Accelerating the electrochemical performance of solid oxide fuel cells using a Ce(Gd, Bi, Yb)O<sub>2-<i>δ</i></sub> diffusion barrier layer acting as an oxygen reservoir at high-current loading conditions

Abstract

Gadolinium-doped ceria (GDC) is widely used as an effective diffusion barrier layer in solid oxide fuel cells (SOFCs) to avoid the undesired reactions between the electrolyte (typically yttria-stabilized zirconia, YSZ) and electrode materials due to impurity interdiffusion. In practice, these reactions cannot be sufficiently suppressed, as the high sintering temperature of GDC hinders the formation of dense and thin barrier layers. To address this problem, we herein investigated the ability of a ternary dopant system Ce(Gd, Bi, Yb)O2-delta (Gd0.135Yb0.015Bi0.02Ce0.83O2-delta, GYBC) deposited as a novel diffusion barrier layer on YSZ to enhance the SOFC performance. A dense and thin GYBC buffer layer was successfully fabricated by ultrasonic spraying followed by low-temperature sintering at 1250 degrees C, and the corresponding unit cell (Ni-YSZ/YSZ/GYBC/La0.4Sr0.6Co0.2Fe0.8O3-delta (LSCF)-GDC/LSCF) delivered a high power density of 2.32 W cm-2 at 800 degrees C. Furthermore, GYBC favored the cathodic oxygen reduction reaction (ORR) by enhancing the oxygen supply capacity. As a result, the replacement of a commercial GDC layer by the GYBC layer increased the oxygen reservoir activity at high current densities and thus enhanced the electrochemical performance by 16%.