A yttria-stabilized zirconia (YSZ) cathode functional layer (CFL) was fabricated using a co-sputtering process to improve the oxygen reduction reaction (ORR) in solid oxide fuel cells (SOFCs). To optimize the yttria molar percentage and achieve a nano-granular structure with enhanced grain boundary density, the DC sputtering power for the metallic yttrium target was varied at 10, 30, and 50 W. Structural and compositional analyses were performed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and X-ray diffraction (XRD). The results indicated that a DC power of 30 W resulted in a well-developed grain structure with high grain boundary density and an yttria composition close to the optimal molar percentage of 8-10 mol %. Under these optimized conditions, the SOFC with the co-sputtered YSZ CFL achieved a maximum power output of 9.22 mW/cm² at 450^oC, representing approximately a 43% enhancement compared to the reference cell. This highlights the significant potential of co-sputtering for future low-temperature SOFC applications.

In this study, we successfully demonstrated a fuel cell fabrication method using a platinum-samarium-doped ceria (Pt-SDC) composite cathode, which could reduce the platinum content while maintaining the same thickness as the functional layer. The Pt-SDC composite cathode was deposited by a sputtering process in which two materials were simultaneously deposited by a co-sputtering system. Despite the decreased platinum content in the composite cathode, we achieved high performance of the fuel cell since Pt-SCD was able to form triple-phase boundaries (TPBs) not only at the interface between the cathode and the electrolyte but at the entire volumetric surface of the cathode. This composite cathode revealed that Pt-SDC could enhance the oxygen reduction reaction rate by enlarging the TPB site in the cathode. The fuel cell fabricated in this study with a composite cathode demonstrated improved performance at 1.66 times the peak power density of a pristine fuel cell.