Structure and Electrocatalytic Properties of Sulfur-Containing Multi-Walled Carbon Nanotubes on a Titanium Substrate Modified by a Helium Ion Beam

In this work, a set of analytical techniques, including scanning electron microscopy (SEM), Raman scattering spectroscopy, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray microanalysis (EDX) and cyclic voltammetry (CV), were used to study the impact of high-energy He⁺ ion irradiation on the structural and electrochemical characteristics of sulfur-containing multi-walled carbon nanotubes (S-MWCNTs) placed on a titanium substrate. The results indicate that the ion beam treatment of the S-MWCNT system led to an increase in the level of imperfections on the surface structures of the nanotubes due to the formation of point defects on their outer walls and the appearance of oxygen-containing functional groups, including SO_x groups, near these defects. At the same time, a significant increase in the sulfur concentration (by 6.4 times) was observed on the surface of the S-MWCNTs compared to the surface of unirradiated nanotubes. This was due to the redeposition of sulfur atoms near the point defects under the action of the ion beam, followed by the subsequent formation of direct S-C chemical bonds. Electrochemical studies demonstrated that the irradiated S-MWCNTs/Ti system exhibit enhanced catalytic activity, with improved oxygen reduction reaction (ORR) performance and a substantial increase in anodic current during the oxidation reaction of hydrogen peroxide under alkaline conditions, highlighting their potential for advanced electrocatalytic applications.