PrBaCo2O5基新型SOEC氧电极的电化学性质及铬忍耐性研究

Solid oxide electrolysis cell (SOEC) is a high-efficient, low emission device for energy conversion, but its practical application is restricted by the oxygen electrode problems of high overpotential and Cr-poisoning. To solve these problems, we will take advantage of the properties of PrBaCo2O5 (PBCO) oxide including fast oxygen transport, high electrical conductivity and free of traditional Mn, Sr nuclei, to develop novel oxygen electrode materials for SOEC with high electrochemical performance and high Cr-tolerance ability. Furthermore, the substitution of Co by Nb can further alleviate the surface segregation and thereby improve the performance. Main objectives of this study include: (1) The electrochemical performance of PBCO based electrodes will be studied by AC impedance spectra and polarization curves, and the O2 revolution mechanism will be elucidated; (2) The possible Cr-deposition and electrode poisoning mechanism under various temperature, atmosphere and polarization current conditions will be clarified by using techniques of XRD, SEM/TEM/EDX etc.; (3) the oxygen transport properties will be performed using a electrical relaxation experiment and changes of surface exchange kinetics under Cr-containing vapor will be obtained. Through this project, new phenomena of Cr- deposition and poisoning under oxygen evolution condition will be clarified and thus the scientific basis and technical support for SOEC development will be presented.

固体氧化物电解池（SOEC）是一种高效、清洁的能量转化装置，但现有氧电极存在的过电位高和容易Cr中毒问题限制了其实际应用。为解决这些问题，我们利用PrBaCo2O5（PBCO）具有快速氧输运、高电导率和不含Sr、Mn传统成核剂的特点，来开发高性能、高Cr忍耐性的新型SOEC氧电极材料。进一步地，希望通过Co位高价Nb掺杂来减少表面偏析、提高电极性能。主要研究内容包括：1）通过交流阻抗谱、极化曲线等方法系统研究PBCO和Nb掺杂PBCO电极的电化学性质，分析氧析出机理；2）利用XRD、SEM/TEM/EDX等技术，揭示不同温度、气氛和极化电流条件下样品表面元素重分布和微结构演变规律，进而阐明相应的Cr沉积、中毒机理；3）采用电导弛豫研究电极的氧输运性能，得到含Cr环境下表面交换动力学的变化规律。希望通过本研究解释氧析出条件下的Cr沉积与中毒的新现象，为推动SOEC发展提供科学依据和技术支撑。

固体氧化物电解池（SOEC）是一种高效、清洁的能量转化装置，但现有氧电极存在的过电位高和不稳定问题限制了其实际应用。本项目以具有快速氧输运、高电导率的双钙钛矿材料为研究对象，主要取得了以下研究进展：1）对 PrBaCo2O5+δ（PBCO）氧电极的电化学活性和稳定性进行研究，发现阳极极化作用会导致PBCO电极表面析出BaO绝缘相和电极活性下降，阴极极化具有相反作用，提出了PBCO电极的失活/恢复机制；2）阳极极化电流会促进Ba在电极表面的偏析，在与含Cr不锈钢连接体接触后，氧电极性能衰退明显，极化电阻和阴极过电位显著增大。证实Cr沉积的机制不是电化学还原，而与表面偏析密切相关。3）发现高温退火导致电极表面发生元素偏析、形成BaO第二相沉淀物，且电极颗粒出现粗化团聚。分析认为偏析物阻塞氧的吸附路径，颗粒团聚降低了电极活性并导致电极性能衰退，此外CO2气体对PBCO电极的活性有明显的毒化作用。本研究加深了对双钙钛矿基氧电极材料高温性质的理解，对SOEC及相关研究起到了很好的促进作用。