Introduction
High temperature steam electrolysis (HTSE) using solid oxide electrolysis cell (SOEC) is a promising way for large-scale hydrogen production with high-efficiency and zero-emission. The overall efficiency of HTSE process is over two times higher than that of the conventional alkaline water electrolysis. Although SOEC is a reversible process of SOFC in principle, SOEC is dramatically different with SOFC considering the reaction and degradation mechanism of cathode under high temperature and humidity conditions. Therefore, it is necessary to investigate the reaction characteristics of SOEC in detail.
In this paper, the electrochemical properties of single SOECs at different reaction conditions were investigated, through voltage-current (V-I) characteristic curves and electrochemical impedance spectroscopy (EIS). The microstructural changes of SOECs under both fuel cell and electrolysis operating mode were also studied
Experimental
The SOEC configuration utilizes a planar Ni-YSZ anode support structure with a thin YSZ film and LSM cathode. The anode and electrolyte were fabricated by tape-casting technology and the cathode was prepared by screen-print method. Cells were tested by self-developed SOEC online-testing apparatus (shown in Fig.1).
Results and Conclusion
The experimental results showed the hydrogen production rate under 1.1 and 1.3V electrolysis voltage were 23 and 55ml/h•cm2 at 850ºC, respectively. The polarization resistances of SOEC decreased with the increase of electrolysis voltage from 1.0V to 1.6V, which is the same trend in fuel cell mode.In addition, the electrolysis performance can be improved significantly through the optimization of anodic microstructure, which will be discussed further in the formal manuscript.