Search

Developing supported catalyst and elucidating the catalyst activation mechanism are of significant importance for large scale synthesis of single-walled carbon nanotubes (SWNTs). In the work, we designed an alumina-supported iron (Fe–Al2O3) catalyst for catalytic growth of carbon nanotubes by CO chemical vapor deposition (CVD). In the temperature range of 800–1000 °C, the prepared powder catalyst only affords the growth of carbon fibers or multi-walled carbon nanotubes. In contrast, when placing the powder catalyst on flat SiO2 substrates, such as SiO2/Si and quartz, SWNTs were observed to grow at the catalyst-substrate interface, highlighting the contributions of the SiO2 substrate in SWNT synthesis. Systematic characterizations on both the catalysts and carbon nanotubes revealed that the SiO2 substrate promotes the reduction of iron oxide in the adjacent Fe–Al2O3 catalyst, facilitating the generation of small Fe particles at the catalyst-substrate interface, which act as the active phase for the subsequent growth of SWNTs. This work opens a new avenue for growing SWNTs from supported catalyst and sheds light on enhancing SWNT growth efficiency by tuning catalyst reduction behaviors.

Exploring non-precious, efficient and earth abundant electrocatalysts plays significant role on the large-scale applications of sustainable hydrogen energy. Herein, a facile and scalable strategy is developed to prepare Fe doped Sb nanoparticles supported on heteroatoms (N, P and S) co-doped carbon matrix (Fe-Sb/NPSC). Electrochemical measurements results demonstrated that the obtained electrocatalyst possesses excellent catalytic activities for hydrogen evolution reaction (HER) in both acid (174 mV@10 mA cm−2) and alkaline (242 mV@10 mA cm−2) media. Moreover, the obtained electrocatalyst also owns excellent long-term stability. This work paves a facile avenue to develop Sb based electrocatalysts for HER and other related energy conversion technologies.

Carbon fibers are placed onto substrate surface with dispersed Co particles to promote the growth efficiency of single-walled carbon nanotubes (SWNTs). During chemical vapor deposition (CVD) process, micro-spaces are fabricated between the carbon fibers and the substrate surface, which modify the Knudsen number of CO and increase its efficient contact with cobalt oxide nanoparticles, enhancing the reduction of catalysts and the nucleation of SWNTs. Compared with surface grown SWNTs without covering carbon fibers, SWNTs grown under carbon fibers demonstrate a much higher catalyst efficiency, i.e. a SWNT density as high as ∼140 SWNTs/μm2. X-ray photoelectron spectroscopy characterizations confirm that the presence of carbon fibers promotes the reduction of cobalt oxide catalyst particles and carbon dissolution inside catalyst particles, which are crucial for catalyst activation and subsequent SWNT nucleation. This work provides a new strategy for the efficient growth of SWNTs, which benefits high-density growth of SWNTs required for future nanoelectronics applications.

Single-walled carbon nanotubes (SWNTs) are synthesized from iron silicide (FeSi) catalyst by the chemical vapor deposition (CVD). During the growth process, Fe atoms migrate onto the FeSi surface and form active Fe nanoparticles, catalyzing the growth of SWNTs. The produced SWNTs demonstrate a narrow diameter/chirality distribution, possibly arising from the solid state of Fe nanoparticles and the use of carbon monoxide (CO) as the carbon source, which facilitates SWNT growth by perpendicular mode. Remarkably, (12, 6) SWNTs occupies more than 40% of all the SWNTs, as detected by Raman spectroscopy. This work opens an avenue for chirality selective synthesis of SWNTs by applying silicide as the catalyst.

Iridium (Ir) nanoparticles with diameters smaller than 5 nm are synthesized by microwave chemical reduction and applied for the chemical vapor deposition growth of SWNTs with CO as the carbon source. Compared with iron-family catalysts, the optimal growth temperature of 1000 °C is a bit higher, which is coherently related to the intrinsic catalytic properties of the Ir nanoparticles. As revealed by molecular dynamics calculations, the Ir nanoparticles preserve the solid state at the reaction temperatures. More interestingly, the diameters of the grown SWNTs show a bicentric distribution and are very close to the average diameter of the SWNT–catalyst interface, which matches the six-fold symmetry of the Ir(111) surface. This work extends the design and development of a novel solid catalyst for synthesizing SWNTs with controlled diameters.