Heteroatom-Cobalt Interface Regulation for Catalytic Growth of Single-Walled Carbon Nanotubes.

The catalytic synthesis of single-walled carbon nanotubes (SWNTs) is highly sensitive to the behavior of catalyst nanoparticles, which can be modulated by interfacial interactions with heteroatoms. However, the underlying mechanisms remain unclear, hindering the rational catalyst design for chirality-controlled growth. Here, we systematically investigate the effects of heteroatoms (Cl and S) on Co and bimetallic PtCo catalysts by using different metal precursors. Heteroatom incorporation is found to regulate catalyst reducibility, alloying behavior, and activation temperature, thereby determining the growth threshold temperature and chiral selectivity of SWNTs. Notably, the PtCo catalyst derived from cobalt nitrate enables SWNT growth at temperatures as low as 600 °C, yielding a high abundance (45.12%) of (6, 5) nanotubes. This performance is attributed to Pt-facilitated reduction of Co oxides and Co-Pt alloy formation, which generate active Co sites at low temperatures. In contrast, Cl species partially poison Co sites and increase the growth temperature, while S strongly inhibits catalyst activation and alloying, leading to deactivation. These findings reveal the critical role of heteroatoms in modulating Co catalyst activation and provide mechanistic insights for chirality-selective SWNT synthesis.