SoA Ni cermet based SOECs is known to be very sensitive to impurities such as sulfur components, especially for CO2 electrolysis, where cleaning of sulfur in CO2 down to sub-ppb level is required, which maybe an expensive process since sulfur is a very common impurity in CO2 captured from post- combustion sources. It is therefore arguable whether co- electrolysis is economical beneficial if SOEC can only be supplied with very high purity CO2. Considering the fact that most of synthetic fuel production processes are performed under elevated temperature and technologies based on the WGSR is at a very mature state. If cheap H2 could be produced by SOEC, and syngas could be made by CO2 hydrogenation or WGSR without large efforts in deep cleaning of the CO2. Understanding the degradation of SOEC under different inlet gas compositions is therefore important from both a technological and economic point of view.