In Situ Synthesis of Multiwalled Carbon Nanotubes over LaNiO₃ as Support of Cobalt Nanoclusters Catalyst for Catalytic Applications

Abstract

In situ synthesis of multiwalled carbon nanotubes (MWCNTs) was performed by chemical vapor deposition of methane on a LaNiO3 perovskite-type growth-promoter prepared by the sol–gel method. The as-produced MWCNTs were purified via a two-step procedure consisting of an oxidation in air and subsequent HNO3 treatment. Nearly monodisperse cobalt nanoparticles with an average size of 11.3 nm have been successfully decorated on MWCNTs by an impregnation–reduction method. The properties of the as-produced carbon nanotubes (CNTs) and Co/CNT catalysts were analyzed by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). It was found that the reduction of LaNiO3 and formation of CNTs occur almost simultaneously under methane atmosphere and that the in situ controlled synthesis of MWCNTs with relatively high purity and uniform diameters could be realized by the chemical vapor deposition method in a tubular reactor. The catalytic activity of the Co/CNT catalyst was tested for the hydrolysis reaction of sodium borohydride (NaBH4) in basic medium to produce hydrogen. The prepared Co/CNT catalyst calcined at 300 °C shows high catalytic activity for hydrogen generation from hydrolysis of NaBH4.

Cobalt nanoparticles embedded in N-doped carbon as an efficient bifunctional electrocatalyst for oxygen reduction and evolution reactions

“…This is well-explained by the fact that the exposure of Co NPs to ambient air could cause the formation of a thin CoO shell since the cobalt(0) nanoclusters are sensitive to aerobic atmosphere. 34,46,47 The peaks at around 795 eV in this spectrum correspond to the Co 2p 1/2 states. Moreover, the high-resolution O 1s spectrum could be fitted into three peaks at 533.7, 531.6 and 529.7 eV, which corresponds to hydroxyls, carboxyls and the oxygen related to the cobalt(II) oxides, respectively (Fig.…”

Cobalt immobilized on hydroxyapatite as a low-cost and highly effective heterogeneous catalyst for alkenes epoxidation under mild conditions

“…Therefore, we wondered other metals immobilized on HAP might be more efficiency for alkenes epoxidation, especially for Co because of the special oxidizing property reported in the literatures. [24][25][26][27][28][29][30][31][32][33] Herein, we indeed nd that Co immobilized on hydroxyapatite even with very low loading of 0.05 wt% (denoted as 0.05 wt% Co/HAP) is a highly effective heterogeneous catalyst for alkenes epoxidation under mild condition. It could catalyze partial oxidation of cyclic alkenes, aromatic alkenes and aliphatic alkenes to yield epoxide products with excellent selectivity at 30 C with O 2 and iso-butyraldehyde as co-oxidant.…”

Epoxidation of styrene using carbon nanotubes-supported cobalt catalysts

“…The survey scan of XPS of the 10% Co/CNT catalyst showed the peak at 284.6 eV ( Figure 4A), due to the sp 2 C−C bond in the CNTs [48]. The curve-fitting of the Co 2p photoelectron peaks was performed and characterized by two components due to spin−orbital splitting Co 2p 3/2 and Co 2p 1/2 , along with two shakeup satellites ( Figure 4B).…”