Carbon nanotube@microporous carbon
core–shell nanowires
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 + O2)ads molecular
group confined in the micropore acts as the transition state, is proposed
for the carbon-catalyzed NO oxidation.