Comparison of the Electrochemical and Degradation Behaviour of Ni-YSZ and Ni-GDC Electrodes Under Steam, Co- and CO2 Electrolysis

Abstract

This present study aims to investigate and compare the long-term stability of Ni-GDC and Ni-YSZ under three different electrolysis modes; steam electrolysis, co-electrolysis and CO2 electrolysis. Firstly, electrolyte-supported single cells of Ni-GDC (NiO-GDC//8YSZ//GDC//LSCF) and Ni-YSZ (NiO-GDC//8YSZ//GDC//LSCF) were fabricated and investigated using electrochemical impedance spectroscopy (EIS). Furthermore, the impedance data were also recorded under polarization (0.7 to 1.4V) as well as at OCV. Finally, stability tests of the single cells were carried out under steam (H2O:H2, 50:50), co- (H2O:CO2:CO, 40:40:20) and CO2 electrolysis (CO2:CO, 80:20) conditions at 900 °C with -0.5 A/cm2 current density. The results reveal that Ni-GDC exhibits higher current density and lower polarization resistance (Rp) than Ni-YSZ in all the electrolysis modes. Furthermore, the Ni-GDC cells show a lower degradation rate than Ni-YSZ. However, Ni migration and agglomeration were observed in both electrodes. The detailed electrochemical and microstructural properties of the operated cells will be presented and discussed.