Effects of Co Doping on the Electrochemical Performance of Double Perovskite Oxide Sr 2 MgMoO 6−δ as an Anode Material for Solid Oxide Fuel Cells (original) (raw)
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The Journal of Physical Chemistry C, 2014
The suitability of double perovskite oxides of composition Sr 2 Mg 1−x Ni x MoO 6−δ (SMNM, x = 0−0.9) as anode materials for solid oxide fuel cells (SOFCs) was evaluated. Single double perovskite structures could be obtained up to x = 0.9 in syntheses at ambient atmosphere. However, after reduction at 800°C, trace amounts of impurities were detected in the sample with x = 0.9, suggesting that the upper limit for the Ni content (x) in SMNM is less than 0.9 under SOFC operating conditions. The electrical conductivity of SMNM increases with increasing Ni content because of the increase in the concentration of electronic defects, [Mo Mo 6+ 5+ ′], and the decreased band gap energy, as revealed by first-principles calculations. The substitution of Ni can facilitate the charge-transfer process of the electrode reaction, decrease the polarization resistance, and thus increase the power density of a single cell. Xray photoelectron spectroscopy and temperature-programmed reduction measurements were used to explain the reason for the performance improvement. SMNM showed good chemical compatibility with Ce 0.8 Sm 0.2 O 2−δ (SDC) but a slight reactivity with the electrolyte La 0.8 Sr 0.2 Ga 0.83 Mg 0.17 O 3−δ (LSGM) at 1300°C. The use of an SDC buffer layer could avoid the interface reaction between the SMNM anode and the LSGM electrolyte, resulting in better cell performance. The Sr 2 Mg 0.3 Ni 0.7 MoO 6−δ electrode exhibited a maximal power density of 160 mW cm −2 at 800°C with an electrolyte (LSGM, 400 μm)-supported cell configuration.
Novel Mg-Doped SrMoO3 Perovskites Designed as Anode Materials for Solid Oxide Fuel Cells
Materials, 2016
SrMo 1´x M x O 3´δ (M = Fe and Cr, x = 0.1 and 0.2) oxides have been recently described as excellent anode materials for solid oxide fuel cells at intermediate temperatures (IT-SOFC) with LSGM as the electrolyte. In this work, we have improved their properties by doping with aliovalent Mg ions at the B-site of the parent SrMoO 3 perovskite. SrMo 1´x Mg x O 3´δ (x = 0.1, 0.2) oxides have been prepared, characterized and tested as anode materials in single solid-oxide fuel cells, yielding output powers near 900 mW/cm´2 at 850˝C using pure H 2 as fuel. We have studied its crystal structure with an "in situ" neutron power diffraction (NPD) experiment at temperatures as high as 800˝C, emulating the working conditions of an SOFC. Adequately high oxygen deficiencies, observed by NPD, together with elevated disk-shaped anisotropic displacement factors suggest a high ionic conductivity at the working temperatures. Furthermore, thermal expansion measurements, chemical compatibility with the LSGM electrolyte, electronic conductivity and reversibility upon cycling in oxidizing-reducing atmospheres have been carried out to find out the correlation between the excellent performance as an anode and the structural features.
New SrMo1−xCrxO3−δ perovskites as anodes in solid-oxide fuel cells
International Journal of Hydrogen Energy, 2014
Oxides of composition SrMo 1Àx Cr x O 3Àd (x ¼ 0.1, 0.2) have been prepared, characterized and tested as anode materials in single solid-oxide fuel cells, yielding output powers higher than 700 mW cm À2 at 850 C with pure H 2 as a fuel. All the materials are suggested to present mixed ioniceelectronic conductivity (MIEC) from neutron powder diffraction (NPD) experiments, complemented with transport measurements; the presence of a Mo 4þ /Mo 5þ mixed valence at room temperature, combined with a huge metal-like electronic conductivity, as high as 340 S cm À1 at T ¼ 50 C for x ¼ 0.1, could make these oxides good materials for solid-oxide fuel cells. The magnitude of the electronic conductivity decreases with increasing Cr-doping content. The reversibility of the reductioneoxidation between the oxidized Sr(Mo,Cr)O 4Àd scheelite and the reduced Sr(Mo,Cr)O 3 perovskite phases was studied by thermogravimetric analysis, which exhibit the required cyclability for fuel cells. An adequate thermal expansion coefficient, without abrupt changes, and a chemical compatibility with electrolytes make these oxides good candidates for anodes in intermediate-temperature SOFC (IT-SOFCs).
Membranes, 2022
In this work, magnesium-doped Sr2Fe1.2Mg0.2Mo0.6O6−δ and Sr2Fe0.9Mg0.4Mo0.7O6−δ double perovskites with excellent redox stability have been successfully obtained. The physicochemical properties including: crystal structure properties, redox stability, thermal expansion properties in oxidizing and reducing conditions, oxygen content as a function of temperature and transport properties, as well as the chemical compatibility with typical electrolytes have been systematically investigated. The in situ oxidation of reduced samples using high-temperature XRD studies shows the crystal structure of materials stable at up to a high-temperature range. The in situ reduction and oxidation of sinters with dilatometer measurements prove the excellent redox stability of materials, with the thermal expansion coefficients measured comparable with electrolytes. The oxygen nonstoichiometry δ of compounds was determined and recorded in air and argon up to 900 °C. Sr2Fe1.2Mg0.2Mo0.6O6−δ oxide presents satisfactory values of electrical conductivity in air (56.2 S·cm−1 at 600 °C) and reducing conditions (10.3 S·cm−1 at 800 °C), relatively high coefficients D and k, and good ionic conductivity (cal. 0.005 S·cm−1 at 800 °C). The stability studies show that both compounds are compatible with Ce0.8Gd0.2O1.9 but react with the La0.8Sr0.2Ga0.8Mg0.2O3−d electrolyte. Therefore, the magnesium-doped double perovskites with excellent redox stability can be potentially qualified as electrode materials for symmetrical SOFCs and are of great interest for further investigations.
Synthesis and characterization of Perovskites based oxides for solid oxides fuel cells materials
2008
Double perovskite structure with composition of Sr2Mg1-xMnxMoO6 (SMMMO) and Sr2Mg1-xFexMoO6 (SMFMO) for anode materials in solid oxide fuel cell have been synthesized by means of solid state reaction and sol gel method, respectively. Crystal structure of those materials were characterized by X-ray diffraction technique and refined using Rietveld method implemented in the Rietica program and their conductivity were determined by DC conductivity measurement technique. The higher Mn concentration the lower the cell volume of SMMO, whilst for SMFO the higher Fe content the larger the cell. For SMMO the ionic conductivity tends to increase with increased Mn, whilst for SMFMO conductivity decreases as Fe concentration increases.
Eastern-European Journal of Enterprise Technologies, 2021
The main obstacle to solid oxide fuel cells (SOFCs) implementation is the high operating temperature in the range of 800–1,000 °C so that it has an impact on high costs. SOFCs work at high temperatures causing rapid breakdown between layers (anode, electrolyte, and cathode) because they have different thermal expansion. The study focused on reducing the operating temperature in the medium temperature range. SmBa0.5Sr0.5Co2O5+δ (SBSC) oxide was studied as a cathode material for IT-SOFCs based on Ce0.8Sm0.2O1.9 (SDC) electrolyte. The SBSC powder was prepared using the solid-state reaction method with repeated ball-milling and calcining. Alumina grinding balls are used because they have a high hardness to crush and smooth the powder of SOFC material. The specimens were then tested as cathode material for SOFC at intermediate temperature (600–800 °C) using X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), electrochemical, and scanning electron microscopy (SEM) tests. The...
Latest development of double perovskite electrode materials for solid oxide fuel cells: a review
Frontiers in Energy, 2019
Recently, the development and fabrication of electrode component of the solid oxide fuel cell (SOFC) have gained a significant importance, especially after the advent of electrode supported SOFCs. The function of the electrode involves the facilitation of fuel gas diffusion, oxidation of the fuel, transport of electrons, and transport of the byproduct of the electrochemical reaction. Impressive progress has been made in the development of alternative electrode materials with mixed conducting properties and a few of the other composite cermets. During the operation of a SOFC, it is necessary to avoid carburization and sulfidation problems. The present review focuses on the various aspects pertaining to a potential electrode material, the double perovskite, as an anode and cathode in the SOFC. More than 150 SOFCs electrode compositions which had been investigated in the literature have been analyzed. An evaluation has been performed in terms of phase, structure, diffraction pattern, electrical conductivity, and power density. Various methods adopted to determine the quality of electrode component have been provided in detail. This review comprises the literature values to suggest possible direction for future research.
Electrochemical performance of La0.75Sr0.25Cr0.9M0.1O3 perovskites as SOFC anodes in CO/CO2 mixtures
Journal of Applied Electrochemistry, 2012
The performance of La 0.75 Sr 0.25 Cr 0.9 M 0.1 O 3 (M = Mn, Fe, Co, and Ni) perovskitic materials as anodes was studied for a CO-fueled solid oxide fuel cell. The electrocatalytic performance and the tolerance to carbon deposition were investigated, while electrochemical characterization was carried out via AC impedance spectroscopy and cyclic voltammetry. The La 0.75 Sr 0.25 Cr 0.9 Fe 0.1 O 3 perovskite showed the best anode performance at temperatures above 900°C; while at temperatures below 900°C, the best performance was achieved with the La 0.75 Sr 0.25 Cr 0.9 Co 0.1 O 3 material. AC impedance spectroscopy was used for a semi-quantitative analysis of the LSC-M 0.1 anodes performance in view of total cell and charge transfer resistance. All anode materials exhibit high electronic conductivity and presumably do not substantially contribute to the overall cell resistance and concomitant ohmic losses.