Polarization loss of single solid oxide electrolysis cells and microstructural optimization of the cathode

Abstract

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. © Editorial office of Acta Physico-Chimica Sinica.