As a new carbon allotrope, carbon nanotubes have attracted wide attention and brought great commercial value since they were discovered. The stable existence of carbon nanotubes can be divided into two categories, which is single wall CNTs and multi wall CNTs. Among them, multi wall CNTs are important nanomaterials and have been widely used in many fields. With the advantages of light weight, perfect hexagon structure connection and nanoscale size, multi wall CNT has been a research hotspot in the field of nanotechnology. In terms of structure, the multi wall CNT can be regarded as seamless and hollow tubular materials coiled into multi-layered concentric graphene sheets formed by carbon atoms. With the rapid development of science and technology, great progress has been made in the study of multi wall CNTs, including the preparation process, the modification method and the others.
Figure 1. The structure of multi wall CNT.
Figure 2. An example of multi wall CNTs applied in catalytic field.
According to the dispersion and solubility of multi wall CNTs in various solvents, they can be divided into water-soluble multi wall CNTs and non-water-soluble multi wall CNTs.