镓酸镧基薄膜电解质电池阴极的浸渍制备及性能研究

Tremendous efforts to develop high-efficiency low-temperature solid oxide fuel cells (SOFC) (below 600oC) are motivated by their potentials for reduced materials cost, less engineering challenge, and better durability. Sluggish oxygen reduction kinetics on the cathodes remains a main barrier for such fuel cells. Scaling of the cathode feature size down to nanometer will enhance surface vacancy concentration, increase ionic and electronic conductivities, and make more surface area available for the electrocatalytic reduction of oxygen. Wet chemical impregnation provides an important approach for obtaining nanostructured cathodes. LSGM is an ideal electrolyte for low-temperature SOFCs as it exhibits high oxide ionic conductivity and is chemically stable with negligible electronic conductivity over a wide oxygen partial pressure range. In this proposal, novel dual micron- and nano-scale cathodes will be fabricated by impregnating mixed ionic and electronic conducting oxides such as Sm0.5Sr0.5CoO3, Ba0.5Sr0.5Co0.8Fe0.2O3, (La, Sr)(Co, Fe)O3, LnBaCo2O5, Ln2NiO4 and LnFeO3 (Ln = Rare Earth Metal) onto the internal surfaces of the porous substrates in the tri-layer structure of porous｜dense｜porous LSGM. The detailed mechanism of oxygen reduction reactions in the dual-scale cathodes will be explored using electrochemical impedance spectroscopy. Quantitative microscopy, spectroscopy, diffraction, as well as chemisorption and physisorption techniques will be used to characterize the microscopic features of the porous composite cathodes, such as pore structure, local chemistry, surface area, pore volume, pore size distribution, and adsorptive properties. The primary goal of the proposed work is to gain a profound understanding of the principles of dual-scale cathodes, including simultaneous transport of ionic and electronic defects in the cathode (influenced primarily by the defect structure), gas transport through the pores of the cathode (influenced mainly by the pore structure), and the reaction kinetics at the cathode/gas interface (influenced mostly by the surface structures and catalytic properties). An in-depth understanding of the correlation between the microscopic features and their electrochemical and catalytic behavior will provide us with valuable guidance in designing cathodes and cathode｜electrolyte interfaces with desired microstructures for high performance.

开发高催化活性阴极是实现低温固体氧化物燃料电池（SOFC）高效发电的重要前提和基础，本项目基于新型低温固体电解质材料锶镁掺杂镓酸镧(LSGM)的一体化复合膜结构设计即多孔｜致密｜多孔LSGM，发展多孔陶瓷孔内壁上阴极电催化薄膜的化学液相浸渍沉积技术，通过表面活性剂和模板剂的选择，实现阴极电催化薄膜成分、形貌和纳微结构的可控构筑，研究纳微结构阴极电催化薄膜的界面反应动力学行为，揭示其结构与性能包括缺陷结构与离子电子传输性能、多孔结构与气相传输性能以及表面结构与催化性能等之间的内在关联和科学规律；构建一体化LSGM薄膜电解质电池，优化阴极电催化薄膜的化学组成和纳微结构，提高阴极对氧气还原反应的催化活性，降低阴极界面极化电阻，提高低温SOFC的功率输出及其长期稳定性。本项目的顺利实施对于丰富和完善高性能阴极电催化薄膜的结构设计理论和制备科学并促进低温SOFC的低成本开发具有重要的研究价值。

课题通过流延工艺制备了“多孔|致密|多孔”LSGM一体化基体，然后通过浸渍工艺向基体中浸渍不同的阴极材料（Sm0.5Sr0.5CoO3，SmBaSrCo2O5，Sr2Fe1.5Mo0.5O6，La0.6Sr0.4Fe0.9Sc0.1O3-δ），研究不同阴极材料对一体化单电池性能的影响，并考察不同阴极材料氧气还原反应动力学过程。成功制备出具有良好性能的Ni-LSGM/LSGM/SBSCO-LSGM单电池，在550℃下的最大功率密度为1.80 W/cm2，极化阻抗为0.036Ω cm2，为高性能中低温SOFC的设计制备提供了新的创新性方案。