Carbon Nanofibers Synthesized by Catalytic Decomposition of Methane and Their Electrochemical Performance in a Direct Carbon Fuel Cell

Various carbon nanofibers (CNFs) have been synthesized by catalytic decomposition of methane over Ni−Al2O3 and Ni−Cu−Al2O3 catalysts at 500−700 °C. On the basis of the physical and chemical characterization of these CNFs, their electrochemical reactivities are evaluated in a novel direct carbon fuel cell (DCFC). It is found that the microstructures and electrochemical reactivities of CNFs are highly dependent on the decomposition temperature, catalyst composition and operation times in the DCFC. Decreasing decomposition temperature and introducing Cu into Ni−Al2O3 catalyst can produce electrochemically reactive CNFs, due to their enlarged surface area and decreased degrees of graphitic structure. The electrochemical reactivity of synthesized CNFs can be further promoted by the preoxidation in the high temperature molten carbonates, owing to an obvious increase in the oxygen functional groups on the surface of the CNFs