Xianying Wang

A Highly Efficient Sunlight Driven ZnO Nanosheet Photocatalyst: Synergetic Effect of P-Doping and MoS2 Atomic Layer Loading

A novel kind of highly efficient photocatalyst composed of ultrathin P‐doped ZnO nanosheets decorated with atomic MoS2 layers is reported. Under natural sunlight, 95 % of the organic dyes can be degraded within six minutes. The photodegradation rate constant reaches up to 1.413 min−1, which is 3.4 times larger than that of commercial P25 under the same reaction conditions. The superior photocatalytic activity of the hybrid photocatalyst can be attributed to the synergetic effects of many advantages, including enhanced light adsorption efficiency, suppression of charge recombination, improvement of interfacial charge transfer, and an increase in the number of reaction sites.

Synthesis, optical and electrochemical properties of ZnO nanowires/graphene oxide heterostructures.

Large-scale vertically aligned ZnO nanowires with high crystal qualities were fabricated on thin graphene oxide films via a low temperature hydrothermal method. Room temperature photoluminescence results show that the ultraviolet emission of nanowires grown on graphene oxide films was greatly enhanced and the defect-related visible emission was suppressed, which can be attributed to the improved crystal quality and possible electron transfer between ZnO and graphene oxide. Electrochemical property measurement results demonstrated that the ZnO nanowires/graphene oxide have large integral area of cyclic voltammetry loop, indicating that such heterostructure is promising for application in supercapacitors.

Superior photocatalytic properties of phosphorous-doped ZnO nanocombs

We demonstrated that phosphorous (P)-doped ZnO nanocombs exhibited extremely high photocatalytic efficiency, which was evaluated by photodegrading methylene blue dyes in aqueous solutions. The photocatalyst takes advantage of the large surface to volume ratio (S/V) and abundant surface defect states of ZnO nanostructures. To maximize the S/V for more efficient light irradiation, the morphologies of the P-doped ZnO nanostructures were tailored by controlling the ratio of argon and oxygen in the carrier gas. P-doping caused a bunch of surface defects in ZnO, which could effectively restrain the recombination of photogenerated carriers and improve the photocatalytic behavior. Superior photocatalytic behaviors of P-doped ZnO nanocombs, as well as the availability of catalyst-free large scale synthesis, provide a new paradigm for rational synthesis of high efficient photocatalysts.

Homoepitaxial regrowth habits of ZnO nanowire arrays

Synthetic regrowth of ZnO nanowires [NWs] under a similar chemical vapor transport and condensation [CVTC] process can produce abundant ZnO nanostructures which are not possible by a single CVTC step. In this work, we report three different regrowth modes of ZnO NWs: axial growth, radial growth, and both directions. The different growth modes seem to be determined by the properties of initial ZnO NW templates. By varying the growth parameters in the first-step CVTC process, ZnO nanostructures (e.g., nanoantenna) with drastically different morphologies can be obtained with distinct photoluminescence properties. The results have implications in guiding the rational synthesis of various ZnO NW heterostructures.

Graphitic carbon nitride nanoribbon for enhanced visible-light photocatalytic H2 production

Chemical scissors provide a new vision to manufacture unique carbon nitride nanostructures with improved photocatalytic performance. Herein, graphitic carbon nitride nanoribbon (GCNR), with a typical length of 1.75 μm, width of 210 nm and thickness of 3 nm, was obtained by acid treatment of bulk g-C3N4 with HNO3/H2SO4 mixtures. The C/N molar ratio of GCNR (around 0.629) was much smaller than that of pristine g-C3N4 (0.758). It was demonstrated that larger amounts of carbon vacancies on the ultra-thin ribbon structures could contribute to improved electron–hole separation efficiency and excellent photocatalytic H2 production. The average H2 production rate of GCNR under visible light was 49.4 μmol h−1, which was 20 times that of the original catalyst.

The comparison of macroporous ceramics fabricated through the protein direct foaming and sponge replica methods

The macroporous ceramic samples fabricated using the sponge replica and protein direct foaming methods were compared in terms of porosity, density, compressive strength and microstructure. The egg white protein was applied in both fabrication methods as the binder or foaming agent. The samples fabricated using the protein direct foaming method were stronger and more uniform pore structures in the similar porosity. This result was supported through the Weibull modulus analysis and the scanning electron microscope microstructure observation.

New Understanding on Photocatalytic Mechanism of Nitrogen-Doped Graphene Quantum Dots-Decorated BiVO4 Nanojunction Photocatalysts

Bismuth vanadate (BiVO4) is a promising candidate as a visible-light-driven photocatalyst in the aspect of practical applications. To investigate the origin of active species from BiVO4 and understand the influence of the variations of the photocatalytic process, comparative studies on zero-dimensional nitrogen-doped graphene quantum dot (NGQD)-decorated BiVO4 have been carried out for methylene blue photodegradation. It was found that the hydroxyl group-rich NGQD surface and the established heterojunction structure between NGQDs and BiVO4 were greatly beneficial for the conversion of the •OH radical. With NGQD decoration, the dominant oxidant species for NGQDs/BiVO4 were confirmed to be •OH and H2O2, rather than holes originating from the valence band of unmodified BiVO4. The synergistic photocatalytic mechanism with respect to the interfacial charge transport and the conversion of active species was proposed. The achievement of the controllable active species significantly altering the activity may be applied for different photocatalytic reactions.

Graphene nanodots decorated ultrathin P doped ZnO nanosheets as highly efficient photocatalysts

A novel kind of highly efficient photocatalyst composed of ultrathin P doped ZnO (ZnO:P) nanosheets decorated with graphene nanodots (GNDs) was fabricated. Taking the unique advantages of the ultrathin ZnO nanosheet structure, and the excellent properties of the GNDs, a 1.6 wt% ZnO:P/GNDs nanosheet composite exhibited an optimum visible-light photocatalytic oxidation activity of 0.442 min−1 for RhB degradation and an excellent photostability over five cycles. This can be attributed to the synergistic effect between the ZnO:P nanosheets and GNDs, leading to a significantly enhanced charge efficiency and visible light absorption.

Effects of precursor-substrate distances on the growth of GaN nanowires

GaN nanowires were synthesized through the Ni-catalyzed chemical vapor deposition (CVD) method using Ga2O3/GaN mixtures as gallium sources, and precursor-substrate distances were investigated as the important factor for the growth of GaN nanowires. The microstructure, composition, and photoluminescence property were characterized by X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and photoluminescence spectra. The results showed that single crystalline GaN nanowires with the diameter of about 90 nm and the length up to tens of micrometers had been grown thickly across Si (100) substrates with uniform density. Moreover, the variations of the GaN nanowire morphology, density, and size were largely attributed to substrate positions which would influence Ga precursor density in the carrier gas, the saturation degree of gaseous reactants, and the catalyst activity, respectively, in the fabrication of GaN nanowires by the vapour liquid solid mechanism.

Temperature-dependent gas transport performance of vertically aligned carbon nanotube/parylene composite membranes

A novel composite membrane consisting of vertically aligned carbon nanotubes (CNTs) and parylene was successfully fabricated. Seamless filling of the spaces in CNT forests with parylene was achieved by a low-pressure chemical vapor deposition (CVD) technique and followed with the Ar/O2 plasma etching to expose CNT tips. Transport properties of various gases through the CNT/parylene membranes were explored. And gas permeances were independent on feed pressure in accordance with the Knudsen model, but the permeance values were over 60 times higher than that predicted by the Knudsen diffusion kinetics, which was attributed to specular momentum reflection inside smooth CNT pores. Gas permeances and enhancement factors over the Knudsen model firstly increased and then decreased with rising temperature, which confirmed the existence of non-Knudsen transport. And surface adsorption diffusion could affect the gas permeance at relatively low temperature. The gas permeance of the CNT/parylene composite membrane could be improved by optimizing operating temperature.