Tomoki MIYASHITA
The anodic oxidation of methane at the NiCo and samaria-doped ceria (SDC) cermet anode
Kazunori SATO
In order to avoid the poisoning by the adsorption of carbon monoxide for the nickel-based anode, substitution of cobalt atoms for nickel atoms, which forms a solid solution, has been attempted for direct methane fuel cells. The electrocatalytic activity of the NiCo and samaria-doped ceria (SDC) cermet anode was examined for the anodic oxidation of methane. The role of Co atoms for this electrochemical oxidation of methane was discussed. The current-voltage characteristic and anodic overvoltage of the cells using SDC disks as the electrolyte were evaluated for methane and hydrogen as well as the analysis of the products by gas chromatography. The microstructure of the anode was investigated by scanning electron microscopy. The Ni0.5Co0.5-SDC cermet anode cell had showed the highest power density among the cells using Ni1-XCoX-SDC cermet anode. It was found that an appropriate amount of the Co content in the Ni1-XCoX alloy system is required in order to obtain the highest cell performance. The production rates of hydrogen, carbon monoxide, and carbon dioxide corresponded to the electric current. This result indicates that the mass balance between the oxide ions supplied through the electrolyte and the reactants supplied from the gaseous phase to the anode-electrolyte interface determine the anodic oxidation of methane. It was suggested that Co atoms in the Ni1-XCoX-SDC cermet did not contribute to an increase in the catalytic activity but an improvement of the microstructure of the cermet anode favorable for the formation of reaction sites at the anode-electrolyte interface.
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