Review on Synthesis Methods of Carbon Nanotubes as Activated Carbon Composites Based on Biomass for Supercapacitors in Electric Vehicles

Biomass can be converted into carbon through carbonization processes (pyrolysis and hydrothermal carbonization) and activation (physical and chemical). The resulting carbon has a high potential as a supercapacitor electrode material due to its porous structure, which supports rapid ion transport. Various methods have been developed to extract or transform biomass into porous carbon. One of the newly developed nanocarbon materials is carbon nanotubes (CNTs) because they have advantages in terms of mechanical, physical, chemical, and electrical properties. This review discusses various kinds of CNT synthesis as activated carbon composites for supercapacitors. The synthesis of these CNTs can be conducted through chemical and physical methods, including arc discharge, laser vaporization, and chemical vapor deposition (CVD). This work reviews various methods of CNT synthesis and analyzes the best methods to be used as composites for supercapacitors for electric vehicles. It is concluded that CVD is the best method for synthesizing CNTs. Its main advantage is that CNTs can be used directly without purification unless the catalyst particles need to be removed. However, further experimental studies are required to find the most optimal conditions for each composite from a type of mesoporous activated carbon and CNTs in terms of preparation and performance outcome.