相转变-原位析出法制备低温固体氧化物燃料电池阴极及其氧还原机理研究

Solid oxide fuel cell (SOFC) is an electrochemical energy conversion device that can efficiently convert chemical energy into electricity. Developing low-temperature cathode materials with high oxygen reduction reaction (ORR) catalytic activity is the key to the commercialization of SOFC. The control of the electrode channel structure, together with the introduction of nanoparticles on electrode surfaces, represents one feasible strategy to improve the electrode oxygen reduction activity. Herein, a low-temperature cathode modified by nanoparticles prepared through a phase-inversion and in-situ exsolution method was used to systematically investigate the structure-activity relationship between the electrode microstructure and oxygen reduction activity. First, the appropriate SrCoO3-δ-based perovskite oxide is selected as the host of the cathode material. Second, Ag, Pd, Pt, Ni, and other elements, which are easily exsolved, are doped into the perovskite lattices. The electrode channel structure was then prepared on the electrode surface by the phase-inversion method. Finally, the nano-catalyst was exsolved in-situ by controlling the atmosphere in order to obtain the nanoparticle modified electrode with special micro-morphology and high ORR activity at low temperatures. An in-depth study is also carried out to illuminate the diffusion behavior of metal cations in the perovskite strutures and the effect of interfacial properties of the nanoparticles and perovskites on the ORR. Using the optimized electrode material as the cathode of SOFC, we further develop a high-performance stack system operating at reduced temperatures. This project aims to open up a new research direction for the research of SOFC cathodes and can provide guidelines for the industrialization of SOFC.

固体氧化物燃料电池(SOFC)是一种高效的电化学能量转化装置，开发高氧还原活性的阴极、降低电池的操作温度是其商业化应用的关键。电极孔道结构的调控和纳米催化剂的引入可以有效提高电极的氧还原活性。本项目将采用相转变-原位析出法制备特殊孔道结构的纳米颗粒修饰的低温阴极，系统研究电极微观形貌与氧还原活性的构效关系。选择合适锶钴基钙钛矿氧化物作为阴极的主体；将易于析出的Ag、Pd、Pt、Ni等元素掺杂进入钙钛矿晶格中；利用相转变法制备特殊孔道结构的电极；通过调控气氛原位析出掺杂元素获得具有特殊孔道结构的纳米颗粒修饰的高性能阴极并阐明金属离子在钙钛矿中的扩散行为以及纳米颗粒与钙钛矿界面性质对氧还原性能的影响；将优化后的电极进行电堆放大应用于低温操作的电堆系统。通过本项目的研究，为SOFC阴极领域开辟一个崭新的研究方向，为SOFC的产业化提供支持。

为降低成本以及将SOFC应用到小的移动式发电系统，其操作温度需要降低到400-600 °C的低温区间。因此，开发新型阴极材料和优化电极结构，提高电极在低温下操作的性能以及稳定性显得尤为重要。在本项目中，我们选择BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY)材料作为研究主体，确认了其A位缺陷或B位缺陷可以有效提高阴极表面氧交换能力和体相扩散能力，从而提高阴极氧还原活性，这为研究A位或者B位金属析出后性能提升提供理论支撑。进一步我们研究了包括Ni在内的一系列B位掺杂的BCFZY阴极材料，解释了B位Ni掺杂的优势及其高性能机理。随后通过原位析出法制备NiO纳米颗粒修饰的BCFZY电极以及相转变法制备的BCFZY电极，确认了两种提高阴极的策略、机理及他们协同作用。最后，通过相转变-原位析出法制备的Ba(Co0.4Fe0.4Zr0.1Y0.1)0.95Ni0.05O3-δ电极在500°C时电化学阻抗谱仅为0.11Ωcm2，单电池SOFC峰值功率密度最高接近1.5Wcm-2。由于相转变法和原位还原法操作简单，便于规模化放大，我们将优化后的电极进行平板放大，单片电池在650°C时功率输出可以达到46W。同时，研究A位缺陷对Ni掺杂的BCFZY氧还原活性影响时，发现当A位一定缺陷时，B位Ni可以以氧化物形式与主体钙钛矿氧化物原位混合，性能优于相转变-原位析出的阴极。总之，通过本项目的研究，可以为SOFC阴极领域开辟一个崭新的制备方法，提高我国在该领域的国际竞争力。该项目的研究也为其他领域，如透氧膜及膜反应器，氧传感器，低温氧催化剂等材料的开发和制备提供借鉴。