Dispersion-Enhanced Supported Pd Catalysts for Efficient Growth of Carbon Nanotubes through Chemical Vapor Deposition

Abstract

Supported Pd nanoparticle catalysts over Mg–Al mixed metal oxides derived from layered double hydroxides were prepared by three different approaches, including coprecipitation, anion-exchange, and impregnation, in order to enhance the metal dispersion and thus facilitate the growth of uniform multiwalled carbon nanotubes (CNTs) via catalytic chemical vapor deposition of methane. The effects of preparation methods for supported Pd catalysts on the morphologies and microstructures of CNTs formed were investigated. The results revealed that the characteristics of CNTs were strongly correlated to the dispersion of active Pd species in the catalysts, and the structural defects and the diameter of CNTs were reduced with the increasing metal dispersion. Especially, the anion-exchange route for preparation of supported Pd catalyst was appropriate for the growth of uniform bamboo-like CNTs with fewer defects, which could be contributed to the presence of more uniform and smaller Pd0 nanoparticles highly dispersed over Mg–Al mixed-metal oxides.