基于离子动态重排稳定新机制的钙钛矿型固体氧化物燃料电池低温阴极材料的设计和研究

As one type of efficient electrochemical energy conversion devices, solid oxide fuel cells (SOFCs) have recently attracted numerous attentions owing to their high energy efficiency, low pollutant emissions, all solid-state structure and excellent fuel flexibility. However, the widespread use of SOFCs is hindered by their high operating temperature, leading to substantially high capital investment for commercialization. Therefore, reducing the operating temperature is critical for developing SOFCs for commercial use and one key solution is to develop new cathode materials with high activity and stability for the oxygen reduction reaction (ORR) at intermediate temperatures and low temperatures (IT and LT). We have reported a series of cobalt-based perovskite-type oxides as the cathodes for IT- and LT-SOFCs showing good ORR activity at reduced operating temperatures, which unfortunately exhibit high thermal expansion coefficient (TEC) and poor ORR stability in CO2-containing atmospheres. This project aims to develop a series of novel cathode materials that feature a dynamic ion-rearrangement capability which allows the materials’ self-regeneration in CO2-containing atmospheres. This project begins with a rational screening of the metal cations that can dynamically rearrange between the A- and B-site within the perovskite structure, followed by the doping of these cations into iron-containing perovskite oxides with low TEC values. By precisely controlling the selection, the doping amount, and the pristine doping site of the dynamically rearrangeable cations as well as the phase composition in cathode materials, excellent ORR activity, outstanding operational stability, low TEC, and superior CO2 tolerance can be achieved at the same time. An in-depth investigation into the mechanisms for the dynamic ion-rearrangement, the ORR process, and the CO2 poisoning is also conducted. This project creates a new strategy to design active and stable cathode materials, and offers significant fundamental understanding for the mechanism study of the cathodic process in IT- and LT-SOFCs, which can promote the large-scale application of the SOFC technology.

固体氧化物燃料电池（SOFC）作为一种先进的电化学能量转化装置，具有高能量转换效率等特点，近年来得到研究学者的广泛关注。SOFC的中低温化是其大规模应用的关键，而核心是设计开发在中低温下具有高氧还原活性和稳定性的阴极。我们已成功研发出一系列高活性的低温钴基阴极，但这些材料的热膨胀系数较大，在含有CO2的气氛中易失活导致性能急剧下降。本项目将设计开发一系列新型的具有离子重排能力且在CO2气氛下自我修复的高活性稳定的中低温阴极材料。项目拟引入可在钙钛矿A、B位动态迁移的金属阳离子到具有较低热膨胀系数的铁基钙钛矿氧化物中，通过对掺杂元素的种类、含量、起始位置及各相的含量进行有效调控，实现高活性、稳定性、低热膨胀系数、高CO2抗中毒能力的共赢。同时将对这种新型阴极的离子重排机制、氧还原机理和抗CO2中毒原理进行深度研究，为SOFC阴极的研发开辟崭新方向和提供有效理论基础，加速SOFC商业化进程。

固体氧化物燃料电池技术的开发和利用，可以优化我国的能源结构，降低传统火力发电所带来的环境污染，还将带动和促进相关高新技术产业的发展，对我国经济发展和国防建设具有重要意义。为满足SOFC商业化对成本和稳定性的要求，传统的高温体系逐渐向中低温发展成为一种必然趋势。阻碍中低温SOFC阴极材料的实际应用的主要因素包括以下四个方面：电化学性能低；热膨胀系数大；化学稳定性差；抗CO2中毒能力差。为了解决这些问题，本项目遴选出高活性钙钛矿型氧化物作为主体材料，引入具有动态迁移的金属阳离子（如Y3+，Ce4+/Ce3+），通过对主体材料进行合理的A/B位掺杂、一锅法制备以及有利相反应等方式最终实现阳离子在钙钛矿氧化物晶格内合理迁移和动态重排，进而提高氧还原活性（ORR），并有效降低电极材料的热膨胀系数，提高电极的热稳定性以及抗CO2中毒的能力。通过本项目的研究，有效解决具有离子动态重排能力的钙钛矿氧化物的合成及阴极制备问题，阐明阳离子的迁移对ORR活性、电池稳定性的影响机制。项目成功申请和授权国家发明专利15项，发表Nature在内的SCI收录论文35篇，培养研究生12名，在国内外会议上进行学术交流12次。本项目的执行同时培养了一支高素质、高创新能力的科研队伍，探索学术前沿，开拓新研究方向，提高了我国在相关领域的学科竞争力和国际影响力。