Scandia-stabilized zirconia (ScSZ) cathode functional layer fabricated via DC reactive sputtering for low-temperature solid oxide fuel cells

Abstract

Solid oxide fuel cell (SOFC) operation at low temperatures is a promising approach for achieving efficient, stable, and reliable electricity generation while significantly reducing carbon emissions. However, slow oxygen reaction kinetics significantly increase interfacial resistance, presenting a significant challenge in lowering the operating temperature. This study explores the use of scandia-stabilized zirconia (ScSZ) as a cathode functional layer (CFL) to enhance oxygen reduction reaction (ORR) kinetics on the electrolyte surface at a low operating temperature of 450 °C. We prepared ScSZ CFL-coated fuel cells using the direct current (DC) reactive sputtering technique to experimentally validate the electrochemical performance. We confirmed that DC reactive sputtering not only reduces deposition time compared to conventional methods but also enables grain size control by adjusting the applied DC power. The ScSZ CFL-coated fuel cells demonstrated that small grains on the electrolyte surface can improve the electrochemical reaction sites for oxygen incorporation by increasing the grain boundary density. The electrochemical performance measurements indicated that the fuel cells coated with ScSZ CFLs at a DC power of 120 W exhibited a peak power density 1.6-fold higher than that of uncoated fuel cells. Electrochemical impedance spectroscopy analysis also revealed that the nanograin surface of the electrolyte significantly contributed to enhancing fuel cell performance by improving ORR kinetics.