钐掺杂氧化铈-镧锶钴铁纳米复合阴极的微观反应机理及多场耦合优化研究

Infiltrating doped cerium oxide into La1-xSrxCo1-yFeyO3-δ cathode can greatly reduce the cathode polarization impedance in solid oxide fuel cells, however the microscopic reaction mechanism is not clear, systematic and in-depth research of the corresponding oxygen reduction/transport process and the multi-field coupling mechanism are needed. In this project, by adopting the first-principles method, the microscopic mechanism of the fact that samarium-doped cerium oxide can greatly enhance the reaction process of the La1-xSrxCo1-yFeyO3-δ cathode can be explored, the reaction path and the rate-determining steps can be calculated, and the corresponding electrode process kinetics equation can also be deduced. Comprehensively considering the influence of the reaction mechanism, the special microstructure and experimental factors of the nano-particle composite electrode, the analytical expressions for the effective properties of the electrode, including: the electronic/ionic conductivity, the effective area of the electrochemical reaction, the effective pore diameter and the permeability etc. are given. And on this basis, coupling the deduced kinetics equation of the electrode process and other controlling equations, a multi-field coupling model of the cell including several process of gas transmission, electron、ion transport, heat transport and electrochemical reaction etc. is built, which can fulfill the multi-scale and multi-field modeling from the calculation of the microscopic reaction mechanism to the optimization of the electrode structure. This project has the important guiding significance in understanding the mechanism of the oxygen reduction/transport in the SmxCe1-xO2-δ-La1-xSrxCo1-yFeyO3-δ cathode, optimizing the microstructure of it and improving the SOFC power efficiency.

固体氧化物燃料电池中，掺杂的氧化铈浸渍在镧锶钴铁阴极上能够大幅度降低阴极的极化阻抗，但是其微观反应机理却并不明确，相应的氧还原/传输过程和多场耦合机理还有待系统深入的研究。本项目拟采用第一性原理方法探究钐掺杂的氧化铈能显著增强镧锶钴铁阴极反应过程的微观机理，计算出反应路径、控速步骤并推导出相应的电极过程动力学方程；综合考虑纳米复合电极的反应机理、特殊微结构及实验因素的影响，给出电极的电子/离子导率、电化学反应有效区间、有效气孔直径及渗透率等电极有效性质的解析表达式；并在此基础上，耦合已推导出的电极过程动力学方程及其他控制方程，建立起包含气体传输，电子、离子传输，热量输运及电化学反应等多个过程在内的电池多场耦合模型，实现从微观反应机理计算到电极结构优化的多尺度多场模拟。该项目对理解钐掺杂的氧化铈-镧锶钴铁纳米复合阴极的氧还原/传输机理、优化其微结构进而提高SOFC发电效率具有重要的指导意义。

混合导体镧锶钴铁(LSCF)是一种综合性能优异的中低温固体氧化物燃料电池阴极材料。人们发现钐掺杂的氧化铈(SDC)浸渍在LSCF阴极上能够大幅度降低阴极的极化阻抗，然而其微观反应机理却并不明确，相应的氧还原/传输过程和多场耦合机理还有待系统深入的研究。本项目1)利用第一性原理方法及过渡态理论对SDC-LSCF纳米复合阴极的微观反应机理进行研究，给出SDC-LSCF纳米复合阴极材料构建及优化的指导性建议；2)综合考虑纳米复合电极的微观反应机理、特殊微结构及实验因素的影响，结合等效球概念和逾渗理论，推导出SDC-LSCF纳米复合阴极的电子/离子导率、电化学反应有效区间、有效气孔直径及渗透率等有效性质的解析表达式，得到SDC-LSCF纳米复合阴极性能与其微结构的内在关系；3)最终建立起适用于混合导体材料的,包含气体传输，电子、离子传输，热量输运及电化学反应等多个过程在内的燃料电池多场耦合模型，给出SDC-LSCF纳米复合阴极的最优化微结构参数，实现从微观反应机理计算到电极结构优化的多尺度多场模拟。该项目对理解两相界面复杂的氧还原/传输机理，以及对包含混合导体的纳米复合电极微结构优化具有重要的指导意义。项目执行期间，发表或接收标注本项目支持的SCI论文9篇，培养研究生3名，项目负责人多次参加与本项目相关的学术会议，并应邀赴香港访问学习3.5个月。