Preparation and Characterization of Component Materials for Intermediate Temperature Solid Oxide Fuel Cell by Glycine-Nitrate Process

La1-xSrxGa1-y MgyO3-δ(LSGM) electrolyte, La1-xSrxCr1-y MnyO3-δ( LSCM ) anode and La1-xSrxFe1-y MnyO3-aaaaaaa(LSFM) cathode materials were all synthesized by glycine-nitrate process (GNP). The microstructure and characteristics of LSGM, LSCM and LSFM were tested via X-ray diffraction(XRD), scanning electron microcopy (SEM), A C impedance and four-probe direct current techniques. XRD shows that pure perovskite phase LSGM electrolyte and electrode (LSCM anode and LSFM cathode) materials were prepared after being sintered at 1400℃for 20 h and at 1000℃for 5 h, respectively. The max conductivities of LSGM (ionic conductivity), LSCM (total conductivity) and LSFM (total conductivity) materials are 0.02, 10, 16 S·cm-1 in the air below 850℃, respectively. The conductivity of LSCM becomes smaller when the atmosphere changes from air to pure hydrogen at the same temperature and it decreases with the temperature like metal. The porous and LSGM-based LSCM anode and LSFM cathode films were prepared by screen printing method, and the sintering temperatures for them were 1300 and 1250℃, respectively. LSGM and electrode (LSCM and LSFM) materials have good thermal and chemical compatibility.

Performance of La_(1-x)Sr_xCr_(1-y)Mn_yO_(3-δ) anode materials for intermediate temperature solid oxide fuel cell

La1-xSrxCr1-yMnyO3-δ(LSCM) anode materials were synthesized by glycine nitrate process(GNP). Thermo-gravimetric analysis(TGA) and differential scanning calorimetric(DSC) methods were adopted to investigate the reaction process of LSCM anode materials. The oxides prepared were characterized via X-ray diffraction(XRD),scanning electron microscope and energy dispersive spectroscopy(SEM-EDS),direct current four-electrode and temperature process reduction(TPR) techniques. XRD patterns indicate that perovskite phase created after the precursor was sintered at 1 000 ℃ for 5 h,and single perovskite-type oxides formed after the precursor were sintered at 1 200 ℃ for 5 h. The powders are micrometer size after sintering at 1 000 ℃ and 1 200 ℃,respectively. The conductivities of LSCM samples increase linearly with increasing the temperature from 250 ℃ to 850 ℃ in air and the maximum value is 32 S/cm for La0.7Sr0.3Cr0.5Mn0.5O3-δ. But it is lower about two orders of magnitude in pure hydrogen or methane than that of the same sample in the air. TPR result indicates that LSCM offers excellently catalytic performance.

Radio-frequency magnetron sputtered thin-film La_(0.5)Sr_(0.5)Co_(0.95)Nb_(0.05)O_(3-δ) perovskite electrodes for intermediate temperature symmetric solid oxide fuel cell(IT-SSOFC)

The present work explores the application of La_(0.5)Sr_(0.5)Co_(0.95)Nb_(0.05)O_(3-δ)(LSCNO)perovskite as electrode material for the symmetric solid oxide fuel cell.Symmetric solid oxide fuel cells of thin-film LSCNO electrodes were prepared to study the oxygen reduction reaction at intermediate temperature.The Rietveld refinement of syn-thesized material shows a hexagonal structure with the R-3c space group of the prepared perovskite material.Lattice parameter and fractional coordinates were utilized to calculate the oxygen ion diffusion coefficient for molecular dynamic simulation.At 973 K,the oxygen ion diffusion of LSCNO was 1.407×10^(-8)cm^(2)s^(-1) higher by order of one magnitude than that of the La_(0.5)Sr_(0.5)Co_(0.95)Nb_(0.05)O_(3-δ)(7.751×10^(-9)cm^(2)^(-1)).The results suggest that the Nb doping provide the structural stability which improves oxygen anion diffusion.The enhanced structural stability was analysed by the thermal expansion coefficient calculated experimentally and from molecular dynamics simulations.Furthermore,the density functional theory calculation revealed the role of Nb dopant for oxygen vacancy formation energy at Sr-0 and La-O planes is lower than the undoped structure.To understand the rate-limiting process for sluggish oxygen diffusion kinetics,80 nm and 40 nm thin films were fabricated using radio frequency magnetron sputtering on gadolinium doped ceria electrolyte substrate.The impedance was observed to increase with an increasing thickness,suggesting the bulk diffusion as a rate-limiting step for oxygen ion diffu-sion.The electrochemical performance was analysed for the thin-flm symmetric solid oxide fuel cell,which achieved a peak power density of 390 mW cm^(-2) at 1.02 V in the presence of H_(2) fuel on the anode side and air on the cathode side.

Status and prospects of intermediate temperature solid oxide fuel cells

Compared with conventional electric power generation systems, the solid oxide fuel cell （SOFC） has many advantages because of its unique features. High temperature SOFC has been successfully developed to its commercial applications, but it still faces many problems which hamper large-scale commercial applications of SOFC. To reduce the cost of SOFC, intermediate temperature solid oxide fuel cell （IT-SOFC） is presently under rapid development. The status of IT-SOFC was reviewed with emphasis on discussion of their component materials. 2008 University of Science and Technology Beijing. All rights reserved.

Temperature Gradient Analyses of a Tubular Solid Oxide Fuel Cell Fueled by Methanol

Thermal management in solid oxide fuel cells(SOFC)is a critical issue due to non-uniform electrochemical reactions and convective fl ows within the cells.Therefore,a 2D mathematical model is established herein to investigate the thermal responses of a tubular methanol-fueled SOFC.Results show that unlike the low-temperature condition of 873 K,where the peak temperature gradient occurs at the cell center,it appears near the fuel inlet at 1073 K because of the rapid temperature rise induced by the elevated current density.Despite the large heat convection capacity,excessive air could not eff ectively eliminate the harmful temperature gradient caused by the large current density.Thus,optimal control of the current density by properly selecting the operating potential could generate a local thermal neutral state.Interestingly,the maximum axial temperature gradient could be reduced by about 18%at 973 K and 20%at 1073 K when the air with a 5 K higher temperature is supplied.Additionally,despite the higher electrochemical performance observed,the cell with a counter-fl ow arrange-ment featured by a larger hot area and higher maximum temperature gradients is not preferable for a ceramic SOFC system considering thermal durability.Overall,this study could provide insightful thermal information for the operating condition selection,structure design,and stability assessment of realistic SOFCs combined with their internal reforming process.

Development of nickel based cermet anode materials in solid oxide fuel cells–Now and future

High temperature solid oxide fuel cell(SOFC)is the most efficient and clean energy conversion technology to electrochemically convert the chemical energy of fuels such as hydrogen,natural gas and hydrocarbons to electricity,and also the most viable alternative to the traditional thermal power plants.However,the power output of a SOFC critically depends on the characteristics and performance of its key components:anode,electrolyte and cathode.Due to the highly reducing environment and strict requirements in electrical conductivity and catalytic activity,there are limited choices in the anode materials of SOFCs,particularly for operation in the intermediate temperature range of 500–800C.Among them,Ni-based cermets are the most common and popular anode materials of SOFCs.The objective of this paper is to review the development of Ni-based anode materials in SOFC from the viewpoints of materials microstructure,performance and industrial scalability associated with the fabrication and optimization processes.The latest advancement in nano-structure architecture,contaminant tolerance and interface optimization of Ni-based cermet anodes is presented.And at the end of this paper,we propose and appeal for the collaborative work of scientists from different disciplines that enable the inter-fusion research of fabrication,microanalysis and modelling,aiming at the challenges in the development of Ni-based cermet anodes for commercially viable intermediate temperature SOFC or IT-SOFC technologies.

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 30.9×10-6 K-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 interracial polarization resistance （ASR） decreased with increasing SDC content of the composite. The area specific interracial 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.

Ln_2MO_4 cathode materials for solid oxide fuel cells

One of the major challenges to develop "intermediate temperature" solid oxide fuel cells is finding a novel cathode material, which can meet the following requirements: (1) high electronic conductivity; (2) chemical compatibility with the electrolyte; (3) a matched thermal expansion coefficient (TEC); (4) stability in a wide range of oxygen partial pressure; and (5) high catalytic activity for the oxygen reduction reaction (ORR). In this short review, a survey of these requirements for K2NiF4-type material with the formula Ln2MO4, Ln = La, Pr, Nd, Sm; M = Ni, Cu, Fe, Co, Mn, is presented. The composition-dependent TEC, electrical conductivity and oxygen transport property are considered. The Ln2MO4 materials exhibit improved chemical stability and compatibility with most of the traditional electrolytes. The complete fuel cells integrated with Ln2MO4 materials as cathodes show promising results. Furthermore, these materials are considered as cathodes of protonic ceramic fuel cell (PCFC), and/or anodes of high temperature steam electrolysis (HTSE). First results show excellent performances. The versatility of these Ln2MO4 materials is explained on the basis of structural features and the ability to accommodate oxygen non-stoichiometry.

Oxidation resistance,thermal expansion and area specific resistance of Fe-Cr alloy interconnector for solid oxide fuel cell

It is promising for metal especially ferritic stainless steel（FSS）to be used as interconnector when the solid oxide fuel cell（SOFC）is operated at temperature lower than 800℃.However,there are many challenges for FSS such as anti-oxidant,poisoning to cathode and high area specific resistance（ASR）when using as SOFC interconnector.The effect of Cr content（12-30 mass%）in Fe-Cr alloys on thermal expansion coefficient（TEC）,oxidation resistance,microstructure of oxidation scale and ASR was investigated by thermo-gravimetry,scanning electron microscopy,energy dispersive spectroscopy and four-probe DC technique.The TEC of Fe-Cr alloys is（11-13）×10^（-6） K^（-1）,which excellently matches with other SOFC components.Alloys have excellent oxidation resistance when Cr content exceeds 22mass% because of the formation of chromium on the surface of alloy.The oxidation rate constants kdand ksdecrease rapidly with increasing the Cr content and then increase slowly when the Cr content is higher than 22mass%.The kinetic results indicate that Cr evaporation must be considered at high temperature for Fe-Cr alloys.After the alloys were oxidized in air at 800℃ for500 h,log（ASR/T）（Tis the absolute temperature）presents linear relationship with 1/T and the conduct activation energy is 0.6-0.8eV（Cr16-30）.Optimal Cr content is 22-26mass%considering the oxidation resistance and ASR.

Analysis of Heat and Mass Transfer for a Single-Planar-Anode-Supported Solid Oxide Fuel Cell Considering Internal Reforming

The temperature uniformity and component concentration distributions in solid oxide fuel cells during operating processes can influence the cell electrochemical and thermal characteristics.A three-dimensional thermal-fluid numerical model including electrochemical reactions and water-gas-shift(WGS)reaction for a single channel solid oxide fuel cell was developed to study the steady-state characteristics,which include distributions of the temperature(T),temperature gradient((35)T/(35)x),and fuel utilization.It was shown that the maximum temperature(Tmax)changed with operating voltage and the maximum temperature gradient(((35)T/(35)x)max)occurred at the inlet of the channel of a solid oxide fuel cell by simulation.Moreover,the natural convection condition had a great influence on T and(35)T/(35)x.The thermal stress generated by temperature differences was the key parameter and increasing the convection heat-transfer coefficient can greatly reduce the thermal stress.In addition,the results also showed that there were lower temperature gradients and lower current density at high working voltage;therefore,choosing the proper operating voltage can obtain better cell performance.

SOFC temperature evaluation based on an adaptive fuzzy controller

The operating temperature of a solid oxide fuel cell (SOFC) stack is a very important parameter to be controlled, which impacts the performance of the SOFC due to thermal cycling. In this paper, an adaptive fuzzy control method based on an affine nonlinear temperature model is developed to control the temperature of the SOFC within a specified range. Fuzzy logic systems are used to approximate nonlinear functions in the SOFC system and an adaptive technique is employed to construct the controller. Compared with the traditional fuzzy and proportion-integral-derivative (PID) control, the simulation results show that the designed adaptive fuzzy control method performed much better. So it is feasible to build an adaptive fuzzy controller for temperature control of the SOFC.

基于CuO-ZnO的低温固体氧化物燃料电池性能

制备具有优异离子导电性和低温高化学性能的电解质是固体氧化物燃料电池实际应用的重要发展方向.基于p型CuO和n型ZnO构建p-n半导体异质结材料,并将其作为电解质应用于低温固体氧化物燃料电池.制备了不同质量比例CuO-ZnO的电解质材料,并组装Ni_(0.8) Co_(0.15)Al_(0.05)LiO_(2-δ)/CuO-ZnO/Ni_(0.8)Co_(0.15)Al_(0.05)LiO_(2-δ)单电池进行性能测试.结果表明,基于纯ZnO电解质材料的燃料电池性能最低(在550℃开路电压为为0.8 V,最大功率密度为187.5mW/cm^(2)),复合质量比例为1∶9的燃料电池性能最为优异(在550℃开路电压为1.065V,瞬时最大功率密度为555mW/cm^(2)).通过对CuO-ZnO异质结复合材料的电化学阻抗分析,发现构建的p-n半导体异质结为离子传输提供了通道,提高了离子电导率.研究表明p-n型电解质复合材料在低温固体氧化物燃料电池的应用中具有很大潜力.

基于CuO-ZnO的低温固体氧化物燃料电池性能

制备具有优异离子导电性和低温高化学性能的电解质是固体氧化物燃料电池实际应用的重要发展方向。基于p型CuO和n型ZnO构建p-n半导体异质结材料,并将其作为电解质应用于低温固体氧化物燃料电池。制备了不同质量比例CuO-ZnO的电解质材料,并组装Ni_(0.8)Co_(0.15)Al_(0.05)LiO_(2-δ)/CuO-ZnO/Ni_(0.8)Co_(0.15)Al_(0.05)LiO_(2-δ)单电池进行性能测试。结果表明,基于纯ZnO电解质材料的燃料电池性能最低(在550℃开路电压为为0.8 V,最大功率密度为187.5 mW/cm^(2)),复合质量比例为1∶9的燃料电池性能最为优异(在550℃开路电压为1.065 V,瞬时最大功率密度为555 mW/cm^(2))。通过对CuO-ZnO异质结复合材料的电化学阻抗分析,发现构建的p-n半导体异质结为离子传输提供了通道,提高了离子电导率。研究表明p-n型电解质复合材料在低温固体氧化物燃料电池的应用中具有很大潜力。

基于龙伯格-滑模观测器的固体氧化物燃料电池温度估计模型

固体氧化物燃料电池(solid oxide fuel cell,SOFC)作为一种新型发电装置,因高效无污染、全金属固态结构、燃料来源广等优点,在未来各个领域具有广阔应用前景。电堆内部的温度分布对其安全稳定运行至关重要,针对其内部温度难以获取的问题,该文设计一种龙伯格-滑模观测器估计电堆内部温度分布。首先,观测器的输入考虑系统可观性和工程应用,并结合能观矩阵条件数筛选出最优组合;然后,基于龙伯格和滑模观测器理论构造观测器具体结构;其次,为提升观测器性能,将电堆误差系统进行解耦,通过极点配置重新构造反馈增益;最后,通过平滑非线性不连续项,抑制观测器抖振现象。结果表明,所设计观测器相较于龙伯格和滑模观测器在收敛速度和误差波动方面具有明显优越性。

不同支撑结构的固体氧化物燃料电池数值模拟分析

固体氧化物燃料电池(SOFC)是一种高效的发电系统,能够直接将化学能转换为电能。如何保证电池高效且稳定地运行是亟待解决的问题。本工作建立了单片的平板式固体氧化物燃料电池的三维模型,涉及电化学、传质和传热等多个物理场的耦合,通过COMSOL Multiphysics有限元仿真软件对模型进行数值计算并验证模型,其I-V曲线表明数据误差小于6%。在该模型基础上,开发了基于阴极及电解质支撑的SOFC的三维模型,并继续研究了不同操作参数、支撑结构对SOFC的输出功率、温度等诸多因素对电池的输出功率、温度等物理参数带来的影响,对电池的影响情况通过极化曲线和功率曲线来反映。仿真结果表明,连接肋板会影响电池内部气体的扩散,进而发现电流密度与物质的分布有紧密联系。通过进一步的研究表明,支撑层厚度、压力以及输入燃料流量等因素均会对电池的输出功率、温度等带来影响,增大工作压力、燃料输入流量等均能提高输出功率,但这也会导致电池内部温度上升,而输出功率与电池支撑层厚度成反比。相同条件下,阴极支撑型SOFC的输出功率大于电解质支撑型SOFC的输出功率,本研究对SOFC的结构设计、实验工作具有一定的指导作用。

S44535铁素体不锈钢高温氧化行为

为了探究稀土La对S44535铁素体不锈钢高温氧化行为的影响,采用加速氧化对添加0.26%La的S44535钢在800、900、1000℃下的静态空气中进行高温氧化研究。采用恒温氧化法对比S44535铁素体不锈钢在三种温度下的氧化动力学曲线,用扫描电镜(SEM)、能谱分析仪(EDS)和X射线衍射(XRD)对钢的氧化层进行表征分析,探究了稀土La对铁素体不锈钢高温抗氧化性能的影响。结果表明,氧化产物主要为Cr2O3和MnCr2O4,随着温度的升高,表面氧化膜增厚且更加致密,其外层富含Mn,内层富含Cr,说明稀土改变了氧化膜的生长方式,且呈现出较为优异的高温抗氧化性能。

氨燃料管状SOFCs中热冲击影响与性能的模拟研究

研究氨燃料固体氧化物燃料电池(solidoxidefuel cells,SOFCs)热冲击的产生机理将会给电池的温度管理、可靠性管理及电池的性能优化提供更多可能性。但由于化学、电化学的反应过程复杂、模型仿真所涉物理场较多,鲜有关于氨燃料SOFCs的仿真研究。为此,该文通过建立耦合了吸热的氨气裂解反应、电化学反应、局部电流分布、温度分布以及物质流动的仿真模型,分析了单个阴极支撑的管状直接氨气裂解SOFCs的热冲击(热应力和热对流)形成机理。研究得出,过快且不均衡的氨气裂解反应是电池局部低温产生的主要原因,这会直接造成电池整体出现376K的温差。通过采用氨气预重整的方法能使氨SOFCs在相同操作电压下温度分布更均匀,平均温度更高,在800℃的环境温度下96%预重整的氨SOFCs能将阳极的温度极值差从62.16 K降为1.0 K,电池内部的温度分布得到显著改善。该研究可为氨燃料SOFCs的热管理优化提供重要理论依据,此外,该文详细展示的氨燃料SOFCs耦合模型的建模方法可以为用其他富氢气体做燃料的SOFCs的模拟仿真研究提供思路。

氨燃料固体氧化物燃料电池低温化性能分析

在氨燃料固体氧化物燃料电池(solid oxide fuel cell,SOFC)低温化发展趋势下,降低工作温度将会提高电池寿命,但随之带来的化学及电化学反应速率降低和电解质欧姆损失增加等问题,这会直接影响电池的输出性能。该文基于COMSOL仿真平台,构建SOFC的多物理模型仿真模型,对SOFC内部化学及电化学反应、质量传递、能量传递和温度场分布进行耦合求解,着重量化分析工作温度和电解质厚度参数对氨燃料SOFC输出性能的敏感性影响。结果表明:降低工作温度至700℃可以显著降低电池内部热应力,尤其入口和出口侧降幅达14.37%。增加阳极厚度和氨气浓度导致功率密度下降48.76%。采用10μm电解质厚度和氧化钆参杂氧化铈(gadolinia-doped ceria,GDC)材料可以提高电池平均功率密度至785.87 W/m^(2),增幅达77.25%。因此,降低温度可以有效降低电池内部的热应力及分布差异,可提高电池的寿命,但阳极氨气平均浓度增加56.57%,镍基氮化作用随之增强可能会对电池稳定性造成不利影响,可采用减小电解质厚度和换用电解质材料两种方法对电池的输出性能进行提升。

BaO-CaO-Al_(2)O_(3)-B_(2)O_(3)-SiO_(2)中温SOFC封接玻璃的失效性分析与性能改进研究

热稳定性及致密度是影响中温固体氧化物燃料电池封接玻璃实际应用的两大重要因素。通过传统固相熔融退火法制备32.96BaO-14.45CaO-4.87Al_(2)O_(3)-14.62B_(2)O_(3)-33.10SiO_(2)(BCS1)基础玻璃,采用X射线衍射分析、扫描电镜、高温显微镜等表征手段来探究其封接失效原因,并提出改进方法,以获得性能稳定的致密封接材料。结果表明,BCS1基础玻璃中的六方BaAl_(2)SiO_(8),经1073 K热处理会转变为低膨胀单斜相,造成基础玻璃与Ni-YSZ阳极的热膨胀系数不匹配,再者BCS1玻璃易过烧发泡,内部存在的大量孔隙容易引发气体泄漏。通过额外增加Al_(2)O_(3)含量,可以提高封接玻璃的热稳定性、热匹配性和致密性,并使封接玻璃与Ni-YSZ阳极具有良好的界面结合。该研究为中温固体氧化物燃料电池封接玻璃的性能改进提供了有效的途径,有助于推动该领域技术的发展和应用。

流道扰流体对固体氧化物燃料电池温度梯度的影响研究

固体氧化物燃料电池(solid oxide fuel cell,SOFC)内部过高的温度梯度会导致电池失效,如何降低SOFC温度梯度、提高电池温度分布的均匀性至关重要。结合电、热、流动和传质物理场建立了SOFC多物理场耦合模型,通过与实验数据对比验证了模型准确性;通过SOFC模型研究了SOFC温度和温度梯度分布情况,确定了电池反应区最大温度梯度为优化指标,提出了扰流体流道结构设计,并在考虑功率密度的影响情况下,证明了扰流体结构的有效性。对扰流体结构的形状、高度和宽度进行了分析讨论,分析发现:扰流体主要是通过改变流体流速和反应层氧气浓度来影响反应区最大温度梯度的,扰流体对于流道压降的改变主要影响了损失功率密度;最终确定了圆弧扰流体结构(h=0.8 mm,d_(1)=4.0 mm)为较优结构,在净功率密度与传统直流道相同时,最大温度梯度为43.35 K/cm,相比传统直流道,降低了9.4%。