Coating of Vertically Aligned Carbon Nanotubes by a Novel Manganese Oxide Atomic Layer Deposition Process for Binder‐Free Hybrid Capacitors

A novel atomic layer deposition process of manganese oxide from methylcyclopentadienyl manganese tricarbonyl and ozone has been developed. It is used to coat vertically aligned carbon nanotubes (VACNTs) grown on a conductive Inconel substrate in order to produce a 3D array of metal oxide‐carbon nanotube electrode. Electron microscopy studies show that a conformal polycrystalline film can be deposited on the VACNTs arrays. X‐ray diffraction, small area electron diffraction, and X‐ray photoelectron spectroscopy analysis determine the formation of hausmannite (Mn 3 O 4 ). The electrochemical properties of the as‐prepared VACNTs/Mn 3 O 4 nanocomposite electrodes are studied using cyclic voltammetry, galvanostatic charge and discharge cycling in 1 m Na 2 SO 4 aqueous electrolyte. Capacitances as high as 78.62 mF cm −2 at 5 mV s −1 are demonstrated which is one order of magnitude higher than that of pristine VACNTs. In addition, the as‐prepared VACNTs/Mn 3 O 4 nanocomposite electrode showed a good reversibility and cycling stability.