Chunming Zheng

Container Effect in Nanocasting Synthesis of Mesoporous Metal Oxides

We report a general reaction container effect in the nanocasting synthesis of mesoporous metal oxides. The size and shape of the container body in conjunction with simply modifying the container opening accessibility can be used to control the escape rate of water and other gas-phase byproducts in the calcination process, and subsequently affect the nanocrystal growth of the materials inside the mesopore space of the template. In this way, the particle size, mesostructure ordering, and crystallinity of the final product can be systemically controlled. The container effect also explain some of the problems with reproducibility in previously reported results.

Ordered mesoporous hematite promoted by magnesium selective leaching as a highly efficient heterogeneous Fenton-like catalyst

Ordered mesoporous hematite with an ultrahigh surface area (up to 200 m2 g−1) was prepared through a hard templating method of Mg and Fe in mesoporous silica KIT-6 (meso-Mg/Fe2O3) and used for highly efficient wet peroxide oxidation of methylene blue. The obtained results showed that approximately two thirds of Mg cations were removed in the leaching process, resulting in a highly porous hematite with a significant amount of defects in the structure. The activated mesoporous iron oxide exhibited excellent catalytic activity for the degradation of methylene blue, achieving above 95% removal of 60 mg L−1 methylene blue after 3 h at reaction conditions of initial pH, 0.6 mg L−1 catalyst and 2600 mg L−1 H2O2 dosage. The apparent rate constant of used meso-Mg/Fe2O3 is 1.972 h−1, which is 1.22, 3.02 and 4.53 times those of meso-Fe2O3, con-Mg/Fe2O3 and α-Fe2O3, respectively. With the increase of reusability of the meso-Mg/Fe2O3 catalyst, both the leaching concentration of Mg and the catalytic activity of the catalyst increased, which is quite different with the catalytic mechanism of composite components in heterogeneous Fenton-like processes, such as Fe–Cu and Fe–Zn composites. The leaching concentrations of iron in the catalysts were found to be low (<5 mg L−1) in consecutive runs. Hence, the meso-Mg/Fe2O3 catalyst has proved to be an attractive alternative in the treatment of environmental refractory organic pollutants and has a unique and superb catalytic activity in the heterogeneous Fenton-like system.

Hydrophilic modification of ordered mesoporous carbon supported Fe nanoparticles with enhanced adsorption and heterogeneous Fenton-like oxidation performance

In this study, an ordered mesoporous carbon catalyst containing uniform iron oxide nanoparticles (Fe/meso-C) has been synthesized and underwent hydrophilic surface modification with hydrogen peroxide, which shows excellent adsorption and heterogeneous Fenton degradation performance for methylene blue (MB). Characterization using XRD, TEM, SEM, TG and N2 sorption–desorption isotherms showed that Fe/meso-C treated with hydrogen peroxide (H-Fe/meso-C) maintained a hexagonally arranged mesostructure, uniform mesopore size (∼2.3 nm), high surface area (up to 530 m2 g−1) and moderate pore volume (0.29 cm3 g−1) as an untreated catalyst. The Fe2O3 nanoparticles were highly dispersed in the carbon framework and mesopore channels. The hydrophilicity of the catalyst surface also improved after H2O2 modification. As a milder oxidizing agent, hydrogen peroxide was used to introduce the oxygen-containing group on the carbon surface. Due to the hydrophilic surface and retaining mesoporous structure, the H-Fe/meso-C catalyst presents a better Fenton-like catalytic performance than Fe/meso-C. The adsorption and heterogeneous Fenton-like degradation of MB reached 96% in 220 min with optimal oxidation conditions of 30 mg L−1 MB solution, 0.7 g L−1 catalyst, 50 mmol L−1 H2O2 and the initial pH value.

Scaling up of ethanol production from sugar molasses using yeast immobilized with alginate-based MCM-41 mesoporous zeolite composite carrier.

Microporous and mesoporous zeolites, including ZSM-5, H-β, H-Y, and MCM-41, were modified with 3-aminopropyl-triethoxysilane (APTES), then inorganic fillers, such as abovementioned zeolites or mesoporous materials, (α-AlOOH or γ-Al(2)O(3)), were mixed with alginate embedded with yeast; and finally these carriers were cross-linked through the double oxirane. The alginate-based immobilized yeast with MCM-41 exhibited much shorter fermentation time and higher ethanol concentration than pure alginate and other composite carriers with the highest cell concentration of 4.8×10(9) cells/mL. The composite carrier maintains the highest ethanol productivity of 6.55 g/L/h for 60 days in continuous fermentation process, implying good operational durability for commercial applications. The reason for the higher bio-catalytical function of the immobilized yeast might lay in the uniformly yeast distribution in the bio-reactor and high yeast cell concentration, which contributed by the improved transmission of fermentation media and combined effects of yeast adsorption by MCM-41 and embedment by alginate.

Calcination system-induced nanocasting synthesis of uniform Co3O4 nanoparticles with high surface area and enhanced catalytic performance

Co3O4 catalytic materials with varying mesoporous periodicity and crystallinity have been successfully synthesized via a calcination system-induced nanocasting method. N-Co3O4 with uniform nanoscale morphology, high specific surface area, and large pore size distribution was obtained in an open system as a calcination process, while M-Co3O4 with long-range mesoporous periodicity and high crystallinity was synthesized using a closed system as the calcination condition. The control of the mesostructure and morphology was carried out by tuning the diffusion rate of the cobalt precursor in the template channel resulting from the different escape rates of the decomposed byproducts via the varied calcination containers. The CO oxidation testing indicated that N-Co3O4 exhibited better catalytic performance than that of M-Co3O4. The difference in activity could be attributed to the uniform nanoscale structure of N-Co3O4, which mesoporous M-Co3O4 lacked. N-Co3O4 had a better performance for CO oxidation due to the uniform nanoparticle structure, higher specific surface area, larger pore size distribution, abundant active oxygen species and Co3+ cationic species on the surface, which accelerated the adsorption and diffusion of reactant molecules and finally improved the reaction activity of N-Co3O4. The resulting catalytic behaviors lead to a better understanding of designing and using such metal oxides for a number of catalytic applications.

A Simple One-Pot Strategy for Synthesizing Ultrafine SnS2 Nanoparticle/Graphene Composites as Anodes for Lithium/Sodium-Ion Batteries

SnS2 /graphene composites have attracted extensive attention in energy storage owing to their excellent electrochemical performance. However, most of the previous methods to synthesize SnS2 /graphene composites require long times, high temperatures, or high pressures, which are obstacles for practical low-cost production. A simple one-pot strategy to prepare SnS2 /graphene composites has been developed, which is not time-consuming (1 h) and requires moderate temperature (75 °C) in atmosphere. Through this method, ultrafine SnS2 nanoparticles anchored on graphene nanosheets are prepared and exhibit excellent electrochemical performance for both lithium and sodium storage. Specifically, as anodes for lithium-ion batteries, the SnS2 /graphene electrode delivers a high capacity of 1480 mAh g-1 after 50 cycles at 0.2 A g-1 . Even at 10 A g-1 , the SnS2 /graphene electrode can achieve a capacity of 666 mAh g-1 . A constructed full lithium-ion cell exhibits a capacity of 957 mAh g-1 after 50 cycles at 1 A g-1 . This simple one-pot strategy may pave the way for large-scale production and practical application of SnS2 /graphene composites in energy storage.

Perchlorate ion doped polypyrrole coated ZnS sphere composites as a sodium-ion battery anode with superior rate capability enhanced by pseudocapacitance

Considering the inferior rate capability of conversion-type transition-metal sulphides (TMSs) caused by severe volume expansion and poor electronic conductivity, a composite of perchlorate ion (ClO4−) doped polypyrrole (PPy) coated ZnS spheres (denoted as ZnS@d-PPy) has been synthesized via a soft chemistry method. Benefiting from the improved conductivity, the protection of the PPy coating and ClO4− doping, ZnS@d-PPy exhibits decent cycling performance (419 mA h g−1 after 30 cycles at 100 mA g−1) and superior rate capability (203 mA h g−1 at 4 A g−1), which is enhanced by pseudocapacitance when being applied in sodium-ion batteries (SIBs).

Phosphate-assisted one-pot synthesis of zirconium phosphate-containing mesoporous silica with unique photodegradation ability for rhodamine B

A facile one-pot method for zirconium phosphate-containing mesoporous silica (ZrP–MS) using sodium silicate and zirconium oxychloride was reported under acidic P123 aqueous solution followed by an aid of phosphate. The obtained ZrP–MS material is a new type of mesoporous silica composite, which had a structure similar to SBA-15 but with larger mean pore diameter. Zirconium phosphate was uniformly distributed in the silica, and it was found to be a unique photocatalyst for the degradation of rhodamine B (RhB) by comparison with ZrP–MS, silver-activated ZrP–MS and silver phosphate–mesoporous silica composites on degradation of RhB and methyl orange, in which the reaction kinetics, luminescence properties of the final products of RhB degradation, fluorescence of ZrP–MS-adsorbed RhB, and free radical capture experiment were performed. The formation and photodegradation mechanism of ZrP–MS are discussed.

Treatment of dye wastewater nanofiltration concentrates containing high anion levels by a pH-sensitive nano-sized Fe(III)@silica microgel

Herein, Fe(III) ions showed a pH-sensitive dual function on the surface of an L-cysteine-modified nano-sized silica microgel (Cys-Fe(III)@mSiO2). The total color and COD degradation efficiencies of Cys-Fe(III)@mSiO2 are higher than 95% and 83%, respectively, for high salt level nanofiltration concentrates without other post-treatment methods. In the first stage, Fe(III) ions act as an enhanced Fenton-like degradation catalyst on the surface of Cys-Fe(III)@mSiO2 for the treatment of actual nanofiltration concentrates in dye wastewater under acidic conditions (pH 7.5) upon the simple addition of Ca(OH)2, and the same Fe(III) ions act as an excellent coagulant component for the nanofiltration concentrates with the aid of the silica microgel in the second stage. Characterization via transmission electron microscopy (TEM), X-ray diffraction (XRD), infrared (FTIR) spectroscopy, and related techniques demonstrates that the Fe(III)/Fe(II) redox cycle in Cys-Fe(III)@mSiO2 is accelerated with the addition of L-cysteine; this increases the Fe(II) concentration and enhances the generation rate of hydroxyl radicals (˙OH). Additionally, the apparent rate constant of Cys-Fe(III)@mSiO2 is almost 5 times higher than that of Fe(III) Fenton-like degradation systems.

Fabrication of highly ordered mesoporous silica with the assistance of phosphate

A simple route to prepare ordered mesoporous silica with a uniform pore size distribution was reported, which was synthesized at quasi-neutral pH with the assistance of phosphate using sodium silicate as a silicon source. The products prepared at various pH were investigated and ordered mesoporous silica with a uniform pore structure was synthesized at a pH of 6.15.