阳极支撑中温固体氧化物燃料电池的数值模拟

该文针对阳极支撑中温固体氧化物燃料电池建立了三维数学模型,以氢气作为燃料、空气为氧化剂,模拟了单电池内的组分扩散、气体流动、热量扩散、电荷运输等主要物理化学过程。将自己制备的电池各组元材料性能代入模型中进行了计算。计算出阴阳极催化层与扩散层交界面的O2、H2和H2O浓度的分布;扩散层中间和气体通道的燃料气与氧化剂气体速度矢量分布;各流场的压力分布及电极催化层的电流密度分布等电池特性。为阳极支撑中温固体氧化物燃料电池的设计和优化提供了充分合理的参考依据。     

Strontium and copper doped LaCoO3: New cathode materials for solid oxide fuel cells?

In the field of solid state electrochemistry, lanthanum cobaltites are very good electronic conductors used as SOFC cathode materials. In this work, Sr and Cu-doped LaCoO₃ perovskites (LaCo_0.5Cu_0.5O_3?δ, La_0.5Sr_0.5Co_0.5Cu_0.5O_3?δ) have been prepared by means of the citrate route procedure and investigated. XRD confirms the formation of the desired phase and no secondary phases are detected. XPS and EDX results suggest that doping affects cations' surface segregation: lanthanum and copper are surface segregated in the LaCo_0.5Cu_0.5O_3?δ whereas this is not observed in the La_0.5Sr_0.5Co_0.5Cu_0.5O_3?δ. TPD experiments revealed that doping greatly increases the desoprtion of α and β oxygen species. The oxygen permeability was also determined in order to evaluate mixed ionic and electronic conductivity in addition to the surface activity in oxygen reduction reaction: in particular copper doping was observed to enhance permeability even at rather low temperature (500 °C). Finally, electrochemical impedance spectroscopy measurements carried out on a symmetrical half-cell with Ce_0.9Gd_0.1O₂ as electrolyte to characterize the effect of doping on electrochemical properties, revealed that the Cu and Sr doping enhances the performance as SOFC cathode.     

PMMA含量对水系流延IT-SOFC性能的影响

通过向阳极添加单一分散性的球形造孔剂PMMA改善阳极的微观结构,研究不同含量的PMMA对阳极的孔隙率、显微结构、电性能的影响。文中分别制备了造孔剂(PMMA)含量分别为6wt.%、8wt.%、10wt.%和12wt.%四种阳极材料的单电池,通过测试阳极还原前的开口气孔率分别为17vol.%,22.4vol.%,30.6vol.%和42.1vol.%;单电池的最大功率密度分别为0.66W/cm2、0.78W/cm2、1.15W/cm2和1.01W/cm2;极化电阻分别为1.12Ω.cm2、1.03Ω.cm2、0.88Ω.cm2和1.02Ω.cm2。实验结果表明:以单一分散性的球形PMMA为SOFC阳极材料的造孔剂,其最佳添加量为10wt.%,所制备的单电池可以获得最佳的电化学性能,即以3%H2O+H2为燃料气,750℃下,单电池的开路电压(OCV)为1.01V,最大功率密度为1.15W/cm2,极化电阻为0.88Ω.cm2。     

Cobalt-free Composite Ba_(0.5)Sr_(0.5)Fe_(0.9)Ni_(0.1)O_(3-δ)-Ce_(0.8)Sm_(0.2)O_(2-δ) as Cathode for Intermediate-Temperature Solid Oxide Fuel Cell

New cobalt-free composites consisting of Ba0.5Sr0.5Fe0.9Ni0.1O3-δ(BSFN) and Ce0.8Sm0.2O2-δ(SDC) were investigated as possible cathode materials for intermediate-temperature solid oxide fuel cell (IT-SOFC). BSFN, which was synthesized by auto ignition process, was chemically compatible with SDC up to 1100℃ as indicated by X-ray diffraction analysis. The electrical conductivity of BSFN reached the maximum value of 57 S·cm-1 at 450℃. The thermal expansion coefficient (TEC) value of BSFN was 30.9×10-6K-1 , much higher than that of typical electrolytes. The electrochemical behavior of the composites was analyzed via electrochemical impedance spectroscopy with symmetrical cells BSFN-SDC/SDC/BSFN-SDC. The area specific interfacial polarization resistance (ASR) decreased with increasing SDC content of the composite. The area specific interfacial polarization resistance (ASR) at 700℃ is only 0.49, 0.34 and 0.31 Ω·cm2 when 30, 40, and 50 wt% SDC was cooperated to BSFN, respectively. These results suggest that BSFN-SDC is a possible candidate for IT-SOFC cathode.     

Molten-salt fuel cells—Technical and economic challenges

This paper presents a personal view of the status and research needs of the MCFC and other molten-salt fuel cells. After an overview of current MCFC performance, compared with performance and cost of other fuel cells, improvements in power density and lifetime as well as cost reduction are identified as key priorities to accelerate the commercialization of the MCFC. In spite of its unfavorable public image (compared to, in particular, PEMFC and planar SOFC) MCFC technology has progressed steadily and cost reduction has been significant. Large-scale commercialization, especially in the distributed generation and cogeneration market, remains a possibility but its chances are highly dependent on a forceful and consistent energy policy, for example taking into account the externalities associated with various modes of electric power production from fossil fuels. In spite of steady improvements in performance, important defects in fundamental knowledge remain about wetting properties, oxygen reduction kinetics, corrosion paths and control mechanisms. These must be addressed to stimulate further simplification of design and find solutions to lifetime issues. Recently, alternative concepts of molten-salt fuel cells have been capturing attention. The direct carbon fuel cell (DCFC), reviving an old concept, has caught the attention of energy system analysts and some important advances have been made in this technology. Direct CO and CH₄ oxidation have also been a focus of study. Finally, the potential of nanotechnology for high-temperature fuel cells should not be a priori excluded.     

Sm and Sr co-doped ceria prepared by citrate–nitrate auto-combustion method

A few compositions in the system, Ce_{1 − x − y}Sm_xSr_yO_1.90 have been prepared by citrate–nitrate auto-combustion method. X-ray diffraction data show that all the compositions are solid solution having cubic fluorite structure. Density of the samples sintered at 1350 °C has been found to be more than 95% of the theoretical value. Surface morphology has been studied by scanning electron microscope. AC impedance spectroscopy measurements have been carried out to study the grains, grain boundaries and total ionic conductivity of the samples in the temperature range 200–600 °C. The composition, Ce_0.82Sm_0.16Sr_0.02O_1.90 shows the maximum conductivity i.e. 2.67 × 10⁻² S-cm⁻¹ at 600 °C among all the compositions investigated. This is about two times higher than that of Ce_0.80Sm_0.20O_1.90.     

IT-SOFC复合阳极材料CDC-LSCMCo的制备及性能

采用甘氨酸-硝酸盐法(GNP法)一次性合成固体氧化物燃料电池复合阳极材料Ce0.8Ca0.2O2-La0.7Sr0.3Cr0.5Mn0.5-xCoxO3-δ(CDC-LSCMCo)。XRD、SEM和EDS分析结果表明:1350℃下烧结5h能够得到单一萤石-钙钛矿结构且粒度较小(1μm左右)的复合阳极粉体。电导率的测试研究发现,温度大于750℃时,电导率随Co含量的增加而增大。800℃时,CDC-LSCMCo0.15分别在空气与氢气气氛下的电导率分别为10.5和0.7S·cm-1。SEM和XRD分析表明:CDC-LSCMCo与La0.9Sr0.1Ga0.8Mg0.2O3-δ电解质材料有很好的热与化学相容性,是一种应用前景良好的IT-SOFC阳极材料。     

多层电解质型中温SOFC

采用柠檬酸法合成了Gd0.1Ce0.9O1.95(GDC)、La0.45Ce0.55O2-α/2(LDC)、La0.9Sr0.1Ga0.8Mg0.2O2.85(LSGM)电解质材料,并制备了阳极负载型GDC-LSGM、LDC-LSGM和LDC-LSGM-LDC多层薄膜电解质单体电池,考察了单体电池的U-J特性和功率输出性能.结果显示:GDC-LSGM电解质电池没有电流产生;LDC-LSGM电解质电池最大输出功率密度最高,800℃时约为0.72W/cm2,但不稳定;LDC-LSGM-LDC多层电解质电池的开路电压最高,800℃时可达0.814 V.     

Development of co-sintering process for anode-supported solid oxide fuel cells with gadolinia-doped ceria/lanthanum silicate bi-layer electrolyte

Gadolinia-doped ceria (GDC) and lanthanum silicate (LS) are expected to be promising materials for electrolytes of solid oxide fuel cells (SOFCs) because of their high ionic conductivities at intermediate temperatures. However, performance degradation of SOFCs is caused by current leakage through GDC and poor densification of LS. In the present study, LS was used as a blocking layer for preventing the current leakage of GDC electrolyte. Thermal shrinkage measurements and scanning electron microscopy (SEM) observation suggested that the addition of Bi₂O₃ in LS electrolyte (LSB) contributed to the decrease in the sintering temperature of the LS and improved densification of the GDC/LS bi-layer electrolyte. Consequently, the open-circuit voltage for the cell with GDC/LS and GDC/LSB bi-layer electrolytes increased effectively in comparison with that of the cell with GDC single-layer electrolyte. The electrical conductivity and fuel cell characteristics were compared among the cells with GDC, GDC/LS, and GDC/LSB electrolytes.     

High conductive (LiNaK)2CO3Ce0.85Sm0.15O2 electrolyte compositions for IT-SOFC applications

Composite electrolytes of lithium, sodium, and potassium carbonate ((LiNaK)₂CO₃), and samarium doped ceria (SDC) have been synthesized and the carbonate content optimized to study conductivity and its performance in intermediate-temperature solid oxide fuel cell (IT-SOFC). Electrolyte compositions of 20, 25, 30, 35, 45 wt% (LiNaK)₂CO₃–SDC are fabricated and the physical and electrochemical characterization is carried out using X-ray diffraction, scanning electron microscopy, electrochemical impedance spectroscope, and current–voltage measurements. The ionic conductivity of (LiNaK)₂CO₃–SDC electrolytes increases with increasing carbonate content. The best ionic conductivity is obtained for 45 wt% (LiNaK)₂CO₃–SDC composite electrolyte (0.72 S cm^?1 at 600 °C) followed by the 35 wt% (LiNaK)₂CO₃–SDC composite electrolyte (0.55 S cm^?1 at 600 °C). The symmetrical cell of the 35 wt% (LiNaK)₂CO₃–SDC composite electrolyte with lanthanum strontium cobalt ferrite (LSCF) electrode in air gives an area specific resistance of 0.155 Ω cm² at 500 °C. The maximum power density of the fuel cell using 35 wt% (LiNaK)₂CO₃–SDC composite electrolyte, composite NiO anode and composite LSCF cathode is found to be 801 mW cm^?2 at 550 °C.