High-performance solid oxide electrolysis cell based on ScSZ/GDC (scandia-stabilized zirconia/gadolinium-doped ceria) bi-layered electrolyte and LSCF (lanthanum strontium cobalt ferrite) oxygen electrode

•Thin bi-layered ScSZ/GDC electrolyte SOEC is developed for H2O/CO2 electrolysis.•ScSZ blocks the electron leakage across GDC, but reacts with GDC on co-sintering.•The cell shows very high electrolysis current density of >−2 A/cm2 at 800 °C.•High cell performance hail from LSCF electrode instead of thin ScSZ/GDC electrolyte.

The work presented focuses on the development and performance evaluation of Ni-YSZ (nickel-yttria-stabilized zirconia) supported solid oxide cell with bi-layered ScSZ/GDC electrolyte structure and LSCF (lanthanum strontium cobalt ferrite) oxygen electrode in high-temperature steam and carbon dioxide electrolysis. At 800 °C, the cell exhibited a very high electrolysis current density of about −2.2 A/cm2 and −1.9 A/cm2 in steam and CO2 electrolysis, respectively. A slightly lower ASR (area specific resistance) is observed in electrolysis mode when compared to fuel-cell mode. Moreover, the ASR is increased when increasing the CO2 concentration in both modes of operation. The OCV (open circuit voltage) of SOEC with bi-layered electrolyte structure is significantly improved than the cell with single-layered GDC (gadolinium-doped ceria) electrolyte but at the cost of an increase in the ohmic resistance (Rs) of cell. The formation of (Zr, Ce)O2−x solid solution by the mutual diffusion of zirconium and cerium during co-sintering is found to be the origin of the increase in the Rs. Impedance spectra revealed that the high electrolysis performance is caused by the low polarization losses at LSCF oxygen electrode rather than the thin bi-layered ScSZ/GDC electrolyte structure.