An original technique of chemical deposition (CVD) by catalytic pyrolysis of ethanol vapor was used to directly grow multiwall carbon nanotubes (MWCNTs) layers on aluminum foil. The grown nanotubes had excellent adhesion and direct electrical contact to the aluminum substrate. This material was perfect for use in electrochemical supercapacitors. In this work, the possibility of a significant increase in the specific capacity of MWCNTs by simple electrochemical oxidation was investigated. The optimal conditions for improving the characteristics of the MWCNT/Al electrodes were found. Electrochemical treatment of MWCNT/Al electrodes in a 0.005 M Na₂SO₄ solution at a potential of 4–5 V for 20–30 min increased the specific capacity of MWCNTs from 30 F/g to 140 F/g. The properties of modified nanotubes were investigated by X-ray photoelectron spectroscopy, cyclic voltammetry (CV), and impedance spectroscopy. A significant increase in the concentration of oxygen-containing functional groups on the surface of MWCNTs was found as a result of electrochemical oxidation. The modified MWCNT/Al electrodes maintained excellent stability to multiple charge–discharge cycles. After 20,000 CVs, the capacity loss was less than 5%. Thus, the results obtained significantly expanded the possibilities of using MWCNT/Al composite materials obtained by the method of direct deposition of carbon nanotubes on aluminum foil as electrodes for supercapacitors.

The process of carbon nanotubes (CNTs) synthesis by the method of catalytic pyrolysis of ethanol vapor was studied. It was shown that the synthesis can be carried out in a simple flow reactor by feeding liquid ethanol into the reactor without using carrier gas and hydrogen. Nickel nitrate hexahydrate (Ni(NO₃)₂•6H₂O) was used as a catalyst precursor. A new method of preliminary preparation of the catalyst by decomposition of the precursor in alcohol vapor has been proposed. The activity of catalysts obtained by thermal decomposition of the precursor in air (type I) and in alcohol vapor (type II) was compared. The influence of the synthesis temperature, the process duration, and the reagent consumption rate on the output of CNTs and the degree of alcohol conversion was studied. The obtained carbon nanomaterials were examined by scanning electron microscopy and Raman spectroscopy. It is shown that the type II catalyst in all parameters exceeds the type I catalyst. The yield of CNTs to the mass of the catalyst exceeds 10000%, the degree of ethanol conversion approaches 100%, which roughly corresponds to the synthesis of 100 g of product from 1 liter of alcohol. Proposed improvements make the described method one of the most simple and appropriate for the production of large quantities of inexpensive CNTs that are promising for use as sorbents, catalyst carriers, supercapacitor materials, etc.

Recently, significant progress has been made in the performance of supercapacitors through the development of composite electrodes that combine various charge storage mechanisms. A new method for preparing composite binder-free MnO₂/MWCNT/Al electrodes for supercapacitors is proposed. The method is based on the original technique of direct growth of layers of multi-walled carbon nanotubes (MWCNTs) on aluminum foil by the catalytic pyrolysis of ethanol vapor. Binder-free MnO₂/MWCNT/Al electrodes for electrochemical supercapacitors were obtained by simply treating MWCNT/Al samples with an aqueous solution of KMnO₄ under mild conditions. The optimal conditions for the preparation of MnO₂/MWCNT/Al electrodes were found. The treatment of MWCNT/Al samples in a 1% KMnO₄ aqueous solution for 40 min increased the specific capacitance of the active material of the samples by a factor of 3, up to 100–120 F/g. At the same time, excellent adhesion and electrical contact of the working material to the aluminum substrate were maintained. The properties of the MnO₂/MWCNT/Al samples were studied by electron probe microanalysis (EPMA), Raman spectroscopy, cyclic voltammetry (CV), and impedance spectroscopy. Excellent charge/discharge characteristics of composite electrodes were demonstrated. The obtained MnO₂/MWCNT/Al electrodes maintained excellent stability to multiple charge-discharge cycles. After 60,000 CVs, the capacitance loss was less than 20%. Thus, this work opens up new possibilities for using the MWCNT/Al material obtained by direct deposition of carbon nanotubes on aluminum foil for the fabrication of composite binder-free electrodes of supercapacitors.

This work presents a method for preparing an Fe₂O₃/MWCNT/Al composite electrode without the use of a binder. Synthesizing the composite material directly on conductive substrates allows one to obtain ready-made supercapacitor electrodes characterized by high values of specific capacity, as well as resistance to numerous charge/discharge cycles. Using an array of multi-walled carbon nanotubes (MWCNTs) as a conductive base for the synthesis of iron oxide allows for the production of a composite material that combines the positive properties of both materials. The Fe₂O₃/MWCNT/Al composite was formed using electrochemical oxidation of the MWCNT/Al material in a mixture of 0.1 M aqueous solution of Fe(NH₄)₂(SO₄)₂ (iron ammonium sulfate) and 0.08 M CH₃COONa (sodium acetate) in a 1:1 ratio. The proposed approaches to fabricating composite electrodes provide excellent performance characteristics, namely high cyclic stability and fast response time. For the first time, an Fe₂O₃/MWCNT/Al composite was obtained using electrochemical oxidation of Fe²⁺ on the surface of MWCNTs grown directly on aluminum foil. The specific capacitance of the obtained composite material reaches 175 F/g at a scanning rate of 100 mV/s. The capacity loss during cyclic measurements does not exceed 25% after 10,000 charge/discharge cycles.

In this work, a method has been developed for the to prepare a Fe2O3/MWCNT/Al composite electrode without the use of a binder. The synthesis of the compo-site material directly on conductive substrates allows to obtain ready-made supercapacitor elec-trodes characterised by high values of specific capacity as well as resistance to numerous charge/discharge cycles. The use of an array of multi-walled carbon nanotubes (MWCNTs) as a conductive base for the synthesis of iron oxide allows the production of a composite material that combines the positive properties of both materials. The Fe2O3/MWCNT/Al composite was formed by electrochemical oxidation of the MWCNT/Al material in a mixture of 0.1 M aqueous solution of Fe(NH4)2(SO4)2 ( iron ammonium sulfate) and 0.08 M CH3COONa (sodium acetate) in a 1:1 ratio. The proposed approaches to fabricate composite electrodes provide excellent performance characteristics: excellent cyclic stabil-ity and high response time. For the first time, the Fe2O3/MWCNT/Al composite was obtained by electrochemical oxidation of Fe2+ on the surface of MWCNTs grown directly on aluminum foil. The specific capacitance of the obtained composite material reaches 175 F/g at a scanning rate of 100 mV/s. The capacity loss during cyclic measurements does not exceed 25% after 10,000 charge/discharge cycles.

The possibility of creating a composite based on iron polyphthalocyanine (FePPc) and multi-walled carbon nanotubes (MWCNTs) grown directly on a flexible conductive substrate has been studied. The FePPc/MWCNT/Al composite has been formed by treating the prefunctionalized MWCNT/Al material in a solution of 100 mL of 1,2,4,5-tetracyanobenzene and 100 mg of ferrocene in 2 mL of acetone. The obtained material has been annealed for 4 h at a temperature of 360°C in a flow of argon and hydrogen mixed in a ratio of 1 : 1. The composite obtained under these conditions is characterized by a high specific capacitance: 141 mF/cm² at a charging current of ‒1 mA and 73 mF/cm² at a scanning speed of 2 mV/s. In addition to the high capacitive characteristics, the material is characterized by a good response speed (τ_r = 0.59 s) and a resistance against numerous charge‒discharge cycles (30 000 cycles).