| dc.description.abstract | Oxide anodes such as doped ceria offer improved tolerance for nonidealities in anode environment such as redox cycles, sulfur and other poisons, and hydrocarbons. Mixed-valence transition element in ceria provides an additional redox couple besides Ce4+∕Ce3+ in reduced atmosphere, facilitating its electrocatalytic reaction for oxidation of fuels. This paper presents the electrochemical characteristics of Ce0.8M0.2O2−δ(M=Mn,Fe,Ni,Cu) for oxidation of hydrogen and methane. Ce0.8M0.2O2−δ was synthesized, and crystal phase analysis by X-ray diffraction was performed. Single-phase Ce0.8M0.2O2−δ(M=Mn,Fe,Ni) were formed. A second phase, CuO, was found in the powders with the nominal composition of Ce0.8Cu0.2O2−δ. Ce0.8M0.2O2−δ exhibited stability in reducing atmosphere. In comparison, similar microstructural characteristics were found for Ce0.8M0.2O2−δ(M=Mn,Fe,Cu). However, Ce0.8Ni0.2O2−δ exhibits poor microstructure with large cracks. The electrochemical oxidation of wet hydrogen and wet methane was investigated with impedance spectroscopy by using the three-electrode configuration. It was found that Ce0.8M0.2O2−δ(M=Mn,Fe,Ni,Cu) demonstrates relatively low electrochemical activity in both hydrogen and methane. Regarding low n-type conductivity of transition metal cation-containing ceria, it was suggested that an oxide with a high electronic conductivity be added into the Ce0.8M0.2O2−δ matrix for improvement of the electrode performance. | |
