Xinjuan Liu

Microwave-assisted synthesis of ZnO–graphene composite for photocatalytic reduction of Cr(VI)

ZnO–graphene composites are successfully synthesized via microwave-assisted reaction of zinc sulfate in aqueous solution with a graphite oxide dispersion using a microwave synthesis system. Their morphology, structure and photocatalytic performance in reduction of Cr(VI) are characterized by scanning electron microscopy, X-ray diffraction spectroscopy and UV-vis absorption spectrophotometer, respectively. The results show that in the composite the graphene nanosheets are decorated densely by ZnO nanosheets, which display a good combination between graphene and ZnO nanosheets. The ZnO–graphene composite exhibits an enhanced photocatalytic performance in the reduction of Cr(VI) with a removal rate of 98% under UV light irradiation as compared with pure ZnO (58%) due to the increased light absorption intensity and range, as well as the reduction of electron–hole pair recombination with the introduction of graphene.

Microwave-assisted synthesis of TiO2-reduced graphene oxide composites for the photocatalytic reduction of Cr(VI)

TiO2-reduced graphene oxide (RGO) composites are successfully synthesized via the microwave-assisted reduction of graphite oxide in a TiO2 suspension using a microwave synthesis system. Their morphology, structure and photocatalytic performance in the reduction of Cr(VI) are characterized by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray diffraction spectroscopy and UV-vis absorption spectrophotometer. The results show that in the composite the RGO nanosheets are densely decorated by TiO2 nanoparticles, which displays a good combination between RGO and TiO2. TiO2–RGO composites exhibit enhanced photocatalytic performance for the reduction of Cr(VI) with a maximum removal rate of 91% under UV light irradiation as compared with pure TiO2 (83%) and commercial TiO2 P25 (70%) due to the increased light absorption intensity and range as well as the reduction of electron-hole pair recombination in TiO2 with the introduction of RGO.

Review on carbon-based composite materials for capacitive deionization

The last five decades have witnessed the rapid development of capacitive deionization (CDI) as a novel, low-cost and environment-friendly desalination technology. During the CDI process, salt ions are sequestered by the porous electrodes once exposed to an electric field. These electrodes, acting as an ion storage container, play a vital role during desalination. In this review, various carbon-based composite electrode materials, including carbon–carbon composites, carbon–metal oxide composites, carbon–polymer composites and carbon–polymer–metal oxide composites, are systematically presented. Applications of these carbon-based composite materials for the removal of the salt ions from solution are demonstrated and they exhibit improved CDI performances compared with pristine carbon electrodes.

Enhanced photocatalytic degradation of methylene blue by ZnO–reduced graphene oxide–carbon nanotube composites synthesized via microwave-assisted reaction

ZnO–reduced graphene oxide (RGO)–carbon nanotube (CNT) composites were successfully synthesized via microwave-assisted reduction of a graphite oxide dispersion in zinc nitrate solution with a CNT suspension. Their photocatalytic performance in the degradation of methylene blue was investigated and the results show that the CNTs play an important role in the enhancement of the photocatalytic performance and the ZnO–RGO–CNT composite with 3.9 wt% CNTs achieves a maximum degradation efficiency of 96% under UV light irradiation for 260 min as compared with ZnO–RGO (88%) due to the increased light absorption and the reduced charge recombination with the introduction of CNTs.

Nanophotocatalysts via microwave-assisted solution-phase synthesis for efficient photocatalysis

Nanostructured photocatalysts have attracted considerable interest due to their wide range of applications in processes such as organic pollutant degradation, heavy metal reduction, air and water purification, hydrogen production, etc. Pursuing high catalytic efficiency is the foremost goal in the field. One of the current key issues is to search for suitable photocatalysts to enhance light harvesting in the UV or visible light region. In this treatise, the microwave-assisted solution-phase synthesis of various nanomaterials including semiconductor oxides and sulfides, Bi-based oxides, as well as nanocomposites including carbon nanotube-based and graphene-based composites is systematically presented with demonstrations of the advantages of the microwave-assisted process over traditional synthesis methods including solid state or vapor reactions and hydrothermal or solvothermal processes. Application of these nanomaterials as photocatalysts for the degradation of pollutants in water or air, removal of Cr(VI) as well as hydrogen evolution is also demonstrated, showing the improved photocatalytic activities compared with the ones synthesized via traditional methods.

MoS2–reduced graphene oxide composites synthesized via a microwave-assisted method for visible-light photocatalytic degradation of methylene blue

MoS2–reduced graphene oxide (RGO) composites were successfully synthesized via microwave-assisted reduction of graphite oxide in a MoS2 precursor aqueous solution using a microwave system. The morphology, structure and photocatalytic performance in the degradation of methylene blue (MB) were characterized by scanning electron microscopy, X-ray diffraction, electrochemical impedance spectra and UV-vis absorption spectroscopy, respectively. The results show that the MoS2–RGO composites exhibit enhanced photocatalytic performance in the degradation of MB with a maximum degradation rate of 99% under visible light irradiation for 60 min. This excellent photocatalytic activity is due to the contribution from the reduced electron–hole pair recombination, the enhanced light absorption and the increased dye adsorptivity with the introduction of RGO in the composite.

In situ growth of NiCo2S4@Ni3V2O8 on Ni foam as a binder-free electrode for asymmetric supercapacitors

A hierarchical NiCo2S4@Ni3V2O8 core/shell hybrid was in situ grown on nickel foam through a facile hydrothermal process combined with a simple co-precipitation method. Further characterization shows that the hybrid consists of highly conductive NiCo2S4 as the core and uniformly distributed Ni3V2O8 nanoparticles as the shell. When used as the binder-free electrode, the hybrid material takes advantage of both components and exhibits excellent electrochemical activity, demonstrating a higher specific capacity of 512 C g−1 at a current density of 1 A g−1 and a better rate capability of 396 C g−1 at 10 A g−1. The enhanced pseudocapacitive performance of the NiCo2S4@Ni3V2O8 hybrid is mainly attributed to its unique core/shell structure, which provides fast ion and electron transport. Finally, a NiCo2S4@Ni3V2O8//activated carbon asymmetric supercapacitor is successfully assembled and it can deliver a maximum energy density of 42.7 W h kg−1 at a power density of 200 W kg−1, making it a promising candidate for superior electrodes for supercapacitor applications.

ZnO meso-mechano-thermo physical chemistry.

Jianwei Li,† Shouzhi Ma,‡ Xinjuan Liu, Zhaofeng Zhou,† and Chang Q Sun*,†,‡ †Institute for Quantum Engineering and Micro-Nano Energy Technology, Key Laboratory of Low-Dimensional Materials and Application Technologies, and Faculty of Materials and Optoelectronics and Physics, Xiangtan University, Hunan 411105, China ‡School of Electrical, and Electronic Engineering, Nanyang Technological University, Singapore 639798 Engineering Research Center for Nanophotonics & Advanced Instrument, Ministry of Education, Department of Physics, East China Normal University, Shanghai, 200062 China

One-step synthesis of CdS–TiO2–chemically reduced graphene oxide composites via microwave-assisted reaction for visible-light photocatalytic degradation of methyl orange

One-step synthesis of CdS–TiO2–chemically reduced graphene oxide (RGO) composites was carried out using microwave-assisted reduction of graphite oxide in CdS precursor solution with TiO2 suspension. The photocatalytic performance of CdS–TiO2–RGO composites in degradation of methyl orange was examined. Results show that the RGO addition could enhance the photocatalytic performance of CdS–TiO2 composites with maximum degradation efficiency of 99.5% under visible light irradiation as compared with the pure TiO2 (43%) and CdS–TiO2 (79.9%) composites due to the increase of specific surface area for more adsorbed MO and the reduction of electron–hole pair recombination with the introduction of RGO.

Visible light photocatalytic degradation of dyes by bismuth oxide-reduced graphene oxide composites prepared via microwave-assisted method

Bi2O3-reduced graphene oxide (RGO) composites were successfully synthesized via microwave-assisted reduction of graphite oxide in Bi2O3 precursor solution using a microwave system. Their morphologies, structures, and photocatalytic performance in the degradation of methylene blue (MB) and methyl orange (MO) were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectroscopy, UV-vis absorption spectroscopy, and electrochemical impedance spectroscopy, respectively. The results show that the RGO addition can enhance the photocatalytic performance of Bi2O3-RGO composites. Bi2O3-RGO composite with 2 wt.% RGO achieves maximum MO and MB degradation rates of 93% and 96% at 240min under visible light irradiation, respectively, much higher than those for the pure Bi2O3 (78% and 76%). The enhanced photocatalytic performance is ascribed to the increased light adsorption and the reduction in electron-hole pair recombination in Bi2O3 with the introduction of RGO.