Creating and Preserving Nanoparticles during Co-Sintering of Solid Oxide Electrodes and Its Impact on Electrocatalytic Activity (original) (raw)
Related papers
Ultra-fine Gd-doped ceria (GDC) powders were synthesized via co-precipitation using ammonium car-bonate as the precipitant. The crystallite size of the resultant GDC powders was measured as ~33 nm. The dilatometry test of the powder compacts and the relative density measurement of sintered pellets with various sintering temperatures revealed the synthesized nano-GDC powders had superior sinterability compared to commercial GDC powders (e.g., 96% vs 78% in relative density at 1300 C, respectively). Based on the total conductivity measurement of the co-precipitated GDC via electrochemical impedance spectroscopy, we found there was an optimum sintering temperature range (1300e1400 C) to achieve both high density and high conductivity due to significant increase in grain boundary resistance at higher temperature (1500 C). Moreover, the nano-sized and highly sinterable co-precipitated GDC effectively enhanced oxygen reduction reaction at the La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3Àd /GDC composite cathode due to increase in active reaction sites as well as enhanced phase connectivity in 3D-bulk at lower sintering temperatures.
Ceramics International, 2015
The effects of sintering temperature on the surface morphology, roughness, and electrical properties of samarium-doped ceria (SDC)-carbonate (SDCC) composite electrolyte were examined. SDCC composite pellets were fabricated and sintered at various temperatures ranging from 500 1C to 650 1C. Brunauer-Emmett-Teller technique and atomic force microscopy were used to investigate the surface area and surface roughness of the composite materials, respectively. Conductivity measurements using impedance spectroscopy were conducted from 350 1C to 550 1C. The specific surface area of the pure SDC powder decreased from 8.85 m 2 /g to 4.24 m 2 /g after the carbonate phase was incorporated into the SDC phase with increasing particle size. The composite pellet sintering temperature affected the continuity between the two phases [SDC and (Li/Na) carbonate], roughness, mean particle size, and conductivity of the composite electrolyte. A fully dense SDCC composite electrolyte pellet sintered at 550 1C exhibited a maximum ionic conductivity of 0.077 S/cm at 550 1C. In addition, 550 1C was the minimum sintering temperature to achieve good wetting between the two phases, moderate particle size, low surface roughness, and high ionic conductivity.
Journal of Electroanalytical Chemistry, 2022
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ECS Transactions, 2013
Samaria doped ceria (SDC) co-doped with Nd 2 O 3 (Nd-SDC) and doubly co-doped with Nd 2 O 3 and Pr 2 O 3 (Pr-Nd-SDC) was prepared by solution combustion synthesis. X-ray diffraction studies confirmed the nanocrystalline nature of the powder with cubic fluorite phase. Raman spectroscopy showed the characteristic cubic fluorite peak (464 cm -1 ) of ceria and the vacancy concentration calculated from the peak area ratio (A 550 /A 464 ) was found to be higher in Pr-Nd-SDC (0.556) compared to Nd-SDC (0.168). The powder was compacted into discs and sintered to obtain dense pellets. The sintering temperature was found to be considerably lower than that required for microcrystalline SDC. The electrical conductivity was obtained by impedance spectroscopy. The doubly co-doped sample (Pr-Nd-SDC) exhibited higher conductivity and lower activation energy compared to the co-doped sample (Nd
Applied Sciences, 2020
Perovskite-based composite cathodes, La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF)–Ce0.8Sm0.2O1.9-carbonate (SDCC), were investigated as cathode materials for low-temperature solid-oxide fuel cells. The LSCF was mixed with the SDC–carbonate (SDCC) composite electrolyte at different weight percentages (i.e., 30, 40, and 50 wt %) to prepare the LSCF–SDCC composite cathode. The effect of SDCC composite electrolyte content on the diffraction pattern, microstructure, specific surface area, and electrochemical performances of the LSCF–SDCC composite cathode were evaluated. The XRD pattern revealed that the SDCC phase diffraction peaks vary according to its increasing addition to the system. The introduction of SDCCs within the composite cathode did not change the LSCF phase structure and its specific surface area. However, the electrical performance of the realized cell drastically changed with the increase of the SDCC content in the LSCF microstructure. This drastic change can be ascribed to the poor ...
Transactions of the Materials Research Society of Japan, 2010
Doped ceria (CeO 2) compounds are fluorite related oxides which show oxide ionic conductivity higher than yttria-stabilized zirconia in oxidizing atmosphere. As a consequence of this, considerable interest has been shown in application of these materials for intermediate temperature (300-500C) operation of solid oxide fuel cells (SOFCs). In this review paper, our experimental data was reintroduced to propose a new design paradigm for development of high quality doped CeO 2 electrolytes. Based on our experimental data, our original idea a control of nano-inhomogeity of doped CeO 2 electrolytes was proposed. In our work, the nano-sized powders and dense sintered bodies of M doped CeO 2 (M: Sm, Gd, Y, Yb, Dy, Ho, Tb and La) specimens were fabricated using ammonium carbonate co-precipitation method, conventional sintering method and pulsed electric current sintering method. Also nano-structural features of those specimens were carefully observed for conclusion of relationship between electrolytic properties and microstructure in doped CeO 2. It is essential that the electrolytic properties of doped CeO 2 reflect in changes of microstructure even down to the atomic scale. Accordingly, a combined approach of ultimate analysis, simulation and processing route design is required to develop the superior quality doped CeO 2 electrolytes for the intermediate temperature operation of SOFCs.
International Journal of Hydrogen Energy, 2013
Ceria carbonate Nanocomposites materials a b s t r a c t Ceria-based electrolyte materials have great potential in low and intermediate temperature solid oxide fuel cell applications. In the present study, three types of ceria-based nanocomposite electrolytes (LNK-SDC, LN-SDC and NK-SDC) were synthesized. One-step coprecipitation method was adopted and different techniques were applied to characterize the obtained ceria-based nano-composite electrolyte materials. TGA, XRD and SEM were used to analyze the thermal effect, crystal structure and morphology of the materials.
The effects of sintering temperature on the current-voltage (I-V) performance of symmetrical cells with an SDCC electrolyte composite were evaluated in this study. The SDCC electrolyte composite was prepared by mixing 80 wt% SDC with 20 wt% Li and Na carbonate (Li/Na ratio of 2/1) via a solid state reaction method. The resultant SDCC electrolyte composite powder was uniaxially pressed into a circular pellet and sintered at 500 1C, 550 1C, 600 1C and 650 1C for 5 h. A symmetrical cell was finally fabricated by painting a conductive silver paste on both sides of the dense SDCC electrolyte composite pellet, and its I-V performance was measured using hydrogen and air as the fuel and oxidant, respectively. The phase structure and microstructure of the composite powders were investigated using an X-ray diffractometer, field emission scanning electron microscope, and transmission electron microscope. Ceramic pellets sintered at 550 1C exhibited a maximum power density of 63.3 mW/cm 2 and an open circuit voltage of 1.14 V at an operating temperature of 650 1C. This study contributes to the development of SDCC electrolyte composite substrates for electrolyte-supported low-temperature SOFCs.
Journal of the Iranian Chemical Society, 2010
The use of alternate cathode materials with improved performance and without any chemical reaction with adjoining electrolyte is required for a reduction in operating temperature of SOFC from 1273 K to about 1073 K (ITSOFC). Cobalt containing perovskite oxides such as LaCoO 3 tend to exhibit a higher ionic conductivity due to a greater concentration of oxygen vacancies than other perovskite oxides. The mixed ionic and electronic conducting cathode of the La 1-x Sr x CoO 3-δ systems has shown the lowest cathodic overpotential for an SOFC air electrode. In this research work, fine powders of La 0.70 Sr 0.30 CoO 3-δ (LSC) cathode and Ce 0.90 Gd 0.10 O 2-δ (GDC) and Ce 0.80 Sm 0.20 O 2-δ (SDC) are synthesized by glycine nitrate combustion synthesis and systematically characterized by XRD and particle characteristics. The electrical properties of LSC cathode and GDC and SDC electrolytes are also studied. But, the crucial requirement for applicability of LSC cathode is its chemical compatibility in conjunction with the alternate solid electrolytes, GDC and SDC without any phase formation. The XRD studies showed no reaction products when the La 0.70 Sr 0.30 CoO 3-δ cathode is mixed and calcined with GDC and SDC electrolyte at 1573 K. Hence, the LSC cathode may be combined with CeO 2 based electrolytes in ITSOFC application.
Fuel and Energy Abstracts
a b s t r a c t A fundamental step for a sustainable industrial development based on "H 2 Economy" is the implementation of fuel cell technology, in terms of new devices, materials and convenient processes for their production. Rare earth doped ceria oxides are suitable materials for the new generations of cells and their cost effective production becomes fundamental as the price of rare earths is increasing. In this view, our study investigates a modified method of co-precipitation of Ce 0.8 Sm 0.2 O 1.9Àx (SDC) evaluating the effects of adding of H 2 O 2 in the process. The parameters controlled were the molar ratio [H 2 O 2 ]/[M 3þ ], (M 3þ ¼ Ce 3þ , Sm 3þ present in starting nitrate salts solutions) and the pH of precipitation; in some cases the precipitates were also treated under reflux at 373 K overnight. The powder catalysts, both as fresh precipitates and calcined oxides were analyzed via N 2 adsorption (BET), X-Ray diffraction (XRD) and temperature programmed reduction (TPR) techniques and their morphological, structural and redox properties were correlated with the synthesis parameters used. The electrical conductivity properties of these materials have also been investigated via electrochemical impedance spectroscopy (EIS) and the results compared with those of a commercial oxide. The synthesis approach was shown to be very versatile in the development of materials with properties exploitable for applications in catalysis and in intermediate temperature Solid Oxide Fuel Cell (IT-SOFC) systems.