Mechanistic aspects of the formation of carbon-nanofibers on the surface of Ni foam: A new microstructured catalyst support

Abstract

This paper describes the catalytic formation of a layer of carbon nanofibers (CNFs) on Ni foam, resulting in a new catalytic route for preparing thin, highly macroporous layers. The effect of morphology and surface properties (i.e., grain size and presence of NiO) on the rate formation and properties of CNFs is explored. The formation of CNFs on polycrystalline Ni starts with the formation of metastable Ni 3C, which later decomposes into Ni and C. As a result, Ni nanoparticles are created with a suitable size (20–70 nm) to catalyze the formation of CNFs. The formation of CNFs on polycrystalline Ni reveals an inhibition time in accordance with the formation and decomposition of Ni 3C resulting in Ni nanoparticles necessary for the growth of CNFs. Grain boundaries in the parent Ni material appear to enhance this process. The presence of NiO increases the formation rate of CNFs by one order of magnitude. NiO is reduced in situ, and Ni nanoparticles are formed directly, as opposed to sluggish formation of Ni nanoparticles via decomposition of Ni 3C particles formed from relatively large (1–10 μm) Ni crystals.