An investigation of Cr vaporization from SUS430 metallic interconnect and deposition on (La,Sr)MnO3 cathode of intermediate temperature solid oxide fuel cells

Abstract

In solid oxide fuel cells (SOFCs), chromium deposition and poisoning of metallic interconnect is one of the most important issues in the electrochemical activity and stability of the cathode for the oxygen reduction reaction (ORR). In this paper, the chromium evaporation characteristics, oxide scale growth, and deposition of chromium on the ORR on (La,Sr)MnO3 (LSM) cathode are studied at 700–800 °C for SUS430 alloy interconnect material in the intermediate-temperature solid oxide fuel cells. The chromium vaporization rate is measured using the transpiration technique and the surface morphologies, and cross-sections of oxide scales are examined by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The results indicate that chromium volatilization is correlated with the composition and morphology of the oxide scale, the Cr volatilization process presents two stages according to the structural evolution of the oxide scale. In addition, deposition and poisoning of Cr species released from metallic interconnect on the LSM cathode are studied and the formation of MnCr2O4 phase on the LSM backbone degrades the ORR electrochemical activity, causing the increase of overpotential of the cathode. The results obtained give insight into the mechanism of the Cr poisoning effect in intermediate-temperature.