Long-term performance prediction of solid oxide electrolysis cell (SOEC) for CO2/H2O co-electrolysis considering structural degradation through modelling and simulation

Abstract

Solid oxide electrolysis cells (SOECs) are promising devices for CO2 and H2O co-electrolysis into syngas. Degradation occurring within SOECs is still of great concern for their commercial deployment. Therefore, it is important to understand the degradation mechanisms and optimize SOEC long-term operation. A 1-dimensional (1D) pseudo-dynamic model was developed for SOEC operating under CO2/H2O co-electrolysis and implemented in Aspen Plus® using Fortran® routines. The structural degradation of a typical SOEC material set: Ni-YSZ cathode, YSZ electrolyte and LSM-YSZ anode were also accounted for. The model was dynamically validated for different current densities (0.5, 0.75 and 1.0 A/cm2). The effects of operating conditions and structural degradation on SOEC long-term electrochemical performance and syngas production are assessed. Performance prediction indicated that increasing the current density and operating temperature initially enhance SOEC performance. However, the operating voltage increases at faster rates at higher current densities and temperatures causing the syngas production efficiency to decrease due to higher power utilisation. Long-term SOEC degradation is mostly due to LSM-YSZ anode delamination with a degradation rate of 3.96 %/1000hrs at 750 °C, 1 bar and 1.5 A/cm2. Applying an anti-oxidant layer on the interconnect surface and adjusting La/Sr ratio in the A-site of LSM considerably reduce the degradation rate by roughly 78% at the anode.