Overview of the effects of rare-earth elements used as additive materials in molten carbonate fuel cell systems

From the viewpoint of materials issues, there are some problems in molten carbonate fuel cell (MCFC) systems due to the corrosive and evaporative electrolytes and the high pressure caused by a stack in temperature of 650°C. The rare earth metals (RE) in as material additives primarily improve the creep resistance, corrosion resistance and high temperature resistance of materials. However, efforts to enhance the properties of MCFC materials using RE have not yielded the marked effects associated with their use in solid oxide fuel cells (SOFC). Therefore, we have conducted this review in order to describe and discuss the effects of RE as additive materials in the context of MCFC. This review also provides information regarding the development of MCFC materials using RE. The incorporation of low concentrations of RE into previously RE-free materials may improve the stability of these materials to some degree, and also effect an increase in the cell efficiency of MCFC. La ₂O₃-added cathode materials have primarily been applied as alternative materials, for the reduction of the dissolution of conventional NiO cathodes. Ce and Dy have both been theorized to possibly enhance the stability of anode electrode materials. Ce and La can both be employed as additives which enhance the stability of reforming catalysts. The addition of La ₂O₃ to electrolytes has been previously shown to reduce the degree of dissolution in cathodes. Ce-based ceramics are thought to be promising coating materials, and it is believed that they may help to prevent the corrosion of the separator. However, future research into materials which exhibit long-term stability and low electrical conductivity is clearly warranted, as the field is in its infancy.