基于原位SERS技术的低温SOFC双钙钛矿阴极的性能衰减机制研究

It is crucial to clarify performance degradation mechanism of common cathode materials for enhancing stability of solid oxide fuel cell (SOFC). In this proposal, double perovskite cathode materials LnBaCo2-xMxO5+δ（Ln= Pr, Nd, Sm, Y；M=Fe, Cu）are investigated as research object. The aim is to get the molecular structure evolution and how to influences variation of electrochemical performance by in situ SERS characterization technology, and on this basis we research mechanism of cathode performance degradation from microscopic view point of oxygen vacancies concentration. The detailed contents include: Firstly, we will calculate peak position, peak intensity and peak width by the Density Functional Theory; Secondly, we will measure the Raman peak position, peak intensity, peak width and electrochemical performance of cathode materials under working conditions (temperature, oxygen partial pressure, current polarization) by in situ SERS-Electrochemical technology, and analyze the relationships of them. Subsequently, clarify the structure- function relationship between molecular structure evolution and catalytic performance of the cathodes. Finally, we discuss the thermodynamics and dynamics mechanism of oxygen adsorption/dissociation and diffusion with variation of oxygen vacancy concentration for cathode and reveal the mechanism of performance degradation of cathodes. The experiment and theretical basis for solving stability problem of cathodes will be provided by the above results.

分析常用阴极材料的性能衰减机制，是提高固体氧化物燃料电池(SOFC)工作过程中稳定性的关键问题所在。本项目拟以双钙钛矿LnBaCo2-xMxO5+δ（Ln= Pr, Nd, Sm, Y；M=Fe, Cu）阴极材料为研究对象，利用原位SERS技术研究SOFC工作状态下阴极的分子结构演变及其对阴极电化学性能的影响规律，从氧空位浓度的微观角度对阴极性能衰减进行深入研究。主要内容包括：利用密度泛函理论计算确定阴极材料的拉曼峰位、峰强和峰宽；利用SERS-电化学技术原位检测在工作条件(工作温度，氧分压，电流极化)下阴极材料的拉曼峰位、峰强和峰宽变化对电化学性能的影响，阐明分子结构演变与阴极的催化性能之间的构效关系，探讨氧空位浓度变化影响阴极中氧的吸附/解离和扩散的热力学和动力学机理，揭示阴极性能衰减机制。该研究成果将为解决LnBaCo2-xMxO5+δ阴极稳定性问题提供实验依据和理论指导。

AA′BB′′O5+δ型固体氧化物燃料电池双钙钛矿阴极近年来一直被广泛研究。本项目利用EDTA-柠檬酸溶胶凝胶法合成LnBaCoCuO5+δ（Ln= Pr, Nd, Sm, Y）阴极材料，研究烧结温度对LnBaCoCuO5+δ的晶体结构、晶粒尺寸和表面微观结构影响规律，阐明Cu元素的不同比例掺杂对 YBaCo2-xCuxO5+δ 的晶体结构，热学，电学和电化学性能的影响规律和机制；采用EDTA-柠檬酸溶胶凝胶法制备LnBaCoFeO5+δ（Ln= Pr, Nd, Sm, Y）阴极材料，研究Fe元素掺杂对LnBaCoFeO5+δ的晶体结构，电导率，热膨胀系数和电化学性能的影响规律和机制；优选SmBaCoCuO5+δ、SmBaCoFeO5+δ 和YBaCo1.4Cu0.6O5+δ电极材料，研究电解质Ce0.8Sm0.2O1.9 (SDC) 和Ce0.9Gd0.1O1.95 (GDC)的引入对复合电极的晶体结构，热学，电学和电化学性能的影响规律，弄清复合电极电化学性能提升的机制；首次制备无钴基Pr1-xBaFe2O5+δ（x=0.00, 0.03, 0.07, 0.10）阴极材料，研究A位缺陷量对Pr1-xBaFe2O5+δ晶体结构，热学，电学和电化学性能的影响规律和机制。此外，采用丝网印刷技术制备薄膜电极，研究粘结剂配比和烧结温度对晶粒尺寸大小和薄膜孔隙率的影响；利用电化学工作站，高温加热装置和拉曼光谱仪组装SOFC原位拉曼测试系统，研究不同波长的拉曼系统与SOFC电化学系统匹配性；利用磁控溅射技术在阴极薄膜上制备Ag@SiO2活性基底，研究基底厚度对拉曼光谱的影响规律；利用第一性原理PBE泛函理论，研究氧的吸附/解离和扩散过程，分析Ln-O层氧的吸附、解离和氧离子扩散机制。