Abstract: Semiconducting single-walled carbon nanotubes (s-SWCNTs) with narrow diameters are promising for future applications in many fields, especially in nanoelectronics and optoelectronics. In this study, the oxygen vacancy concentration modulating strategy was utilized for growing narrow diameters s-SWCNTs by the chemical vapor deposition (CVD) method. The Fe_0.01Mg_0.99O solid solution based catalyst was synthesized to anchor the Fe particles and inhibit aggregation for growing SWCNTs with uniform diameters. CeO₂ was introduced into the catalyst to provide oxygen vacancies through H₂ prereduction. These oxygen vacancies could form an oxidative environment during the growth of SWCNTs, and the chemically active metallic carbon nanotube caps are selectively etched away under this environment. The Fe/Ce molar ratio and H₂ prereduction time were optimized to modulate the oxygen vacancy concentration. Ultimately, using the Fe_0.01Mg_0.99O/CeO₂(3) catalyst with 10 min of H₂ prereduction time, high purity s-SWCNTs with diameters ranging from 1.41 to 1.71 nm and a content of 95.1% were obtained with high selectivity and carbon yield (1.33 wt%). The mechanism behind this phenomenon was elucidated through experimental characterizations and first-principle simulations, further expanding the understanding of the growth of s-SWCNTs through the modulation of oxygen vacancy concentration.

Key words: Semiconducting single-walled carbon nanotubes, Oxygen vacancy concentration, Fe_0.01Mg_0.99O/CeO₂ catalyst