Wenzhi Zhang

Synthesis of three-dimensionally ordered macroporous composite Ag/Bi2O3–TiO2 by dual templates and its photocatalytic activities for degradation of organic pollutants under multiple modes

In this study, polystyrene latex spheres and triblock copolymer surfactant EO20PO70EO20 were used simultaneously as dual templates, with TiO2 as a substrate to fabricate the three-dimensionally ordered macroporous (3DOM) composite Ag/Bi2O3–TiO2 by a sol–gel method and post-processing calcination. The phase structure, chemical composition, morphology, and surface physicochemical properties of as-prepared samples were well characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Ultraviolet-visible diffuse reflectance (UV-Vis/DRS), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Nitrogen adsorption–desorption measurements. The investigations revealed a distinct crystalline phase structure of the composite with a uniform and ordered spherical cavity array of periodic arrangement, attributed to highly three-dimensionally ordered macroporous structure with mesoporous walls. Compared to TiO2, the light absorption of 3DOM Ag/Bi2O3–TiO2 was red-shifted, ca. 100 nm, to the visible region. The effectiveness of 3DOM Ag/Bi2O3–TiO2 mediated methods for photocatalytic degradation of crystal violet by employing multi-modes such as UV, simulated solar light, and microwave-assisted irradiation was significantly enhanced compared to that of P25, Bi2O3, and Ag/Bi2O3–TiO2. Moreover, the 3DOM Ag/Bi2O3–TiO2 composite displayed excellent photocatalytic activity toward degradation of different organic pollutants using UV light irradiation. TOC analysis of the water solution phase of centrifuged samples indicated that water solution products formed and that with continued ultraviolet radiation, the intermediates eventually mineralized, volatilized, or were converted to other products. Importantly, the photocatalytic activity of 3DOM Ag/Bi2O3–TiO2 was retained even after three cycles. Furthermore, based on the experimental results, the possible photocatalytic reaction mechanism of the as-prepared material was proposed.

Multi-layer three-dimensionally ordered bismuth trioxide/titanium dioxide nanocomposite: synthesis and enhanced photocatalytic activity.

Taking polystyrene latex spheres (PS) and EO20PO70EO20 (P123) as dual templates, and TiO2 was used as substrate, a series of multi-layer three dimensionally ordered macroporous (3DOM) composites Bi2O3/TiO2 were successfully synthesized with sol-gel method and post-processing calcination. The fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), UV-vis diffuse reflectance (UV-vis/DRS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM) and nitrogen adsorption-desorption measurements were employed to analyze the crystalline phase, chemical composition, morphology, and surface physicochemical properties of as-synthetized samples. The results showed that as-composites were provided with obvious crystalline phase structure and periodically highly uniform ordered macroporous structure with mesoporous walls; moreover, of which was multi-layer three dimensionally ordered structure. As a result of unique optical properties of Bi2O3 and composite material structural characteristic being propitious to reactant molecular transmission and diffusion, the photocatalytic activities of 3DOM Bi2O3/TiO2 were enhanced, and the sample 3DOM Bi2O3/TiO2-2 was significantly higher than that of direct photolysis, P25, Bi2O3, and other 3DOM Bi2O3/TiO2-X (X=1, 3, 4) during the photocatalytic degradation of crystal violet under multi-modes such as UV, visible light, simulated solar light, and microwave-assisted irradiation. The centrifugal samples water solution phase of TOC analysis indicated that water solution products formed with continued ultraviolet radiation, the intermediates eventually mineralized, volatilized, or were converted to other products. In addition, the photocatalytic activity of 3DOM Bi2O3/TiO2-2 composite was basically kept even after three cycles. Meanwhile, the possible photocatalytic reaction mechanism of as-synthesized material based on the experimental results was proposed.

Litchi-like CdS/CdTiO3–TiO2 composite: synthesis and enhanced photocatalytic performance for crystal violet degradation and hydrogen production

Using the programmed temperature hydrothermal or microwave-assisted hydrothermal method combined with the ion exchange method, a series of CdS/CdTiO3–TiO2 composites were prepared by adjusting the Cd : Ti element molar ratio and microwave synthesis conditions. The crystal structure, morphology, and surface physicochemical properties of the as-prepared composites were well characterized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (UV-vis/DRS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and N2 adsorption–desorption measurements. The results showed that the composites prepared under different synthesis conditions contained mixed crystal phases of CdS, CdTiO3 and TiO2; moreover, compared to samples prepared by the programmed temperature hydrothermal method, the conditions of the microwave-assisted hydrothermal synthesis showed greater impact on the as-prepared CdTiO3 phase. The as-prepared composites basically showed a litchi-like structure, in which CdS/CdTiO3–TiO2 synthesized by the programmed temperature hydrothermal method had a smoother surface, but the dispersibility of the particles was not favorable, while compared with the composites just mentioned above, the CdS/CdTiO3–TiO2 composites prepared by the microwave-assisted hydrothermal method possessed a coarser surface, more irregular particles and better separation conditions. Simultaneously, compared with the monomer CdS, the Brunauer–Emmett–Teller surface area of these composites increased remarkably, and the optical absorption extended to the visible region. Moreover, a series of CdS/CdTiO3–TiO2 composites were tested under multiple conditions including ultraviolet light, visible light, simulated solar light and microwave-assisted irradiation to study the photocatalytic properties towards crystal violet (CV) photodegradation. The results showed that the composites presented the best photocatalytic activity when the microwave synthesis conditions were 160 °C for 6 h with 0.4 : 1 (40%) Cd : Ti molar ratio. Meanwhile, the composite also had an excellent photocatalytic hydrogen production capacity. According to trapping experimental results, we proposed the possible mechanism of the photodegradation and photocatalytic hydrogen production in aqueous systems.

Catalytic helix-sense-selective polymerisation of achiral substituted acetylenes containing bulky π-conjugated planar substituents yielding soluble and statically stable one-handed helical polymers

Helix-sense-selective polymerisation of three new achiral substituted acetylenes containing two bulky π-conjugated planar substituents via imino groups by using catalytic amounts of a chiral source yielded soluble and statically stable one-handed helical polymers which were stabilized by intramolecular steric hindrance.

Microwave-Assisted Synthesis of a Series of Ag/ZnO Nanocomposites and Evaluation of Their Photocatalytic Activities under Multi-Mode Photodegradation

A series of Ag/ZnO nanocomposites were prepared under microwave irradiation of different powers (100, 200, and 300 W). The crystal structure, morphology, and surface physicochemical properties of the as-synthesized samples were characterized by X-ray diffraction, UV–visible diffuse reflectance spectroscopy, scanning electron microscopy, and nitrogen adsorption–desorption analyses. Compared with the Ag/ZnO prepared by conventional sedimentation process, the crystal structures of Ag and ZnO did not exhibit any transformation after microwave irradiation; however, slight increases or decreases were observed in their absorption spectra and the specific surface areas. Moreover, the morphologies of all Ag/ZnO samples were changed dramatically by microwave irradiation, showing morphologies such as octagonal nano-pyramidal and multi-angled nano-pyramidal. The multi-mode photocatalytic degradation studies showed that the photocatalytic activities of the Ag/ZnO nanocomposites prepared under microwave irradiation of different powers were enhanced to different extents and were much higher than that of P25, ZnO, and Ag/ZnO prepared in the absence of microwave irradiation.

Controllable design of natural gully-like TiO2–ZrO2 composites and their photocatalytic degradation and hydrogen production by water splitting

Using polystyrene (PS) spheres as self-assembling templates, a series of natural gully-like TiO2–ZrO2 nanocomposites were prepared using instant centrifugation with one-step hydrolysis in combination with a vacuum and calcination post-processing method. XRD, UV-vis/DRS, XPS, SEM, and N2 adsorption–desorption measurements are employed to analyze and characterize the composition, structure, and morphology of the gully-like TiO2–ZrO2 composites. The results show that this series of TiO2–ZrO2 composite materials have an obvious gully structure, and the gully distribution is uniform. Imitating the formation process of natural ravines, the friction and adhesion between the PS spheres and the TiO2–ZrO2 nanoparticles could be changed by adjusting the reactant ratio. In the meantime, the water in the reaction system continuously flushes the formed loose cover, resulting in a cross-section or a fault with different shapes. Increasing the reaction time or accelerating the stirring speed can be beneficial for the formation of three-dimensional gully erosion, resulting in samples with different gully widths, which provides a new approach for the design of samples with controllable morphology. In this paper, the prepared gully-like TiO2–ZrO2 composites show a high specific surface area and a smaller band gap. We prepared a sample using titanium isopropoxide and n-butoxy polyethylene zirconium with the precursor volume ratio being about 1 : 0.25 (TZ 1 : 0.25), which shows excellent photocatalytic performance under UV light and simulated sunlight, and presents the ability to degrade organic pollutants with different structures. In addition, the cumulative H2 evolution quantity, which the sample (TZ 1 : 4) brings out via photocatalytic H2 evolution from water splitting under 8 h light irradiation, reaches 97.1 μmol g−1, indicating that the sample has the capacity of photocatalytic water splitting into hydrogen. Furthermore, a trapping experiment was performed, indicating that the active radicals ˙O2−, h+, and ˙OH− are responsible for the photocatalytic reaction, and the possible reaction mechanism of gully-like TiO2–ZrO2 in both photocatalytic degradation and photocatalytic H2 evolution from water splitting is also proposed.

Microwave-assisted hydrothermal synthesis of chrysanthemum-like Ag/ZnO prismatic nanorods and their photocatalytic properties with multiple modes for dye degradation and hydrogen production

A series of Ag/ZnO composites were prepared by microwave-assisted hydrothermal synthesis. Their composition, structure, and morphology were well characterized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (UV-vis/DRS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and N2 adsorption–desorption analyses. The results showed that the microwave-assisted synthesis method did not significantly alter the crystal structure of the composites. However, light absorption by the composite was clearly enhanced, its Brunauer–Emmett–Teller surface area values changed, and excellent surface morphology was observed. Moreover, the Ag/ZnO composite formed via microwave-assisted hydrothermal synthesis exhibited more regular stacking piled into a chrysanthemum-like structure. Under ultraviolet, visible-light, simulated sunlight, and microwave-assisted irradiation, the composite exhibited better photocatalytic properties for the photocatalytic degradation of rhodamine B compared to that of P25 and ZnO. Moreover, the composite was investigated as a catalyst for the degradation of four dyes with different structures under UV conditions, exhibiting good degradation performance. Furthermore, the degradation efficiency did not change significantly after three cycles, indicating a certain degree of stability. In addition, the photocatalytic hydrogen production experiments showed that the nanocomposite Ag/ZnO had some ability to produce photocatalytic hydrogen.