Dispersion-EnhancedSupported Pd Catalysts for Efficient Growth of Carbon Nanotubes throughChemical Vapor Deposition.

Supported Pd nanoparticle catalystsover Mg–Al mixed metal oxides derived from layered double hydroxideswere prepared by three different approaches, including coprecipitation,anion-exchange, and impregnation, in order to enhance the metal dispersionand thus facilitate the growth of uniform multiwalled carbon nanotubes(CNTs) via catalytic chemical vapor deposition of methane. The effectsof preparation methods for supported Pd catalysts on the morphologiesand microstructures of CNTs formed were investigated. The resultsrevealed that the characteristics of CNTs were strongly correlatedto the dispersion of active Pd species in the catalysts, and the structuraldefects and the diameter of CNTs were reduced with the increasingmetal dispersion. Especially, the anion-exchange route for preparationof supported Pd catalyst was appropriate for the growth of uniformbamboo-like CNTs with fewer defects, which could be contributed tothe presence of more uniform and smaller Pd0nanoparticleshighly dispersed over Mg–Al mixed-metal oxides. [ABSTRACT FROM AUTHOR]