A correlation between structural changes in a Ni-Cu catalyst during decomposition of ethylene/ammonia mixture and properties of nitrogen-doped carbon nanofibers

Changes of a 65Ni25Cu10Al2O3 catalyst consisting of Ni-enriched and Cu-enriched alloys were investigated in the bulk and on the surface during the growth of nitrogen-doped carbon nanofibers (N-CNFs) by decomposition of a 50%C2H4/50%NH3 mixture using in situ X-ray diffraction (XRD) analysis, ex situ X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) techniques. It was shown that N-CNF growth at 450–650 °C is accompanied by dissolution of carbon and nitrogen in the Ni-enriched alloy, whereas Cu-enriched alloy remains inactive. A correlation between nickel and copper surface concentrations and properties of N-CNFs in relation to the nitrogen content was found. It was demonstrated that phase composition of the catalyst during N-CNF growth determines the type of N-CNFs structure.