Joji UEDAĦĦ07528690
Enhancement of Anodic Activity by Adding Magnesium Oxide to the (Ni0.5Co0.5)O-SDC Cermet Anode
Kazunori SATO
In this study, we aimed at development of Solid Oxide Fuel Cell (SOFC) anode having high methane oxidation activity to raise the energy conversion efficiency of SOFC. In order to enhance the anodic activity for direct oxidation of methane, (Ni0.5Co0.5)O-SDC (SDC:Samaria-Doped Ceria) cermet anode was chosen. Because cobalt oxide has high oxidation activity to carbon monoxide (CO), and SDC has also high electric conductivity at high temperature in reducing atmosphere. However, addition of Co into the cermet anode causes metal agglomeration of Ni-Co particles and SDC particles in the anode composition. The metal agglomeration affects to decrease of the triple-phase-boundary which is reactive site. For this problem, MgO was added into the Ni0.5Co0.5O-SDC cermet anode. We investigated the effective of addition of MgO by using two type cermet anode; (Ni0.5Co0.5)0.9MgO0.1O-SDC and Ni0.5Co0.5O/SDC-MgO cermet anode.
It was confirmed that the Ni-Co metal particles and SDC particles size of (Ni0.5Co0.5)0.9MgO0.1O/SDC and Ni0.5Co0.5O/SDC-MgO cermet anode were smaller than NiCo-SDC anode from secondary electron images (SEM). Ohmic resistance from Impedance Spectroscopy was increased by addition of MgO, but polarization resistance from Impedance Spectroscopy was decreased. These results suggested that the triple-phase-boundary in the anode composition were increased and enhanced cell performance. Ni0.5Co0.5O/SDC-MgO showed low polarization resistance compared with (Ni0.5Co0.5)0.9MgO0.1O/SDC anode. It was confirmed that the MgO and NiCo particles formed solid solution at anode sintering condition from X-ray diffraction. The electronic conductivity of anode material was decreased for solid solution that has low electric conductivity. The cell performance was found to be improved by addition of MgO to SDC in the Ni0.5Co0.5O/SDC cermet anode.
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