We have developed a simple and unique metal-free chemical vapor deposition technique in mild condition for the
synthesis of carbon nanotubes on carbon black and graphite surfaces. The existence of topologically heterogeneous
surfaces is a key factor for inducing the growth of the CNTs. Surface functional groups also play an important role in
manipulating the reaction path of the carbon deposition reaction. A surface structure-related model was proposed to
describe the growth procedure of CNTs on carbon surfaces. We anticipate that this method will be useful for controlling
the growth of metal-free CNTs at desired sites on various carbon surfaces.