Co-sputtered nanocomposite nickel cermet anode for high-performance low-temperature solid oxide fuel cells

Abstract

Nickel-samaria-doped ceria (Ni-SDC) nanocomposite anodes with various compositions are fabricated by co-sputtering technique. The film compositions are effectively controlled by adjusting the applied power to the SDC target while applying a constant power to the Ni target. The microstructure, crystallinity and electrical conductivity of the deposited films are analyzed and their optimal composition is investigated based on fuel cell performance and electrochemical impedance spectroscopy (EIS) analysis. Among various deposition conditions, the lowest polarization resistance is achieved at Ni-SDC 80W condition, which is attributed to the difference in the film composition and expected reaction site densities. Thin film fuel cells with the optimal nickel cermet anode are fabricated on a nanoporous supporting structure to achieve a high cell performance and compared with noble Pt electrode. The fuel cell with the optimal nickel cermet anode yields a maximum power density of 178 mW/cm2 and polarization resistance of 0.55 Ω cm2 at 450 °C, which is significantly improved from the reference Pt anode cell (113 mW/cm2 and 1.69 Ω cm2). Impedance analysis clearly demonstrates that the enhancement in the cell performance originates from the difference in the polarization resistance, resulting from the expanded reaction sites owing to the mixed ion electronic conducting characteristics of the nickel cermet nanocomposite anode.