二维失配层状Ca3Co4O9-δ阴极及其纳米复相阴极的电化学性能和氧催化作用机理

The 2D-misfit-layered structure Ca3Co4O9-δ(Ca349)oxide is an emerging material in the field of thermoelectric materials. But it also has the potential application as the cathode material of SOFCs due to its similar thermal expansion coefficient (TEC) with electrolyte, appropriate electrical conductivity and good oxygen catalytic properties. The project contraposes the high TEC of the preceding cathode materials and low oxygen ion conductivity and insufficient surface oxygen exchange dynamics characteristics of single-phase cathode materials, proposes research and development of the novel materials for the Ca349 cathode prepared by a polyacrylamide.gel route with low TEC and Ca349 nano-particles impregnated SDC composite cathode, in order to solve the thermal mismatch problem caused by high TEC, and at the same time, play a synergistic catalytic effect of oxygen between the Ca349 nano-particles and the SDC electrolyte, and promote the oxygen adsorption ability and surface oxygen exchange kinetics of the cathode.Study the microstructure, the transport properties, thermal and physical properties and its electrochemical properties of Ca349 cathode and nanoparticles impregnated cathode, revealing their microscopic mechanism of oxygen catalysis. And in SOFCs, study the stability and electrochemical properties of the cells, to further explore the inherent laws of the cathode material system and the relationship between microcosmic structure and physical and chemical properties.

二维失配型层状结构Ca3Co4O9-δ（Ca349）氧化物是热电材料领域新兴的一种材料，但它有与电解质相近的热膨胀系数（TEC）、适宜的电导率和较好氧催化活性，在固体氧化物燃料电池（SOFCs）阴极方面有良好的应用前景。本项目针对以往阴极材料中高TEC及单相阴极氧离子电导率低和表面氧交换动力学不足的特点，提出采用高分子网络凝胶法制备具有低TEC的Ca349材料，并研发Ca349及其纳米颗粒浸渍Ca349-SDC复相新型材料的阴极性能，以解决由于高TEC而引起的热失配问题，同时，发挥纳米Ca349微粒和SDC电解质之间对氧的协同催化作用，促进阴极吸氧能力和表面氧交换动力学。研究Ca349阴极及纳米浸渍阴极的微结构、输运性能、热物理性能及其电化学性能，揭示它们的氧催化作用微观机理。并将其应用于SOFCs中，研究电池稳定性和电化学特性，进一步探索阴极物质体系及微结构与物理、化学性能的内在规率。

阴极材料作为固体氧化物燃料电池的关键材料，其氧的电催化性能和与电解质间的匹配性能直接影响电池的输出和应用。本项目采用高分子网络凝胶法开发了与铈基电解质（SDC、SNDC）有良好匹配性能的Ca3Co4O9-δ（Ca349）阴极材料，对单相Ca349阴极及纳米离子溶液浸渍Ca349-SDC复相阴极材料进行了深入的实验研究和理论分析。在对单相Ca349阴极的电催化性能研究的基础上，发现铈基电解质的加入能进一步促进阴极的电化学性能。首次研究和开发了Ca349阴极纳米离子液浸渍的纳米结构Ca349-SDC复相阴极和SDC电解质纳米离子液浸渍的纳米结构Ca349-SDC复相阴极，深入探讨了这两种纳米结构Ca349-SDC复相阴极中Ca349和SDC之间对氧的协同催化作用机理，并在电池中评估了纳米结构Ca349-SDC复相阴极的电化学性能。在800oC，前者纳米结构Ca349-SDC复相阴极的界面极化电阻(Rp)为0.2305 Ω•cm2, 单电池最大输出功率为489.5 mWcm-2，后者的纳米结构复相阴极的Rp为0.068 Ω•cm2, 单电池最大输出功率可达662 mWcm-2，这远优于单相Ca349阴极的性能（Rp为0.238 Ω•cm2，功率密度为209 mWcm-2）。其原因主要是纳米结构Ca349-SDC复相阴极中Ca349和SDC协同催化作用极大地增加了三相界面长度的结果。而银（Ag）纳米离子液浸入纳米结构Ca349-SDC复相阴极增加了电导率，改善了氧的输运，进一步促进了阴极的性能（Rp进一步降低为0.1346 Ω•cm2）。此研究为新型纳米结构阴极材料的开发与设计提供了新思路，也为进一步阐明纳米结构阴极协同催化作用机理提供了理论依据。