High-Yield Single-Walled Carbon Nanotubes Synthesized on the Small-Pore (C10) Co-MCM-41 Catalyst

Abstract

High-quality single-walled carbon nanotubes (SWNT) with high yield were produced by using small-pore Co-MCM-41 catalyst, templated by a C10 surfactant and containing 3 wt % Co. A complete incorporation of Co ions in the silica matrix without formation of surface Co oxides and the contact time of the reaction, in the catalyst synthesis and the SWNT production, respectively, were the most critical factors to be considered. By controlling the reduction temperature and contact time in the reaction, the carbon yield could reach 34 wt % or higher with a selectivity of 96 wt % to SWNT. The metal content after purification of SWNT by base-acid treatments was 0.7 wt %, and the surface area was as high as 1800 m 2 /g. The metal surface occlusion effect by amorphous silica might play a key role in the stabilization of the completely reduced Co metallic clusters in the SWNT synthesis procedure, using small-pore C10 Co-MCM-41.

Diameter controlled growth of single-walled carbon nanotubes

“…为了充分发挥有序介孔载体孔道的限制作用以 及锚定作用, 催化剂金属的前驱体最好与载体充分混 合. 通过溶胶凝胶法, 可以让Co离子混入SiO 2 的O-Si-O 网络中 [44,59,64] . Resasco等 [11,12,73~76] 对Co-Mo双金属催化剂体系进 行了一系列探究, 针对Co、Mo在前驱体制备、还原生 [18] (网络版彩图) .…”

One-step synthesis of a Pt–Co–SWCNT hybrid material from a Pt–Co–MCM-41 catalyst

“…The Pt-Co-MCM-41 catalyst was synthesized using a hydrothermal synthesis method described in detail elsewhere. 41,42 A mixed silica source containing both colloidal silica (fumed silica, Cab-O-Sil M-5, from Cabot Corporation) and soluble silica (tetramethylammonium silicate (TMASi), from Sachem Inc.) was mixed with a sufficient amount of water under magnetic stirring for 30 min. Then both the cobalt source (CoSO 4 $7H 2 O, from Sigma-Aldrich) and the platinum source (K 2 PtCl 4 , from Sigma-Aldrich) were added to the suspension mixture, and stirred for another 30 min.…”

“…44 It should be noted that in most of the literature MCM-41 is synthesized using cetyltrimethylammonium bromide (CTAB, C 16 H 33 (CH 3 ) 3 NBr) or cetyltrimethylammonium hydroxide (C 16 H 33 (CH 3 ) 3 NOH) as the surfactant, while here another surfactant with a shorter alkyl chain length was used, which produces smaller pores and has been demonstrated to have better performance than CTAB for our application. 41…”

“…31,[36][37][38][39] Co-MCM-41, a cobalt incorporated mesoporous silica catalyst, has been used for the synthesis of SWCNTs via a catalytic CVD method by both others and us. [40][41][42][43] High yield synthesis of SWCNTs has been achieved with good diameter selectivity. 42 However, to synthesize SWCNT supported bimetallic catalysts, one typically would first produce SWCNTs, clean the catalyst residue, and then decorate the metallic components.…”

Chirally selective synthesis of single walled carbon nanotubes on novel catalysts

“…The DTG profile in Figure 5-5a shows that 92% of carbon deposits are SWCNTs, which are oxidized at 563 o C. The other three peaks in Figure 5-5b and 5-5c at 486, 586, and 490 o C can also be credited to SWCNTs of different diameters, which have been confirmed in the earlier works. 56,136,160,161 The selectivity to…”