固体氧化物燃料电池电解质材料的研究进展(英文)

固体氧化物燃料电池(solid oxide fuel cells,SOFCs)因具有能量转换率高,燃料适应性强,环境友好和操作方便等优点,受到了人们的普遍关注.发展中低温SOFCs是其商业化必然趋势.电解质材料是SOFCs的关键材料.对用于中低温SOFCs电解质材料的研究现状和进展进行了论述,并着重介绍了近年来受人们广泛关注的磷灰石型电解质材料.阐述了SOFCs电解质材料的研究趋势.     

Catalytic and Electrochemical Properties of Doped Lanthanum Chromites as New Anode Materials for Solid Oxide Fuel Cells

Defective perovskites contained in the general formula La(Sr)Cr(Ru,Mn)O_3–δ are successfully synthesized by spray pyrolysis. Powders of high phase purity are obtained after annealing, and they are used to prepare homogeneous films by spray printing. From a catalytic point of view for the methane steam reforming, these powdered perovskites do not generate a carbon deposit. Catalytic results, focused on doped ruthenium perovskites, confirm that the insertion of ruthenium in the structure of the lanthanum chromite presents a real benefit for the methane steam reforming. The electrochemical properties of La(Sr)CrO_3–δ, either pure and doped with manganese, show that the perovskite films can be potential electrodes, depending on their doping, for hydrogen anodic oxidation in solid oxide fuel cells.     

Structural Characterization of Lanthanum Chromite Perovskite Coating Deposited by Magnetron Sputtering on an Iron-Based Chromium-Containing Alloy as a Promising Interconnect Material for SOFCs

Chromium-containing stainless steel (SS) is a prospective material for use as an interconnect in solid oxide fuel cells (SOFCs). However, during operations at high temperatures, the growth of oxide scales causes the performance of the interconnect and SOFC as a whole to deteriorate. The coating of SS 446 with a conducting perovskite is a potential method of slowing the growth of oxide scale and, therefore, improving overall SOFC performance. In the present research, the structural characterization of a pure LaCrO₃ thin film on the SS 446 substrates has been performed as a model material that can be used as a barrier coating for the metallic interconnect. The deposition of an amorphous La-Cr-O thin film on SS 446 was performed using radio-frequency (rf) magnetron sputtering. The deposited amorphous film was annealed in air to form the desired perovskite phase. The film underwent an amorphous to LaCrO₄ phase transition during annealing at 500°C with further transformation to LaCrO₃ orthorhombic phase during annealing at 700°C. A self-organized dendritic structure was reported as a result of the perovskite-phase formation. Although formation of various oxides, such as Fe₂O₃ and Fe₃O₄, was observed during the annealing of uncoated SS 446 in air, the coating of SS 446 surface with LaCrO₃ film prevented formation of various oxide phases at the interconnect surface. The structural characterization of the films and SS 446 surfaces was accomplished using scanning electron microscopy with energy-dispersive X-ray analysis, X-ray diffractometry, micro-Raman spectroscopy, and nanoindentation.     

Control of the Thermal Expansion of Strontium-Doped Lanthanum Chromite Perovskites by B-site Doping for High-Temperature Solid Oxide Fuel Cell Separators

The thermal expansion of La_0.9Sr_0.1Cr_{1- x} M _x O₃(M = Mg, Al, Ti, Mn, Fe, Co, Ni; 0 ≤ x ≤ 0.1) perovskites has been studied in oxidizing and reducing atmospheres in the temperature range from 50° to 1000°C. Cobalt doping of La_0.9Sr_0.1CrO₃was an effective way of increasing the average linear thermal expansion coefficient (TEC), whereas titanium doping showed a negative effect. No effect on the TECs was observed for the B-site dopants in perovskites with the remaining dopants. Linear thermal expansion behavior was observed in the La_0.9Sr_0.1Cr_{1- x} M _x O₃ perovskites with doping of ≥1 mol% aluminum or 10 mol% cobalt. TECs of La_0.9Sr_0.1Cr_0.96Co_0.02Al_0.02O₃ were 10.5 × 10⁻⁶/°C in air, 10.7 × 10⁻⁶/°C under He–H₂ atmosphere (oxygen partial pressure of 4 × 10⁻¹⁵ atm at 1000°C), and 11.8 × 10⁻⁶/°C in H₂ atmosphere.     

Pore orientation of the gadolinia‐doped ceria cathode interlayer for a tubular SOFC using dip‐coating

An active region of cathode interlayer in a tubular solid oxide fuel cell (SOFC) is structurally analyzed using a dual‐beam focused ion beam/scanning electron microscope (FIB/SEM). The GDC (10 mol% gadolinia‐doped ceria) cathode interlayer (about 1 μm in thickness) is dip‐coated, and then sintered on YSZ (8 mol% yttria‐stabilized zirconia) electrolyte. At 1150°C sintering temperature, the pores oriented more along the axial direction than the radial direction. The anisotropy of pore shape is accounted for the withdrawal force during the dip‐coating of the GDC interlayer.     

Advances in novel SDC@Al2O3 core−shell electrolyte for low-temperature solid oxide fuel cell

The preparation of electrolyte with excellent ionic conduction is an important development direction in the practical application of solid oxide fuel cell (SOFC). Traditional methods to improve ion conduction was structure doping to develop electrolyte materials. In this work, the ionic conductor Ce_0.8Sm_0.2O_2-δ (SDC) was modified by insulator Al₂O₃ to enhance ion conduction and apply as electrolytes for the SOFC. The transmission electron microscopy (TEM) characterization clearly clarified that a thin Al₂O₃ layer in the amorphous state coated on SDC to form the SDC@Al₂O₃ core−shell structure. The SDC@Al₂O₃ electrolyte with the core−shell structure possesses a super ionic conductivity of 0.096 S cm⁻¹ and results in advanced cell performance of 1190 mW cm⁻² at 550°C. The X-ray photoelectron spectroscopy (XPS) analysis revealed that the concentration of oxygen vacancies in the SDC@Al₂O₃ core–shell structure significantly improved in comparison with pure SDC, the newly produced oxygen vacancies can promote the oxygen ion transport. Moreover, the interface between SDC and Al₂O₃ provides a fast channel for the proton transport. In addition, the SDC-based SOFC was usually suffered from the reduction of the SDC electrolyte and the accompanying generated electron conduction should deteriorate the cell performance, this is the main challenge for the SDC electrolyte application. In our case, the Al₂O₃ shell on the SDC surface not only can avoid the contact between SDC and hydrogen to eliminate the reduction of SDC but also can restrain electron conduction due to the electron insulation characteristic of the Al₂O₃ shell. This work demonstrates an efficient approach to develop the advanced low-temperature SOFC technology from material fundamentals.     

Interaction of a ceria‐based anode functional layer with a stabilized zirconia electrolyte: Considerations from a materials perspective

We report on the materials interaction of gadolinium‐doped ceria (GDC) and yttria‐stabilized zirconia (YSZ) in the context of high‐temperature sintering during manufacturing of anode supported solid oxide fuel cells (AS–SOFC). While ceria‐based anodes are expected to show superior electrochemical performance and enhanced sulfur and coking tolerance in comparison to zirconia‐based anodes, we demonstrate that the incorporation of a Ni–GDC anode into an ASC with YSZ electrolyte decreases the performance of the ASC by approximately 50% compared to the standard Ni–YSZ cell. The performance loss is attributed to interdiffusion of ceria and zirconia during cell fabrication, which is investigated using powder mixtures and demonstrated to be more severe in the presence of NiO. We examine the physical properties of a GDC–YSZ mixed phase under reducing conditions in detail regarding ionic and electronic conductivity as well as reducibility, and discuss the expected impact of cation intermixing between anode and electrolyte.     

Novel Compressive Mica Seals with Metallic Interlayers for Solid Oxide Fuel Cell Applications

A novel hybrid compressive mica seal was developed that showed an exceptionally low leak rate of ∼8.9 × 10⁻⁴ sccm/cm (standard cubic centimeters per minute per unit leak length of seal) at 800°C and a compressive stress of 100 psi, about 740 times lower than that of the conventional compressive mica seals (6.6 × 10⁻¹ sccm/cm), at a pressure gradient of 2 psi. The hybrid compressive mica seals were composed of two compliant metallic layers and a mica layer. Three commercially available micas were tested in this study. All showed substantial improvements in reducing the leak rates by using the hybrid design. The best results were obtained using muscovite single-crystal mica and 125 μm silver layers. Using the paper form of muscovite and phlogopite mica, the leak rates were still far superior (∼1 × 10⁻¹ sccm/cm) compared with mica without the compliant silver layer (about 6–9 sccm/cm). The microstructure of the mica was examined before and after the 800°C leak tests. These results are compared with results for hybrid seals using glass interlayers. In addition, an explanation for the substantial reduction of the leak rates is proposed, and the application of the hybrid compressive mica seals in planar SOFC stacks is briefly addressed.     

SOFC单相氧化物MIEC阳极材料的研究进展

综述了近年来国内外固体氧化物燃料电池复合导电性能(MIEC)单相氧化物阳极材料的研究进展。阐述了钙钛矿结构、立方萤石结构以及其它诸如烧绿石结构的单相氧化物阳极材料的导电性能以及应用于电池阳极的发电性能。指出了阳极材料研究亟待解决的问题及发展方向。     

中低温固体氧化物燃料电池陶瓷阴极材料

综述了中低温固体氧化物燃料电池（SOFC）陶瓷阴极材料的研究和发展动态，这些陶瓷材料包括焦绿石结构的A2Ru2O7-δ陶瓷，Ag-YDB(Y2O3dopedBi2O3)复合陶瓷以及具有钙钛矿结构的La1-xSrxCo1-yFeyO3(LSCF)型陶瓷。     

固体氧化物燃料电池CuCoNi/SDC阳极微结构与电性能的研究

本论文采用溶胶-凝胶低温燃烧合成法制作CuxCo0.5-xNi0.5O1.75-0.5x固溶体阳极粉末,并将电解质粉末和阳极合金粉末按1:1的比例制作了CuCoNi/SDC阳极片。采用热重差热仪检测粉末的处理情况,采用x射线衍射仪(XRD)检测了粉末的成相情况。并且采用四端子法检测了不同组成阳极片的电导率值。分析了固体氧化物燃料电池CuCoNi/SDC阳极的显微结构。结果显示,用上述方法合成的粉体成相很好,阳极片的电导率和组成、温度有着极强的联系,氢气还原前后微结构有明显的变化。     

固体氧化物燃料电池阴极材料的研究进展

简述了固体氧化物燃料电池阴极材料研究近况及重要进展。     

造孔剂含量对固体氧化物燃料电池阳极的结构与电性能的影响

通过向阳极添加造孔剂（PMMA）改善阳极的微观结构,研究不同含量的造孔剂（PMMA）对阳极的显微结构、电性能的影响。利用SEM、电化学1二作站等测试手段对单电池的结构和电性能进行了表征。研究结果表明,添加7wt．％的PMMA造孔剂制备的单电池,阳极的孔隙率高,阳极中的气孔分布均匀,结构规整,降低了燃料气的传输阻力,提高了三相反应界面,获得了良好的电性能。以H2＋3％H：0为燃料气,在750℃下单电池的开路电压（OCV）为1．08V、最大功率密度为0．82W／cm2、欧姆阻抗为0．20Ω·cm2、两极阻抗为0．53Ω·cm2。     

Improvement of Mechanical and Electrical Properties of Scandia-Doped Zirconia Ceramics by Post-Sintering with Hot Isostatic Pressing

Significant improvement in the fracture strength, accompanied by an enhancement in the electrical conductivity, of zirconia polycrystals that were doped with 3–7 mol% Sc₂O₃ was obtained by sintering at 1300°C for 1 h in air, followed by hot isostatic pressing (HIP) at 196 MPa at 1300° and 1450°C for 1.5 h in an argon-gas atmosphere. Dense bodies (with an average grain size of <0.5 μm) that were doped with 3.5 mol% of Sc₂O₃ showed the highest average fracture strength up to 1770 MPa and an electrical conductivity of 0.08 S/cm at 1000°C. The present zirconia ceramics, which consisted of submicrometer-sized grains of tetragonal phases and were stabilized with 5 and 6 mol% of Sc₂O₃, exhibited high strength (1330 and 1140 MPa, respectively) and good conductivity (0.15 and 0.18 S/cm, respectively); values for both properties were greater than those previously reported. The present HIPed zirconia ceramics, which have excellent properties, are candidates for an electrolyte of planar-type solid oxide fuel cells.     

复合掺杂钙钛矿氧化物La0.6Sr0.4-xCaxCo1-yNiyO3-δ阴极的制备和电性能

采用固相反应法合成了中温固体氧化物燃料电池新型复合掺杂阴极La0.6Sr0.4-xCaxCo1-yNiyO3-δ（LSCCN）钙钛矿材料。借助XRD对不同掺杂含量所制备的粉体的成相过程和晶体结构进行了研究。实验结果表明：当x=0.4时,Ca元素已经不能很好的掺入到LaCoO3晶格中去。Ni元素含量较小的情况下,不会影响材料的晶体结构,不过当NiO含量稍有增高,制备的粉体的结构发生了明显的变化,已不再具有钙钛矿型的晶体结构,出现了较强的四方K2NiF4结构的LaSrCoO4衍射峰。将制备的LSCCN粉体掺入一定的淀粉和粘结剂制备成固体氧化物燃料电池（SOFC）的阴极。在空气气氛下使用直流四探针法测量了样品从100℃到800℃的电导率值,发现LSCCN系列材料中保持了钙钛矿结构的阴极片具有很高的电导率值,其中Ca2+和Sr2+掺杂各半的情况下制备的阴极片的电导率值最高。掺入较多的Ca2+或较多的Ni2+不仅影响了材料的单一的晶体结构,并且大大降低了材料的电导率值。     

Synthesis of Perovskite-Type Lanthanum Iron Oxide by Glycothermal Reaction of a Lanthanum–Iron Precursor

Perovskite-type lanthanum iron oxide (LaFeO₃) powders were synthesized by glycothermal reaction at 300°C of a precursor that had been previously prepared by solvothermal decomposition of a mixture of lanthanum(III) isopropoxide and iron(III) butoxide (or methoxide) in toluene. Direct glycothermal reaction of the mixture yielded no double oxide, indicating that preparation of the precursor was important for crystallization of LaFeO₃ by the glycothermal method.