A Ce(Mn,Fe)O2 dense nanofilm as an improved active anode for metal-supported solid oxide fuel cells

Abstract

The application of a mixed ionic and electronic conductor, doped CeO2, as a dense anode was investigated in this study. The mixed electronic and oxide ionic conductivity in CeO2 was significantly improved through the double doping of Mn and Fe. Although the solid solubility limit of Mn was approximately 20 mol%, no impurity phase was observed at 30 mol% Mn when Mn was co-doped with 10 mol% Fe; this result suggests that the solubility limit of Mn was expanded through the addition of Fe. The nano-sized Fe- and Mn-doped CeO2 (CMF) film was highly active toward the anode reaction despite its high density. In addition, the CMF thin film was effective in preventing Ni diffusion into the LaGaO3 electrolyte film; CMF therefore exhibits bi-functional properties for solid oxide fuel cells with LaGaO3 perovskite electrolyte films. Furthermore, the insertion of a CMF dense film between the Ni–Fe substrate and the LSGM (La0.9Sr0.1Ga0.8Mg0.2O3) electrolyte resulted in a significant increase in the power density of the cell, particularly at intermediate temperatures. The maximum power density was ca. 3.0 W cm−2 at 973 K and ca. 0.2 W cm−2 at 673 K. The high power density of the cell was explained by the enhanced anodic activity. Compared with porous anodes, the nano-sized film showed a significantly lower overpotential because of the improved oxygen ion conductivity and charge-transfer steps. Therefore, the nano-sized CMF dense film described here can serve as a unique active anode material.