Materials and wetting issues in molten carbonate fuel cell technology: a review

Molten carbonate fuel cell (MCFC) technology continues to attract significant attention due to its high performance over a range of carbon-containing fuel gases and non-toxic chemistry of its carbonate electrolyte which makes it especially suitable for biofuels. Steady improvements in performance have been achieved by optimizing the properties of MCFC components, including anode, cathode and LiAlO2 matrix. Issues related to creep and sintering of porous Ni anodes have been resolved by adding Al as an alloying element, which improves not only the mechanical strength but also the wettability of the anode. Ni electrodes oxidized and lithiated during initial operation of a fuel cell or fuel cell stack (“in situ lithiation”) are commonly used as the cathodes, which generates optimal pore structure while decreasing the dissolution of NiO into the molten carbonate electrolyte to an acceptably low level. Porous LiAlO2, as a bed of very fine particles tape-cast and sintered to form a matrix for the molten carbonate electrolyte, serves as the membrane between anode and cathode. Despite these continuing improvements, fundamental understanding of the factors which determine the long-term stability of the MCFC components (anode, cathode, and matrix) in the extremely corrosive molten carbonate environment is still incomplete. In particular, the wetting behavior of the complex solid/liquid/gas phase in MCFC system remains to be understood more completely, which is essential to reduce the cost and improve the lifetime of MCFC. In the present review, the technical issues of the components and their wetting properties are addressed and insights to guide future research are provided.