Wet-etched Ni foils as active catalysts towards carbon nanofiber growth

A study of wet-chemical etching treatments for nickel foils and the growth parameters for carbon nanostructures on them using hot-filament chemical vapour deposition (CVD) is described. Catalytically-active protrusions were produced on the Ni foils with sizes and densities in the range ∼24-42 nm and ∼202-314 P μm⁻², respectively. These protrusions are found to have a key role in the growth process as they determine the yield and morphology of the carbon deposits. It is shown that well-shaped, nano-sized protrusions are required to achieve high yield growth of hollow-herringbone carbon nanofibers (CNFs) with an in-plane crystallite size of ∼23 nm. Good correlation was seen between the statistical distributions of the protrusion size (sp) and the CNF diameters (df) depicting sp/df ratios close to unity. This work sheds light on the mechanisms behind CVD growth on metal foils.