Hironori AOYAMA
Enhancement of the Activity of Anodic Methane Oxidation by the Dispersed Transition Metal Oxide Particles
Kazunori SATO
New metal oxides which enable direct methane use in use in solid oxide fuel cells (SOFCs) have been investigated. The dispersion of LiCoO2, LiMn2O4 or a mixture of 80 mass%LiCoO2 and 20 mass%LiMn2O4 particles into a porous-gold-based anode increased the electromotive force (EMF) for methane particularly at temperatures below about 500 degrees Celsius, which was generated by
a cell using a stabilized-zirconia cell. As for hydrogen fuel cell using an anode dispersed with 80 mass%LiCoO2 and 20 mass%LiMn2O4 particles showed the highest EMF among the cells examined.
The increase in EMF for hydrogen at low temperature is probably caused by the sufficient electronic conduction of the metal oxide. The LiMn2O4 phase decomposed into the Li2MnO3 phase, which shows a good electronic conduction and a mixed valence state, Mn3+ and Mn4+, in a reducing atmosphere. The appropriate mixture of LiCoO2 and LiMn2O4 particles seems to be favorable for the anodic oxidation of hydrogen. As for the anodic oxidation of methane the dispersed oxides contributed to an increase in EMF, which is caused by an increase in the catalytic activity for the anodic oxidation of methane. The transition metal ions with their mixed valence state play an important role for the formation of surface active sites in relation to the electronic conduction in these oxides.
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