Effect of Short Current on the Open Circuit Voltage in a Solid Oxide Fuel Cell

Abstract

The solid oxide fuel cell (SOFC) is a promissing power source with its strong point of solid oxide electrolyte. It allows long time operation without electrolyte supplying. But the electroylte in the SOFC must be very thin to reduce the internal resistance. Thinner electrolyte provides better performance. In my laboratory, a 100 cm 2 class SOFC has been operated. It was supplyed from a SOFC maker in Korea. Since it has several tenth micrometer of electrolyte thickness, it showed voltage behavior of short current when the inert gas step addition (ISA) method [1] was employed. The ISA was firstly used to investigate the flow and partial pressure effect on the performance of molten carbonate fuel cell (MCFC). The method adds nitrogen gas to the anode flow, simultaneously it raises reactant gas flow until the added nitrogen arrives at the cell. Indeed, the nitrogen addition port places about 5 m ahead of the anode cell with 1/4 inch stainless tube, thus several seconds are required to reach to the cell. In the MCFC, there was no voltage change during the period of seveal seconds at open circuit state. Since there was no applied current, it has no doubt. But the SOFC showed clear voltage increase at the tiem period by the nitrogen addition although it was at open circuit state. It is clearly compared with that behavior of MCFC. In this presentation, the difference will be investigated in terms of short current at the SOFC. [1] C.-G. Lee, B.-S. Kang, H.-K. Seo, H.-C. Lim, J. Electroanal. Chem., 540 , 169–188 (2003).