Unexpected Spontaneously Dynamic Oxygen Migration on Carbon Nanotubes

TL;DR

This study reveals spontaneous, dynamic oxygen migration behaviors on the interior surface of carbon nanotubes driven by low energy barriers, offering insights into designing new carbon-based dynamic materials.

Contribution

It demonstrates for the first time the spontaneous dynamic migration of oxygen functional groups on SWCNT interiors via DFT calculations, highlighting new mechanisms of oxygen mobility.

Findings

Oxygen groups exhibit spontaneous migration on SWCNT interiors.

Energy barriers for migration are comparable to thermal fluctuations.

Stable intermediate states facilitate successive oxygen migrations.

Abstract

Using the density functional theory calculations, we show that the oxygen functional groups exhibit unexpected spontaneously dynamic behaviors on the interior surface of single-walled carbon nanotubes (SWCNT). Two types of dynamic oxygen migrations - hydroxyl and epoxy migrations - are achieved by the breaking/reforming of C-O bond reaction and the proton transfer reaction. It is demonstrated that the spontaneously dynamic characteristic is attributed to the sharply reduced energy barrier less than or comparable to thermal fluctuations. We also observe a stable intermediate state with a dangling C-O bond, which permits the successive migration of oxygen functional groups. However, on the exterior surface of SWCNT, the oxygen groups are difficult to migrate spontaneously due to the relatively high energy barriers, and the dangling C-O bond prefers to transform into the more stable epoxy configuration. The spontaneous oxygen migration is further confirmed by the long-distance oxygen migration, which comprises three hydroxyl migration reactions and one C-O bond reaction. Our work provides a new understanding of the behavior of oxygen functional groups on interfaces and gives a potential route to design new carbon-based dynamic materials.