Systematic mapping of bimetallic catalyst combinations for floating catalyst chemical vapor deposition growth of single-walled carbon nanotubes

<jats:p> Floating-catalyst chemical vapor deposition (FC-CVD) is a widely used method for the continuous synthesis of single-walled carbon nanotubes (SWCNTs), yet the rational design of multi-component catalyst systems remains limited by insufficient systematic mapping of secondary-metal effects. This work presents a systematic screening of 22 secondary-metal precursor combinations (spanning post-transition, transition and lanthanide metals) with a primary Fe catalyst to evaluate how secondary-metal chemistry influences SWCNT growth characteristics, including specific yield, SWCNT diameter, crystallinity, and bundle length. Statistical analysis revealed a moderate positive correlation between the bulk melting point of the secondary metal and specific yield, suggesting that thermal stability may contribute to improved SWCNT growth output under FC-CVD conditions. In addition, an effective activity parameter, N <jats:sub>eff</jats:sub> , was introduced to separate the contribution of characteristic nanotube dimensions from the measured yield and to compare the relative effective active-catalyst population among different precursor combinations. The resulting N <jats:sub>eff</jats:sub> –bundle length map showed that secondary-metal addition can shift the balance between effective active particle generation and sustained nanotube elongation. Notably, Fe-Ti exhibited a favorable balance between relatively high N <jats:sub>eff</jats:sub> (9.4%) and elongated bundle length (85.5%). Overall, this catalyst-property mapping provides a comparative framework for identifying promising secondary-metal combinations and guiding future FC-CVD catalyst design toward targeted SWCNT structures and assemblies. </jats:p>