Carbon Nanotube@Microporous Carbon Core-Shell Nanowires for NO Oxidation: The Multiple Roles of Micropore Structure

Carbon nanotube@microporous carbon core-shell nano wires with tunable shell thicknesses and controllable pore size distributions were prepared by a one-pot resorcinol-formaldehyde resin coating of the carbon nanotubes, followed by carbonization and activation. The carbon nanowires were investigated experimentally and theoretically as the NO oxidation catalysts to identify the impact of a microporous structure on the NO conversion and oxidation mechanism. Shortening the diffusion path by decreasing the diameter of the nanowires could eliminate the microporous diffusion limitation and improve the catalytic activity. NO conversion is related to the presence of ultramicropore. Ultramicropore with pore sizes of 0.61-0.7 nm play a dominant role in the catalytic oxidation, which could concentrate the reactant and facilitate the formation of reaction products. A two-step reaction mechanism, in which the (2NO + O-2)(ads) molecular group confined in the micropore acts as the transition state, is proposed for the carbon-catalyzed NO oxidation.