Q. Shen

Bio: Q. Shen is an academic researcher from Shaanxi University of Science and Technology. The author has contributed to research in topics: Graphene & Nanosheet. The author has an hindex of 6, co-authored 14 publications receiving 126 citations.

TiO2: Si nanotube/1T-MoSe2 nanosheet hybrids with highly efficient hydrogen evolution catalytic activity.

Abstract: Transition metal dichalcogenides exhibit an excellent catalytic activity for hydrogen evolution reaction and continue to attract many studies. Some heterojunctions are also used to enhance the catalytic activity. In this work, the TiO2 nanotubes/MoSe2 and Si-doped TiO2 NTs/MoSe2 hybrids were synthesized. The MoSe2 in the hybrids exhibited nanosheet morphology and metallic (1T) structure with high conductivity and catalytic activity for hydrogen evolution reaction. Moreover, MoSe2 decoration provided high light absorbance for the hybrids and highly efficient interface-induced effect at the heterojunction. Furthermore, the Si-doping increased specific surface area and hydrophilicity. Thus, the Si-doped TiO2 NTs/MoSe2 hybrids showed remarkably greater photocatalytic and electrocatalytic activities than the nanotubes.

Magnetic and microwave-absorbing properties of SrAl4Fe8O19 powders synthesized by coprecipitation and citric- combustion methods

Abstract: Al-substituted M-type hexaferrite is a highly anisotropic ferromagnetic material. In the present study, the coprecipitation and the citric-combustion methods of synthesis for SrAl4Fe8O19 powders were explored and their microstructure, magnetic properties, and microwave absorptivity examined. X-ray diffraction (XRD), scanning electron microscopy (SEM), a vibrating sample magnetometer, and a vector network analyser were used to characterize the powders. The XRD analyses indicated that the pure SrAl4Fe8O19 powder was synthesized at 900°C and 1000°C for 3 h by coprecipitation, but only at 1000°C for the citric-combustion processes. The SEM analysis revealed that the coprecipitation process yielded a powder with a smaller particle size, near single-domain structure, uniform grain morphology, and smaller shape anisotropy than the citric-combustion process. The synthesis technique also significantly affected the magnetic properties and microwave-absorptivity. Conversely, calcining temperature and calcining time had less of an effect. The grain size was found to be a key factor affecting the property of the powder. The powders synthesized by coprecipitation method at calcining temperature of 900°C exhibited the largest magnetization, largest coercivity, and best microwave absorptivity.

Janus Monolayer Transition Metal Dichalcogenides

Abstract: A novel crystal configuration of sandwiched S-Mo-Se structure (Janus SMoSe) at the monolayer limit has been synthesized and carefully characterized in this work. By controlled sulfurization of monolayer MoSe2 the top layer of selenium atoms are substituted by sulfur atoms while the bottom selenium layer remains intact. The peculiar structure of this new material is systematically investigated by Raman, photoluminescence and X-ray photoelectron spectroscopy and confirmed by transmission-electron microscopy and time-of-flight secondary ion mass spectrometry. Density-functional theory calculations are performed to better understand the Raman vibration modes and electronic structures of the Janus SMoSe monolayer, which are found to correlate well with corresponding experimental results. Finally, high basal plane hydrogen evolution reaction (HER) activity is discovered for the Janus monolayer and DFT calculation implies that the activity originates from the synergistic effect of the intrinsic defects and structural strain inherent in the Janus structure.

Synthesis and applications of nano-TiO 2 : a review

Abstract: TiO2-based nanomaterials have attracted prodigious attention as a photocatalysts in numerous fields of applications. In this thematic issue, the mechanism behind the photocatalytic activity of nano-TiO2 as well as the critical properties have been reviewed in details. The synthesis routes and the variables that affect the size and crystallinity of nano-TiO2 have also been discussed in detail. Moreover, a newly emerged class of color TiO2, TiO2 in aerogel form, nanotubes form, doped and undoped form, and other forms of TiO2 have been discussed in details. Photocatalytic and photovoltaic applications and the type of nano-TiO2 that is more suitable for these applications have been discussed in this review.

Two-dimensional materials as catalysts for solar fuels: hydrogen evolution reaction and CO2 reduction

Abstract: The issues of global warming and fossil fuel shortage have increased the demand for clean and renewable energy. Many researchers are investigating strategies to produce hydrogen and reduce CO2 by using solar power. Two-dimensional (2D) materials, such as graphene, graphene derivatives, and transition metal dichalcogenides (TMDs), have been extensively used owing to their extraordinary electronic and optical properties. In this review, we investigate the recent developments in 2D materials for photocatalytic applications involving the hydrogen evolution reaction and CO2 reduction. The synthesis methods and the photocatalytic properties of TMDs and graphene-based 2D materials are thoroughly discussed. Moreover, a summary of the recently developed 2D nanostructures and devices for solar hydrogen production and CO2 reduction is presented, and it is revealed that the use of 2D catalyst materials has great potential for commercialization in the near future to help overcome the energy crisis.

Graphene-based materials supported advanced oxidation processes for water and wastewater treatment: a review.

Abstract: Advanced oxidation processes (AOPs) received much attention in the field of water and wastewater treatment due to its ability to mineralize persistent organic pollutants from water medium. The addition of graphene-based materials increased the efficiency of all AOPs significantly. The present review analyzes the performance of graphene-based materials that supported AOPs in detail. Recent developments in this field are highlighted. A special focus has been awarded for the performance enhancement mechanism of AOPs in the presence of graphene-based materials.