Abstract
In this study, the effect of hydrogen, on the degradation of AISI 441 interconnect, under solid oxide fuel cell operating conditions was investigated between 500−800 °C for 336 h. As a new hypothesis, it is concluded that, hydrogen impedes Cr diffusion, probably in the grain boundaries, leading to the breakdown of the protective oxide scale. This effect is most severe at 600 °C, while at lower or higher temperatures the effect is attenuated. Cr diffusion is enhanced at high temperatures, whereas protective scales can be obtained at low temperatures with a lower amount of Cr.
Highlights
Solid oxide fuel cells (SOFC) have received considerable attention because they combine the typical advantages of fuel cells, such as high electrical efficiency, and silent and mechanically reliable operation, with wide fuel flexibility [1,2]
For the samples exposed at 500 ◦C, no apparent difference was observed between samples exposed to single or dual atmosphere as both samples exhibited thin protective oxide scales
This study investigated the effect of temperature and pre-oxidation on the dual atmosphere effect by exposing 0.2 mm thick non-preoxidized and 20 min pre-oxidized AISI 441 steel to temperatures ranging from 500 ◦C to 800 ◦C for 336 h under dual and single atmo sphere conditions
Summary
Solid oxide fuel cells (SOFC) have received considerable attention because they combine the typical advantages of fuel cells, such as high electrical efficiency, and silent and mechanically reliable operation, with wide fuel flexibility [1,2]. The most well-known mechanism for cell degradation is Cr poisoning, where volatile Cr(VI) evaporates from the interconnect sur face and deposits on the cathode, blocking electrochemically active sites [8,9,10,11]. Another important degradation mechanism is the increase in area specific resistance (ASR) due to the growth of Cr2O3. Cr2O3 has only moderate conductivity; its growth, at higher temperatures, results in an increase in ASR [12] Both of these problems can be miti gated by applying protective coatings, which mitigate Cr evaporation and often slow down the growth rate of an oxide scale [13,14].
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