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1.
Proton-conducting solid oxide fuel cells, incorporating BaZr0.1Ce0.7Y0.2O3−δ (BZCY) electrolyte, NiO–BZCY anode, and Sm0.5Sr0.5CoO3−δ–Ce0.8Sm0.2O2−δ (SSC–SDC) cathode, were successfully fabricated by a combined co-pressing and printing technique after a one-step co-firing process at 1100, 1150, or 1200 °C. Scanning electron microscope (SEM) results revealed that the co-firing temperature significantly affected not only the density of the electrolyte membrane but the grain size and porosity of the electrodes. Influences of the co-firing temperature on the electrochemical performances of the single cells were also studied in detail. Using wet hydrogen (2% H2O) as the fuel and static air as the oxidant, the cell co-fired at 1150 °C showed the highest maximum power density (PDmax) of 552 and 370 mW cm−2 at 700 and 650 °C, respectively, while the one co-fired at 1100 °C showed the highest PDmax of 276 and 170 mWcm−2 at 600 and 550 °C, respectively. The Arrhenius equation was proposed to analyze the dependence of the PDmax on the operating temperature, and revealed that PDmax of the cell co-fired at a lower temperature was less dependent on operating temperature. The influences of the co-firing temperature on the resistances of the single cells, which were estimated from the electrochemical impedance spectroscopy measured under open circuit conditions, were also investigated.  相似文献   

2.
Diffusion behavior of Ni during high temperature co-sintering was quantitatively investigated for anode-supported solid oxide fuel cells (SOFCs) that had BaZr0.1Ce0.7Y0.1Yb0.1O3?δ (BZCYYb) proton-conducting electrolyte and NiO-BZCYYb anode. Although diffused Ni in such SOFCs effectively acts as a sintering aid to densify the BZCYYb electrolyte layer, it often negatively affects the electrolyte conductivity. In the present study, field emission electron probe microanalysis (with wavelength dispersive X-ray spectroscopy) clearly revealed that Ni diffused into the BZCYYb electrolyte layer, and that the amount of diffused Ni increased with increasing co-sintering temperature. In particular, relatively high Ni concentration within the electrolyte layer was observed near the electrolyte/anode interface, e.g., approximately 1.5 and 2.8 wt% at co-sintering temperature of 1300 and 1400 °C, respectively. Electrochemical measurements showed that, compared with the lower co-sintering temperatures (1300–1350 °C), the highest co-sintering temperature (1400 °C) led to the highest ohmic resistance because of lower electrolyte conductivity. These results suggest that high co-sintering temperature causes excessive Ni diffusion into the BZCYYb electrolyte layer, thus degrading the intrinsic electrolyte conductivity and consequently degrading the SOFC performance.  相似文献   

3.
The effects of palladium (Pd) on Sm0.2Ce0.8O2−δ coated Sr0.92Y0.08TiO3−δ (SDC/SYT) anodes were investigated for H2 and CH4 fuels. The electrochemical oxidations of both H2 and CH4 were accelerated by Pd impregnation. Moreover, Pd in the SDC/SYT (Pd-SDC/SYT) anode improved the cell performance by a factor of approximately 2 for H2 and 1.5 for CH4. The open circuit voltage (OCV) of the wet CH4 fuel increased with increasing temperature for both the SDC/SYT anode cell and Pd-SDC/SYT anode cell, which differs from that of the H2 fuel. Notably, the OCV values of the Pd-SDC/SYT anode cell using wet CH4 were much higher than those using wet H2. We observed differing potentials for the reformed gases after the out-of-cell catalyst experiment, and the CH4 fuel with the Pd-SDC catalyst layer agreed well with the OCVs of the Pd-SDC/SYT anode cell with directly introduced wet CH4 fuel. These results indicate the OCVs were higher than the theoretical values based on electrochemical hydrogen oxidation at increased temperatures in the Pd-SDC/SYT anode cell because of the lower water partial pressure caused by the increased steam reformation activity of Pd.  相似文献   

4.
A novel liquid-phase synthesis strategy is demonstrated for the preparation of the Nb-containing ceramic oxide SrCo0.9Nb0.1O3-δ (SCN). In comparison with the traditional solid-state reaction (SSR) method, the liquid-phase synthesis route offers a couple of advantages, including a lower phase formation temperature and a smaller particle size of the SCN materials that are beneficial for applications as proton-conducting fuel cell cathode. With BaCe0.4Zr0.4Y0.2O3-δ (BCZY442) as the electrolyte and the SCN synthesized in this work as the cathode, a proton-conducting solid oxide fuel cell (SOFC) shows a peak power density of 348 mW cm?2 at 700 °C, significantly higher than that of a SOFC fabricated with SCN cathode prepared using the SSR method, which can only deliver 204 mW cm?2 at the same temperature. Additionally, this new synthesis strategy allows impregnation of Sr2+, Co3+and Nb5+ on the solid backbone in aqueous solution, further improving cell performance to reach a peak power density of 488 mW cm?2 at 700 °C.  相似文献   

5.
Haitao Gu 《Electrochimica acta》2009,54(13):3532-3537
Electrochemical properties of Co-doped Sr0.8Ce0.2MnO3−δ cathode were investigated at the cathode/Sm0.2Ce0.8O1.9 electrolyte interface. The electrochemical impedance spectroscopy was measured under applied cathodic voltages (E = −0.4 to 0 V). At E = 0 V, the area-specific resistance decreased from 2.20 Ω cm2 to 0.19 Ω cm2 at 700 °C with Co doping. Under the cathodic polarization, the rate determining step of oxygen reduction process was different for both cathodes: the charge transfer for Sr0.8Ce0.2MnO3−δ and the diffusion process for Sr0.8Ce0.2Mn0.8Co0.2O3−δ. Besides, the overpotential also decreased from 124 mV to 19 mV at the current density of 0.1 A cm−2 at 800 °C with Co doping. The improved electrochemical properties of Co-doped Sr0.8Ce0.2MnO3−δ can be ascribed to the formation of more oxygen vacancies and more active sites for oxygen reduction reaction.  相似文献   

6.
La0.8Sr0.2MnO3-δ-Ce0.9Gd0.1O1.95 (LSM-CGO) nanostructured cathodes are successfully prepared in a single process by a chemical spray-pyrolysis deposition method. The cathode is composed of nanometric particles of approximately 15 nm of diameter, providing high triple-phase boundary sites for the oxygen reduction reactions. A low polarization resistance of 0.046 Ω cm2 is obtained at 700 °C, which is comparable to the most efficient cobaltite-based perovskite cathodes. A NiO-YSZ anode supported fuel cell with the nanostructured cathode generates a power output of 1.4 W cm?2 at 800 °C, significantly higher than 0.75 W cm?2 for a cell with conventional LSM-CGO cathode. The results suggest that this is a promising strategy to achieve high efficiency electrodes for Solid Oxide Fuel Cells in a single preparation step, simplifying notably the fabrication process compared to traditional methods.  相似文献   

7.
In order to clarify the effect of grain size on the electrical performance of BaZr0.1Ce0.7Y0.1Yb0.1O3-δ (BZCYYb) solid electrolytes with addition of NiO, microcrystalline (~1.5?µm) and ultrafine-grained (~280?nm) BZCYYb electrolytes (with 1?wt% NiO) were fabricated by the conventional and two-step sintering method, respectively. The results show that compared with microcrystalline electrolytes, the ultrafine-grained electrolytes have similar grain-interior conductivities, but much lower grain-boundary conductivities, illustrating that the grain boundary is not conducive for ionic transport. As a result, the electrical conductivity of microcrystalline electrolytes (1.9?×?10?2 S?cm?1 at 600?°C in wet air) is higher than that of ultrafine-grained electrolytes (1.1?×?10?2 S?cm?1 at 600?°C in wet air). In addition, the OCV (open-circuit voltage) values of electrolyte-supported single cells show that the undesired electronic conduction exists in the electrolytes due to the BaY2NiO5 impurity formed by the reaction of NiO and BZCYYb. The ultrafine-grained electrolytes show lower OCV values than that of microcrystalline ones, due to the prolonged electronic transport paths. Therefore, large-grained or grain boundary-free microstructure are necessary for improving the electrical performance of BZCYYb electrolytes.  相似文献   

8.
《Ceramics International》2017,43(14):10960-10966
In this research, nanofiber-structured Pr0.4Sr0.6Co0.2Fe0.7Nb0.1O3-δ (PSCFN) electrode scaffolds were impregnated with Gd0.2Ce0.8O1.9 (GDC) nanoparticles to prepare PSCFN-GDC nanofiber-structured composite electrodes, which could function well as a novel electrode material for symmetrical solid oxide fuel cells (SSOFCs). The polarization resistances of PSCFN-GDC (1:0.56) composite electrodes as cathode and anode were 0.044 and 0.309 Ω cm2 at 800 °C, respectively, indicating that the composite electrodes demonstrated excellent electrochemical performances for both oxygen reductions and fuel oxidation reactions. La0.8Sr0.2Ga0.8Mg0.2O3-δ (LSGM) electrolyte-supported single cells with the PSCFN-GDC symmetrical composite electrodes showed excellent long-term stability in wet H2 (97% H2-3% H2O) and wet CH4 (97% CH4-3% H2O) for 100 h with constant current density at 800 °C. A conversion electrode method was applied by interchanging the atmosphere of cathode and anode to solve the problem of PSCFN-GDC symmetrical single cell's carbon deposition in wet CH4. After working three cycles for 384 h, carbon deposition was not found in the symmetrical electrode scaffold. Taken together, the results described above demonstrated that the PSCFN-GDC composite material acted as a promising symmetrical electrode for SSOFCs, and the conversion electrode method would make for a good application to process carbon deposition generated by hydrocarbon fuels.  相似文献   

9.
Haitao Gu 《Electrochimica acta》2009,54(27):7094-9945
The electrochemical properties of LaBaCo2O5+δ-xSm0.2Ce0.8O1.9 (LBCO-xSDC, x = 20, 30, 40, 50, 60, wt%) were investigated for the potential application in intermediate-temperature solid oxide fuel cells (IT-SOFCs). The LBCO-50SDC composite cathode exhibited the best electrochemical performance in the LBCO-xSDC cathodes. With x = 50 wt%, the ASR was 1.308 Ω cm2 at 500 °C (0.267 Ω cm2 at 600 °C and 0.052 Ω cm2 at 700 °C). The maximum of exchange current density i0 was 0.5630 A cm−2 at 700 °C. The improved electrochemical properties of LBCO-50SDC were ascribed to the porous structures of the cathode and more cathode/electrolyte/gas triple phase boundary (TPB) areas.  相似文献   

10.
The performance of the LaBaCuFeO5+δ-Ce0.8Sm0.2O1.9 (LBCF-SDC) composite cathodes was studied in this paper. Electrical conductivity, thermal expansion and electrochemical properties were investigated by four probing DC technique, dilatometry, AC impedance and polarization techniques, respectively. The thermal expansion coefficients of the LBCF-SDC were between (16.3 and 13.4) × 10−6 K−1 from 30 to 850 °C, which was lower value than LBCF (17.0 × 10−6 K−1). AC Impedance spectroscopy measurements of LBCF-SDC/SDC/LBCF-SDC test cell were carried out. Polarization resistance values for the LBCF-SDC10 cathode was as low as 0.097 Ω cm2 at 750 °C.  相似文献   

11.
To produce a Nd1.8Ce0.2CuOδ solid solution, the oxide form of the reagents were milled for 36 h and sintered at 1173 K for 8 h in a microwave furnace. The transition from a negative temperature coefficient (NTC) of conductivity to a positive temperature coefficient (PTC) was suppressed due to the submicron size of the crystallites. The low-frequency response in the complex impedance plane fit the Gerischer element. At 973 K, the area specific resistance (ASR) of Nd1.8Ce0.2CuOδ/GDC/Nd1.8Ce0.2CuOδ sintered at 1073 K for 2 h was 1.92 ohm cm2.  相似文献   

12.
Composite cathodes with La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) and Ce0.9Gd0.1O1.95 (GDC) are investigated to assess for solid oxide fuel cell (SOFC) applications at relatively low operating temperatures (650–800 °C). LSCF with a high surface area of 55 m2g−1 is synthesized via a complex method involving inorganic nano-dispersants. The fuel cell performances of anode-supported SOFCs are characterized as a function of compositions of GDC with a surface area of 5 m2g−1. The SOFCs consist of the following: LSCF-GDC composites as a cathode, GDC as an interlayer, yttrium stabilized zirconia (YSZ) as an electrolyte, Ni-YSZ (50: 50 wt%) as an anode functional layer, and Ni-YSZ (50: 50 wt%) for support. The cathodes are prepared for 6LSCF-4GDC (60: 40 wt%), 5LSCF-5GDC (50: 50 wt%), and 4LSCF-6GDC (40: 60 wt%). The 5LSCF-5GDC cathode shows 1.29 Wcm−2, 0.97 Wcm−2, and 0.47 Wcm−2 at 780 °C, 730 °C, and 680 °C, respectively. The 6LSCF-4GDC shows 0.92 Wcm−2, 0.71 Wcm−2, and 0.54 Wcm−2 at 780 °C, 730 °C, and 680 °C, respectively. At 780 °C, the highest fuel cell performance is achieved by the 5LSCF-5GDC, while at 680 °C the 6LSCF-4GDC shows the highest performance. The best composition of the porous composite cathodes with LSCF (55 m2g−1) and GDC (5 m2g−1) needs to be considered with a function of temperature.  相似文献   

13.
In the present study, a nanocomposite cathode comprising Fe rich La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) based pervoskite semiconductor oxide and Sm-Gd co-doped ceria rich Ce0.8Sm0.1Gd0.1O1.90 (CSGO) in the ratio of 1:1 has been successfully synthesized by a simple glycine nitrate auto combustion method. The structural properties of the two phase nanocomposite were evaluated by X-ray diffraction and Raman spectroscopy. A detailed electrical properties of co-doped LSCF-CSGO nanocomposites have been studied with a comparison of LSCF added with 10?mol% and 20?mol% Gd singly doped ceria (LSCF-GDC10 and LSCF-GDC20) nanocomposites as a function of temperature in the range of 673–1073?K at air atmosphere by AC impedance spectroscopy. The total electrical conductivity of the co-doped LSCF-CSGO nanocomposites has been found to be 0.043?S?cm?1 at 973?K which is higher than that of the LSCF composite containing singly doped compositions. The Sm co-doping in GDC phase has effectively helped to reduce the undesired electronic conduction produced in the doped ceria as the electron concentration of LSCF-CSGO was found to be ??2.62?×?1015 cm?3 which was lower than the electron concentration of LSCF containing singly doped nanocomposite (LSCF-GDC20, ??2?×1016 cm?3) estimated by Hall-Effect measurement. The activation energy of LSCF-CSGO nanocomposite has been found to be 0.05?eV for the oxygen reduction reaction by temperature dependent Arrhenius equation. The improved electrical properties in terms of high ionic conductivity and low activation energy have been achieved through the incorporation of Sm into GDC10 electrolyte phase in LSCF nanocomposite. The combustion synthesis method has also effectively helped to produce microstructure containing large grain size (~?6?µm) which is beneficial for enlarging triple phase boundary (TPB) area of cathodes utilized in solid oxide fuel cells (SOFC) operated at reduced/intermediate temperature (673–973?K).  相似文献   

14.
The LaBaCo2O5+δx wt.% Bi2O3 (LBCO-xBi2O3, x=10, 20, 30, and 40) were prepared as composite cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs) via the conventional mechanical mixing method. The effect of Bi2O3 on polarization resistance, overpotential, and long-term stability of the LBCO cathode was investigated. An effective sintering aid for LBCO cathode, Bi2O3 not only lowers its sintering temperature by ~200 °C, but also improves the electrochemical performance within the intermediate temperature range of 600–800 °C. Electrochemical impedance spectroscopy measurements showed that the addition of 20 wt% Bi2O3 to LBCO exhibited the lowest area-specific resistance of 0.020 Ω cm2 at 800 °C in air, which was about a seventh of that of the LBCO cathode at the same condition. At a current density of 0.2 A cm−2, the cathodic overpotential of LBCO-20Bi2O3 was about 12.6 mV at 700 °C, while the corresponding value for LBCO was 51.0 mV. Compared to B2O3–Bi2O3–PbO frit, the addition of Bi2O3 significantly improved the long-term stability of cathode. Therefore, LBCO-20Bi2O3 can be a promising cathode for IT-SOFCs.  相似文献   

15.
This study investigates the structure, phase stability, and electrical properties of BaCe0.8Y0.2−xNdxO3−δ (x = 0-0.2) in humid air. XRD results indicate that a BaCe0.8Y0.2−xNdxO3−δ sample has an asymmetric orthorhombic structure, and this structure becomes more symmetric as the amount of Nd doping increases. The conductivity of BaCe0.8Y0.2−xNdxO3−δ depends on the amount of Nd doping and the operation temperature. AC impedance results indicate that the resistance of BaCe0.8Y0.2−xNdxO3−δ decreases as the temperature increases, with the majority of resistance coming from oxygen ion diffusion. The XRD peak intensity of BaCe0.8Y0.2O3−δ apparently decreased with time, forming Ba(OH)2 and CeO2 second phases. The phase stability of BaCe0.8Y0.2−xNdxO3−δ (x = 0.05-0.2) samples is much better than that of BaCe0.8Y0.2O3−δ, and it exhibited no second phase after tested in an 80 °C water bath for 18 h.  相似文献   

16.
The key issue that limits the electrochemical performance of proton-conducting solid oxide fuel cells (H+-SOFCs) is the sluggish kinetics of the oxygen reduction reaction (ORR) of cathode at intermediate and low temperatures. Herein, oxygen vacancy engineering is conducted on cobalt-free Ba0.95La0.05FeO3?δ (BLF) by nickel substitution, which is confirmed by density functional theory computations. Nickel-substituted BLF material (Ba0.95La0.05Fe1?xNixO3?δ (x = 0, 0.1, 0.2, 0.3)) can promote the generation of oxygen vacancies and improve catalytic activity, which is found to be in line with the experimental results of XPS. The phase structure, microstructure, and electrochemical performance of Ba0.95La0.05Fe0.8Ni0.2O3?δ (BLFNi0.2) are well-investigated. The single cells with the BLFNi0.2-BaCe0.7Zr0.1Y0.1Yb0.1O3?δ (BCZYYb) composite cathode achieve low polarization resistance (Rp) of 0.099 Ω cm2 and a peak power density of 631 mW cm?2 at 700 °C while maintaining good durability for 120 h with no observable degradation. The results demonstrate that Ni-doped BLF is a promising cobalt-free cathode material for H+-SOFCs.  相似文献   

17.
《Ceramics International》2015,41(7):8411-8416
In this work, we examine the benefits of alternative powder processing methods, with a primary focus on microwave-based synthesis, that could both lower material manufacturing costs and further enhance cathode performance for solid oxide fuel cell applications. La0.3Ca0.7Fe0.7Cr0.3O3−δ (LCFCr), formed using conventional solid-state methods, has been shown in earlier work to be a very promising catalyst for the oxygen reduction reaction. To further increase its performance, microwave methods were used to increase the surface area of LCFCr and to decrease the synthesis time. It was found that the material could be obtained in crystalline form in only 7 h, with the synthesis temperature lowered by roughly 300 °C as compared to conventional methods.  相似文献   

18.
采用柠檬酸–硝酸盐燃烧法制备了质子导体固体氧化物燃料电池(SOFC)电解质材料BaZr0.7Pr0.1Y0.2O3–δ(BZPY)和BaZr0.7Pr0.1Y0.16Zn0.04O3–δ(BZPYZn)。研究了Zn掺杂对材料烧结、热膨胀系数和电性能的影响;利用X射线衍射仪和扫描电子显微镜对样品物相和微观结构进行了表征。结果表明:BZPYZn经1 100℃煅烧5h后呈单一的钙钛矿结构。随烧结温度的升高(从1 300℃到1400℃),BZPYZn陶瓷体的晶粒尺寸增大,而孔隙率减小;1350℃保温5h烧结的BZPYZn陶瓷样品的相对密度达到97.3%;500~800℃范围内,离子电导率介于10–3~10–2S/cm之间。室温至1 000℃范围内,样品的热膨胀系数为9.2×10–6/K,表明其与电极材料(Ni)的热匹配性好。预示BZPYZn有望成为良好的质子传导型中温SOFC电解质材料。  相似文献   

19.
Perovskite-type Ce0.9Sr0.1Cr0.5Mn0.5O3−δ (CSCMn) was synthesized and evaluated as anode for solid oxygen fuel cells based on Ce0.8Sm0.2O1.9 (SDC). The conductivities of CSCMn were evaluated with DC four-probe method in 3% H2-N2 and 5% H2S-N2 at 450–700 °C, respectively. The compositions of CSCMn powders were studied by XRD and thermodynamic calculations. Meanwhile, sintering temperatures affecting phases of CSCMn is also proposed with XRD, and the analysis is given with thermodynamic calculations. CSCMn exhibits good chemical compatibility with electrolyte (SDC) in N2. After exposure to 5% H2S-N2 for 5 h at 800 °C, CSCMn crystal structures change and some sulfides are detected, as evidenced by XRD and Raman analyses. The electrochemical properties are measured for the cell comprising CSCMn-SDC/SDC/Ag in 5% H2S-N2 at 600 °C and in 3% H2-N2 at 450 and 500 °C. The electrochemical impedance spectrum (EIS) is used to analyze ohm and polarization resistance of the cell at various temperatures.  相似文献   

20.
Layered perovskite oxides have ordered A-cations localizing oxygen vacancies, and may potentially improve oxygen ion diffusivity and surface exchange coefficient. The A-site-ordered layered perovskite PrBa0.5Sr0.5Co2O5+δ (PBSC) was evaluated as new cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). The material was characterized using electrochemical impedance spectroscopy in a symmetrical cell system (PBSC/Ce0.9Sm0.1O1.9 (SDC)/PBSC), exhibiting excellent performance in the intermediate temperature range of 500-700 °C. An area-specific-resistance (ASR) of 0.23 Ω cm2 was achieved at 650 °C for cathode polarization. The low activation energy (Ea) 124 kJ mol−1 is comparable to that of La0.8Sr0.2CoO3−δ. A laboratory-scaled SDC-based tri-layer cell of Ni-SDC/SDC/PBSC was tested in intermediate temperature conditions of 550 to 700 °C. A maximum power density of 1045 mW cm−2 was achieved at 700 °C. The interfacial polarization resistance is as low as 0.285, 0.145, 0.09 and 0.05 Ω cm2 at 550, 600, 650 and 700 °C, respectively. Layered perovskite PBSC shows promising performance as cathode material for IT-SOFCs.  相似文献   

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