Gas sensing properties of multiwall carbon nanotubes decorated with Rh nanoparticles

TL;DR

This study demonstrates that decorating multiwalled carbon nanotubes with Rh nanoparticles via plasma treatment, especially with oxygen, significantly enhances their room temperature gas sensing capabilities for various gases and moisture.

Contribution

It introduces a simple, scalable plasma-based method for decorating CNTs with Rh nanoparticles, improving gas response and stability, especially with oxygen-assisted treatment.

Findings

Oxygen in plasma treatment enhances gas response of Rh-CNT hybrids.

Oxygenated vacancies act as active sites and Rh anchoring points.

Oxygen treatment facilitates charge transfer upon gas adsorption.

Abstract

In the present work, multiwalled carbon nanotubes were decorated with rhodium nanoparticles using a colloidal solution in the post-discharge of an RF atmospheric plasma of argon (Ar) or argon/oxygen (Ar:O$_2$). The properties of these hybrid materials towards the room temperature detection of NO$_2$, C$_2$H$_4$, CO, C$_6$H$_6$ and moisture were investigated and discussed in view of compositional and morphological studies. It was found that the presence of oxygen in the plasma treatment is essential to significantly enhance the gas response of Rh-decorated multiwalled carbon nanotubes and to avoid response saturation even at low gas/vapor concentrations. These desirable effects are attributed to the presence of oxygen during the CNT plasma treatment since oxygenated vacancies act both as active adsorption sites for gases and as anchoring sites for Rh nanoparticles (the presence of Rh nanoclusters is nearly doubled in Ar-O$_2$ treated samples as compared to Ar treated samples). The oxygen treatment also makes easier the charge transfer between Rh nanoparticles and carbon nanotubes upon gas adsorption. The method for treating and decorating multiwalled carbon nanotubes used here is simple, fast and scalable for producing gas sensitive nanohybrid materials with uniform and well-controlled properties.