Applications of carbon nanotubes in the twenty-first century

Carbon nanotubes, which consist of rolled graphene sheets built from sp² hybridized carbon atoms, are now attracting scientists from various disciplines due to their fascinating physico-chemical properties. In this account, we will review the recent progress on the synthetic techniques for the large-scale production of carbon nanotubes, especially focusing on the floating-catalyst method used in the chemical vapour deposition (CVD) process. We will also describe effective purification methods avoiding structural damage, and discuss the electrochemical applications of these systems including the fabrication of: (i) lithium-ion secondary batteries; (ii) lead-acid batteries; (iii) electric double-layer capacitors; (iv) fuel cells; and (v) multifunctional fillers in polymer composites. We foresee that carbon nanotubes will find numerous applications and take an important place in the development of emerging technologies in the near future.