Wet chemical synthesis and characterisation of Ba 0.5 Sr 0.5 Ce 0.6 Zr 0.2 Gd 0.1 Y 0.1 O 3−δ proton conductor (original) (raw)
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Highly dense and novel proton conducting materials for SOFC electrolyte
International Journal of Hydrogen Energy
Highly dense proton conducting materials of BCZYSZn (BaCe 0.8-x Zr x Y 0.15 Sm 0.05 O 3-δ (x = 0.15, 0.20) with 4 wt.% ZnO as sintering additive), to be used as an intermediate temperature solid oxide fuel cells (IT-SOFCs) electrolyte, have been processed by the conventional solid state reaction method. The crystalline phase, microstructure, electrical properties, cell performance and chemical stability of the materials have been investigated. The ionic conductivity of BCZYSZn 3 (x = 0.20) material has been measured to be ~2.56 10-3 S cm −1 and ~8.32 10-3 S cm −1 at 600 °C and 850 °C, respectively in wet 5%H 2 in Ar atmosphere. Microstructural characterizations of the zinc containing materials (BCZYSZn) show the formation of highly dense morphology with very large grains. The chemical stability test of BCZYSZn in pure CO 2 2 shows that the material is very stable up to 1000 °C. The maximum power density for the BCZYSZn 3 electrolyte cell is found to be 0.42 W/cm 2 at 700 °C under the testing atmosphere. The performed characterizations reveal that these are suitable proton-conducting candidate materials for efficient electrochemical devices.
Processing and Application of Ceramics, 2018
The new compositions of BaCe 0.5 Zr 0.3 Y 0.15-x Yb x Zn 0.05 O 3-δ perovskite electrolytes (x = 0.1 and 0.15) were prepared by solid state synthesis and final sintering at 1500°C. The obtained ceramics were investigated using X-ray diffraction, scanning electron microscopy, thermo-gravimetric analysis and impedance spectroscopy. The refinement of XRD data confirmed cubic crystal structure with Pm3m space group for both samples. SEM morphology showed larger and compacted grains which enables obtaining of high density and high protonic conductivity. The relative densities of the samples were about 99% of the theoretical density after sintering at 1500°C. The protonic conductivities at 650°C were 2.8×10-4 S/cm and 4.2×10-3 S/cm for x = 0.1 and 0.15, respectively. The obtained results showed that higher Yb-content increases the ionic conductivity and both of these perovskites are promising electrolyte for intermediate temperature solid oxide fuel cells to get high efficiency, long-term stability and relatively low cost energy system.
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.
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.
Scientific Reports
In this study, the Ho-substituted BaZrO 3 electrolyte ceramics (BaZr 1-x Ho x o 3-δ , 0.05 ≤ x ≤ 0.20) were synthesized through a low-cost flash pyrolysis process followed by conventional sintering. The effects of Ho-substitution in BaZrO 3 studied in terms of the structural phase relationship, microstructure and electrical conductivity to substantiate augmented total electrical conductivity for intermediate temperature solid oxide fuel cells (IT-SOFCs). The Rietveld refined X-ray diffraction (XRD) patterns revealed that pure phase with Pm m 3 space group symmetry of cubic crystal system as originated in all samples sintered at 1600 °C for 8 h. The Raman spectroscopic investigations also approved that Ho incorporation in BaZro 3 ceramics. Field Emission Scanning Microscopic (FESEM) study informed a mixture of fine and coarse grains in the fracture surface of Ho-substituted BaZrO 3 sintered samples. The relative density and average grain size of samples were observed to decrease as per the addition of Hosubstitution in BaZro 3 ceramics. The electrical conductivity study was accomplished by Electrical Impedance Spectroscopy (EIS) under 3% humidified O 2 atmosphere from 300 to 800 °C. Furthermore, the total electrical conductivity of BaZr 0.8 Ho 0.2 o 3-δ ceramic was found to be 5.8 × 10 −3 S-cm −1 at 600 °C under 3% humidified atmosphere, which may be a promising electrolyte for IT-SOFCs. Recently, the proton conductive oxide ceramics have fascinated worldwide attention due to widespread applications in intermediate temperature solid oxide fuel cells (IT-SOFCs), hydrogen separation and electrolysis of steam, etc. In this context, the rare-earth cerates and zirconates with the perovskite-type A(II)B(IV)O 3 crystallographic structure are the two foremost families of proton-conducting oxides for electrochemical applications 1-4. Generally, in these categories of oxide materials, oxygen vacancies are increased by replacement of tetravalent cation B(IV) by trivalent cation M(III) as given in the Eq. (1) using Kröger-Vink notation.
Renewable and Sustainable Energy Reviews, 2017
The aims of this review article is to understand the mechanism of proton-conducting solid oxide fuel cells (SOFCs) and compare it with conventional SOFC, to understand how dopants help to improve the conductivity and stability of doped materials, to investigate and analyze the effect or impact (in terms of conductivity and stability) of different types of dopants on the materials as proton-conducting electrolyte in intermediate temperature solid oxide fuel cell (IT-SOFC) and to study the experimental reviews on the methods in synthesizing the materials. Emphasis is given on the relationship between structural and mechanistic features of the crystalline materials and their ion conduction properties. This review will be focusing more on BaCeO 3 and BaZrO 3 as these electrolyte materials were in the focus of research during the past decades due to their considerable proton conductivity and stability.
Fuel Cells, 2008
Proton conducting perovskite oxides have been widely investigated because of their potential as electrolytes for intermediate temperature solid oxide fuel cells. Among them, BaCeO3- based materials exhibit good proton conductivity under a humidified hydrogen-containing atmosphere, but rather poor chemical stability in CO2 atmosphere. The substitution with Zr for Ce improves the chemical stability but reduces proton conductivity due to difficulties in fabricating dense materials. In the present work, single phase nanostructured powders of Ba1+xCe0.65Zr0.20Y0.15O3–δ (x = 0, 0.05, 0.10) solid solutions have been prepared by a modified sol–gel Pechini method with the final aim of evaluating the role of barium on their chemical and electrical properties. A significant influence of barium excess on the preparation and on properties of these materials has been demonstrated. In fact, density measurements evidenced that a 5 or 10 mol% nominal barium excess sensibly favoured the sintering process. Impedance analyses of sintered pellets confirmed the necessity of barium excess in order to avoid the lowering of proton conductivity, which has been evidenced for samples having stoichiometric barium content. Moreover, an unforeseen increase in chemical stability in CO2-containing atmosphere with the growth of the barium excess was detected by thermogravimetric analyses.
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.
2010
The sinterability, conductivity and chemical stability in CO2 atmosphere are compared for a series of doped barium cerate perovskite oxides BaCe0.7Zr0.1Y0.2-xNdxO3- (0 ≤ x ≤ 0.2) which synthesized using a solid state reaction method. Among the series of electrolytes doped with various amounts of Nd and Y, BaCe0.7Zr0.1Y0.15Nd0.05O3- has the optimal combination of sinterability and conductivity, and shows high CO2 resistance. A solid oxide fuel cell using the BaCe0.7Zr0.1Y0.15Nd0.05O3- proton conducting electrolyte at 650-700 o C efficiently co-produces electrical power and value-added ethylene from ethane.