The use of carbon nanotubes with and without nitrogen doping as support for ruthenium catalysts in the ammonia decomposition reaction

Ru catalysts were supported on two different carbon materials, multiwall carbon nanotubes and bamboo-like carbon nanotubes doped with nitrogen, which were synthesized by catalytic chemical vapour deposition of C2H2/H2/N2 or C2H2/NH3/H2/N2, respectively, over Fe/SiO2 catalyst. All the carbon supports and/or the prepared Ru catalysts were characterized by several techniques including transmission electron microscopy, X-ray photoelectron spectroscopy, N2 adsorption isotherms and CO chemisorption. The Ru catalysts were tested in the catalytic ammonia decomposition reaction. High yields towards hydrogen production were achieved. Carbon nanotubes were heated in an inert atmosphere at temperatures up to 1773 K in order to study the effects of such support treatments on the ammonia decomposition reaction. The elimination of acidic groups from the surfaces, prior to catalyst preparation, and/or the surface graphitization of the materials produced a higher catalytic activity during the reaction. The catalytic activity of Ru particles was significantly improved when supported on carbon nanotubes doped with nitrogen.