Near‐Armchair‐Enriched Growth of Single‐Walled Carbon Nanotubes via W‐Containing Fe‐Based Catalyst Systems in Mist FC‐CVD

ABSTRACT

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 single‐walled CNT (SWCNT) growth, enabling systematic modulation of the chiral‐angle distribution 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 create a W‐containing Fe‐based catalyst system under atmospheric‐pressure FC‐CVD conditions. This catalyst system promotes pronounced near‐armchair enrichment, shifting the CNT chiral‐angle distribution away from achiral limits while narrowing the distribution compared with W‐free synthesis. Analysis based on a theoretical abundance expression for CNT growth on solid catalysts is consistent with a stabilization‐based interpretation, in which W‐containing species may increase the effective thermal/structural stability of Fe‐based catalyst nanoparticles and the catalyst–CNT interface, thereby strengthening chiral‐angle selectivity. Furthermore, tuning the 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.