Richuan Rao

A novel route of enhancing oxidative catalytic activity: hydroxylation of MWCNTs induced by sectional defects

As metal-free catalysts, the functionalization of multi-walled carbon nanotubes (MWCNTs) can usually provide the activated sites for oxidative dehydrogenation (ODH). In this paper a novel functionalization of MWCNTs has been proposed via an alkali-assisted hydrothermal treatment on the sectional defects produced by ball milling. The as-prepared hydroxylated MWCNTs exhibit twice the catalytic activity of MWCNTs without ball milling, because the ball-milled treatment leads to the production of more sectional defects located on exposed edges or terminals of MWCNTs and these defects can induce the creation of more hydroxyl groups by an alkali-assisted hydroxylation. The research on the reaction mechanism reveals that the ODH of ethylbenzene (EB) in the presence of CO2 for the hydroxylated MWCNTs takes on a possible mechanism of two-step dehydrogenation by coupling a reverse water–gas shift reaction and CO2 may oxidize hydroxyl groups into carbonyl groups to maintain the catalytic cycle.

Facile synthesis of Fe3O4/MWCNTs by spontaneous redox and their catalytic performance

Fe(3)O(4) nanoparticles with a size range of 4-8 nm were formed by the spontaneous redox reaction between Fe(3 + ) and multi-walled carbon nanotubes (MWCNTs). Cyclic voltammetry, Raman spectroscopy and x-ray photoelectron spectroscopy were employed to study the thermodynamic and dynamic conditions for the Fe(3)O(4)/MWCNTs formation. It is found that the high defect density of MWCNTs was thermodynamically favorable for the spontaneous reduction of Fe(3 + ) ions and a reaction time of above 2.5 h should be guaranteed. As the catalysts for benzene hydroxylation to phenol, the as-obtained Fe(3)O(4)/MWCNTs exhibit superior catalytic performance to those prepared by the hydrothermal method. Therefore, the spontaneous redox between the Fe(3 + ) and MWCNTs supplies an attractive facile route for the preparation of Fe(3)O(4) nanoscale catalysts.

Formaldehyde-assisted hydrothermal synthesis of one-dimensional CeO2 and their morphology-dependent properties

CeO2 nanobelts, nanorods and nanowires have been synthesized by a formaldehyde-assisted hydrothermal system. It is found that the morphologies of these one-dimensional (1D) CeO2 nanomaterials are dependent on the components of the corresponding precursors, which is achieved to control the reaction degree of Cannizzaro disproportionation tuned by Na/Ce molar ratio, hydrothermal temperature and type of strong alkali. The characterization results indicate that the morphologies of 1D CeO2 nanomaterials are closely correlated to their structural features, such as lattice cell parameters, specific surface area and pore volume. These 1D nanomaterials show excellent morphology-dependent optical absorption and catalytic performance. From nanowires, nanorods to nanobelts, the visible absorption gradually decreases along with the increasing of band gap values, whereas the catalytic activity of CO oxidation increases along with lattice cell expansion. This synthetic route using formaldehyde may open a new insight into fabricating one-dimentional rare earth oxides with different morphologies and extending their potential applications.