Interactions Between SOFC Interconnect Coating Materials and Chromia

Abstract

Manganese cobalt oxides are promising coating materials for reducing chromium volatilization, and thus the associated cathode poisoning, from interconnect alloys in solid oxide fuel cells (SOFCs). Interaction between this coating and the oxide scale formed on the alloy during fuel cell operation can lead to changes in the coating composition and thus its performance. In this study, the properties of manganese cobalt spinel oxides and the reaction between manganese cobalt spinel oxides and chromia were investigated. The reaction product consists of two layers: a layer in contact with chromia that grows by the diffusion of cobalt and manganese from (Mn,Co)3O4 toward the chromia and an intermediate layer that grows by the diffusion of chromium through the reaction layer. The effect of dopants on the coating performance was also investigated. With the addition of iron or titanium, the rate of reaction between the spinel coating and the chromia scale can be decreased significantly, which would reduce the risk of scale spallation and provide an increase in the lifetime of the interconnect and thus the fuel cell.