Rational recipe for bulk growth of graphene/carbon nanotube hybrids: New insights from in-situ characterization on working catalysts

The graphene/carbon nanotube (CNT) hybrids are considered as one of the most advanced nanostructures with intrinsically self-dispersion properties for large-volume applications. However, owing to the limited understanding on the complex growth mechanism and non-linear kinetics, rational design of growth procedures and related multiphase reactors for the production of the hybrids remain great challenges. In this contribution, the in-situ monitoring of graphene/CNT hybrid synthesis on layered double oxide bifunctional catalysts was carried out in an online thermogravimetric reactor. The rapid growth of CNTs occurred at the initial 90 s and the slow deposition of graphene was throughout the whole process, becoming the dominant reaction in the second stage. Based on this unique growth behavior, a two-stage growth strategy was proposed to improve the quality of hybrid products. The deposition of amorphous carbon byproduct was significantly suppressed and the quality of the hybrids was significantly enhanced through the two-stage growth process. (C) 2015 Elsevier Ltd. All rights reserved.