In-situ diagnosis and assessment of longitudinal current variation by electrode-segmentation method in anode-supported microtubular solid oxide fuel cells

Electrochemical performance of Solid Oxide Fuel Cells (SOFC) is highly dependent on the spatial distribution of the reactant and product species. The structure degradation processes are also associated with the spatial quantities. In fact, spatially measured current variations provide profound information about the local processes. Due to the geometry of microtubular SOFCs (mt-SOFC), notable current variations can develop along the cells and cause temperature variations. By applying the electrode-segmentation method, the longitudinal current variation is thus experimentally investigated in an anode-supported mt-SOFC for various cell voltage and fuel flow rates. As a result, a remarkable current variation is shown among the segments for various flow rates. The current of the downstream segment rapidly decreases with the declining cell voltage implying the fuel starvation while the other segments continue to increase their currents. The conventional polarization curve drawn for the whole cell overlaps with the midstream polarization curve, considerably differing from the other segments. The higher N₂ flow rate with the identical H₂ flow enhances the overall performance. In comparison with the estimated practical power generation capacity of the whole cell, a notable performance-loss is found due to the inhomogeneity.