Zhu Yue-Xiang

Effect of carbon content on photocatalytic activity of C/TiO2 composite

A series of carbon-covered titania (CCT) were prepared via pyrolysis of sucrose highly dispersed on titania surface in flowing N2. The samples were characterized by XRD, BET, DTA-TG, UV—Vis, and their photocatalytic properties were evaluated with two model pollutants, methylene blue (MB) and rhodamine B (RB), at room temperature. The effect of carbon content on photocatalytic activity of the C/TiO2 composite was investigated. It was found that the effect of carbon content is different for different pollutants or different light sources. For three tested samples, under UV illumination CCT01 has the highest activity for MB photocatalytic degradation, while in the case of RB, CCT02 is the most active photocatalyst. Under visible light illumination, CCT005 has the highest activity for both MB and RB photocatalytic degradation.

Synthesis of high surface area nanometer magnesia by solid-state chemical reaction

Nanometer MgO samples with high surface area, small crystal size and mesoporous texture were synthesized by thermal decomposition of MgC2O4 · 2H2O prepared from solid-state chemical reaction between H2C2O4 · 2H2O and Mg (CH3COO)2 · 4H2O. Steam produced during the decomposition process accelerated the sintering of MgO, and MgO with surface area as high as 412 m2 · g−1 was obtained through calcining its precursor in flowing dry nitrogen at 520°C for 4 h. The samples were characterized by X-ray diffraction, N2 adsorption, transmission electron microscopy, thermogravimetry, and differential thermal analysis. The as-prepared MgO was composed of nanocrystals with a size of about 4–5 nm and formed a wormhole-like porous structure. The MgO also had good thermal stability, and its surface areas remained at 357 and 153 m2·g−1 after calcination at 600 and 800°C for 2 h, respectively. Compared with the MgO sample prepared by the precipitation method, MgO prepared by solid-state chemical reaction has uniform pore size distribution, surface area, and crystal size. The solid-state chemical method has the advantages of low cost, low pollution, and high yield, therefore it appears to be a promising method in the industrial manufacture of nanometer MgO.

Applications of Monolayer-Dispersed Organic Compounds in the Preparation of Related Materials

Many organic compounds will spontaneously disperse on the surface of a solid support to form monolayers,in a manner similar to that of inorganic salts and oxides,and numerous materials with useful properties can be designed and prepared based on this phenomenon.The dispersion behavior and orientation of organic compounds in monolayers depend not only on the molecular structure of organic compounds but also on the surface features and pore structure of the support.This short review summarizes the applications of monolayer-dispersed organic compounds in the preparation and texture control of related materials,including carbon/oxide composites,various other oxides,and mesoporous carbon with thin pore walls.Pyrolysis of organic monolayers can be used to prepare carbon/oxide composites with a uniformly thin carbon layer for use as photocatalysts,catalyst supports,and adsorbents for dyes.During the sol-gel preparation of porous oxides,organic monolayers can also prevent the aggregation of sol particles,thus producing oxides with high specific surface areas and adjustable pore volumes;γ-Al2O3 with a specific surface area as high as 506m2·g-1 can be prepared in this manner.During calcining under an inert atmosphere,the carbon layer in the aforementioned carbon/oxide composites can significantly inhibit the phase transformation of oxides.Calcining carbon/γ-Al2O3 in oxygen at high temperatures,however,results in a rapid γ to α phase transformation.The oxides in these composites can also act as templates for the preparation of carbon materials.Dissolving the support oxides is a convenient method for the preparation of mesoporous carbon materials with high specific surface areas,large pore volumes,high mesopore ratios,and thin pore walls.The morphology and size distribution of pores in these carbon materials can be controlled by choosing oxides with different textures.

Delicately Controlled Synthesis of Mesoporous Carbon Materials with Thin Pore Walls

Mesoporous carbon materials with a range of pore sizes were synthesized by a delicately controlled procedure using disordered γ-alumina as template and sucrose as carbon source.Under optimized conditions,the carbon materials had narrow pore size distribution,large surface area (1000 m 2 · g-1),large pore volume (up to 3.82 cm 3 · g-1),high mesopore ratio (99%),and thin pore walls with thickness of 1-2 graphene layers.In the present work,we employed three types of alumina,and investigated the correlation of their texture with that of the resultant carbon materials.A mechanism for the formation of the carbon materials was proposed and tested against experimental data.A carbon sample prepared by this method can approximately duplicate the pore structure of the template,if the carbon layer in the precursor carbon-covered alumina is complete and sufficiently robust.The mesopores of the carbons had two sources,one from the removal of the template particles and the other from the original pores of the template.Calculated pore volumes strongly support the proposed mechanism.