【作者】 国星；

【导师】 路文江； 汤富领；

【作者基本信息】 兰州理工大学 ， 材料加工工程， 2012， 硕士

【摘要】 固体氧化物燃料电池是一种将碳氢化合物的化学能通过电化学反应转化成电能的最有效的装置，近年来其在清洁、高效分布式发电领域中越来越受到人们的重视。固体氧化物燃料电池（SOFC）是已发明的由化学燃料直接转化为电能的最有效的装置。综合考虑La_1-xSr_xMnO₃为最合适的SOFC阴极材料。阴极/电解质界面（LSC），阴极将氧分子还原为氧离子，该反应是在强的氧化气氛中进行的，而且钙钛矿材料表面对氧的吸附和扩散机理对其电化学性能的影响非常重要。利用同位素(¹⁸O₂)示踪法分析反应机理，发现O₂/LSC表面发生氧吸附决定了阴极反应的速率；也就是说，第一步的吸附反应决定了固体阴极材料的性能好坏。因此采用基于密度泛函的第一性原理方法，系统研究La/SrMnO₃电学性能及导电机理并比较La/SrMnO₃（001）三种外表面对O原子的吸附，以及O₂分子在各表面解离过程具有重要的现实意义。我们对La/SrMnO₃采用vasp和castep软件进行了系统的晶格结构和电学基本性能计算的基础上，采用基于密度泛函的第一性原理的方法，同时结合Nudged Elastic Band方法，系统研究了O原子和O₂分子在La/SrMnO₃（001）表面的吸附过程。详细比较MnO₂、LaO和SrO作为（001）外层表面O原子吸附的性能和表面结构变化；给出O₂分子在MnO₂、LaO和SrO外表面的解离路径和势垒；研究O原子在三种表面的扩散过程，计算出各扩散路径的势垒和最稳定的吸附位置的基本情况。在此基础上，通过比较解离、扩散和放氧环节的激活能数据，提出O₂的解离和表面放氧过程均为速率控制步骤。进一步为La/SrMnO₃作为固体阴极材料时决定性能的第一步吸附反应提供了理论数据的支持。更多还原

【Abstract】 More and more attention has been paid on the field of clean, efficient distributedgeneration in recent years. At the same time, the solid oxide fuel cell is the most effectivedevice to transform hydrocarbon energy to electrical energy through the electrochemicalreaction. The solid oxide fuel cell （SOFC） was invented to transform the chemical fueldirectly into electricity. So, it is most appropriate SOFC cathode materials.Cathode/electrolyte interface restore the oxygen molecules to oxygen ions. The reaction is astrong oxidizing atmosphere; perovskite surface oxygen adsorption and diffusion mechanismof their electrochemical performance is very important. Analysis of reaction mechanism, theisotope tracer method (¹⁸O₂) found that O₂/LSC surface oxygen adsorption decide the cathodereaction rate. In other words, the first step of the adsorption reaction determines theperformance of the solid cathode materials. Therefore, using the first principles method basedon density functional theory. We study La/SrMnO₃electrical properties and conductivemechanism and compare La/SrMnO₃on （001） three exterior face of the adsorption of O atoms,and O₂molecules in each surface during the dissociation process, because it has importantpractical significance.We adopt VASP software to calculate lattice structure and electrical performance ofLa/SrMnO₃,using first-principle pseudopotential plane wave calculations and the NudgedElastic Band method based on density functional theory, to study the dissociation ofmolecular oxygen on La/SrMnO₃（001） surface and the subsequent diffusion of atomicoxygen into the magnesium substrate. We provide O₂molecules dissociation path on the outerMnO₂, LaO and SrO surface and the energy barrier, investigate diffusion processes of O atomon three outer surfaces La/SrMnO₃（001） by calculation for each position potential barrier andthe stability of the basic situation of the adsorption position. On this basis, we compare thevalues of the activation energies for the steps of dissociation, diffusion, and desorption,propose dissociation of O₂and release oxygen during surface rate-determining step. Finally,we propose that solid cathode material for the La/SrMnO₃as the first step in determiningperformance when the adsorption reaction provides a theoretical support for data.更多还原