Synthesis of nitrogen-containing carbon nanofibers by catalytic decomposition of ethylene/ammonia mixture

The formation of carbon nanofibers (CNFs) doped with nitrogen was investigated during decomposition Of C2H4/NH3 mixtures at 450-675 degrees C over metal catalysts: 90Ni-Al2O3, 82Ni-8Cu-Al2O3, 65Ni-25Cu-Al2O3, 45Ni-45Cu-Al2O3, 90Fe-Al2O3, 85Fe-5Co-Al2O3, 62Fe-8Co-Al2O3, 62Fe-M-Al2O3. It was found that the yield of CNFs, their structural and textural properties, as well as nitrogen content in CNFs are strongly dependent on the synthesis conditions such as: catalyst used, feed composition, temperature and duration. The 65Ni-25Cu-Al2O3 was proved to be the most efficient catalyst for the production of nitrogen-containing carbon nanofibers (N-CNFs) with nitrogen content up to 7 wt.%. Ammonia concentration in the feed equal 75 vol.%, temperature 550 degrees C and duration I h were found to be the optimum reaction parameters to reach the maximum nitrogen content in N-CNFs. TEM studies revealed that the nanofibers have a helical morphology and a "herringbone" structure composed of graphite sheets. According to the XPS data, the nitrogen incorporation in the N-CNF structure leads to the formation of two types of nitrogen coordination: pyridinic and quaternary, and their abundance depends on the reaction conditions. (c) 2007 Elsevier Ltd. All rights reserved.