Comparative Study of the Structural Features and Electrochemical Properties of Nitrogen-Containing Multi-Walled Carbon Nanotubes after Ion-Beam Irradiation and Hydrochloric Acid Treatment.

Petr M Korusenko,Dmitry A Smirnov,Sergey N Nesov,Alexander S Vinogradov,Valery V Bolotov,Ekaterina O Fedorovskaya,Sergey N Povoroznyuk,Anna A Iurchenkova

doi:10.3390/nano11092163

Abstract

Using a set of microscopic, spectroscopic, and electrochemical methods, a detailed study of the interrelation between the structural and electrochemical properties of the as-prepared nitrogen-containing multi-walled carbon nanotubes (N-MWCNTs) and their modified derivatives is carried out. It was found that after treatment of nanotubes with hydrochloric acid, their structure is improved by removing amorphous carbon from the outer layers of N-MWCNTs. On the contrary, ion bombardment leads to the formation of vacancy-type structural defects both on the surface and in the bulk of N-MWCNTs. It is shown that the treated nanotubes have an increased specific capacitance (up to 27 F·g−1) compared to the as-prepared nanotubes (13 F·g−1). This is due to an increase in the redox capacitance. It is associated with the reversible Faraday reactions with the participation of electrochemically active pyridinic and pyrrolic nitrogen inclusions and oxygen-containing functional groups (OCFG). Based on the comparison between cyclic voltammograms of N-MWCNTs treated in HCl and with an ion beam, the peaks on these curves were separated and assigned to specific nitrogen inclusions and OCFGs. It is shown that the rate of redox reactions with the participation of OCFGs is significantly higher than that of reactions with nitrogen inclusions in the pyridinic and pyrrolic forms. Moreover, it was established that treatment of N-MWCNTs in HCl is accompanied by a significant increase in the activity of nitrogen centers, which, in turn, leads to an increase in the rate of redox reactions involving OCFGs. Due to the significant contribution of redox capacitance, the obtained results can be used to develop supercapacitors with increased total specific capacitance.

Highlights

The development of new materials for electrochemical applications in nanoelectronics and biotechnology is a promising area of modern materials science
It was established that as a result of N-multi-walled carbon nanotubes (MWCNTs) irradiation, the average size of graphene sp2 domains decreases from 12.73 to 5.52 nm, which is explained by the rupture of graphene layers of nanotubes with the formation of graphene fragments oriented differently relative to the nanotube axis
It is shown that the selective attachment of hydroxyl groups to defects on the surface of nanotubes is observed when nanotubes are treated with an ion beam, and their concentration increases with increasing beam fluence

Summary

Introduction

The development of new materials for electrochemical applications in nanoelectronics and biotechnology is a promising area of modern materials science. The CV curves of the as-prepared and treated samples (Figure 3a) show the peaks A, B, and C, which indicate the presence of three types of redox processes on the surface of materials in the 1M aqueous solution of H2 SO4 electrolyte.

Results

Conclusion