide Fuel Cells

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Performance of Ultra-Thin Film Solid Oxide Fuel Cells in Methane and Natural Gas Fuels: The Role of Electrode Microstructure

This proceedings manuscript describes representative results of thin film micro-solid oxide fuel cells (micro-SOFCs) utilizing nano-porous ruthenium (Ru) and Ru – gadolinia doped ceria (CGO) nano-composite anodes, investigated for operation with various fuels. 8 mol% yttria-stabilized zirconia (8YSZ) and compositionally graded CGO-8YSZ thin films were fabricated on silicon substrates as self-supported electrolytes. Performance of devices integrating such electrodes and electrolytes are presented with methane and natural gas as fuels. Oscillations in fuel cell current were observed when nano-porous Ru and Ru-CGO anode micro-SOFCs were operated at constant voltage with methane. Degradation mechanisms of pure metallic electrodes are then compared to composite electrodes at the intermediate temperature range of 300 - 500 °C. New synthesis methods to realize percolating ultra-thin composite electrodes is highlighted as a promising research direction.

Nanostructured Vanadium Oxide Anodes for Thin Film Solid-Oxide Fuel Cells

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Nanostructured Anodes for Direct Methane Thin Film Solid Oxide Fuel Cells

This proceedings manuscript describes in brief representative results on porous Ru anodes incorporated into thin film solid oxide fuel cells (SOFCs). Thin film of 8 mol% yttria-stabilized zirconia (YSZ) was fabricated as free-standing electrolytes, with porous platinum (Pt) and porous Ru deposited as cathode and anode electrodes, respectively. μSOFCs were tested with methane as the fuel and air as the oxidant, exhibiting an open circuit voltage of 0.71 V and a peak power density of 450 mW/cm2 at 500 °C. Anode electrodes were investigated for structural change and was found that morphology evolution in anode electrodes were strongly dependent on the fuels used. Auger electron spectroscopy was carried out on Ru anodes before and after methane operation, and revealed minimal amount of carbon existing on Ru surface, possibly being reaction intermediates. On-going studies on Ru-CGO composite anodes are discussed.

Bi-layered YSZ Electrolyte Using Combined CVD and PVD Methods for Thin Film Solid Oxide Fuel Cell

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Performance of Compact Cell Stack of Thin Film Solid Oxide Fuel Cell Prepared by RF Magnetron Sputtering

Performance of a compact cell stack of thin film solid oxide fuel cell (SOFC) using yttria-stabilized zirconia (YSZ) electrolyte films between 7 μm and 9 μm thick grown by RF magnetron sputtering was studied to power generation property at intermediate temperatures from 700 to 900°C. The series connected SOFC using YSZ film of 7 to 9 μm thick showed a stable generation property at intermediated temperature of 700°C. Moreover, the V-I property of series connected SOFC using YSZ film of 9 μm thick obtained higher than that of the cell prepared with YSZ film of 7 μm thick. As the result, it was found that series connection of two cells could improve the cell performance, and a compact cell stack of thin film SOFC could be operable at intermediate temperatures.

STEM/EELS Characterization of Thin Film Solid Oxide Fuel Cell Cathodes with Improved Electrocatalytic Properties

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Thin Film Solid Oxide Fuel Cells Deposited by Spray Pyrolysis

Two techniques of spray pyrolysis, namely, electrostatic and pneumatic spray deposition, were used to deposit samaria-doped ceria (SDC) electrolyte and lanthanum strontium cobalt ferrite (LSCF) cathode on cermet or metal supported anodes for solid oxide fuel cells (SOFCs) operated at reduced temperature. The deposition processes, the properties of the deposited films, and the electrochemical performances of the fabricated cells are reported in this paper. The deposited SDC electrolytes were dense and gas-tight, and had good adhesion to the underlying anodes. The deposited LSCF cathode had a preferred morphology to facilitate the transport of oxygen gas and effective contact with the electrolyte. Button cell testing indicated that the SOFCs with electrolyte or cathode deposited by spray pyrolysis had good electrochemical performance. This study demonstrated that spray pyrolysis is a cost-effective process for fabricating thin film SOFCs, especially metal supported SOFCs.