Surface concavity-convexity sensitive oxidation dynamics of carbon nanotubes

Carbon nanotubes (CNTs) exhibit remarkable oxygen-exposure sensitive behavior with their hollow interiors providing an environment for enhanced chemical reactions, but the mechanisms remain elusive. Here we show by first-principles calculations that oxidation dynamics of CNTs are highly sensitive to surface concavity-convexity. Careful kinetic analyses indicate that oxygen chemisorption is much easier to occur on a convex surface, while diffusion of dissociated oxygen atoms is more favorable on a concave surface. Motivated by these findings, we demonstrate that turning the concavity-convexity of the tube wall via reversible nanomechanical deformation can achieve simultaneous reduction of the diffusion barrier on the outer surface and the chemisorption barrier on the inner surface of CNTs. It greatly facilitates the access for oxygen into the CNTs and leads to significantly enhanced oxidation of CNTs on both outside and interior walls. These results suggest a new route to efficient oxidation of CNTs and may open a new avenue for biasing reaction dynamics via surface curvature in tubular nanostructures in general.