Evaluation of Electrolyte Materials of Gd- and Ce-Doped Scandia-Stabilized Zirconia and Yb- and Bi-Doped Gadolinium-Doped Ceria for Highly Durable Solid Oxide Fuel Cells

Abstract

Solid oxide fuel cells (SOFCs) have attracted significant attention as a highly efficient type of fuel cell. Recent research proposes the use of co-doped scandium-stabilized zirconia with Gd and Ce (denoted as 10Sc0.5Gd0.5CeSZ) and Yb and Bi co-doped gadolinium-doped ceria (denoted as GYBC) as promising materials for the electrolyte and buffer layers, respectively. 10Sc0.5Gd0.5CeSZ exhibits excellent structural stability and ionic conductivity, which can be attributed to the doping of Ce for enhanced stability and Gd for improved ionic conductivity. On the other hand, GYBC demonstrates good sinterability and ionic conductivity due to the ability of Bi to lower the sintering temperature and the high ionic conductivity of Yb. To evaluate the feasibility of 10Sc0.5Gd0.5CeSZ and GYBC at the single cell level. X-ray diffraction (XRD) peaks and Rietveld refinements show good structural stability with slight increase in the lattice parameter by doping. The particle morphologies, size distributions, and BET surface areas are evaluated for the basic material characterizations. Then, lanthanum strontium cobalt ferrite (LSCF)–gadolinium-doped ceria (GDC) was selected as cathode material with 10Sc0.5Gd0.5CeSZ and GYBC. Finally, a single cell composed of Ni-Yttria stabilized zirconia (YSZ)/10Sc0.5Gd0.5CeSZ/GYBC/LSCF-GDC (6.5:3.5) is fabricated by sequential 3-layer co-tape casting technique, and it shows good open circuit voltage of > 1.0 V, high electrochemical performance of 0.73 W/cm² and low ohmic resistance of 0.17 Ωcm² at 750 °C. Then, the electrochemical characteristics and long-term durability of this single cell are evaluated over 500 h without degradation issues. Based on these results, it is concluded that 10Sc0.5Gd0.5CeSZ and GYBC are promising candidate materials for SOFCs.