From macro- to micro-single chamber solid oxide fuel cells

Single chamber solid oxide fuel cells (SC-SOFCs) with interdigitating electrodes were prepared and operated in CH4/air mixtures. Both electrodes (Ni-Ce0.8Gd0.2O1.9 cermet and Sm0.5Sr0.5CoO3−δ perovskite) were placed on the same side of a Ce0.8Gd0.1O1.95 electrolyte disc. The separating gap between the electrodes was varied from 1.2 to 0.27 mm and finally down to 10 μm. Screen-printing was used for the preparation of the cells with a gap in the millimetre range, whereas micromolding in capillaries (MIMIC) was used for the preparation of the micro-SC-SOFCs. The prepared micro-SC-SOFCs consisted of an array of 19 individual cells that were connected in parallel having 100 μm wide electrodes. An open circuit voltage of 0.65–0.75 V was measured in flowing mixtures of methane and air. The maximum power density of 17 mW cm−2 was limited by the ohmic resistance of the long conduction paths along the thin electrodes to the active sites of the individual cells. The feasibility of the micro-cell was demonstrated by comparing the performance with the performance of the cells having feature sizes in the millimetre range. The cell resistance of micro-SC-SOFCs may be significantly reduced when connecting the cells in series using interconnections between anode and cathodes of adjacent cells.