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.

Recently, new perovskite cathode material, SrCo_0.8Nb_0.1Ta0.1O_3-δ (SCNT) was reported, showing high oxygen reduction reaction (ORR) activity. This study demonstrates thin film deposition of SCNT by pulsed laser deposition technique applied to anodic aluminum oxide (AAO) based thin-film solid oxide fuel cells (TF-SOFCs) to assess the possibility of SCNT application to TF-SOFCs. The SCNT powder and the target were prepared by the solid state reactive sintering method (SSRS). This target was then mounted to the pulsed laser depositing machine and deposited on the Si wafer, and the nano-porous substrate, AAO. The physical structure and the chemical phase were investigated by the field emission scanning electron microscope, focused ion beam scanning electron microscope, and X-ray diffraction. On the top of the AAO, thin Pt film and yttria stabilized zirconia (YSZ) were first deposited by sputtering and the SCNT was deposited on the top of it afterward. The open circuit voltage of AAO cell was tested at 500°C, and successful polarization activity of SCNT was observed.

Solid oxide fuel cells (SOFCs) are at a technological level close to commercialization, which could be enabled by new material research. Especially, not only an electrolyte, but also a cathode material becomes very important to further increase electrochemical performance, due to the effort to lower operating temperature of SOFCs to intermediate range (400-600℃) to take advantage of high and low temperature operation. Unfortunately, this trend inevitably results in demand for new cathode materials with high oxygen reduction reaction activity, as well as high mechanical durability. Recently, ceramic materials which conduct oxygen ion, proton, and electron, thereby called ‘triple conducting oxide’ are being highlighted, due to their excellent material properties, to be used for cathodes of SOFCs. This paper reviews the three representative triple-conducting oxides, which were already used and tested in SOFC operating conditions.