钙钛矿类超高氧离子导体的原子层次结构设计与可控制备

It is the pivotal step to clarify the underlying oxgyen self-diffusion mechanism in order to obtain next-generation superior oxgyen ionic conductors. Perovskite oxides provide a broad platform for the development of new functional materials due to their versatile stoichiometry and flexible structural distortions. Taking perovskite oxdies (such as double perovskite with AA`BB`O6-d formula, Ruddsen-Popper type and A-site ordering doule perovskite with formula REAB2O5+d, in which RE means rare earth elements) as object, the main task of this project is to investigate the relationship between atomic-scale microstructures and oxygen ionic conductivity by employing the combination of first-principles simulation and experimental efforts. First, by comprehensive first-principles calculation based on density functional thoery (DFT), the atomic-scale microstructural control is carried out by optimal configuration of chemical stoichiometry (here we pay much attention on the effect of rare earth element as “fine tuning swith of microstructures”), senior regulation of cation ordering degree and deliberate strain engineering sequentially. The goal of this project is to increase the oxygen vacancy concentration in the crystaline perovskites and optimize the oxgyen transportation, simulatenously revealing the intrinsic mechanism of superior oxygen ionic conductivity and enriching the physics of functional defects. For the promising compounds obtained from the theoretical simulations, we will intentionally carry out controlled synthesis of the compounds, crystal structural characterization and electrochemical measurement to obtain the new material with superior oxgyen ionic conductivity. This will provide a fundemental guidance and new materials for the application of solid oxide fuel cells in low-intermediate temperature.

阐明晶态体系中氧离子自扩散的基本规律是获得新一代低温高氧离子导体的关键。钙钛矿类氧化物由于其组分和结构的多样性，为新材料的开发提供了广阔的平台。该项目拟以钙钛矿类氧化物(如AA`BB`O6型，Ruddsen-Popper型以及A位层状有序双钙钛矿REAB2O5型，RE为稀土离子)为研究对象，采用计算机模拟与实验相结合的方法，研究材料原子尺度微观结构与氧离子导电性能的关系。首先采用基于密度泛函理论的第一性原理计算，逐次通过组分优化配置(尤其着重研究稀土离子作为“结构微调谐开关”作用)、阳离子有序度调谐及引入界面应力三方面来实现微结构的调控，目的是增加晶态材料内氧离子空位浓度并优化氧离子传输，揭示超高氧离子传导的微观本质，并丰富功能化缺陷物理学。对理论发现的潜在材料进行制备，微观结构解析及电化学性能测试，最终获得超高氧离子导电材料。为固体氧化物燃料电池的应用提供理论指导及新型材料。

在世界能源与环境危机下，发展清洁可持续的的能源是一项重要任务。燃料电池被认为是一种非常具有应用前景的器件，其中固体氧化物燃料电池因其燃料的可选择性，全固态等优势被广泛关注。阻碍其应用的就是在低温度时(500-700C)其较低的氧化还原活性和稳定性。因此发展具有高氧离子传导的电催化活性材料成为解决这一问题的有效途径。该项目以钙钛矿类氧化物为研究对象，采用A位离子掺杂，B位氧离子有序度调控及表面修饰手段，以提高氧离子传导为目的，最终获得优异电催化活性材料为目标。结果表明Bi离子掺杂有利于细化晶粒并提高氧空位生成能，微量的Mg掺杂可以大大提高La2NiO4+的阴极材料的综合性能，发现了一条非常有效且简单的提高固体氧化物燃料电池阴极材料性能的途径；Pr的掺杂量为x = 0.1 时样品具有最高的电催化活性，在700 和650 °C时，界面极化阻抗分别为0.026和0.038 Ω cm2，以H2为燃料的阳极支撑单电池峰值功率密度分别为1236.4 和905.9 mW cm−2，并且在600 °C时，表现出优异的长期稳定性（~150 h），Sr掺杂使得B位阳离子有序度降低而提高氧空位浓度，从而提高氧离子传导性能，通过通过一种简便而有效的喷雾浸渍工艺，在多孔的La0.6Sr0.4Co0.8Fe0.2O3-δ（LSCF）阴极骨架上引入了大量的直径为10-20 nm的LSCF纳米颗粒，大大提高了电极的比表面积电极化处理；浸润，过渡金属纳米粒子出溶及氧化还原活性氧化物复合均可提高电极表面催化活性。如La0.6Sr0.4Co0.2Fe0.8O3-/CeO2复合纳米纤维作为固体氧化物燃料电池高活性的阴极催化剂其极化阻抗（0.158 Ω cm2）为La0.6Sr0.4Co0.2Fe0.8O3-的1/5；以H2为燃料的阳极支撑单电池峰值功率密度达到1221.6 mW cm−2，远高于单相LSCF粉末阴极的单电池峰值功率密度 （861.8 mW cm−2）。该复合阴极也表现出优异的长期稳定性（在600 °C连续稳定输出200 h）。所有相关成果发表SCI论文14篇，包括J. Mater. Chem. A, J. Power Sources, ACS Appl. Materials & Interface等。培养博士研究生5名，硕士研究生1名。