Performance and degradation of Ni-based cermet anode for solid oxide fuel cells

Abstract

Solid oxide fuel cells (SOFCs) have high conversion efficiency and excellent fuel flexibility for various fuels. The possibility of internal reforming of methane and other hydrocarbons for power generation has been investigated. Fuel flexibility is important for high conversion efficiency and simplified generation systems. Carbon deposition may cause deterioration. Deposition of carbon was effectively avoided by steam and CO 2 formed by power generation. Another approach to avoid carbon deposition is to design catalysts less active for carbon formation. The deposition rates were significantly affected by types of metal and oxide in the cermet material and were related to the ionic/electronic conductivities of oxides and dissolution of carbon in the metal species. Extensive dilution of hydrocarbon fuel with water may lead to extremely high water concentrations in the downstream region of the fuel cell under discharge condition. High water content damages the Ni surface and catalytic activity by strong adsorption of water. Reconstruction and analyses of three-dimensional microstructures by focused ion beam-scanning electron microscopy were effective to clarify the degradation of the fuel electrode.