High temperature steam electrolysis (HTSE)，which is the electrolysis of steam at high temperature with high efficiency using planar solid oxide electrolysis cell (SOEC) technology, has received an increasing amount of international interest because of its potential for large-scale hydrogen production using nuclear hydrogen in future.However, it is of great importance to control polarization energy loss and performance degradation for a practical HTSE process.In this paper, the distributions of the polarization resistances of the LSM/YSZ/Ni-YSZ (LSM: Sr doped LaMnO3; YSZ: Y2O3 stabilized ZrO2) cell under a real operating state and using different operating modes were investigated by electrochemical impedance spectroscopy (EIS).We discussed the differences between the SOEC and the solid oxide fuel cell (SOFC) while the steam diffusion process in the cathode support layer of SOEC was determined to be the rate-determining step.Based on the above-mentioned research, the microstructure of the cathode support layer was adjusted and optimized by polymethyl methacrylate (PMMA) pore formers.The results show that the SOEC cell gives much better performance after the optimization.The porosity increased by 50％ when PMMA was used.The hydrogen production rate was as high as 328.1 mL·cm-2·h-1 (nominal) when using an electrolysis voltage of 1.3 V, which was about 2 times as that of the starch pore formers.The cell was operated stably for more than 50 h.Our research provides theoretical data and establishes a technical foundation for further study into and application of this novel technology.%基于高温固体氧化物电解池(SOEC)的高温蒸汽电解(HTSE)制氢技术作为一种非常有前景的大规模核能制氢新方法,受到国际上的迅速关注.但如何控制电解模式下的极化能量损失和性能衰减是HTSE实用化的关键.本文通过在线电化学阻抗测试技术,研究了实际运行状态下的单体固体氧化物池(SOC)在电池模式和电解模式下的极化阻抗分布,阐述了SOEC与高温固体氧化物燃料电池(SOFC)的差异,确定了SOEC氢电极支撑层水蒸气扩散过程极化损失大是制约电解池制氢性能提高的主要因素,在此基础上,采用聚甲基丙烯酸甲酯(PMMA)造孔剂对氢电极支撑层的微观结构进行了调整和优化.微结构优化后,氢电极材料的孔隙率提高了50%,孔隙为规则圆形,分布均匀,更利于气体扩散;电解电压1.3V时,单位面积产氢率高达328.1 mL·cm-2·h-1(标准态),为改进前电解池的2倍,实现50 h以上连续稳定性运行.研究成果可为HTSE的实际应用提供一定的理论数据和技术基础.
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