双钙钛矿阳极反位缺陷与电化学性能的强相关性研究

Double perovskite anodes are promising electrode materials for solid oxide fuel cells due to high tolerance to carbon deposition and sulfur poisoning. However, their further applications are limited due to their inferior redox stability, low ionic-electronic conductivity and insufficient electrochemical performance. Therefore, in order to resolve the above-mentioned problem and challenge from double perovskite anode, based on first principle computation, crystallology and defect chemistry theory, we proposed a new strategy to improve the ionic-electronic conductivity, accelerate the surface exchange kinetics and boost the electrochemical catalytic activity by anti-site defects (ADs) design and control. The lattice structure characteristics, ion features (radius, valence state, coordination tendency, etc.) and material electron configurations information are applied to decorate the structure of ADs. The characteristic of B site cations and cations doping on the anti-site defects structure of double perovskite are investigated to elucidate the inside regulatory mechanism. The strong correlations between anti-site defects and electrochemical properties (ionic-electronic conduction character and electrochemical catalytic activity) of double perovskites are unveiled. This investigation will contribute to clarify the structure−property relationship for double perovskite anode and provide theoretical direction and technical support for further development of high performance double perovskite anode materials.

为解决双钙钛矿阳极材料所面临的离子-电子电导率低、催化活性不理想等问题。本课题从第一性原理计算、晶体学以及缺陷化学的角度出发，结合材料晶格结构特点、离子特性（半径、价态、配位倾向等）以及材料电子组态等信息，提出通过合理调控双钙钛矿阳极晶格中反位缺陷的结构及其数量，提高材料的离子─电子传输性能，改善材料的电化学催化活性，强化阳极的反应动力学过程，提高阳极材料的电极工作特性。阐明材料合成工艺条件、B位离子特性以及离子掺杂对双钙钛矿阳极反位缺陷结构及其数量的调控机制。揭示反位缺陷结构及数量─离子、电子传输特性─电化学催化活性间的强相关性。本课题的研究有助于完善双钙钛矿阳极材料结构与性能间的相关性理论，研究结果可为高性能双钙钛矿阳极材料的研发提供理论指导和技术支持。

为解决双钙钛矿阳极材料所面临的离子-电子电导率低、催化活性不理想等问题，课题选择具有不同金属–氧键强、不同离子半径、离子价态的过渡金属元素M（Mg、Sc、Fe、Co、Ni、Cu、Zn、Al、Ga、In、Y等）对Sr2FeMoO6、Sr2MgMoO6双钙钛矿阳极进行固溶掺杂，调控材料的晶格反位缺陷及电化学性能。系统研究了掺杂元素M对双钙钛矿阳极的晶体结构、反位缺陷、电学性能、电化学性能、氧化还原稳定性、电极反应动力学、电池稳定性的影响规律；解析了双钙钛矿阳极材料晶格反位缺陷结构，总结B位离子种类以及掺杂元素M对双钙钛矿阳极反位缺陷的调控机制；建立双钙钛矿阳极反位缺陷结构─离子、电子传输性能─阳极电化学催化活性间的强相关性。研究筛选出了适宜的掺杂元素M（Mg、Fe、Sc、Ga、Al、Co、Ni）；掺杂元素的离子半径和化学价态对A2BB’O6双钙钛矿阳极晶格反位缺陷有显著调控作用，其总体规律是：Mg2+、Co2+、Ni2+、Cu2+、Zn2+等低价离子，Fe3+、Sc3+、Ga3+、In3+等离子半径大的元素倾向占据B位；而Fe4+、Al3+等价态较高且离子半径较小的离子则倾向占据B’位；随掺杂量增加，Sr2Mg1-xFexMo1-x/2Fex/2O6阳极反位缺陷含量增加，材料有序度降低，晶格从有序结构转变为有序与无序混合，晶格有序与无序结构基元相互交融分布；揭示了双钙钛矿阳极表面Co-Fe纳米金属颗粒的原位拓扑析出机制；开发出系列具有反位缺陷结构的高性能双钙钛矿阳极体系：Sr2Mg1-xFexMo1-x/2Fex/2O6、Sr2FeMo0.6Mg0.25Ga0.15O6-δ、Sr2FeMo0.6Mg0.25Al0.15O6、Sr2FeMo0.5Sc0.5O6、Sr2FeMo0.65Co0.35O6等；研究表明在双钙钛矿阳极晶格中构建一定含量的反位缺陷有利于提高材料的离子-电子传输性能，增强电极表面反应动力学，提高阳极的电化学催化活性，电池性能得到显著提高。本课题相关研究结果为钙钛矿基材料晶格结构调控、表界面结构修饰、电化学性能优化提供了实验支持和理论指导，为SOFC高性能电极催化材料的设计开发提供了新的思路。