Tailoring gadolinium-doped ceria-based solid oxide fuel cells to achieve 2 W cm(-2) at 550 °C (original) (raw)
Related papers
Low temperature anode-supported solid oxide fuel cells based on gadolinium doped ceria electrolytes
Journal of Power Sources, 2007
The utilization of anode-supported electrolytes is a useful strategy to increase the electrical properties of the solid oxide fuel cells, because it is possible to decrease considerably the thickness of the electrolytes. We have successfully prepared single-chamber fuel cells of gadolinium doped ceria electrolytes Ce 1−x Gd x O 2−y (CGO) supported on an anode formed by a cermet of NiO/CGO. Mixtures of precursor powders of NiO and gadolinium doped ceria with different particle sizes and compositions were analysed to obtain optimal bulk porous anodes to be used as anode-supported fuel cells. Doped ceria electrolytes were prepared by sol-gel related techniques. Then, ceria-based electrolytes were deposited by dip coating at different thicknesses (15-30 m) using an ink prepared with nanometric powders of electrolytes dispersed in a liquid polymer. Cathodes of La 1−x Sr x CoO 3 (LSCO) were also prepared by sol-gel related techniques and were deposited on the electrolyte thick films. Finally, electrical properties were determined in a single-chamber reactor where propane, as fuel, was mixed with synthetic air below the direct combustion limit. Stable density currents were obtained in these experimental conditions. Flux rate values of the carrier gas and propane partial pressure were determinants for the optimization of the electrical properties of the fuel cells.
Journal of Electroceramics, 2005
In this study, we report key functional properties of gadolinium-doped ceria (Gd 0.1 Ce 0.9 O 1.95 , GDC) sintered at low temperatures as well as single-cell electrochemical performance of a single-cell prepared there of. GDC solid solutions were sintered at various temperatures ranging 1100-1400 • C and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), density measurements, mechanical strength tests and electrical conductivity measurements. The dry-pressed GDC disc sample sintered at 1100 • C was found to have 96% of the theoretical density and higher sintering temperatures led to higher densities. SEM micrographs of the fracture and plan surfaces of the sintered discs established the absence of any open pores. The sample sintered at 1100 • C exhibited high electrical conductivity of 0.027 S/cm at 650 • C. The mechanical strength of the sintered samples was determined to be in the range of 150-175 MPa. Greater than 96% of theoretical density, good mechanical strength, and high electrical conductivity of GDC disc samples sintered at 1100 • C established the viability of low-temperature processing of GDC for its use as an SOFC electrolyte. Accordingly, a single-cell was prepared by co-sintering of GDC electrolyte and LSCF-GDC cathode at 1100 • C and subsequent firing of CuO-GDC anode at 900 • C. The electrochemical performance of the cell was evaluated in H 2 fuel at 650 • C.
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.
Ceramics International, 2020
The gadolinium-doped ceria is investigated as electrolyte materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) due to its oxide ion conductivity. The doping of Gd 3+ to Ce 4+ can introduce a small strain in the lattice thereby improved conductivity with low activation energy is expected. The 20 mol. % gadolinium doped ceria (Ce 0.8 Gd 0.2 O 2− δ) nanocrystalline powder is prepared here by citrate-complexation method. The XRD, Rietveld refinement, FTIR, UV-Visible, FESEM/EDX, and a c-impedance techniques are used to characterize this sample. The oxide ion conductivity is determined between 523 − 1023 K. The Ce 0.8 Gd 0.2 O 2− δ shows highest oxide ion conductivity of 6.79 × 10 − 3 S cm − 1 and 1.11 × 10 − 2 S cm − 1 at 973 K and 1023 K, respectively. The Ce 0.8 Gd 0.2 O 2− δ showed lower activation energies of 1.09, 0.70, and 0.88 eV for grain, grain boundary, and total conduction, respectively. Thus, the nano crystalline Ce 0.8 Gd 0.2 O 2− δ is proposed as potential electrolyte for IT-SOFCs.
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.
Electrolyte materials for solid oxide fuel cells derived from metal complexes: Gadolinia-doped ceria
Ceramics International, 2012
Gadolinia doped ceria (GDC) powders with different gadolinium contents were successfully prepared by the thermal decomposition of ceria complexes. All the calcined powder samples were found to be ceria-based solid-solutions having a fluorite-type structure. The powders were coldisostatically pressed and sintered in air at 1500 8C for 5 h to attain a sintered density of about 90% of its theoretical value. The electrical conductivity of the GDC pellets in air was studied as a function of temperature in the 225-700 8C range, by using two-probe electrochemical impedance spectroscopy measurements. The highest total conductivity (s 600 8C = 0.025 S/cm) was found for the Ce 0.85 Gd 0.15 O 1.925 composition.
Gd3+ and Sm3+ co-doped ceria based electrolytes for intermediate temperature solid oxide fuel cells
Electrochemistry communications, 2004
Co-doped ceria of Ce 1Àa Gd aÀy Sm y O 2À0:5a , wherein a ¼ 0:15 or 0.2, 0 6 y 6 a, were prepared for intermediate temperature solid oxide fuel cells (ITSOFCs). Their structures and ionic conductivities were characterized by X-ray diffraction and AC impedance spectroscopy. All the electrolytes were found to be ceria based solid solutions of fluorite type structures. However, co-doping effect was observed more apparent for the electrolytes with a ¼ 0:15 than for those with a ¼ 0:2. In comparison to the singly doped ceria, the co-doped ceria of Ce 0:85 Gd 0:15Ày Sm y O 1:925 , wherein 0:05 6 y 6 0:1, showed much higher ionic conductivities at 773-973 K. These co-doped ceria are more ideal electrolyte materials of ITSOFCs.
Composite electrolyte Gadolinium-doped ceria Gadolinium-doped barium cerate a b s t r a c t Composite electrolytes for Intermediate Temperature Solid Oxide Fuel Cell (ITSOFC) based on BaO-CeO 2 -GdO 1.5 ternary system have been synthesized through conventional solid state reaction route. X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) studies confirm a two-phase microstructure. The bulk conductivity in air is found to increase with BaO content, in the temperature range of 150-250 C, while the total conductivity in air at 800 C decreases with BaO content. At 800 C, the Open Cell Voltage (OCV) of Solid Oxide Fuel Cells (SOFCs) constructed using these electrolytes is higher than those for Ce 0.8 Gd 0.2 O 1.9 . .in (P. Gopalan).
Journal of the American Ceramic Society, 2002
Cation-doped CeO 2 electrolyte has been evaluated in singlecell and short-stack tests in solid oxide fuel cell environments and applications. These results, along with conductivity measurements, indicate that an ionic transference number of ϳ0.75 can be expected at 800°C. Single cells have shown a power density >350 mW/cm 2. Multicell stacks have demonstrated a peak performance of >100 mW/cm 2 at 700°C using metallic separators.
International Journal of Hydrogen Energy, 2013
Electrolyte Solegel Impedance spectroscopy Solid oxide fuel cells a b s t r a c t High performance solid oxide fuel cells (SOFCs) based on gadolinia-doped ceria (GDC) electrolyte are demonstrated for intermediate temperature operation. The inherent technical limitations of the GDC electrolyte in sinterability and mechanical properties are overcome by applying solegel coating technique to the screen-printed film. When the quality of the electrolyte film is enhanced by the additional solegel coating, the OCV and maximum power density increase from 0.73 to 0.90 V and from 0.55 to 0.95 W cm À2 , respectively, at 650 C with humidified hydrogen (3% H 2 O) as fuel and air as oxidant. The impedance analysis reveals that the reinforcement of the thin electrolyte with solegel coating significantly reduces the polarization resistance. Elementary reaction steps for the anode and cathode are analyzed based on the systematic impedance study, and the relation between the structural integrity of the electrolyte and the electrode polarization is discussed in detail.