Investigation of performance degradation of SOFC using chromium-containing alloy interconnects

The long-term aging of a stack element (fuel cell, current collectors, and interconnect materials) was studied. A pair of tests were made in which one sample contained an interconnect, a high-temperature stainless steel (Crofer 22 APU), treated with an LSMC coating applied to the cathode-side interconnect plate and the other sample containing a similar fuel cell but no steel interconnect.

The interconnect-bearing sample was evaluated for thermochemical compatibility of cell components, including interconnect materials, under conditions typical of and/or expected during the lifetime of an installed multi-cell stack. This was done in an attempt to gain an understanding of reactions between sealant and cell materials, the oxidation of interconnect steels, and the formation of non-conducting species at the electrode interlaces.

Additionally, it has been proposed by several researchers that the use of chromia-forming stainless steels can lead to the deposition of material at the triple phase boundary (TPB), a process known as chromium poisoning, which leads to a reduction in the electrochemical performance of the cell over time.

Scaling was accomplished using aluminosilicate glass with 30wt. % MgO filler. Longterm degradation of each sample was determined using a current density of 250 mA.cm(-2) using humidified hydrogen as the fuel and air as the oxygen source. Additionally, the stack element was cycled and an investigation into the effect of cathode atmosphere was undertaken to elucidate the aging mechanism.