An electrochemical approach to fabricating honeycomb assemblies from multiwall carbon nanotubes

We report a method for controllably fabricating a structurally stable array of multiwall carbon nanotubes (MWCNTs) with greatly enhanced surface area for catalyst loading as compared with a vertically aligned MWCNT forest. These structures may provide increased electrocatalytic activity for methanol oxidation reactions and oxygen reduction reactions in fuel cells. Potentiodynamic pretreatment is shown to allow the controlled restructuring of a vertically aligned MWCNT forest on a silicon substrate into walled domains of honeycomb-like polygons. Electrochemical parameters, such as the potential scanning ranges and cycles, were found to be capable of tuning the carbon nanotube surface interaction with a solvent and thereby the density and homogeneity of walled-domains that form under solvent dilation stress. Confocal Raman microspectroscopy with a spatial resolution of 200 nm was used to characterize these assemblies along with scanning electron microscopy and X-ray absorption spectroscopy. The MWCNTs in general retained their pristine structural characteristics except in places where they were bent, which showed a slightly reduced wall thickness.