Optimizing the Thickness of Esb-GDC Bilayer Electrolytes for Efficient Low Temperature Operating SOFCs

Abstract

Bilayer electrolytes with high oxide ion conductive materials such as Er2O3-stabilized Bi2O3 (ESB) and Gd-doped CeO2- δ (GDC) were developed to lower the operating temperature of solid oxide fuel cells (SOFCs) without compromising their efficiency[1]. In a bilayer electrolyte design, optimizing the thickness of ESB to GDC (r ESB/GDC) and the total electrolyte thickness (h) can help to maximize the SOFC performance. However, such optimization of electrolyte thicknesses requires elaborate understanding on the voltage drop across SOFC components. In this work, efforts are made to study the voltage drop across various layers of SOFCs on a Ni-GDC based anode-supported cell. The anode-supports were deposited with ESB-GDC bilayer electrolytes with varying r ESB/GDC and h. In particular, the voltage drop across ESB (V ESB), GDC+anode (V GDC+anode) and the whole cell (V total) were determined at open circuit voltage and under load conditions. These measurements were performed by positioning the voltage probes between ESB/GDC and ESB/cathode. The behavior of V ESB, V GDC+anode, and V total with a varying r ESB/GDC and h were monitored and analyzed. Specific losses that could potentially limit the overall SOFC performance with reference to electrolyte thicknesses are addressed. [1] E.D. Wachsman, K.T. Lee, Science, 334 (2011) 935-939.