High‐Performance Electrode for Medium‐Temperature Solid Oxide Fuel Cells: Effects of Composition and Microstructures on Performance of Ceria‐Based Anodes

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 (0 ≦ x ≦ 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 (σ_ion) and electrons (σ_e). 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.