Ultra high-yield one-step synthesis of conductive and superhydrophobic three-dimensional mats of carbon nanofibers via full catalysis of unconstrained thin films

We directly synthesized large conductive and superhydrophobic three-dimensional mats of entangled carbon nanofibers (CNFs) using thermal chemical vapor deposition (CVD). We show that the yield obtained from the catalysis of an unconstrained thin Ni-Pd film is over an order of magnitude higher compared to that of the same thin film when bound to a substrate. The growth mechanism differs from substrate-bound growth, where catalysis occurs only on the top surface of the catalytic film, as the full Ni-Pd catalyst layer participates in the reaction and is totally consumed to bi-directionally grow CNFs. Therefore, the yield further increased with the thin film thickness, in contrast to substrate-bound growth. The unconstrained growth occurred thanks to a weak adhesion layer that delaminated during the thermal process. Additionally, we showed that the supporting substrate material strongly affected the nanostructure morphology obtained. The as-grown CNF mats were used as a three-dimensional electrode for lithium-ion batteries. We envisage these CNF mats to be an ideal platform to be functionalized for multiple applications including high-performance electrodes, sensors, electromagnetic shields, and conductive polymer-coated composites.