In situ X-ray diffraction study of the growth of nitrogen-doped carbon nanofibers by the decomposition of ethylene–ammonia mixtures on a Ni–Cu catalyst

The growth of nitrogen-doped carbon nanofibers (N-CNFs) by the decomposition of ethylene–ammonia mixtures on a Ni–Cu catalyst was studied using in situ X-ray diffraction analysis. The catalyst consists of the Ni-enriched (Ni0.85Cu0.15) and Cu-enriched (Cu0.95Ni0.05) alloys. It was found that the growth of N-CNFs, similar to the growth of carbon nanofibers, proceeds on the Ni-enriched alloy, whereas the Cu-enriched alloy remains inactive. During the N-CNF growth, carbon dissolves in the Ni0.85Cu0.15 alloy with the formation of a oversaturated solid solution, but without formation of bulk nickel carbide. It was supposed that nitrogen also dissolves in this alloy, but the driving force is the primary dissolution of carbon.