High Performance Electrode for Medium-Temperature Solid Oxide Fuel Cells

Abstract

Polarization properties of ceria-based anodes dispersed with nanometer-sized Ru catalysts, which we developed for medium-temperature solid oxide fuel cells, were greatly improved by controlling the composition and microstructure. Among samaria-doped ceria (SDC) anodes with compositions of (CeO2)1–x(SmO1.5)x (0 [less, double equals] x [less, double equals] 0.4) a SDC anode with x = 0.2 was found to exhibit the maximum current density at a given overpotential at temperatures of 800 to 1000 °C, when operating under a hydrogen atmosphere. This high current density is a direct result of improved conductivities of both oxide ions (sigmaion) and electrons (sigmae). Attaching a very thin film of SDC onto a yttria-stabilized zirconia electrolyte before coating the Ru-dispersed SDC layer appreciably lowered the anodic overpotential for the SDC. The current densities on the improved Ru-SDC anode at a potential of –0.9 V vs an air reference electrode were 0.8 and 1.4 A/cm2 at 800 and 900 °C, respectively.