A versatile route for the preparation of Ni–CGO cermets from nanocomposite powders (original) (raw)
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Ni–CGO cermet anodes from nanocomposite powders
A comparative microstructural study between Ni–Ce0.9Gd0.1O1.95 (Ni–CGO) anodes obtained from NiO–CGO nanocomposite powders prepared by in situ one-step synthesis and by mechanical mixture (two-step synthesis) of NiO and CGO powders is reported. The open porosity and microstructure of sintered and reduced pellets were investigated as a function of the citric acid content used as pore forming agent. Nanosized crystallites for the one-step and two-step routes were around 18 nm and 24 nm against 16 nm and 37 nm, for CGO and NiO, respectively. Overall results show that both routes provided suitable microstructures either for anode-support, or for functional anodes for solid oxide fuel cells (SOFCs), with more versatile characteristics in the case of the one-step route. The electrical characterization of selected NiO–CGO samples, carried out between 90 and 260 °C by impedance spectroscopy, confirms electrical percolation of both phases in the composites. However, based on combined microstructural and impedance data, it seems clear that the one-step processing route is the best approach to make SOFC anodes with improved performance.
Ni–CGO cermet anodes from nanocomposite powders: Microstructural and electrochemical assessment
Ceramics International, 2014
In this study, composite powders synthesized by a novel one-step sol-gel method were used to obtain Ni-CGO anodes, while anodes of the same composition prepared from commercial powders were used as reference. The anodes performance was studied by impedance spectroscopy and dc polarization in the temperature range of 650-750 1C in flowing humidified 10% H 2 þ90% N 2 gas mixtures, using a three-electrode configuration cell, with clear advantage for the novel one-step route. One-step anodes fired at 1450 1C showed an area specific resistance of 0.15 Ω cm 2 under open circuit conditions and an anodic overpotential of 91 mV at 750 1C for a current density of 322 mA/cm 2 , which are amongst the best results mentioned in the literature. The enhanced electrochemical performance of one-step anodes is mainly attributed to unique microstructural features, namely small grain size (submicrometer scale even after firing at 1450 1C) and homogeneous phase distribution, which is expected to extend the triple-phase boundary length.
NiO–CGO in situ nanocomposite attainment: One step synthesis
The CeO2-based electrolyte low temperature SOFCs require special electrodes with a higher performance and compatibility. The performance of the CeO2-based composite anodes depends on microstructural features such as particle size, tripe phase boundaries (TPB), surface area, and percolation. Some of the primary parameter can be manipulated during the materials synthesis. In this work the compound NiO–Ce0.9Gd0.1O1.95 (NiO–CGO), used as anode in SOFC, was synthesized by two different processes. Both of them are based on the polymeric precursor method. Characterized by simultaneous thermogravimetry-differential thermal analysis, X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy and dilatometry. The refinement of the XRD data indicated that the composite sample synthesized by the process called “one step synthesis” produced smaller crystallite size in comparison to the sample attained by the two steps process. Simple preliminary performance tests were done with single cells in which such I–V curves indicated that the cell with one step anode had better performance. “One step synthesis” product, in situ nanocomposite, presented similar fine grained particle sizes for both phases Ni and CGO, which would be beneficial to the electrochemical activity, also indicated by first performance tests.
International Journal of Innovative Research in Science, Engineering and Technology, 2014
A precursor to SOFC anode was made via solution combustion technique that is NiO-GDC (Gadolinia doped Ceria) composites by mixing nitrates of cerium, gadolinium and nickel in stoichiometric ratio of composition to form the final precursor product as Ce0.90Gd0.10O1.95 - 0.40 NiO. The fuel for the combustion synthesis that is glycine’s concentration was varied between 0.5 mole% to 1.4 mole%. The temperature of the resultant sintered pellets was varied between 30 to 800oC and electrical properties of the NiO-CGO composite was studied by means of admittance plots between conductivity & susceptance. The results showed that the composite precursor varied in conductivity and activation energy depending on the concentration of the fuel.
Mesoporous NiO-CGO Obtained by Hard Template as High Surface Area Anode for IT-SOFC
2000
Mesoporous nickel-ceria cermets were synthesized and electrically characterized as anodes for intermediate-temperature solid oxide fuel cells using Ce 0.8 Gd 0.2 O 1.9 as the material for the electrolyte. Mesoporous nickel-ceria cermets were prepared from silica hard templates, with KIT-6 structure, and a multistep impregnation process. A comprehensive (micro)structural analysis was carried out in order to determine the stability of the replicated mesoporous cermet at the typical processing temperatures employed in solid oxide fuel cells fabrication, i.e. from 900ºC to 1100ºC. Electrical characterization of the mesoporous cermets in symmetrical cells was carried out in humidified 5%H 2 in N 2 atmosphere. Targeted values of electrode/electrolyte area specific resistance were achieved in the intermediate temperature range showing the suitability of the here-presented mesoporous approach for developing a new class of high performance anodes for IT-SOFC.
Hierarchically-ordered NiO-Ce 0.8 Gd 0.2 O 1.9 (GDC) composite anode powders were synthesized using eggshell membranes as biotemplates. The morphology of the as-synthesized powders depended on the kind of Ni precursor and the use of EDTA as a chelating agent. Hierarchicallyordered anode powders were obtained from Ni chloride and Ni acetate precursors with EDTA. The Ni-GDC anode synthesized from Ni chloride precursor with EDTA exhibited the lowest polarization resistance at 800 1C and an activation energy of 0.01 Ω cm 2 and 0.74 eV, respectively, in humidified H 2 . In accordance with the polarization resistance results, the 0.5-mm thick GDC electrolyte-supported single cell with the Ni-GDC anode synthesized from Ni chloride precursor with EDTA showed a maximum power density of 0.34 W cm À 2 at 800 1C with humidified H 2 fuel.
2021
Low Temperature Solid oxide fuel cells (LTSOFCs) are considered as one of the futuristic electrochemical energy delivering devices because of their good conversion efficiency and eco-friendly technology. To improve the efficiency of SOFC further, research activities are being carried-out across the globe to reduce the operating temperature from 1273 K to around 873 K. For low temperature operation of SOFC, conventional anode such as Ni-YSZ is not suitable because of low ionic conductivity of YSZ. In this research, a set of anode materials, such as, as NiO–Ce0.9Gd0.1O2-δ, NiO– Ce0.8Gd0.2O2-δ, NiO–Ce0.9Sm0.1O2-δ and NiO – Ce0.8Sm0.2O2-δ were prepared by simple soft chemical precipitation method for application in LTSOFC. The prepared materials were nano-structured, porous and highly homogeneous. The phase constituents, spectral characteristics, particle properties, elements analysis and microstructure of the samples were studied by XRD, FTIR, particle size analysis, EDAX and SEM techn...
international journal for research in applied science and engineering technology ijraset, 2020
In the present research work, for solid oxide fuel cell, nano composite anode materials were synthesized using nickel oxide and gadolinium doped ceria (GDC20) and. Anode materials prepared for low temperature operating solid oxide fuel cells, from metallic NiO and ceramic GDC20 powders. These are mechanically mixed as X (NiO) +1-X (Ce 0.8 Gd 0.2 O 2-δ) where (X = 30, 40 ,45,50,55,60 wt. %). The mixed powders were ground and pelletized with respect to X. All the samples were characterized after sintered at the temperature 1300 o C. Systematically studied the structure, purity, phase and structural parameters of as-synthesized NiO-GDC20 anode samples were carried out by XRD and SEM. Electrical characterizations such as A.C Conductivities and D.C conductivities were carried out using impedance spectroscopy and four probe D.C conductivity measurements respectively. The activation energies of the anode samples were estimated from 300-500 o C. The activation energies of A.C conductivities are observed that decrease with increase in frequencies.
Hydrogen, Fuel Cell & Energy Storage, 2022
In this study, nickel oxide-gadolinium doped ceria, NiO-GDC, composite powder was synthesized by the sol-gel method with a new Ni(II) complex. A new Ni(II) complex, chemical formula [Ni(μ-L)] n (NO 3) 2 , L = N'-(pyridine-2-yl)methylene) isonicotinohydrazide), was used as a new precursor. The new Ni(II) complex was prepared by a reaction between ligand, L, and Ni(NO 3).6H 2 O using the hydrothermal method. Then the NiO-GDC powders were synthesized using Ce(NO 3) 3 .6H 2 O, and Gd(NO 3) 3 .6H 2 O, and the as-synthesized new Ni(II) complex [Ni(μ-L)] n (NO 3) 2 with the sol-gel method. The NiO-GDC powder was modified to increase the performance of solid oxide fuel cells (SOFCs) operating at intermediate temperatures (600-800 ℃) by increasing the three-phase boundary region in the anode. Finally, the NiO-GDC anode powders prepared with the new precursor were compared with the NiO-GDC anode powders synthesized from metal nitrates as a precursor. The results showed that the modified NiO-GDC anode had more three-phase boundaries, TPB, a more uniform microstructure, a higher specific surface area, and a porous structure that effectively improved the electrochemical performance of the electrode. SOFC half-cell resistance with this high-performance anode decreased by 85 % at 800 ℃ compared to conventional half-cells.
Electrochemical Performance of Ni-CGO Nano-Grained Thin Film Anodes for Micro SOFCs
ECS Transactions, 2007
NiO-Ce 0.8 Gd 0.2 O 1.9-x (CGO) thin film anodes with thicknesses around 400 nm were prepared by air blast spray pyrolysis. The film composition was 60/40 vol% Ni/CGO in the reduced state. The films were deposited on tape-cast YSZ electrolytes. The material was amorphous after deposition and was crystallized by sintering in air between 650 and 1200°C. The temperature treatment resulted in films with average grain sizes of the NiO and CGO grains between 5 and 250 nm. The area specific resistance of the thin film anodes was measured in a humidified 1:4 H 2 :N 2 atmosphere as a function of grain size within the temperature interval of 400-600°C. The area specific resistance (ASR) was predominantly depending on the grain size of the films. At 550°C, an ASR of 0.5 Ωcm 2 was found for the 5 nm grain size anode. The value increased to 30 Ωcm 2 for the 250 nm grain size anode.