The effect of debris on the adsorption and electron-transfer capacity at the interface of oxidized carbon nanotubes.

• Acid oxidation of MWCNTs generates oxidized polyaromatic fragments called debris. • The debris affects the surface properties of the oxidized MWCNTs. • The presence of debris has impact on the adsorption capacity of the MWCNTs. • The effects of debris on the thermodynamics and adsorption kinetics were evaluated. • The debris limits electron transfer of redox species at the interface of MWCNTs. The functionalization of carbon nanotubes has become a common approach to modify the surface properties of these materials for different applications such as in the formulation of polymeric composites, as electrodes of electrochemical devices and, mainly, in the removal of organic contaminants. On the other hand, these functionalization procedures generates oxidized polyaromatic fragments known as debris , which impacts the material properties. Unfortunately, most papers published in the literature disregard these effects or do not cite experimental procedures for debris removal, which are strongly adsorbed onto the surface of nanotubes. In this study, we evaluated the effects of debris – generated on multiwalled carbon nanotubes (MWCNT) subjected to acid oxidation – on the capacities, kinetics and adsorption mechanism. For this, three different MWCNTs were employed: a pristine unmodified MWCNT; an oxidized MWCNT (obtained by common procedure and without the removal of debris); and an oxidized MWCNT without debris (obtained after reflux in alkaline medium). In addition, methylene blue (MB) has been used as model adsorbate in these experiments. As a second goal, the effects of debris on MB faradic electron transfer at the MWCNT interface were also investigated using cyclic voltammetry and cyclic chronopotenciometry techniques. Finally, we have shown that debris impacts the adsorption capacity, kinetics and limits the performance of MWCNTs as electrodes. [ABSTRACT FROM AUTHOR]