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

Abstract

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.

Polarization Resistance‐Free Mn3O4‐Based Electrocatalysts for the Oxygen Reduction Reaction

“…The reflections in the patterns of the composites situated at 8.3°, 13.2°, 14.7°, 16.4°, 26.6° and 28.5° correspond to the (101), (112), (103), (211), (224), (400) reflections of Mn 3 O 4 hausmannite (JCPDS Card No. 24‐734), respectively (some of them are weak and/or can be observed only in patterns recorded from thick samples deposited at high temperature) . The most intense reflections centered at 14.7° and 16.4° increase with the increasing of the deposition temperatures pointing to an increase of the crystallite size.…”

“…In our previous work, Mn 3 O 4 was deposited by ALD using MeCpMn(I)(CO) 3 and O 3 as precursors. It was shown that this new process could be applied in a large range of deposition temperatures (from 100 °C to 275 °C) . In general, the deposition temperature can significantly affect the materials deposited.…”

“…The manganese oxide coatings deposited at low temperature (below 200 °C) are smooth and amorphous (Figure SI‐1) while an increase of the deposition temperature at or above 200 °C leads to a polycrystalline film (Figure ) . The influence of the number of ALD cycles on the morphology of the Mn 3 O 4 coating was investigated by high resolution transmission electron microscopy (HRTEM) (Figure ).…”

“…Atomic Layer Deposition (ALD) : The Mn 3 O 4 ALD process was reported in our previous work . MeCpMn(I)(CO) 3 (min.97 %, Strem Chemicals, Inc.) was utilized as metal precursor, and kept at 80 °C during deposition, ozone generated from a BMT803N ozone generator was used as the oxygen source.…”

“…In this work, Mn 3 O 4 was deposited onto CNTs using ALD by the novel manganese oxide ALD process, which was recently developed in our group . The Mn 3 O 4 /CNTs system introduced in this work exhibiting a combination of high catalytic activity, low polarization and high stability of the manganese oxide thin films, and good conductivity and large surface area of the carbon nanotube structure, show to reduce oxygen following the same mechanism, similar kinetics and with even an improved stability compared to Pt‐based catalysts.…”