Electro-oxidation of amino-functionalized multiwalled carbon nanotubes

We report the electrochemistry of amino-functionalized multiwalled carbon nanotubes (MWCNTs-NH2) in the pH range from 0.3 to 6.4 using quantitative cyclic voltammetry (CV) and single entity electrochemistry measurements, making comparison with non-functionalized MWCNTs. CV showed the latter to both catalyze the solvent (water) decomposition and to undergo irreversible electro-oxidation forming oxygen containing surface functionality. The MWCNTs-NH2 additionally undergo an irreversible oxidation to an extent which is dependent on the pH of the solution, reflecting the variable amount of deprotonated amino groups present as a function of pH. Nano-impact experiments conducted at the single particle level confirmed the oxidation of both types of MWCNTs, showing agreement with the CV. The pK(a) of the amino groups in MWCNTs was determined via both electrochemical methods giving consistent values of ca. 2.5.

Automated summary

The electrochemistry of amino-functionalized multiwalled carbon nanotubes (MWCNTs-NH2) was investigated in different pH conditions. It was found that non-functionalized MWCNTs can catalyze solvent decomposition and undergo irreversible electro-oxidation. The oxidation of amino-functionalized MWCNTs was dependent on the pH of the solution, reflecting the deprotonation of amino groups.