基于化学缺陷调控低温固体氧化物燃料电池电极结构与电催化性能

Low temperature solid oxide fuel cell (LT-SOFC) is a promising new energy technology for electric power generation. However, the reduction of electro-catalytic activity of electrode material at low temperature becomes a key issue to be solved. The high performance Ba1-xCoFeO3 perovskite electrode material in the low temperature (400-600℃) working temperature range is designed in this project, to synergistically achieve electro catalytic performance improvement for low temperature symmetric SOFC. By controlling the composition and structure of the material, the chemical defective perovskite electrodes with stable structure, high oxygen vacancy concentration and protonic conductivity will be designed and fabricated to improve the carrier conductivity and maintain structural stability, and to reveal the inner mechanism of cathode ORR performance enhancement due to cation deficiency. Nano metal particles are exsolved from A-site deficient Ba1-xCoFeO3 perovskites through in-situ reduction process to enhance the anode catalytic performance for hydrogen oxidation reaction (HOR). At last, symmetrical solid oxide fuel cells (S-SOFC) using Ba1-xCoFeO3 as both cathode and anode are fabricated. The reversibility and stability of the S-SOFC are revealed to promote the development of SOFC. This project will study new type of electrodes and structural design and preparation methods to develop a common method to enhance the electro-catalytic performance for low temperature electrodes, which has great importance to the theoretical development and practical use of LT-SOFC.

低温固体氧化物燃料电池是极具发展前景的下一代发电技术，如何提高低温下电极材料电催化活性成为亟待解决的关键问题。本项目以低温（400-600℃）BaCoFeO3钙钛矿电极材料为研究对象，旨在通过组分设计等缺陷化学手段调控材料的组成与结构，实现双电极电催化活性与稳定性协同提高。设计与制备结构稳定、氧还原活性高的Ba1-xCoFeO3阴极，揭示化学缺陷对其阴极电催化活性提高机制；采用原位技术，阐明纳米金属粒子从Ba1-xCoFeO钙钛矿结构中析出过程中的形核长大机制，实现其阳极氢氧化活性和稳定性提高；在此基础上以Ba1-xCoFeO3为双电极制备对称型全电池，通过表面修饰氧离子导体提高电极/电解质界面的电荷传递，实现界面稳定性提高。本项目的研究及其成果对探究低温电极电催化活性增效机制，发展稳定的电极/电解质界面构筑方法，提高电池器件性能，具有重要的科学意义和应用价值。

低温固体氧化物燃料电池是极具发展前景的下一代发电技术，如何提高低温下电极材料电催化活性成为亟待解决的关键问题。本项目以低温（400-600℃）BaCoFeO3钙钛矿电极材料为研究对象，旨在通过组分设计等缺陷化学手段调控材料的组成与结构，实现双电极电催化活性与稳定性协同提高。本项目设计与制备了结构稳定、氧还原活性高的Ba1-xCoFeO3阴极，采用A位、B位、A/B位离子共掺杂及离子缺位等缺陷调控手段提高钴铁基钙钛矿氧化物结构稳定性及电化学性能，揭示了化学缺陷对其阴极电催化活性提高机制，在A位引入0.05%缺位不改变Ba0.9La0.1Co0.7Fe0.2Nb0.1O3-δ稳定的立方相结构，在提高ORR活性同时也展现出优秀的CO2耐受性，结合DRT分析结果可知，A位缺位会促进低频的氧气表面的吸附解离过程，有效促进氧电极的活性和质子传导性，在引入5vol%水汽后，Rp下降了21.0%，仅为0.083 Ω cm2，Ba0.9Co0.7Fe0.2Zr0.1O3-δ (B90CFZ)单电池在700 ℃的峰值功率密度PPD为586 mW cm-2，相对于B100CFZ提升了约47.9%。结合缺陷化学与高温还原技术，调控A位离子缺陷浓度，促进纳米金属粒子在还原气氛下原位析出，研究化学缺陷浓度对金属离子析出的影响，提高复合阳极在H2燃料下的催化活性与稳定性，实现其阳极高温电催化性能和稳定性提高，750 °C时，(Ba0.9La0.1)0.95Co0.7Fe0.2Nb0.1O3-δ (BL95CFN) 阳极在湿润的氢气下（含3% H2O）的极化电阻仅为0.11 Ω cm2，比未缺位样品降低42.1%；采用表面修饰、机械复合、静电纺丝、一壶法原位合成等多种复合方法协同提高Ba0.9Co0.7Fe0.3O3-δ阴极的电催化活性与稳定性；在此基础上以Ba1-xCoFeO3为双电极制备对称型全电池，通过表面修饰氧离子导体、提高电极/电解质界面的电荷传递，实现界面稳定性提高，电解质支撑型对称单电池BL95CFN|SDC|BL95CFN在750 °C湿润的氢气下最大功率密度达到456 mW cm-2，单电池的输出电压50 h内无明显衰退。本项目的研究及其成果对探究低温电极电催化活性增效机制，发展稳定的电极/电解质界面构筑方法，具有重要的科学意义和应用价值。