Runwei Wang

Strongly Acidic and High-Temperature Hydrothermally Stable Mesoporous Aluminosilicates with Ordered Hexagonal Structure

Publisher Summary This chapter discusses strong acidic and high-temperature hydrothermally stable mesoporous aluminosilicates with well-ordered hexagonal structure. These mesoporous aluminosilicates have been successfully synthesized from the assembly of preformed aluminosilicate precursors with cetyltrimethylammonium bromide (CTAB) surfactant. The MAS-5 shows extraordinary stability both in boiling water and in steam. Temperature-programmed desorption of ammonia (NH3) shows that the acidic strength of MAS-5 is much higher than that of MCM-41.

Sulfated zirconia supported in mesoporous materials

Abstract SO 4 2− /ZrO 2 (SZ) supported on ordered mesoporous hexagonal materials were prepared by dispersion of ZrOCl 2 ·8H 2 O into the mesopores, followed by the hydrolysis and sulfation. These materials have been characterized by X-ray diffraction, nitrogen adsorption isotherms, infrared spectroscopy, and catalytic cracking of n -hexane, cumene and 1,3,5-triisopropylbenzene. The results show that SZ was successfully loaded into the inner pores of MCM-41; the as-synthesized catalyst showed favorable catalytic properties. The factors in the preparative process that affected the final activity were discussed.

Synthesis, optical and gas sensitive properties of large-scale aggregative flowerlike ZnO nanostructures via simple route hydrothermal process

Large-scale aggregative flowerlike ZnO nanostructures, consisting of many bunches of nanorods at different orientations with a diameter of about 60 nm and a length of 1 µm, have been synthesized through a simple hydrothermal process at a lower temperature. The x-ray power diffraction pattern indicates that the novel flowerlike ZnO nanostructures are hexagonal, and the selected area electron diffraction reveals that the ZnO nanorods are single crystal in nature and preferentially grow along [0 0 1]. Raman spectrum, room-temperature photoluminescence and UV–vis absorption spectra are also discussed. Furthermore, the influence of the reaction time on the morphology of the ZnO nanostructures is investigated, and a possible growth model is proposed. Finally, the gas sensor based on the ZnO nanostructures exhibits high sensitivity for ethanol as well as quick response and recovery time due to the high surface-to-volume ratio.

Template-assisted self-assembly of macro–micro bifunctional porous materials

The preparation of macro–micro bifunctional porous materials has been accomplished by a well-controlled, vacuum-assisted technique. Monodisperse polystyrene latex spheres were ordered into close-packed arrays by slow sedimentation, allowing a high flux of water through the interstices between latex spheres. Zeolite LTA, FAU, LTL, BEA, MFI and Si-MFI nanocrystals, synthesized by hydrothermal procedures, permeated the interstices of latex spheres under the driving force of flowing water. After drying and calcination at 500°C, both the latex spheres and zeolite structure-directing molecules were removed, followed by the formation of products consisting of both crystalline micropores and periodic, interconnected networks of submicron macropores. XRD, SEM, TEM, IR, TG/DTA, ICP and N2 adsorption–desorption measurements were performed to monitor the preparation and to characterize the properties of the macro–micro bifunctional porous materials. The materials presented in this paper combine the benefits of both the micropore and macropore regimes. They could potentially improve the efficiency of both separation and catalysis of zeolites.

Cadmium Sulfide and Nickel Synergetic Co-catalysts Supported on Graphitic Carbon Nitride for Visible-Light-Driven Photocatalytic Hydrogen Evolution

Design and preparation of noble-metal-free photocatalysts is of great importance for photocatalytic water splitting harvesting solar energy. Here, we report the high visible-light-driven hydrogen evolution upon the hybrid photocatalyst system consisting of CdS nanocrystals and Ni@NiO nanoparticles grown on the surface of g-C3N4. The hybrid system shows a high H2-production rate of 1258.7 μmol h−1 g−1 in the presence of triethanolamine as a sacrificial electron donor under visible light irradiation. The synergetic catalytic mechanism has been studied and the results of photovoltaic and photoluminescence properties show that efficient electron transfer could be achieved from g-C3N4 to CdS nanocrystals and subsequently to Ni@NiO hybrid.

Cobalt Phosphide Modified Titanium Oxide Nanophotocatalysts with Significantly Enhanced Photocatalytic Hydrogen Evolution from Water Splitting

Production of hydrogen from photocatalytic water splitting holds promise as an alternative energy source with superiority of cleanliness, environment friendliness, low price, and sustainability. Perfectly constructing the noble-metal-free and stable hybrid structure photocatalyst is quite essential; herein, for the first time the authors aim to use cobalt phosphide as the cocatalyst on titanium oxide to form a novel hybrid structure to enhance the utilization of the photoexcited electrons in redox reactions for improved photocatalytic H2 evolution activity. Thus, the achieved significantly increased photocatalytic H2 -evolution rate on the optimized CoP/TiO2 (8350 µmol h-1 g-1 ) is 11 times higher than that of the pristine TiO2 . Moreover, this work is expected to spur more insight into synthesizing such novel photofunctional systems, achieving high photocatalytic H2 evolution activity and sufficient stability for solar-to-chemical conversion and utilization.

Catalytic epoxidation of styrene by molecular oxygen over a novel catalyst of copper hydroxyphosphate Cu2(OH)PO4

Catalytic epoxidation of styrene by molecular oxygen over a novel copper hydroxyphosphate catalyst, Cu2(OH)PO4, was studied. Catalytic data show that the catalyst Cu2(OH)PO4 is very active, and the main products are benzaldehyde and styrene epoxide. Some important factors associated with the catalytic activity and selectivity have been investigated extensively.

A novel and highly efficient earth-abundant Cu3P with TiO2 “P–N” heterojunction nanophotocatalyst for hydrogen evolution from water

Semiconductor-based photocatalytic hydrogen (H2) evolution from water is of great importance for solar-to-chemical conversion processes to boost and promote the future hydrogen economy. Here, for the first time, we demonstrate that p-Cu3P coupled with n-TiO2 forms a novel hybrid structure which accelerates electron-hole pair separation and transfer for improved photocatalytic H2-evolution activity. The rate of H2 evolution of the optimized Cu3P/TiO2 (7940 μmol h-1 g-1) is 11 times higher than that of bare TiO2, with an apparent quantum efficiency (AQE) of 4.6%. This work may provide more insight into the synthesis of novel phosphide-based hybrid materials with high photocatalytic H2-evolution activity and sufficient stability for solar-to-chemical conversion and utilization.

A novel architecture of dandelion-like Mo2C/TiO2 heterojunction photocatalysts towards high-performance photocatalytic hydrogen production from water splitting

In the development of photocatalytic hydrogen (H2) production, designing and optimizing photocatalyst nanostructures with efficient charge transfer and separation for catalytically active sites are still a great challenge. Herein, a well-controlled synthetic strategy is developed to prepare an Mo2C/TiO2 hetero-nanostructure, in which the TiO2 3D hierarchical configuration is loaded with highly dispersed Mo2C nanoparticles. This heterostructure achieves the excellent photocatalytic activity of 39.4 mmol h−1 g−1 with its rate ∼25 times higher than that of pristine TiO2. Also, our photocatalysts process excellent long-term durability (>20 h). The impressive photocatalytic H2 activity of Mo2C/TiO2 indicates favourable charge carrier dynamics, as determined by the results of photoluminescence (PL), time-resolved photoluminescence (TRPL), surface photovoltage (SPV), and open circuit potential (OCP) decay curves. Moreover, this study provides a guide for researchers to design new functional materials with excellent hydrogen production activity.

Design and synthesis of high performance LiFePO4/C nanomaterials for lithium ion batteries assisted by a facile H+/Li+ ion exchange reaction

The main objective of this work is to determine a novel and universal method for the lithiation of amorphous hydrated FePO4, typically a nanoscale FePO4/polyaniline composite, by a facile H+/Li+ ion exchange reaction proceeding in a nonaqueous medium that was rigorously deduced and studied with the help of several chemical/physical analytical techniques. The resulting Li-derivative is proved to be a desirable precursor for fabricating LiFePO4/C nanomaterials with ideal structural features containing highly crystalline LiFePO4 nanoparticles completely coated with N-doped conductive carbon. More importantly, the LiFePO4/C nanomaterial is capable of offering excellent rate capability and appealing cyclability that was strongly supported by the results of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests.