Abstract
This review sums up the techniques used for the synthesis of carbon nanotubes (CNTs), carbon nanofibers (CNFs), and carbon nanospheres (CNSs) by employing catalysts of natural origin. Establishing large-scale production and commercial applications of CNTs for a sustainable society is still of high apprehension. In this regard, one of the major factors is the starting materials such as precursors and catalyst sources. However, natural materials contain a minor quantity of metals or metal oxides and could be employed as a catalyst source for the synthesis of CNTs, providing the possibility to replace expensive catalyst sources. A large number of successful studies have been completed so far and confirm that these developed methods for carbon nanomaterials synthesis exhibiting high quality from common natural materials are not only possible but, most importantly, promising and scalable. This review also highlights purification methods and recent promising applications of as-synthesized CNTs.
Highlights
The realization of carbon nanomaterials intended for advanced applications on a large scale will definitively face routine production issues, such as the checks on limited existing resources, the cost of materials such as precursors and catalyst sources, and the amount and cost of energy used in the synthesis
SEM and nitrogen physisorption measurements did not disclose any major change in the morphological summary and adsorption/desorption, respectively. These results indicate the good mechanical stability of carbon nanotubes (CNTs)/bentonites composites
For the purification of CNTs from natural materials, mainly the use of an acid and an alkaline is conducted to react with the metal catalyst/support present inside the CNTs. [63]
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The realization of carbon nanomaterials intended for advanced applications on a large scale will definitively face routine production issues, such as the checks on limited existing resources, the cost of materials such as precursors and catalyst sources, and the amount and cost of energy used in the synthesis. These standard factors will become the key cost drivers for the final product. The review is concluded with the employed applications of the as-obtained carbon nanomaterials in brief, which should be taken into consideration to spread this sustainable concept for the benefit of society
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