Effect of Manganese Addition to the Co-MCM-41 Catalyst in the Selective Synthesis of Single Wall Carbon Nanotubes

Abstract

The effect of manganese addition to the Co-MCM-41 catalyst on the synthesis of single wall carbon nanotubes (SWNT) by CO disproportionation was characterized. The ratio between the two metals in the MCM-41 framework was varied, and its effect on the resultant SWNT distribution was studied and compared with the results obtained for the monometallic Co-MCM-41 catalyst. Methods including temperature-programmed reduction, X-ray absorption fine structure, thermogravimetric analysis, TEM imaging, and Raman and fluorescence spectroscopy were employed to characterize the behavior of the catalysts under the SWNT synthesis conditions and the diameter and structure distribution of the resultant nanotubes. We found that addition of Mn to the Co-MCM-41 catalyst promotes the growth of SWNT, leading to synthesis of high yield, small diameter SWNT. Manganese does not act in the nucleation of SWNT but acts as an anchoring site for cobalt particles formed during the synthesis process as shown by X-ray absorption.

Diameter controlled growth of single-walled carbon nanotubes

“…Pfefferle等 [78,96] 发现, 使用CoMn-MCM-41催化剂时, 可 [102,106] . 在生长碳纳米管的高温条件下, H 2 O也可以 发挥其氧化性, 刻蚀碳纳米管, 增大平均管径 [25,103] .…”

Preferential synthesis of (6,4) single-walled carbon nanotubes by controlling oxidation degree of Co catalyst

“…For (1-1) using various kinds of catalysts, (6,5), (7,5), and (7,6) SWNTs can be preferentially grown using bi-metal catalysts of Co and Mo (CoMoCAT) 6 . Addition of a small amount of impurities such as Mn and Cr to Co can result in the formation of (6,5) dominant SWNTs 7 , 8 . Au catalyzed growth with hydrogen-assisted plasma CVD can realize the preferential synthesis of (6,5) SWNTs 10 .…”

Chirally selective synthesis of single walled carbon nanotubes on novel catalysts

“…Based on Co-MCM-41, bimetallic CoCr-MCM-41, CoMn-MCM-41 and CoMo-MCM-41 were also developed by incorporation of a second metal such as Cr, Mn or Mo into the structures of MCM-41catalyst. [57][58][59] All of these three catalysts show a high selectivity towards small diameter SWCNTs. For Co-Mn-MCM-41 and Co-Cr-MCM-41catalysts under optimal SWCNT growth conditions, carbon yields( per % Co loading) of these catalysts are 11.7% and 6.3%, and the abundance of (6,5) nanotube in semiconducting nanotubes is 47.4% and 30.9% respectively according to the quantification by PL spectra.…”

“…Therefore, the other approach is to incorporate metal species in high surface area mesoporous substrates. [54][55][56][57][58][59] Incorporation means to replace ions in the substrate with desired metal during substrate formation. Catalysts synthesized by incorporation method, have a very high homogeneity in metal dispersion and large surface area, 60 so that the size of resulting metal particles can be precisely tuned under different process parameters.…”

“…126 Although a few catalysts have shown chiral-specific growth, current chirality control growth has only achieved at small diameter (6,5) and (7,5) nanotubes. 46,[48][49][50]54,58,73 Considering that there are more than 100 different chiral SWCNTs with diameters just between 0.6 and 1.5 nm, novel catalysts with specific single chirality selectivity are highly pursued. Co has been used in a few chirally selective catalysts, 46,49,65,73,127 therefore Co is chosen as the catalytic metal catalyst in this study.…”