Synthesis of Carbon Nanotube/Graphene Composites by One‐Step Chemical Vapor Deposition for Electrodes of Electrochemical Capacitors

To control the packing density of carbon nanotubes (CNTs) and the number of graphene layers, carbon nanotube/graphene composites are directly grown on cobalt (Co) catalysts‐coated nickel foam by one‐step ambient pressure chemical vapor deposition (CVD) at different temperatures and times. The carbon nanotube/graphene composites grown by one‐step CVD at 850°C for 10 min possess the highest specific capacitance. Furthermore, a lower growing temperature leads to a higher packing density of CNTs and a smaller number of layers of graphene. A shorter growing time also leads to a smaller number of layers of graphene.