Mesoscale-structure control at anode/electrolyte interface in solid oxide fuel cell

To enhance the power density of a solid oxide fuel cell, a mesoscale-structure control of an electrode/electrolyte interface was proposed; here, the mesoscale means a size range of 10–100 μm, which is larger than the microscale of the electrode particles but smaller than the macroscale of the cell geometries. Therefore, the mesoscale structure does not only change the local thickness of the electrolyte and electrode but also enlarge the electrode/electrolyte interface area, and thus influence the cell performance. First, to find effective conditions for the mesoscale-structure control, a preliminary theoretical analysis in a conventional flat cell was performed focusing on the ratio of the ion-conducting resistance to the reaction resistance. In the light of this basic knowledge, as a second step, the effects of the mesoscale structure on an anode side of an electrolyte-supported cell were studied numerically and experimentally. A 2D numerical simulation based on an equivalent electrical circuit model and the dusty-gas model was carried out. As a result, the mesoscale-grooved structure was found to be effective for enhancement of the power generation, if the groove scale is sufficiently larger than that of the active reaction region of the electrode. Qualitatively similar results were obtained from the experiments using a segmented electrode with both flat and mesoscale-grooved surface in a button-type cell.