Large-scale and controllable synthesis of metal-free carbon nanofibers and carbon nanotubes over water-soluble Na ₂CO ₃

Previously, various carbon nanomaterials (CNMs) have been synthesized by different methods. All these methods required the use of catalysts that were based on transition metals or their alloys, and there were scabrous problems related to CNM purification. Using acetylene as reactant and Na ₂CO ₃ powder as catalyst, carbon nanofibers (CNFs) and carbon nanotubes (CNTs) were selectively synthesized in this study at acetylene decomposition temperature of 450 and 500 °C, respectively. Because Na ₂CO ₃ is water-soluble, it can be removed from the products through simple washing with water and the nanocarbon materials can be harvested undamaged in high purity. The approach is simple, inexpensive, and environment-friendly; it can be adopted for controlled production of high-purity CNFs or CNTs.