Air/CO2 Stepwise Induction of Fe Nanocluster Enrichment in FeMgAlOx Solid-Solution Catalysts for Single-Walled Carbon Nanotube Growth.

Solid-solution catalysts hold great promise as low-cost catalysts for the growth of small-diameter single-walled carbon nanotubes (SWCNTs); however, their catalytic performance is limited by low metal-site utilization and unfavorable interfacial structures in conventional architectures. Here, we report a facile design strategy for FeMgAlOx solid-solution catalysts featuring abundant active sites and enhanced interfacial structures that suppress nanocluster agglomeration. The successful synthesis of this catalyst relies on a high-temperature-induced two-step strategy: high-temperature oxidation enhances crystallinity, while high-temperature air/CO2 treatment facilitates the formation of strong metal-support interactions (SMSI) on inert metal oxide supports. In this architecture, the ultrathin two-dimensional morphology and ordered atomic arrangement promote active-metal spillover, yielding abundant active sites; meanwhile, CO2 induction significantly enhances the SMSI-mediated confinement capability for Fe nanoclusters. Crystalline evolution and SMSI regulation synergistically facilitate the exsolution of active Fe species from the bulk solid solution, thereby forming thermally stable Fe nanoclusters. Furthermore, optimized single-walled carbon nanotube (SWCNT) growth kinetics confirm that the modified solid solution possesses both a higher density of active sites and enhanced intrinsic catalytic activity. Ultimately, our catalyst enables the growth of SWCNTs with diameters ranging from 0.96 to 3.33 nm, offering a simple and low-cost route for SWCNT synthesis with broad application prospects.