Compatibility analyses of BICUVOX.10 as a cathode in yttria-stabilized zirconia electrolytes for usage in solid oxide fuel cells (original) (raw)
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Electrochimica Acta, 2012
A new SOFC cathode material, La 1.98 NiO 4±ı , was tested in presence of two electrolytes, yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC). XRD analysis showed the absence of undesirable phases at the La 1.98 NiO 4±ı /GDC interface, whereas lanthanum zirconate (La 2 Zr 2 O 7), an insulating phase, is present between electrode La 1.98 NiO 4±ı and YSZ electrolyte. XPS analysis showed that the oxygen lattice can be present in form of La O and LaNiO 3 , which explains the high conductivity for these materials. At temperatures lower than 650 • C, the area specific resistance of the electrodes, measured by electrochemical impedance spectroscopy is significantly inferior when associated to GDC rather than YSZ electrolyte. In addition, in the case of GDC, a lower activation energy of about 0.7 eV was obtained, which could be explained by a higher mobility of oxide ions at the La 1.98 NiO 4±ı /GDC interface compared to the La 1.98 NiO 4±ı /YSZ one.
The composites of Cu-partially substituted bismuth vanadate (BICUVOX.1) mixed with a small amount of partially stabilized zirconia (3Y-TZP) were prepared to investigate their microstructure, mechanical properties and ionic conductivity. It was found that the addition of 0.5 to 1 wt% 3Y-TZP reduces the grain size to lower than 1 µm in diameter, leading to improvements in micro-hardness and toughness by more than 15%. Due to preferential distribution of 3Y-TZP particles along grain boundaries, grain boundary conductivity and total conductivity decreased with increasing 3Y-TZP content at low temperature, but the decrements remained rather modest and, in addition, became less significant at higher temperature to disappear at 700 K and above. C 2002 Kluwer Academic Publishers
Characterisation of Submicron-Grain Sized Yttria-Stabilised Zirconia Electrolyte for SOFCs
Journal of Materials Science and Engineering A
This paper investigates the effect of grain size within the nano to micron regime on ionic conductivity for yttria stabilised zirconia (YSZ) with various yttria levels. The samples were made using either slip casting or die pressing routes and were characterised via the use of 4-point electrical conductivity, AC impedance, high resolution transmission electron microscopy (HRTEM) and a field emission gun scanning electron microscope (FEGSEM). Little variation in ionic conductivity was noted over the range of grain sizes examined; rather the yttria content had the largest effect. The greatest variation was noted between the 3 mol% YSZ and 8 mol% YSZ where the conductivity was seen to vary by ~65% at 850 °C. This work forms part of an investigation into the potential use of fine grained zirconias as electrolytes in solid oxide fuel cell (SOFC) applications.
a b s t r a c t SOFC composite electrodes of yttria-stabilized zirconia (YSZ) and either LaNi 0.6 Fe 0.4 O 3 (LNF) or La 0.91 Sr 0.09 Ni 0.6 Fe 0.4 O 3 (LSNF) were prepared by infiltration to a loading of 40 wt% of the perovskite into porous YSZ using aqueous solutions of the nitrate salts. XRD measurements indicated that the perovskite structures were formed following calcination at 850 • C, at which temperature the LNF and LSNF form small particles that coat the YSZ pores. Heating to 1100 • C causes the particles to form a dense film over the YSZ but caused no solid-state reaction. Calcination of an LNF-YSZ composite to 1200 • C led to an expansion of the LNF lattice, suggesting introduction of Zr(IV) into the perovskite; further heating to 1300 • C caused the formation of La 2 Zr 2 O 7 . For 850 • C calcination, the electrode performance of both LNF-YSZ and LSNF-YSZ composites was similar to that reported for composites of YSZ and La 0.8 Sr 0.2 FeO 3 (LSF), with a current-independent impedance of approximately 0.1 cm 2 at 700 • C in air. For 1100 • C calcination, both LNF-YSZ and LSNF-YSZ composites exhibited impedances that decreased strongly under both anodic and cathodic polarization. The implications of these results for preparing electrodes based on LNF and LSNF are discussed.
Chemical Vapor Deposition, 2012
Dense, crack-free thin films (<5 mm) of the nanostructured scandia-zirconia system (Sc 2 O 3 :ZrO 2 ) stabilized in the cubic-fluorite phase (c-ZrO 2 ) are deposited through conventional low-pressure metal-organic(LP-MO) CVD by using b-diketonate metal complexes as precursors [(Zr(tmhd) and Sc(tmhd) 3 , with -tmhd ¼ 2,2,6,6-tetramethyl-3,5-heptanedionate]. The compositional (energy dispersive X-ray spectroscopy -EDX), structural (X-ray diffraction -XRD) and morphological (field emission gunenvironmental scanning electron microscopy -FEG-ESEM) analyses, confirmed the growth of dense partially and fully stabilized ZrO 2 , a suitable electrolyte for solid oxide fuel cells (SOFC). Results of impedance spectroscopy, which investigates the electrical conductivity of coating, deposited as thin as possible to guarantee the uniform covering of a porous substrate, are reported. Results of thin films of yttria-zirconia system (Y 2 O 3 :ZrO 2 ), deposited with the same method, are also reported for comparison.
Journal of Power Sources, 2009
a b s t r a c t SOFC composite electrodes of yttria-stabilized zirconia (YSZ) and either LaNi 0.6 Fe 0.4 O 3 (LNF) or La 0.91 Sr 0.09 Ni 0.6 Fe 0.4 O 3 (LSNF) were prepared by infiltration to a loading of 40 wt% of the perovskite into porous YSZ using aqueous solutions of the nitrate salts. XRD measurements indicated that the perovskite structures were formed following calcination at 850 • C, at which temperature the LNF and LSNF form small particles that coat the YSZ pores. Heating to 1100 • C causes the particles to form a dense film over the YSZ but caused no solid-state reaction. Calcination of an LNF-YSZ composite to 1200 • C led to an expansion of the LNF lattice, suggesting introduction of Zr(IV) into the perovskite; further heating to 1300 • C caused the formation of La 2 Zr 2 O 7 . For 850 • C calcination, the electrode performance of both LNF-YSZ and LSNF-YSZ composites was similar to that reported for composites of YSZ and La 0.8 Sr 0.2 FeO 3 (LSF), with a current-independent impedance of approximately 0.1 cm 2 at 700 • C in air. For 1100 • C calcination, both LNF-YSZ and LSNF-YSZ composites exhibited impedances that decreased strongly under both anodic and cathodic polarization. The implications of these results for preparing electrodes based on LNF and LSNF are discussed.
Electrochemical characterization of YBaCo3ZnO7+δ as a stable proton-conducting SOFCs cathode
Ceramics International, 2012
YBaCo 3 ZnO 7 + Gd 0.2 Ce 0.8 O 1.9 (GDC) composites with various GDC contents (0-70 wt.%) have been investigated as cathode materials for intermediate temperature solid oxide fuel cells (SOFC). The effect of GDC incorporation on the microstructure, electrochemical properties, and thermal expansion behavior of the YBaCo 3 ZnO 7 + GDC composites has been studied. The composite cathodes consist of smaller particles with larger surface area compared to the pure YBaCo 3 ZnO 7 cathode, which is beneficial for providing extended triple-phase boundary (TPB) where the oxygen reduction reaction (ORR) occurs. Among the various compositions investigated, the YBaCo 3 ZnO 7 + GDC (50:50 wt.%) composite is found to be optimum with the lowest polarization resistance (0.28 cm 2 at 600 • C) compared to that of pure YBaCo 3 ZnO 7 (0.62 cm 2 at 600 • C). Anode-supported single cell SOFC fabricated with the YBaCo 3 ZnO 7 + GDC (50:50 wt.%) composite cathode also exhibits excellent performance with a maximum power density of 743 mW/cm 2 at 750 • C. Additionally, the YBaCo 3 ZnO 7 + GDC (50:50 wt.%) composite shows a low thermal expansion coefficient (TEC) of 10.7 × 10 −6 • C −1 , which provides good compatibility with those of standard SOFC electrolytes.
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 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.
ACS applied materials & interfaces, 2018
Bismuth based oxides exhibit outstanding oxygen ionic conductivity and fast oxygen surface kinetics and have shown great potential as a highly active component for electrode materials in solid oxide fuel cells (SOFC). Herein, a Nb-doped La0.6Sr0.4Co0.2Fe0.7Nb0.1O3-δ (LSCFNb) electrode with 40% Er0.4Bi1.6O3 (ESB) composite electrode was successfully fabricated by decoration method and directly assembled on barrier-layer-free yttrium stabilized zirconia (YSZ) electrolyte cells, achieving a peak power density of 1.32 W cm-2 and excellent stability at 750oC and 250 mAcm-2 for 100 h. ESB decoration also significantly reduces the activation energy from 214 kJ mol-1 for the O2 reduction on pristine LSCFNb electrode to 98 kJ mol-1. Further microstructural analysis reveals that there is a redistribution and migration of the ESB phase in the ESB-LSCFNb composite towards the YSZ electrolyte under the influence of cathodic polarization, forming a thin ESB layer at the cathode/YSZ electrolyte in...