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Platinum (Pt) and Samaria-doped ceria (SDC) as cermet cathodes were investigated to enhance oxygen reduction reaction (ORR) kinetics in low-temperature solid oxide fuel cells (SOFCs). Pt is widely known for its high catalytic activity, whereas SDC is one of the most promising oxide ionic conductors as an LT-SOFC electrolyte. To improve both the catalytic activity and oxygen ionic transportation, a co-sputtering technique was used to fabricate a composite cathode by adjusting the elemental composition of Pt and SDC. This technique demonstrated that the Pt-SDC cermet cathode can increase the electrochemical reaction sites and offer a percolated pathway for rapid electron-ion conduction within the cermet structure. The electrochemical analysis results also revealed that the fuel cells coated with Pt-SDC cermet cathodes outperformed the pure Pt-coated fuel cells in terms of peak power density. The electrochemical impedance spectroscopy analysis indicated that the improved ORR kinetics of Pt-SDC cermet cathodes were the main reason for the improved fuel cell performance by catalyzing both electron and oxygen ion conduction. • Pt-SDC cermet cathodes were fabricated via co-sputtering technique for LT-SOFCs. • The chemical composition of cermet cathodes was controlled by RF power of SDC. • The TPB density can be enlarged by mixing the both Pt and SDC with co-sputtering. • Optimized ratio of Pt and SDC can provide the percolating path for charge transport. • Pt-SDC cermet cathode can increase the performance of fuel cell by catalyzing ORR. [ABSTRACT FROM AUTHOR]

• Screen printed LSCF-GDC composite cathode functional layer was fabricated for IT-SOFCs. • A novel, ultra-fast flash light irradiation was demonstrated as an alternative sintering method. • Interfacial side reactions were successfully suppressed by the novel process. • The maximum power density was 727.4 mW/cm2 at 750 °C. A solid oxide fuel cell (SOFC) requires an elevated operating temperature to achieve high oxygen ion conductivity and the oxygen reduction reaction (ORR). However, at high operating temperatures above 800 °C, performance deteriorates due to the chemical reaction of the electrode and electrolyte materials at the interface. Therefore, it is necessary to lower the operating temperature to the intermediate temperature regime while maintaining the high oxygen reduction reaction kinetics. One approach is adopting the composite cathode material such as La 6 Sr 4 Co 2 Fe 8 O 3-δ -gadolinium doped ceria (LSCF-GDC). However, the high temperature in the fabrication process results in non-conduction material of strontium zirconate (SrZrO 3 , SZO) layers at the cathode/electrolyte interface, which blocks oxygen ion conduction and degrades the fuel cell performance. By utilizing the novel flash light sintering process, which can be completed in a few seconds, high temperature fabrication issues are solved. The surface microstructure and thickness of the composite electrode are inspected using a scanning electron microscope (FE-SEM). The secondary phase generation and chemical reaction are analyzed using XRD (X-ray diffraction), SEM-EDS, and TEM-EDS. The anode supported LSCF-GDC cathode cells are measured from 600 °C to 750 °C. The maximum power density at 750 °C of the novel flash light sintered LSCF-GDC composite cathode cell is 727.4 mW/cm2. In addition to the utilization of high performing cathode structure, the flash light sintering process dramatically reduces the process time and suppresses the side reaction at the cathode/electrolyte interface. [ABSTRACT FROM AUTHOR]

• Samarium doped ceria thin film interlayer is fabricated by electrostatic spray deposition. • The sintering process was performed by flash light sintering with bottom heater. • The sintering time is dramatically reduced from hours to seconds. • By applying the flash light sintered samarium doped ceria thin film interlayer, it can be confirmed that the fuel cell performance is improved by about twice. To commercialize solid oxide fuel cells, many methods for reducing the production time of manufacturing a fuel cell membrane-electrode-assembly (MEA) using a non-vacuum process have been studied and still the post-heat treatment process is an issue. This paper discusses an alternative sintering method to replace the conventional thermal sintering step for ceramic thin film fabrication, which is time consuming and costly. We fabricated samarium-doped ceria (SDC) thin films, which has high ionic conductivity and high surface exchange coefficient for oxygen reactions at the cathode side. The films were deposited by chemical solution deposition (CSD) method utilizing electrostatic spray deposition (ESD) technique. Thermal decomposition and crystallization steps are required as a post-heat treatment process to obtain desired material properties. For this purpose, the flash light sintering method is adopted and compared with the conventional thermal sintering process using halogen furnace. With this flash light sintering method, the conventional post-heat treatment process time can be significantly reduced from tens of hours to a few seconds. Scanning electron microscopy, X-ray diffraction, and transmission electron microscopy analyses were carried out for material characterizations. Additionally, electrochemical impedance analysis and current-voltage behavior measurements were conducted. By successful fabrication of SDC cathodic functional layer utilizing flash light irradiation process, the 2-folds of fuel cell performance enhancement was obtained in terms of the peak power density at the measurement temperature of 450 °C. [ABSTRACT FROM AUTHOR]

Abstract "Samaria-doped ceria (SDC), with exceptional electrochemical catalyzing characteristics, is a promising material for the operating temperature of solid oxide fuel cells (SOFC). Despite its extraordinary electrochemical reactivity, its chemical unstable behavior in terms of reduction phenomenon has made its application to SOFC electrolyte challenging. In regard to the defect chemistry, however, this instability can enhance the oxygen incorporation rate at the surface of the electrolyte. Here, we report a rapid surface treating method for SDC thin films via flash light sintering, which revealed an outstanding crystallinity development with nano-grains and increment of mobile dopant cation-induced oxygen vacancies within few milliseconds. We demonstrated that the flash light sintering-induced rapid development of crystallinity and reduction of ceria increases oxygen reducing surface kinetics, leading to an improvement in the oxygen incorporation rate of the cathodic reaction in SOFCs. The performance of SOFC sintered by flash light indicated more than two-folds enhancement comparing the pristine cell." Highlights • Successful rapid flash light sintering for samaria-doped ceria thin films. • Enhanced crystallinity and surface oxygen vacancy concentration of thin films. • Application of samaria-doped ceria interlayer to increase surface oxygen kinetics. • Two-folds enhanced performance of low-temperature SOFC. [ABSTRACT FROM AUTHOR]