Sr3−3xNa3xSi3O9−1.5x (x = 0.45) as a superior solid oxide-ion electrolyte for intermediate temperature-solid oxide fuel cells (original) (raw)
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As a Superior Solid Oxide-Ion Electrolyte for Intermediate Temperature-Solid Oxide Fuel Cells
2014
Sr 3−3x Na 3x Si 3 O 9−1.5x (x = 0.45) as a superior solid oxide-ion electrolyte for intermediate temperature-solid oxide fuel cells The paper highlights the discovery of a new solid-state oxide-ion conductor using low cost and rare-earth free materials. Its conductivity is the highest among all the known oxide-ion conductors, purely ionic and chemically stable from oxidizing to reducing atmospheres. It exhibits great potential to be a new class of technologically and strategically important materials for commercial solid state ionic devices including solid oxide fuel cells, electrolyzers, sensors and separation membranes.
Novel SrSc 0.2Co 0.8O 3− δ as a cathode material for low temperature solid-oxide fuel cell
Electrochemistry Communications, 2008
The SrSc 0.2 Co 0.8 O 3Àd (SSC) perovskite was investigated as a cathode material for low temperature solidoxide fuel cell. The material showed an almost linear thermal expansion from room temperature to 1000°C in air with the average thermal expansion coefficient of only 16.9 Â 10 À6 K À1 . The Sc-doping made the absence of Co 4+ in SSC, which resulted in not only dramatically reduced thermal expansion coefficient but also extremely high oxygen vacancies concentrations in the lattice at low temperature. The area specific polarization resistance was 0.206 X cm 2 for SSC at 550°C, which is about 52% lower than the value of a Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3Àd -based cathode. A peak power density as high as 564 mW cm À2 was obtained at 500°C based on a 20 lm thick Sm 0.2 Ce 0.8 O 1.9 electrolyte by adopting SSC cathode.
Sr0.7Ho0.3CoO3−δ as a potential cathode material for intermediate-temperature solid oxide fuel cells
Journal of Power Sources, 2012
Sr0.7Ho0.3CoO 3−ı Solid oxide fuel cell a b s t r a c t The oxygen-deficient perovskite Sr 0.7 Ho 0.3 CoO 3−ı (SHCO) operates on the Co(III)/Co(II) redox couple rather than the usual Co(IV)/Co(III) couple for an oxygen reduction reaction(ORR) cathode of an intermediate-temperature solid oxide fuel cell (IT-SOFC). The room-temperature XRD pattern of SHCO prepared by solid-state reaction can be indexed in the tetragonal I4/mmm space group with unit-cell parameters a = 7.617Å, and c = 15.293Å. SHCO exhibits an electrical conductivity with values larger than 488 S cm −1 over the temperature range 560-800 • C. The area specific resistance (ASR) of a SHCO cathode measured on a La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 2.815 (LSGM) electrolyte reaches a relatively low value of 0.14 cm 2 at 800 • C in air. With a 300-m-thick LSGM disk as the electrolyte and NiO-GDC as the anode, a cell with the SHCO cathode exhibited maximum power densities of 1274, 756, and 493 mW cm −2 at 850, 800, and 750 • C, respectively, with hydrogen as fuel and ambient air as oxidant. Cross-section scanningelectron-microscopy measurements confirmed the porous microstructure of the electrodes and good electrode-buffer layer-electrolyte adherence in a single test cell. The ORR activity of a SHCO cathode operating on the Co(III)/Co(II) couple approaches that of the best cathodes operating on the Co(IV)/Co(III) couple, and higher-spin Co(III) ions provide a compatible thermal expansion. Published by Elsevier B.V.
Journal of The Electrochemical Society, 2016
The present study reports thermal and electrical properties of Sr 1-x Y x CoO 2.5+δ (x = 0-0.40) as a promising cathode for intermediatetemperature solid oxide fuel cells. The results show that x = 0.10 is the best composition possessing a single primitive cubic perovskite structure, stable conductivity and the lowest polarization resistance. Thermogravimetric analysis indicates an oxygen intake from RT to ∼375 • C, above which oxygen loss occurs. The oxygen gain-loss behavior corresponds well with the conductivity increase-decrease trending, reflecting that oxygen-nonstoichiometry controls the hole-concentration (or oxidation-state of Co-ions). Electrochemical impedance spectroscopy analysis further reveals that the overall ORR polarization consists of a faster charge-transfer and a slower surface oxygen exchange.
Ionics, 2019
A novel Sr-based perovskite electrolyte, SrCe 0.5 Zr 0.35 Y 0.1 Gd 0.05 O 3-δ , was successfully synthesized and characterized in comparison with SrCe 0.5 Zr 0.35 Y 0.1 Sm 0.05 O 3-δ for possible use in proton-conducting solid oxide fuel cells. Indexing and subsequent Rietveld refinement confirm that both materials crystallize in the orthorhombic symmetry with Pbnm space group. Scanning electron microscopy images show the highly dense structure with the relative densities of 96% and 97% for Gd and Sm-doped sample, respectively. Electrochemical impedance measurements in wet 5% hydrogen at 700°C shows that the conductivity of SrCe 0.5 Zr 0.35 Y 0.1 Gd 0.05 O 3-δ and SrCe 0.5 Zr 0.35 Y 0.1 Sm 0.05 O 3-δ were 5.701 ×10 −3 S cm −1 and 5.257 × 10 −3 S cm −1 , respectively. The ionic conductivities of both samples increase in the wet hydrogen compared with that of dry hydrogen atmosphere. This indicates the enhancement of protonic conduction mechanism from introducing water in electrochemical impedance measurement. The proton conduction takes place at a lower temperature than conventional solid oxide fuel cell (SOFC) which makes SrCe 0.5 Zr 0.35 Y 0.1 (Gd/Sm) 0.05 O 3-δ good electrolytes for intermediate-temperature solid oxide fuel cell (IT-SOFC).
2021
Solid oxide fuel cells (SOFCs) have attracted a lot of attention for their high efficiency, fuel flexibility, lower air pollution, etc. Unfortunately, their operating high temperature is the main shortcoming for commercialization. One of the main hurdles to achieving intermediate temperature SOFCs is the conductivity of their cathode materials at lower temperatures. Therefore, in this study, a conductive Sr3 Fe1.8 Co0.2 O7 cathode material with a Ruddlesden−Popper crystal structure was first successfully synthesized, and then the effect of sintering temperature was investigated. X-ray diffraction analysis results revealed that the powder was approximately pure. Moreover, field emission scanning electron microscope (FESEM) micrographs showed rod-shaped particles with an average particle size of 670 nm. To evaluate the sintering effect on the electrochemical behavior of the synthesized powder, a paste of the powder was painted on both sides of a Gadolinium doped Ceria (CGO) electrolyt...
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.
Scientific Reports
Polycrystalline scheelite type Sr 1−x Ba x Wo 4 (x = 0.1, 0.2 & 0.3) materials were synthesized by the solid state sintering method and studied with respect to phase stability and ionic conductivity under condition of technological relevance for SOFC applications. All compounds crystallized in the single phase of tetragonal scheelite structure with the space group of I4 1 /a. Room temperature X-ray diffraction and subsequent Rietveld analysis confirms its symmetry, space group and structural parameters. SEM illustrates the highly dense compounds. Significant mass change was observed to prove the proton uptake at higher temperature by TG-DSC. All compound shows lower conductivity compared to the traditional BCZY perovskite structured materials. SBW with x = 0.3 exhibit the highest ionic conductivity among all compounds under wet argon condition which is 1.9 × 10 −6 s cm −1 at 1000 °C. Since this scheelite type compounds show significant conductivity, the new series of SBW could serve in IT-SOFC as proton conducting electrolyte. The use of renewable energy and energy conversion and storage have become increasingly important due to the huge demand of energy supply in modern society and emerging ecological concerns in a way which is environmental friendly and low cost 1. Fuel cells, especially solid oxide fuel cells (SOFC), proton exchange membrane fuel cells, supercapacitors, Li-ion batteries, acousto-optic filter, solid state lasers, photo-catalysts and solar cells etc. are the wide range of technological applications for the energy conversion and storage devices 2-7. The performance of these devices depends intimately on the properties of their materials. Because of the high efficiency, fuel flexibility and low pollutant emission, SOFC becomes to be a boundless blessing in alternative energy sector for upcoming generation 8-11. Oxygen ion conduction requires high activation temperature, which are incompatible with low or intermediate temperature operation. Proton conducting materials can be thermally activated at lower temperatures than oxygen ion conducting ones 12. At intermediate temperature range (400-700 °C), some perovskite type oxides shows low activation energy and high proton conductivity in H 2 and H 2 O atmospheres 13-15. Further development of protonic solid oxide fuel cells operating at intermediate temperature (IT, 400-700 °C) is still important technological challenge 16-19. The IT-SOFC has proved to be cost effective over conventional high temperature solid oxide fuel cells (HT-SOFC), as IT-SOFC can be manufactured more economically using less expensive stack interconnect materials 20,21. High-temperature proton conductors have, in general, been found to be oxides with oxygen deficiency in the form of oxygen vacancies, where protons dissolve as hydroxide defects in the oxide at the expense of the vacancies. Getting the best proton conducting electrolyte material with a highly chemical stability is a great challenge. Synthesis of a highly dense ceramic proton conducting electrolyte materials at low sintering temperature is another major challenge as well. Acceptor doped perovskites are examples of oxides containing both oxygen vacancies and protons. Some of the Ba and Sr containing perovskites exhibit state-of-the-art proton conductivity of about 0.01 Scm −1 (e.g. BaCe 0.9 Y 0.1 O 3−δ) 22-25. Meanwhile, BaCeO 3 and BaZrO 3 based materials exhibit a high
Advanced low-temperature solid oxide fuel cells based on a built-in electric field
Energy Materials, 2021
Solid oxide fuel cells (SOFCs) show considerable promise for meeting the current ever-increasing energy demand and environmental sustainability requirements as a result of their high efficiency and low environmental impact. To enable high ionic conductivity, SOFCs are often required to operate at high temperature, which in turn results in high costs [1]. Therefore, lowering the operational temperatures has become a major priority in SOFC research and development [2]. According to the traditional concepts of SOFCs, single semiconductor materials are usually considered as electrolyte membrane due to their higher ionic conductivity, with heterostructures constructed from different semiconductor materials having never been considered. Recently, Meng et al. [3] made an important breakthrough in low-temperature SOFCs by introducing semiconductor heterojunction membranes to function alternatively as electrolytes with better performance. This novel fuel cell design is known as a semiconductor-ionic membrane fuel cell (SIMFC) [3-5]. Zhang et al. [6] , Nie et al. [7] , Deng et al. [8] , Mushtaq et al. [9] , and Afzal [10] used semiconductor materials, including Ni 0.8 Co 0.15 Al 0.05 LiO 2-δ [6] , La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ [7] , Sr 2 Fe 1.5 Mo 0.5 O 6-δ [8] , SrFe 0.75 Ti 0.25 O 3-δ [9] , Not applicable.
Structural and electrical properties of Sr(Ti, Fe)O3-δ materials for SOFC cathodes
Journal of Electroceramics, 2012
Doped strontium titanates are very versatile materials. Iron doped SrTiO 3 can be used, for example, as a material for resistive gas sensors and fuel cell electrodes. In this paper, two compositions based on Fe doped SrTiO 3 were studied as possible candidates for cathode application in SOFCs. Namely, SrTi 0.65 Fe 0.35 O 3 and SrTi 0.50 Fe 0.50 O 3 were examined. A chemical reactivity between electrode and YSZ electrolyte material was investigated, since Sr containing cathode materials in contact with YSZ electrolyte are prone to form insulating phases. Electrical conductivity of bulk samples showed relatively low total conductivities of 0.4 S cm −1 and~2 S cm −1 for STF35 and STF50 respectively. Suitability for cathode application was studied by Electrochemical Impedance Spectroscopy in a symmetrical electrode configuration. Area specific resistance (ASR) was determined in the temperature range from 600°C to 800°C. At 790°C samples show polarization ASR of approximately 0.1Ω cm 2 . It can be expected that further reduction of electrode ASR can be obtained by introduction of ceria barrier layer and tailoring of the electrode microstructure.