Electrochemical behavior of carbon nanorod arrays having different graphene orientations and crystallinity

Abstract

Carbon and carbon/nickel composite nanorod array electrodes possessing different graphene orientations and crystallinities were synthesized using an anodic aluminium oxide film as a template, and their electrochemical behavior was examined by cyclic voltammetry for the redox reactions of ferri/ferro hexacyanide ions. An attempt was made to examine how the structural differences influence the electrochemical behavior of the arrays and thereby to understand key structural factors affecting their behavior. It was found that the carbon nanorods with the edge planes of graphene sheets exposed to the outer surface were more active than the nanorods covered with the basal planes. Moreover, by using the carbon/nickel nanorod array where each nickel nanorod is covered with a very thin carbon layer, it became possible to evaluate the true electrocatalytic activity of the thin carbon layer. This technique revealed that even a poorly crystallized carbon was intrinsically active, but its high activity was usually concealed from ordinary observation, because of the low electric conductivity.