燃料極支持型SOFCにおける燃料極内の水素濃度計測

Abstract

Mass transfers in porous electrodes of fuel cells affect the performance of the fuel cells. The aim of this study is to verify effectiveness of a measurement method of a hydrogen gas concentration in a fuel electrode of a solid oxide fuel cell (SOFC) to clarify the mass transfer mechanism. This technique was applied to a SOFC which was composed of 8 mol % Y2O3-ZrO2 (YSZ) electrolyte and Ni-YSZ fuel electrode. A sensor which was made of a platinum wire coated with zirconia and alumina was inserted into the fuel electrode to measure the oxygen partial pressure. The hydrogen gas concentration was determined from the oxygen partial pressure which was obtained from an electromotive force of the sensor using Nernst's equation. The hydrogen gas concentration decreased with increasing the current density up to 0.45 A/cm2 and also with increasing the operating temperature (1173 K to 1273 K) at the same current density. The measured values of the hydrogen gas concentration were proportional to the values calculated by three dimensional numerical simulation. These results indicated the measurement method had a potential for the measurement of hydrogen gas concentrations in fuel electrodes. Furthermore, the effective diffusivity of hydrogen gas in the fuel electrode could be obtained from the hydrogen gas concentration.