Near-Armchair-Enriched Growth of Single-Walled Carbon Nanotubes via Fe–W Bimetallic Catalysts in Mist FC-CVD

Chiral-angle-controlled synthesis of carbon nanotubes (CNTs) remains a central challenge, particularly in continuous growth processes such as floating catalyst chemical vapor deposition (FC-CVD), where high productivity is attractive but tight structural control is difficult to achieve. In this study, a mist-based FC-CVD platform is established for continuous CNT growth, enabling systematic chiral-angle control through expanded catalyst-precursor design. By introducing ultrasonic aerosol-mist delivery, volatility constraints in precursor feeding are relaxed, allowing co-delivery of a non-volatile W precursor (ammonium metatungstate) with ferrocene to form an Fe–W bimetallic catalyst under atmospheric-pressure FC-CVD conditions. This catalyst system induces pronounced near-armchair-selective growth, shifting the CNT chiral-angle distribution away from achiral limits while also narrowing the distribution compared with W-free synthesis. Analysis based on a theoretical abundance expression for CNT growth on solid catalysts supports an interface-stabilization mechanism, in which W enhances the structural stability of catalyst nanoparticles and the catalyst–CNT interface, thereby strengthening chiral-angle selectivity. Furthermore, tuning the effective carbon supply reveals an optimal regime for maximizing near-armchair enrichment, whereas supply-limited and overfed conditions broaden the distribution through distinct kinetic pathways. These results provide a practical route toward scalable chiral-angle-controlled CNT synthesis in continuous FC-CVD.