Bismuth oxide-based solid electrolytes for fuel cells (original) (raw)
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International Journal of Energy Research, 2019
Solid Oxide Fuel Cells (SOFCs) are an electrochemical energy converter that receives the world's attention as a power generation system of the future owing to its flexibility to consume various types of fuels, low emission of greenhouses gases, and having high efficiency reaching over 70%. A conventional SOFCs operates at high temperature, typically ranges between 800 to 1000°C. SOFCs use yttria-stabilized zirconia (YSZ) as the electrolyte, which exhibits excellent oxide ion conductivity in this temperature range. However, this temperature range poses an issue to SOFCs durability, as it leads to the degradation of the cell components. In addition, SOFCs application is limited and difficult to implement for the transportation sector and portable appliance. A viable solution is to lower the SOFCs operating temperature to intermediate (600 to 800°C) or low (<600°C) operating temperature. The benefit of this way, cell durability will improve, as well as other advantages such as facilitates handling, assembling, dismantling, cost reduction, and expanded the SOFCs application. Nonetheless, the key challenge for the issue is finding suitable electrolyte, as YSZ have lower ionic conductivity at low and intermediate temperature range. The aim of this paper is to review the status and challenges in the attempts made to modify YSZ electrolyte within the past decade. The resulting ionic conductivity, microstructure, and densification, mechanical and thermal properties of these 'new' electrolytes critically reviewed. The targeted conductivity of modification of YSZ electrolyte must be exceeded >0.1 S cm-1 to enable high performance of SOFCs power generation systems to be realized for transportation and portable applications. Based on our knowledge, this paper is the first review which focused on the recent status and challenges of YSZ electrolyte towards lowering the operating temperature.
Copper-substituted bismuth vanadate has been considered a promising material for composite cathodes in SOFC. However, high reactivity of BICUVOX.10 towards the electrolytes still has been its greatest shortcoming. This paper describes reactions between BICUVOX.10 and yttria-stabilized zirconia (YSZ) electrolytes. Secondary phases formed were evaluated by X-ray diffraction, scanning electron microscopy and a.c. impedance spectroscopy. A deleterious interaction between BICUVOX.10 and YSZ was observed, mainly regarding the yttrium depletion from ZrO2 lattice through reaction with VO2.5, resulting in YVO4 phase nucleation and destabilization of the tetragonal and cubic ZrO2 polymorphs to monoclinic. The ZrO2 destabilization and YVO4 nucleation are related phenomena and were interpreted through a theoretical mechanism using charge-compensating dopants description. Thus, these reactions were seen as detrimental to the cathode/electrolyte contact, especially regarding the highly resistive layer formed in the BICUVOX.10/YSZ junction, discouraging further usage of BICUVOX.10 as a cathode in yttria-stabilized zirconia electrolytes.
Prospects of oxide ionic conductivity bismuth vanadate-based solid electrolytes
Reviews in Chemical Engineering, 2014
The benefits of lowering the operation temperature of solid oxide fuel cells (SOFCs) have attracted great attention worldwide. There has been an enormous effort in the literature for the improvement of the electrolyte materials working at lower temperatures. The family of BiMeVOx (Bi–bismuth, Me–dopant metal, V–vanadium, Ox–oxide) materials has been found to have specific properties as oxide ion conductor (electrolyte) for low operation temperature. These materials exhibit uniquely structural features rather different from those of other solid electrolytes. It is possible to use these as the electrolyte in SOFCs. This article attempts to review the main structural and electrochemical characteristics of BiMeVOx materials in order to show a guideline for designing novel BiMeVOx-based electrolyte for low-temperature SOFCs. The prospects and challenges for the application of these materials as the electrolyte are discussed.
A New High‐Performance Proton‐Conducting Electrolyte for Next‐Generation Solid Oxide Fuel Cells
Energy Technology, 2020
Conventional solid oxide fuel cells (SOFCs) are operable at high temperatures (700-1,000 °C) with the most commonly used electrolyte, yttria-stabilized zirconia (YSZ). SOFC R&D activities have thus been carried out to reduce the SOFC operating temperature. At intermediate temperatures (400-700 °C), barium cerate (BaCeO 3) and barium zirconate (BaZrO 3) are good candidates for use as proton-conducting electrolytes due to their promising electrochemical characteristics. Here, we combined two widely studied proton-conducting materials with two dopants and discovered an attractive composition for the investigation of electrochemical behaviors. Ba 0.9 Sr 0.1 Ce 0.5 Zr 0.35 Y 0.1 Sm 0.05 O 3- (BSCZYSm), a perovskite-type polycrystalline material, has shown very promising properties to be used as proton-conducting electrolytes at intermediate temperature range. BSCZYSm shows a high proton conductivity of 4.167×10-3 S cm-1 in a wet argon atmosphere and peak power density of 581.7 mW cm-2 in Ni-BSCZYSm | BSCZYSm | BSCF cell arrangement at 700 °C, which is one of the highest in comparison to proton-conducting electrolyte-based fuel cells reported till now.
International Journal of Hydrogen Energy, 2018
Development of high proton conducting, chemically stable electrolyte for solid oxide fuel cell application still remains as a major challenge. In this work, yttrium (0, 5, 10, 15 and 20 mol%) doped barium zirconate synthesised by hydrothermal assisted coprecipitation exhibited highly crystalline cubic perovskite. The results demonstrate that the proton conductivity is higher than oxygen ion conductivity measured in the temperature range of 200e600 C. The 20 mol% Y doped BaZrO 3 exhibited higher protonic conductivity (6.1 mScm À1) with an activation energy 0.64 eV under the reducing atmosphere. The Mott eSchottky analysis carried out in hydrogen atmosphere at 200 C revealed that the barrier height of doped BaZrO 3 reduced from 0.6 to 0.2 V. The Schottky depletion layer width also decreased from 4 to 2 nm with the increase in yttrium concentration and the boiling water test showed good phase stability. Our study highlights the critical role of space charge in the grain boundary and its suppression with the increase in dopant concentration. The results demonstrate that Y doped BaZrO 3 sintered at low temperature is a promising candidate as the electrolyte material for the intermediate temperature proton conducting solid oxide fuel cells.
International Journal of ChemTech Research
Co-doped sample of electrolyte have been preparedby Solgel method and characterized to explore its use as a solid electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs).The crystal structure, microstructure, and ionic conductivity have been determined by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectrometer (EDX), Raman Spectroscopy (Raman), and impedance spectroscopy, respectively. The XRD result reveals that the sample is single phase with cubic fluorite-type structure. The relative density of sample sintered at 1400 0 C isabout98% of theoretical density. The average grain size of sample found from SEM image is 451.4nm. The Raman spectra result showed formation of two distinctive peaks in the lattice. The peak at lower wavenumber (463) cm-1) can be attributed to F 2g vibration mode (O-Ce-O) of the fluorite-like structure of pure CeO 2. Besides, the peak at higher wavenumber (564) cm-1 can be ascribed to the oxygen vacancies extrinsically introduced into for maintaining the charge neutrality.The ionic conductivity and activation energy of found at 500 0 C was(5.95 x10-3 S/cm, Ea = 0.64eV) respectively. All the results confirmed that is a promising alternative electrolyte for intermediate temperature solid oxide fuel cell (IT-SOFC) applications.
Ceramics International, 2021
Lowering operating temperature and optimizing electrolyte thickness, while maintaining the same high efficiencies are the main considerations in fabricating solid oxide fuel cells (SOFCs). In this study, the effect of yttrium-stabilized bismuth bilayer electrolyte thickness on the electrical performance was investigated. The yttrium-stabilized bismuth bilayer electrolyte was coated on the nickel-samarium-doped composite anode/ samarium-doped ceria electrolyte substrate with varying bilayer electrolyte thicknesses (1.5, 3.5, 5.5, and 7.5 μm) via dip-coating technique. Electrochemical performance analysis revealed that the bilayer electrolyte with 5.5 μm thickness exhibited high open circuit voltage, current and power densities of 1.068 V, 259.5 mA/cm 2 and 86 mW/cm 2 , respectively at 600 • C. Moreover, electrochemical impedance spectroscopy analysis also exhibited low total polarization resistance (4.64 Ωcm 2) at 600 • C for the single SOFC with 5.5 μm thick yttrium-stabilized bismuth bilayer electrolyte. These findings confirm that the yttrium-stabilized bismuth bilayer electrolyte contributes to oxygen reduction reaction and successfully blocks electronic conduction in Sm 0.2 Ce 0.8 O 1.9 electrolyte materials. This study has successfully produced an Y 0.25 Bi 0.75 O 1.5 /Sm 0.2 Ce 0.8 O 1.9 bilayer system with an extremely low total polarization resistance for low-temperature SOFCs.
Electrolytes For Intermediate Temperature Solid Oxide Fuel Cells
Archives of Metallurgy and Materials, 2015
Solid electrolytes for construction of the intermediate-temperature solid oxide fuel cells, IT-SOFC, have been reviewed. Yttrium stabilized tetragonal zirconia polycrystals, YTZP, as a potential electrolyte of IT-SOFC have been highlighted. The experimental results involving structural, microstructural, electrical properties based on our own studies were presented. In order to study aluminum diffusion in YTZP, aluminum oxide was deposited on the surface of 3 mol.% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP). The samples were annealed at temperatures from 1523 to 1773 K. Diffusion profiles of Al in the form of mean concentration vs. depth in B-type kinetic region were investigated by secondary ion mass spectroscopy (SIMS). Both the lattice (D
Fuel Cells, 2008
BaZr 0.8 Y 0.2 O 3-d , (BZY), a protonic conductor candidate as an electrolyte for intermediate temperature (500-700°C) solid oxide fuel cells (IT-SOFCs), was prepared using a sol-gel technique to control stoichiometry and microstructural properties. Several synthetic parameters were investigated: the metal cation precursors were dissolved in two solvents (water and ethylene glycol), and different molar ratios of citric acid with respect to the total metal content were used. A single phase was obtained at a temperature as low as 1,100°C. The powders were sintered between 1,450 and 1,600°C. The phase composition of the resulting specimens was investigated using X-ray diffraction (XRD) analysis. Microstructural characterisation was performed using field emission scanning electron microscopy (FE-SEM). Chemical stability of the BZY oxide was evaluated upon exposure to CO 2 for 3 h at 900°C, and BZY showed no degradation in the testing conditions. Fuel cell polarisation curves on symmetric Pt/BZY/Pt cells of different thicknesses were measured at 500-700°C. Improvements in the electrochemical performance were obtained using alternative materials for electrodes, such as NiO-BZY cermet and LSCF (La 0.8 Sr 0.2 Co 0.8 Fe 0.2 O 3), and reducing the thickness of the BZY electrolyte, reaching a maximum value of power density of 7.0 mW cm-2 at 700°C.
Journal of Alloys and Compounds, 2019
In present work, perovskite structured proton conducting electrolyte materials BaZr 0.8 Y 0.2 (BZY), BaZr 0.8 Gd 0.2 (BZGd) and BaZr 0.8 Sm 0.2 (BZSm) synthesized by cost effective combustion method are investigated for intermediate temperature solid oxide fuel cell (IT-SOFC). The synthesized BZY, BZGd and BZSm materials are sintered at low temperature (1150 C) and the effect of low sintering temperature on electrolyte properties are also explored. Microstructure, surface morphology, elemental composition, functional group and weight loss are studied using different characterization techniques like XRD, SEM, EDX, FTIR and TGA. XRD shows cubic perovskite structure of all synthesized materials. Secondary phase of Y 2 O 3 is observed in BZY while BaO is observed in BZGd and BZSm due to low sintering temperature. SEM micrographs reveals dense microstructure of BZSm compared to BZY and BZGd. EDX analysis confirms the required material composition within all samples with no impurities. FTIR shows the presence of hydroxyl group and metal oxides and it is observed that BZY exhibit more structural symmetry compared to BZSm and BZGd. Highest conductivity observed ð2:2 Â10 À3 S=cmÞ for BZY due to its structural symmetry and characteristic to prefer B-site of perovskite. Also significant power densities of 0.34 Wcm À2 , 0.24 Wcm À2 and 0.32 Wcm À2 for BZY, BZGd and BZSm electrolytes based cells at 650 C implies that BZY, BZGd and BZSm can be used as IT-SOFC electrolytes.