This study focuses on the impact of Gd^(3+),Sm^(3+),Er^(3+).Y^(3+),and Bi^(3+)multi-doping on the crystal structure,microscopic surface features,and ionic conductivity of cerium dioxide in the Ce_(1-x)(Gd_(1/5)Sm_(1/5...This study focuses on the impact of Gd^(3+),Sm^(3+),Er^(3+).Y^(3+),and Bi^(3+)multi-doping on the crystal structure,microscopic surface features,and ionic conductivity of cerium dioxide in the Ce_(1-x)(Gd_(1/5)Sm_(1/5)Er_(1/5)Y_(1/)_5Bi_(1/5))_(x)O_(2-δ)(GSEYB)system.This system holds promise as a solid electrolyte material for low and medium-temperature solid oxide fuel cells.The powders of Ce_(1-x)(Gd_(1/5)Sm_(1/5)Er_(1/5)Y_(1/5)Bi_(1/5))_(x)O_(2-δ)(x=0,0.10,0.15,0.20,0.25,0.30)were synthesized using the solid-phase reaction method.The GSEYB electrolytes were comprehensively investigated for their phase structure,microstructure,oxygen vacancy concentration,and ionic conductivity using X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),and impedance spectroscopy.XRD diffraction patterns confirm a cubic fluorite-type structure with Fm3m space groups in all multi-doped systems.After sintering at 1400℃for 10 h,the relative density of doped samples exceeds 96%.In terms of electrical properties,the Ce_(0.75)Gd_(0.05)Sm_(0.05)Er_(0.05)Y_(0.05)Bi_(0.05)O_(2-δ)(x=0.25)electrolyte exhibits the highest ionic conductivity(σ_(t)=4.45×10^(-2)S/cm)and the lowest activation energy(E_(a)=0.79 eV)at 800℃.The coefficient of thermal expansion of the developed electrolyte aligns well with that of the commonly used electrode materials.This compatibility positions it as a highly promising candidate for utilization as an electrolyte material in solid oxide fuel cells(SOFCs).展开更多
The development of cost-effective solid oxide fuel cells(SOFCs)is crucial for the large-scale application.In this study,anode-supported SOFC single cells were fabricated using a combination of slurry spraying and spin...The development of cost-effective solid oxide fuel cells(SOFCs)is crucial for the large-scale application.In this study,anode-supported SOFC single cells were fabricated using a combination of slurry spraying and spin-coating technique to achieve a dense Yttria Stabilized Zirconia(YSZ)electrolyte layer while maintaining low production cost.The electrochemical performance of the fabricated SOFC was evaluated using hydrogen and dry methane as fuels.Microstructural analysis confirmed that the YSZ electrolyte exhibited high densification with a thickness of approximately 10μm,ensuring excellent gas-tightness and preventing fuel crossover.The NiO-YSZ anode demonstrated favorable porosity,with well-sintered NiO particles forming a robust framework to facilitate electrochemical reactions.Performance evaluations revealed that under hydrogen operation,the SOFC achieved a peak power density of 1.408 W/cm^(2)at 1000℃,with open-circuit voltages(OCVs)closely matching theoretical predictions.When operated with dry methane,the SOFC maintained stable performance,reaching a peak power density of 0.96 W/cm^(2)at 1000℃,highlighting its potential for direct hydrocarbon utilization.Gas composition analysis of the anode exhaust confirmed the absence of excessive carbon deposition,indicating the effectiveness of the anode microstructure in mitigating coking during methane oxidation.These findings demonstrate that the spray-coated and spin-coated SOFC design offers a promising approach to improving fuel cell efficiency and cost-effectiveness.Future research should focus on optimizing electrolyte fabrication methods and enhancing anode stability in hydrocarbon-fueled operation to further advance the commercialization of SOFC technology.展开更多
A sol-gel method and a modified chemical vapour deposition technique were used to produce nanostructured Ce0.6Sr0.4Fe0.8Co0.2O3-δ materials at temperatures as low as 400 ℃. Powders were characterized using Fourier t...A sol-gel method and a modified chemical vapour deposition technique were used to produce nanostructured Ce0.6Sr0.4Fe0.8Co0.2O3-δ materials at temperatures as low as 400 ℃. Powders were characterized using Fourier transform infrared spectroscopy （FTIR）, Raman spectroscopy, thermo gravimetric analysis, powder X-ray diffraction （XRD）, scanning electron microscopy （SEM） with energy dispersive X-ray spectroscopy, high resolution transmission electron microscopy （HRTEM）, and nitrogen sorption at 77 K. FTIR spectra showed that the sol-gel method resulted in residual carbon groups on the materials after calcination, while the Raman and XRD analysis confirmed that both synthesis methods resulted in cubic perovskite structure. However, the chemical va- pour deposition （CVD） method resulted in materials with a smaller crystallite size when compared to those prepared via the sol-gel route. The overall morphology of the powders was irregularly shaped aggregated particles as observed by SEM and HRTEM. In addition, HRTEM analysis showed that the materials were highly crystalline. Textural analysis revealed the powders had some mesoporosity, and the surface areas were 76.69 and 65.90 m2/g for materials synthesized using the CVD and sol-gel methods, respectively. The synthesized perovskite powders were used to fabricate button cells employing samarium doped ceria （SDC） as the electrolyte and NiO/SDC as the anode materials. As cathode materials, the maximum power density observed was 308.4 mW/cm2 at 500℃.展开更多
As a mixed ion-electronic conductor, doped ceria, especially rare earth doped ceria, were used as anodes or components of anodes in SOFCs. In this work, calcium doped ceria （CCO） was synthesized to be used in interm...As a mixed ion-electronic conductor, doped ceria, especially rare earth doped ceria, were used as anodes or components of anodes in SOFCs. In this work, calcium doped ceria （CCO） was synthesized to be used in intermediate-temperature SOFCs （IT-SOFCs） anodes in order to reduce the cost of anode-supported SOFCs. Electrical conductivity of 20% calcium doped ceria （20CCO） reached 0.209 S·cm^-1 in hydrogen at 850 ℃, and 0.041 S·cm^-1 in air at 800℃, which is about 0.04 S·cm^-1 lower than that of conventional samaria-doped ceria （0.079 S·cm^-1）. Electrochemical performance of Ni-20CCO cermet as anode was investigated using a fuel cell with 35μm-thick SDC electrolyte and Sm0.5Sr0.5 Co-SDC cathode. Maximum power density was 623 mW·cm^-2 under humidified （3% H2O） hydrogen at 650 ℃, inferring high catalytic activity of the Ni-20CCO anode.展开更多
Herein,we report the synthesis of a Dy-Gd co-doped cubic phase-stabilized Bi_(2)O_(3) solid electrolyte system via solid-state processing under atmospheric conditions.Doping with Dy^(3+) and Gd^(3+) has been observed ...Herein,we report the synthesis of a Dy-Gd co-doped cubic phase-stabilized Bi_(2)O_(3) solid electrolyte system via solid-state processing under atmospheric conditions.Doping with Dy^(3+) and Gd^(3+) has been observed to significantly enhance the densification process during sintering for stabilization purposes,thereby improving the electrical properties of δ-Bi_(2)O_(3)-type polymorphs.The synthesized ceramics were characterized using X-ray diffraction(XRD),field emission scanning electron microscopy-energy dispersive X-ray spectroscopy(FESEM-EDX),thermal gravimetry/differential thermal analysis(TG/DTA),and the four-point probe technique(4PPT).XRD analysis reveals that the samples Bi_(1-x-y)Gd_(x)Dy_(y)O_(1.5)(y=0.05/x=0.05,0.10,0,15,and 0.20,and x=0.05/y=0.10,0.15,and 0.20) exhibit a stable face-centered cubic δ-phase and a mixed-phase crystallographic structure.The XRD analysis of the stabilized δ-phase suggests that the prepared oxides show a face-centered cubic(FCC) structure with a space group of Fm-3m.FESEM micrographs reveal that the composition Bi_(0.90)Gd_(0.05)Dy_(0.05)O_(1.5) has no significant holes.Nevertheless,an evident increase in the pore formation is observed as the amount of Gd_(2)O_(3) increases until it reaches 20%.This finding suggests that dense pellets are formed during the sintering process at 900-1000℃.The DTA analyses were performed to verify the phase stability,which agrees with the XRD results.The electrochemical performance of the synthesized Dy-Gd co-doped Bi_(2)O_(3)solid electrolyte system was evaluated and analyzed in detail by using the electrochemical impedance spectroscopy(EIS) technique,Based on EIS and conductivity measurements,Bi_(0.75)Gd_(0.20)Dy_(0.05)O_(1.5) exhibits the lowest activation energy of 0.519 eV and the highest conductivity value of 0.398 S/cm at 627℃compared to the other samples;this composition can be used as a solid electrolyte for intermediatetemperature solid oxide fuel cells(SOFCs).展开更多
Ni-Al_(2)O_(3)cermet supported tubular SOFC was fabricated by thermal spraying.Flame-sprayed Al_(2)O_(3)-Ni cermet coating plays dual roles of a support tube and an anode current collector.4.5mol.%yttria-stabilized zi...Ni-Al_(2)O_(3)cermet supported tubular SOFC was fabricated by thermal spraying.Flame-sprayed Al_(2)O_(3)-Ni cermet coating plays dual roles of a support tube and an anode current collector.4.5mol.%yttria-stabilized zirconia(YSZ)and 10mol.%scandia-stabilized zirconia(ScSZ)coatings were deposited by atmospheric plasma spraying(APS)as the electrolyte in present study.The electrical conductivity of electrolyte was measured using DC method.The post treatment was employed using nitrate solution infiltration to densify APS electrolyte layer for improvement of gas permeability.The electrical conductivity of electrolyte and the performance of single cell were investigated to optimize SOFC performance.The electrical conductivity of the as-sprayed YSZ and ScSZ coating is about 0.03 and 0.07 S·cm^(-1)at 1000℃,respectively.The ohmic polarization significantly influences the performance of SOFC.The maximum output power density at 1000℃increases from 0.47 to 0.76 W·cm^(-2)as the YSZ electrolyte thickness reduces from 100μm to 40μm.Using APS ScSZ coating of about 40μm as the electrolyte,the test cell presents a maximum power output density of over 0.89 W·cm^(-2)at 1000℃.展开更多
Eleven steel grades were designed to be used as metallic interconnects for Solid Oxide Fuel Cells (SOFC). Low carbon, high chromium steel with different additives of niobium, vanadium, aluminum, molybdenum, silicon, m...Eleven steel grades were designed to be used as metallic interconnects for Solid Oxide Fuel Cells (SOFC). Low carbon, high chromium steel with different additives of niobium, vanadium, aluminum, molybdenum, silicon, manganese and titanium were produced. Phase transformation temperatures;eutectoid temperature (Ac1) and temperature at which transformation of ferrite to austenite is completed during heating (Ac3) were measured by L75-76 dilatometer. The influence of the alloying elements on transformation temperatures was analyzed using MATLab. Considering the interaction between different alloying elements two equations for predicting Ac1 & Ac3 were obtained. The obtained Ac1 & Ac3 by these equations showed more compatibility than that obtained by traditional ones. In addition, the coefficients of thermal expansion of these steel grades were detected. The influences of chemical composition and temperature on the thermal expansion coefficient were analyzed;the obtained equations were verified to certain extent by using several kinds of steels. The predicted values were in good accordance with the experimental results which proof the validation of calculation model.展开更多
A new cathode material fabricated by solid state reaction method was reported. The SmVO4 powder was obtained by firing the mixture of Sm2O3 and V2O5 powders in the temperature range of 700-1200 ℃. Its structure was i...A new cathode material fabricated by solid state reaction method was reported. The SmVO4 powder was obtained by firing the mixture of Sm2O3 and V2O5 powders in the temperature range of 700-1200 ℃. Its structure was identified by X-ray diffraction method and the electrochemical properties of SmVO4 as cathodes for solid oxide fuel cells (SOFCs) were investigated in single unit cell at the temperature ranged from 450-550 ℃. The results of the single fuel cell unit show that the maximum current densities are 641, 797, 688 mA·cm-2 and the maximum power output are 165, 268, 303 mW·cm-2 and the open circuit voltage are 1.04, 0.96, 0.92 V at 450, 500 and 550 ℃, respectively.展开更多
The cathode material La1-xSrxCuO3-δ(x=0.15, 0.2, 0.3, 0.4) was synthesized by a sol-gel method. X-ray diffraction reveals that a single phase of perovskite is formed. The investigation of the electrical properties su...The cathode material La1-xSrxCuO3-δ(x=0.15, 0.2, 0.3, 0.4) was synthesized by a sol-gel method. X-ray diffraction reveals that a single phase of perovskite is formed. The investigation of the electrical properties suggests that La0.7Sr0.3CuO3-δ has the highest electrical conductivity. La0.7Sr0.3CuO3-δ powder was mixed with different amount SDC (Sm0.15Ce0.85O1.925) powder (5wt.%-30wt.%) as composite cathodes. Electrochemical properties of the composite cathodes were researched further. Investigation suggests that the addition of appropriate amount SDC to La0.7Sr0.3CuO3-δ can improve the electrochemical properties and obtain better cathodic performance. Using La0.7Sr0.3CuO3-δ-SDC composite materials as a cathode based on SDC electrolyte, higher current density and power density at intermediate temperatures can be obtained.展开更多
Glass-ceramics are often used as sealants in solid oxide fuel cells (SOFC). But interfacing components, such as ferritic stainless steel and YSZ electrolyte, may vary in their requirements regarding sealing properties...Glass-ceramics are often used as sealants in solid oxide fuel cells (SOFC). But interfacing components, such as ferritic stainless steel and YSZ electrolyte, may vary in their requirements regarding sealing properties, especially in terms of thermal expansion. A bilayered glass-ceramic system was developed to overcome the mismatch in coefficients of thermal expansion (CTE) between ferritic steel and YSZ. Therefore, two different glass-ceramics with slightly different CTEs were developed, one with good bonding characteristics to the ferritic steel and the other to the YSZ electrolyte. Steel and electrolyte components were coated with a layer of their corresponding glass sealant paste and heated up to form a sandwich sample. During the heat treatment of the sealing process, the glasses are crystallized into glass-ceramics. The resulting interface between the two glass-ceramics is of special interest. Cross-sections of the sandwich samples were cut, polished and investigated using SEM. The glass-ceramics show continuous, gap-free layers and excellent bonding to both steel and YSZ. Energy release rates are measured for single and bilayered glass sealants by mechanical testing. The designed bilayered glass-ceramics fulfill the special requirements of ferritic steel and YSZ. They show excellent potential to become a new outstanding sealant for SOFCs.展开更多
The Ba Ce0.8Y0.2O2.9-Ce0.85Sm0.15O1.925 composite electrolytes were prepared with Ba Ce0.8Y0.2O2.9(BCY) and Ce0.85Sm0.15O1.925(SDC). The SDC and BCY powders were mixed in the weight ratio of 95:5, 85:15, and 75:25, re...The Ba Ce0.8Y0.2O2.9-Ce0.85Sm0.15O1.925 composite electrolytes were prepared with Ba Ce0.8Y0.2O2.9(BCY) and Ce0.85Sm0.15O1.925(SDC). The SDC and BCY powders were mixed in the weight ratio of 95:5, 85:15, and 75:25, respectively(named as BS95, BS85, and BS75). Because of the composite effect between the SDC and BCY phases, the BS95 and BS85 exhibit improved conductivity compared with the pure SDC and BCY. The conductivity of BS95 is higher than that of BS85, indicating that the composite effect of BS95 is greater than that of BS85. Nevertheless, the composite effect in BS75 does not exist. Hence, we conclude that the composite effect in the BCY-SDC composites will decrease with the increase of the amount of BCY and even disappear when the amount of BCY exceeds a certain value. In our case, the optimum composition of the composite electrolyte is 95 wt% SDC and 5 wt% BCY. The BS95 has the highest conductivity(σ1t=0.07808 S cm-1, at 800 °C) and the fuel cell based on the BS95 shows the best performance(the maximum power density reaches as high as 526 mw cm-2 at 750 °C). The encouraging results suggest that the BCY-SDC composites are the very promising electrolyte materials for IT-SOFCs.展开更多
This study focused on meeting the stringent stability requirements of tubular segmented-in-series solid oxide fuel cells(SOFCs) in reducing and oxidizing atmospheres.To address this challenge,a bi-layer perovskite cer...This study focused on meeting the stringent stability requirements of tubular segmented-in-series solid oxide fuel cells(SOFCs) in reducing and oxidizing atmospheres.To address this challenge,a bi-layer perovskite ceramic interconnect was designed by controlling the oxygen partial pressure,because of the strong correlation between the conductivity of strontium-doped lanthanum titanate(LST) and the oxygen partial pressure.The LST powder was prepared using solid-phase and sol-gel methods,and their influence on particle size and sintering behavior was compared.LST/lanthanum strontium manganite(LSM) bi-layer ceramic interconnects with varying thicknesses were fabricated through screen printing and co-sintering.The results demonstrate favorable interfacial bonding and excellent chemical compatibility between the ceramic layers.The conductivity of the bi-layer interconnect exhibits a temperature-dependent behavior,peaking at 550℃.Simulation calculations and research findings validate that the co nductivity of the bi-layer interconnect is determined by the thickness of the LSM layer and the oxygen partial pressure at the interconnect interface.Optimal conductivity is achieved with a bilayer interconnect consisting of approximately 15 μm of LST and 4 μm of LSM.This can be attributed to the efficient regulation of oxygen partial pressure at the interface,effectively mitigating LSM decomposition caused by low oxygen partial pressure and the subsequent reduction in conductivity.These results provide valuable fundamental data and methodology for the development of high-performance interconnects for tubular segmented-in-series SOFCs.展开更多
基金supported by the Guangdong Provincial Basic and Applied Basic Research Foundation(2021A1515010671,2020A1515011221)the Guangdong Provincial Key Discipline Research Capacity Enhancement Project(2021ZDJS071)the Guangdong Provincial College Innovation Project(2021KTSCX122,2022KQNCX077)。
文摘This study focuses on the impact of Gd^(3+),Sm^(3+),Er^(3+).Y^(3+),and Bi^(3+)multi-doping on the crystal structure,microscopic surface features,and ionic conductivity of cerium dioxide in the Ce_(1-x)(Gd_(1/5)Sm_(1/5)Er_(1/5)Y_(1/)_5Bi_(1/5))_(x)O_(2-δ)(GSEYB)system.This system holds promise as a solid electrolyte material for low and medium-temperature solid oxide fuel cells.The powders of Ce_(1-x)(Gd_(1/5)Sm_(1/5)Er_(1/5)Y_(1/5)Bi_(1/5))_(x)O_(2-δ)(x=0,0.10,0.15,0.20,0.25,0.30)were synthesized using the solid-phase reaction method.The GSEYB electrolytes were comprehensively investigated for their phase structure,microstructure,oxygen vacancy concentration,and ionic conductivity using X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),and impedance spectroscopy.XRD diffraction patterns confirm a cubic fluorite-type structure with Fm3m space groups in all multi-doped systems.After sintering at 1400℃for 10 h,the relative density of doped samples exceeds 96%.In terms of electrical properties,the Ce_(0.75)Gd_(0.05)Sm_(0.05)Er_(0.05)Y_(0.05)Bi_(0.05)O_(2-δ)(x=0.25)electrolyte exhibits the highest ionic conductivity(σ_(t)=4.45×10^(-2)S/cm)and the lowest activation energy(E_(a)=0.79 eV)at 800℃.The coefficient of thermal expansion of the developed electrolyte aligns well with that of the commonly used electrode materials.This compatibility positions it as a highly promising candidate for utilization as an electrolyte material in solid oxide fuel cells(SOFCs).
基金supported by JSPS KAKENHI Grant Number 22K04732,Japan.
文摘The development of cost-effective solid oxide fuel cells(SOFCs)is crucial for the large-scale application.In this study,anode-supported SOFC single cells were fabricated using a combination of slurry spraying and spin-coating technique to achieve a dense Yttria Stabilized Zirconia(YSZ)electrolyte layer while maintaining low production cost.The electrochemical performance of the fabricated SOFC was evaluated using hydrogen and dry methane as fuels.Microstructural analysis confirmed that the YSZ electrolyte exhibited high densification with a thickness of approximately 10μm,ensuring excellent gas-tightness and preventing fuel crossover.The NiO-YSZ anode demonstrated favorable porosity,with well-sintered NiO particles forming a robust framework to facilitate electrochemical reactions.Performance evaluations revealed that under hydrogen operation,the SOFC achieved a peak power density of 1.408 W/cm^(2)at 1000℃,with open-circuit voltages(OCVs)closely matching theoretical predictions.When operated with dry methane,the SOFC maintained stable performance,reaching a peak power density of 0.96 W/cm^(2)at 1000℃,highlighting its potential for direct hydrocarbon utilization.Gas composition analysis of the anode exhaust confirmed the absence of excessive carbon deposition,indicating the effectiveness of the anode microstructure in mitigating coking during methane oxidation.These findings demonstrate that the spray-coated and spin-coated SOFC design offers a promising approach to improving fuel cell efficiency and cost-effectiveness.Future research should focus on optimizing electrolyte fabrication methods and enhancing anode stability in hydrocarbon-fueled operation to further advance the commercialization of SOFC technology.
基金Project supported by Eskom-Tertiary Education Support Programthe National Research Foundation of South Africa(Thuthuka Program,76318)
文摘A sol-gel method and a modified chemical vapour deposition technique were used to produce nanostructured Ce0.6Sr0.4Fe0.8Co0.2O3-δ materials at temperatures as low as 400 ℃. Powders were characterized using Fourier transform infrared spectroscopy （FTIR）, Raman spectroscopy, thermo gravimetric analysis, powder X-ray diffraction （XRD）, scanning electron microscopy （SEM） with energy dispersive X-ray spectroscopy, high resolution transmission electron microscopy （HRTEM）, and nitrogen sorption at 77 K. FTIR spectra showed that the sol-gel method resulted in residual carbon groups on the materials after calcination, while the Raman and XRD analysis confirmed that both synthesis methods resulted in cubic perovskite structure. However, the chemical va- pour deposition （CVD） method resulted in materials with a smaller crystallite size when compared to those prepared via the sol-gel route. The overall morphology of the powders was irregularly shaped aggregated particles as observed by SEM and HRTEM. In addition, HRTEM analysis showed that the materials were highly crystalline. Textural analysis revealed the powders had some mesoporosity, and the surface areas were 76.69 and 65.90 m2/g for materials synthesized using the CVD and sol-gel methods, respectively. The synthesized perovskite powders were used to fabricate button cells employing samarium doped ceria （SDC） as the electrolyte and NiO/SDC as the anode materials. As cathode materials, the maximum power density observed was 308.4 mW/cm2 at 500℃.
基金Project supported bythe National Natural Science Foundation of China (20271047)
文摘As a mixed ion-electronic conductor, doped ceria, especially rare earth doped ceria, were used as anodes or components of anodes in SOFCs. In this work, calcium doped ceria （CCO） was synthesized to be used in intermediate-temperature SOFCs （IT-SOFCs） anodes in order to reduce the cost of anode-supported SOFCs. Electrical conductivity of 20% calcium doped ceria （20CCO） reached 0.209 S·cm^-1 in hydrogen at 850 ℃, and 0.041 S·cm^-1 in air at 800℃, which is about 0.04 S·cm^-1 lower than that of conventional samaria-doped ceria （0.079 S·cm^-1）. Electrochemical performance of Ni-20CCO cermet as anode was investigated using a fuel cell with 35μm-thick SDC electrolyte and Sm0.5Sr0.5 Co-SDC cathode. Maximum power density was 623 mW·cm^-2 under humidified （3% H2O） hydrogen at 650 ℃, inferring high catalytic activity of the Ni-20CCO anode.
文摘Herein,we report the synthesis of a Dy-Gd co-doped cubic phase-stabilized Bi_(2)O_(3) solid electrolyte system via solid-state processing under atmospheric conditions.Doping with Dy^(3+) and Gd^(3+) has been observed to significantly enhance the densification process during sintering for stabilization purposes,thereby improving the electrical properties of δ-Bi_(2)O_(3)-type polymorphs.The synthesized ceramics were characterized using X-ray diffraction(XRD),field emission scanning electron microscopy-energy dispersive X-ray spectroscopy(FESEM-EDX),thermal gravimetry/differential thermal analysis(TG/DTA),and the four-point probe technique(4PPT).XRD analysis reveals that the samples Bi_(1-x-y)Gd_(x)Dy_(y)O_(1.5)(y=0.05/x=0.05,0.10,0,15,and 0.20,and x=0.05/y=0.10,0.15,and 0.20) exhibit a stable face-centered cubic δ-phase and a mixed-phase crystallographic structure.The XRD analysis of the stabilized δ-phase suggests that the prepared oxides show a face-centered cubic(FCC) structure with a space group of Fm-3m.FESEM micrographs reveal that the composition Bi_(0.90)Gd_(0.05)Dy_(0.05)O_(1.5) has no significant holes.Nevertheless,an evident increase in the pore formation is observed as the amount of Gd_(2)O_(3) increases until it reaches 20%.This finding suggests that dense pellets are formed during the sintering process at 900-1000℃.The DTA analyses were performed to verify the phase stability,which agrees with the XRD results.The electrochemical performance of the synthesized Dy-Gd co-doped Bi_(2)O_(3)solid electrolyte system was evaluated and analyzed in detail by using the electrochemical impedance spectroscopy(EIS) technique,Based on EIS and conductivity measurements,Bi_(0.75)Gd_(0.20)Dy_(0.05)O_(1.5) exhibits the lowest activation energy of 0.519 eV and the highest conductivity value of 0.398 S/cm at 627℃compared to the other samples;this composition can be used as a solid electrolyte for intermediatetemperature solid oxide fuel cells(SOFCs).
基金The present project was supported by Foundation of China Education Ministry for Talented Young ScholarEducation Promotion ProjectDoctoral Thesis Foundation of Xi'an Jiaotong University.
文摘Ni-Al_(2)O_(3)cermet supported tubular SOFC was fabricated by thermal spraying.Flame-sprayed Al_(2)O_(3)-Ni cermet coating plays dual roles of a support tube and an anode current collector.4.5mol.%yttria-stabilized zirconia(YSZ)and 10mol.%scandia-stabilized zirconia(ScSZ)coatings were deposited by atmospheric plasma spraying(APS)as the electrolyte in present study.The electrical conductivity of electrolyte was measured using DC method.The post treatment was employed using nitrate solution infiltration to densify APS electrolyte layer for improvement of gas permeability.The electrical conductivity of electrolyte and the performance of single cell were investigated to optimize SOFC performance.The electrical conductivity of the as-sprayed YSZ and ScSZ coating is about 0.03 and 0.07 S·cm^(-1)at 1000℃,respectively.The ohmic polarization significantly influences the performance of SOFC.The maximum output power density at 1000℃increases from 0.47 to 0.76 W·cm^(-2)as the YSZ electrolyte thickness reduces from 100μm to 40μm.Using APS ScSZ coating of about 40μm as the electrolyte,the test cell presents a maximum power output density of over 0.89 W·cm^(-2)at 1000℃.
文摘Eleven steel grades were designed to be used as metallic interconnects for Solid Oxide Fuel Cells (SOFC). Low carbon, high chromium steel with different additives of niobium, vanadium, aluminum, molybdenum, silicon, manganese and titanium were produced. Phase transformation temperatures;eutectoid temperature (Ac1) and temperature at which transformation of ferrite to austenite is completed during heating (Ac3) were measured by L75-76 dilatometer. The influence of the alloying elements on transformation temperatures was analyzed using MATLab. Considering the interaction between different alloying elements two equations for predicting Ac1 & Ac3 were obtained. The obtained Ac1 & Ac3 by these equations showed more compatibility than that obtained by traditional ones. In addition, the coefficients of thermal expansion of these steel grades were detected. The influences of chemical composition and temperature on the thermal expansion coefficient were analyzed;the obtained equations were verified to certain extent by using several kinds of steels. The predicted values were in good accordance with the experimental results which proof the validation of calculation model.
文摘A new cathode material fabricated by solid state reaction method was reported. The SmVO4 powder was obtained by firing the mixture of Sm2O3 and V2O5 powders in the temperature range of 700-1200 ℃. Its structure was identified by X-ray diffraction method and the electrochemical properties of SmVO4 as cathodes for solid oxide fuel cells (SOFCs) were investigated in single unit cell at the temperature ranged from 450-550 ℃. The results of the single fuel cell unit show that the maximum current densities are 641, 797, 688 mA·cm-2 and the maximum power output are 165, 268, 303 mW·cm-2 and the open circuit voltage are 1.04, 0.96, 0.92 V at 450, 500 and 550 ℃, respectively.
文摘The cathode material La1-xSrxCuO3-δ(x=0.15, 0.2, 0.3, 0.4) was synthesized by a sol-gel method. X-ray diffraction reveals that a single phase of perovskite is formed. The investigation of the electrical properties suggests that La0.7Sr0.3CuO3-δ has the highest electrical conductivity. La0.7Sr0.3CuO3-δ powder was mixed with different amount SDC (Sm0.15Ce0.85O1.925) powder (5wt.%-30wt.%) as composite cathodes. Electrochemical properties of the composite cathodes were researched further. Investigation suggests that the addition of appropriate amount SDC to La0.7Sr0.3CuO3-δ can improve the electrochemical properties and obtain better cathodic performance. Using La0.7Sr0.3CuO3-δ-SDC composite materials as a cathode based on SDC electrolyte, higher current density and power density at intermediate temperatures can be obtained.
文摘Glass-ceramics are often used as sealants in solid oxide fuel cells (SOFC). But interfacing components, such as ferritic stainless steel and YSZ electrolyte, may vary in their requirements regarding sealing properties, especially in terms of thermal expansion. A bilayered glass-ceramic system was developed to overcome the mismatch in coefficients of thermal expansion (CTE) between ferritic steel and YSZ. Therefore, two different glass-ceramics with slightly different CTEs were developed, one with good bonding characteristics to the ferritic steel and the other to the YSZ electrolyte. Steel and electrolyte components were coated with a layer of their corresponding glass sealant paste and heated up to form a sandwich sample. During the heat treatment of the sealing process, the glasses are crystallized into glass-ceramics. The resulting interface between the two glass-ceramics is of special interest. Cross-sections of the sandwich samples were cut, polished and investigated using SEM. The glass-ceramics show continuous, gap-free layers and excellent bonding to both steel and YSZ. Energy release rates are measured for single and bilayered glass sealants by mechanical testing. The designed bilayered glass-ceramics fulfill the special requirements of ferritic steel and YSZ. They show excellent potential to become a new outstanding sealant for SOFCs.
基金supported by the Natural Science Foundation of Liaoning Province(2013020010)
文摘The Ba Ce0.8Y0.2O2.9-Ce0.85Sm0.15O1.925 composite electrolytes were prepared with Ba Ce0.8Y0.2O2.9(BCY) and Ce0.85Sm0.15O1.925(SDC). The SDC and BCY powders were mixed in the weight ratio of 95:5, 85:15, and 75:25, respectively(named as BS95, BS85, and BS75). Because of the composite effect between the SDC and BCY phases, the BS95 and BS85 exhibit improved conductivity compared with the pure SDC and BCY. The conductivity of BS95 is higher than that of BS85, indicating that the composite effect of BS95 is greater than that of BS85. Nevertheless, the composite effect in BS75 does not exist. Hence, we conclude that the composite effect in the BCY-SDC composites will decrease with the increase of the amount of BCY and even disappear when the amount of BCY exceeds a certain value. In our case, the optimum composition of the composite electrolyte is 95 wt% SDC and 5 wt% BCY. The BS95 has the highest conductivity(σ1t=0.07808 S cm-1, at 800 °C) and the fuel cell based on the BS95 shows the best performance(the maximum power density reaches as high as 526 mw cm-2 at 750 °C). The encouraging results suggest that the BCY-SDC composites are the very promising electrolyte materials for IT-SOFCs.
基金Project supported by the National Key Research and Development Program of China (2021YFB4001400)。
文摘This study focused on meeting the stringent stability requirements of tubular segmented-in-series solid oxide fuel cells(SOFCs) in reducing and oxidizing atmospheres.To address this challenge,a bi-layer perovskite ceramic interconnect was designed by controlling the oxygen partial pressure,because of the strong correlation between the conductivity of strontium-doped lanthanum titanate(LST) and the oxygen partial pressure.The LST powder was prepared using solid-phase and sol-gel methods,and their influence on particle size and sintering behavior was compared.LST/lanthanum strontium manganite(LSM) bi-layer ceramic interconnects with varying thicknesses were fabricated through screen printing and co-sintering.The results demonstrate favorable interfacial bonding and excellent chemical compatibility between the ceramic layers.The conductivity of the bi-layer interconnect exhibits a temperature-dependent behavior,peaking at 550℃.Simulation calculations and research findings validate that the co nductivity of the bi-layer interconnect is determined by the thickness of the LSM layer and the oxygen partial pressure at the interconnect interface.Optimal conductivity is achieved with a bilayer interconnect consisting of approximately 15 μm of LST and 4 μm of LSM.This can be attributed to the efficient regulation of oxygen partial pressure at the interface,effectively mitigating LSM decomposition caused by low oxygen partial pressure and the subsequent reduction in conductivity.These results provide valuable fundamental data and methodology for the development of high-performance interconnects for tubular segmented-in-series SOFCs.
