▎ 摘　　要

The composite of graphene and carbon nanotubes (CNTs) can increase the electrical conductivity and the electrochemical active sites in favor of the application in energy storage and conversion. However, the fabrication of graphene/CNT hybrid material requires multiple steps to introduce two kinds of catalysts for separate growth of graphene and CNTs. Here, we report a one-step process to in situ grow a seamless graphene/CNT heterojunction using a single catalyst of copper foil. Through precise tuning of the evaporation temperature of ethanol, creation of a method for seamlessly bonding CNTs on the graphene surface without assistance of metal particles has been realized. A study of the growth mechanism shows that the self-limited surface reaction of copper foil leads to many defects in multilayer graphene films, which provides the nucleation sites for the seamless growth of CNTs. The as-grown graphene/CNT heterojunctions have a higher electrical conductivity than the single graphene film, and its optical transmittance is almost equal to that of graphene film.