Surface basicity-directed growth of single-walled carbon nanotubes on MgO-supported monometallic Fe catalysts

Porous magnesia (MgO) is widely employed as a support for anchoring metal catalysts in the synthesis of single-walled carbon nanotubes (SWNTs), where its surface properties significantly influence catalytic behavior. In this study, MgO supports with different surface basicity are prepared through calcination at different temperatures and loaded with iron (Fe) to probe the influence of support basicity on SWNT growth. Using carbon monoxide as the carbon source, all Fe catalysts supported by different MgO carriers are active for the chemical vapor deposition synthesis of SWNTs. Remarkably, the Fe catalyst supported on MgO pre-calcinated at 600 °C enables SWNT growth with a yield of 2.2% at a temperature as low as 600 °C. This enhanced low-temperature activity is attributed to the strong surface basicity of the MgO support, which promotes the adsorption and dissociation of carbon-containing molecules on Fe nanoparticle surfaces, thereby facilitating SWNT nucleation and growth at reduced temperatures. Upon increasing the growth temperature to 700 °C, SWNTs grown over all Fe/MgO catalysts exhibit a pronounced enrichment of the (6, 5) chirality, highlighting the critical role of active catalyst composition in dictating SWNT chirality distribution. This work highlights the synergistic importance of catalyst composition and support surface basicity in achieving low-temperature growth and narrow chirality distribution of SWNTs