Carbon dioxide-boosted growth of high-density and vertically aligned carbon nanotube arrays on a stainless steel mesh

Vertically aligned carbon nanotubes (VACNTs), a unique group of highly aligned CNTs normal to a substrate, have been extensively studied during the past decades. However, it is a long-standing challenge to improve the height of VACNTs due to the incidental deactivation of catalysts during growth. Herein, we demonstrate a facile strategy toward synthesizing high-density and well-aligned CNT arrays from in situ formed Fe-based catalysts on a stainless steel (SS) mesh. These catalysts were generated by direct oxidation-reduction treatment to the SS, which had excellent adhesion on the mesh substrate, and thus suppressed catalyst aggregation and promoted CNT growth under the flow of C₂H₂. In particular, by feeding additional CO₂ at an optimal rate, the height of CNT arrays could be boosted from ca. 15 μm to ca. 80.0 μm, one of the highest heights observed for VACNTs on SS-based substrates so far. This is attributed to the prolonged activity of the catalysts by CO₂ induced removal of extra carbon. Our study might provide an insight into the development of efficient strategies for VACNT growth on conductive substrates.