1995 Fiscal Year Final Research Report Summary
Rate Analysis of Solid Oxide Fuel Cells by Potential-step Chronoamperometry
| Project/Area Number |
06680458
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
エネルギー学一般・原子力学
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| Research Institution | Muroran Institute of Technology |
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Principal Investigator |
KENJO Tadao Muroran Institute of Technology, Professor, 工学部, 教授 (00005977)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Fuel Cell / Solid electrolyte / Zirconia / Chronoamperometry |
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| Research Abstract |
This study aims at revealing the reaction mechanism of solid oxide fuel cell air electrodes by potential-step chronoamperometry. Yttria-stabilized zirconia (YSZ) disks were used as electrolytes, and noble metal pastes were painted on both sides of the disk for anode and cathode. The transient current was measured on an oscilloscope screen as the potential response to the potential-step applied to the cathode. A theoretical transient current was derived from Ficks second law and fitted to the experimental one by adjusting parameters involved in the equation. Two reaction mechanisms were assumed i.e., (1) interfacial diffusion mechanism and (2) bulk diffusion mechanism. The two mechanisms were discriminated by the slope of current transients. The potential-step chronoamperometry was applied to Au/YSZ,Pt/YSZ and Ag/YSZ electrodes. It was found that the first two electrodes reduce oxygen by the interfacial diffusion mechanism while the last one by the bulk diffusion mechanism. The interfacial diffusion electrode sustains the load current only at the peripheral area of the electrode-electrolyte interface, so that a very small portion of the interface is electrochemically active. The bulk diffusion electrode sustains the load over the entire interface since oxygen is supplied through the electrode bulk so that no concentration gradient occurs along the interface. This large active area explains why the Ag/YSZ electrode has a much higher performance than the Au/YSZ and Pt/YSZ electrodes.
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