If they could be easily exfoliated, layered materials would become a diverse source of two-dimensional crystals whose properties would be useful in applications ranging from electronics to energy storage. We show that layered compounds such as MoS2, WS2, MoSe2, MoTe2, TaSe2, NbSe2, NiTe2, BN, and Bi2Te3 can be efficiently dispersed in common solvents and can be deposited as individual flakes or formed into films. Electron microscopy strongly suggests that the material is exfoliated into individual layers. By blending this material with suspensions of other nanomaterials or polymer solutions, we can prepare hybrid dispersions or composites, which can be cast into films. We show that WS2 and MoS2 effectively reinforce polymers, whereas WS2/carbon nanotube hybrid films have high conductivity, leading to promising thermoelectric properties.

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Two-Dimensional Nanosheets Produced by Liquid Exfoliation of Layered Materials

As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Sustainable hydrogen production is an essential prerequisite of a future hydrogen economy. Water electrolysis driven by renewable resource-derived electricity and direct solar-to-hydrogen conversion based on photochemical and photoelectrochemical water splitting are promising pathways for sustainable hydrogen production. All these techniques require, among many things, highly active noble metal-free hydrogen evolution catalysts to make the water splitting process more energy-efficient and economical. In this review, we highlight the recent research efforts toward the synthesis of noble metal-free electrocatalysts, especially at the nanoscale, and their catalytic properties for the hydrogen evolution reaction (HER). We review several important kinds of heterogeneous non-precious metal electrocatalysts, including metal sulfides, metal selenides, metal carbides, metal nitrides, metal phosphides, and heteroatom-doped nanocarbons. In the discussion, emphasis is given to the synthetic methods of these HER electrocatalysts, the strategies of performance improvement, and the structure/composition-catalytic activity relationship. We also summarize some important examples showing that non-Pt HER electrocatalysts could serve as efficient cocatalysts for promoting direct solar-to-hydrogen conversion in both photochemical and photoelectrochemical water splitting systems, when combined with suitable semiconductor photocatalysts.

Noble metal-free hydrogen evolution catalysts for water splitting

Semiconductor-based photocatalysis is considered to be an attractive way for solving the worldwide energy shortage and environmental pollution issues. Since the pioneering work in 2009 on graphitic carbon nitride (g-C3N4) for visible-light photocatalytic water splitting, g-C3N4 -based photocatalysis has become a very hot research topic. This review summarizes the recent progress regarding the design and preparation of g-C3N4 -based photocatalysts, including the fabrication and nanostructure design of pristine g-C3N4 , bandgap engineering through atomic-level doping and molecular-level modification, and the preparation of g-C3N4 -based semiconductor composites. Also, the photo-catalytic applications of g-C3N4 -based photocatalysts in the fields of water splitting, CO2 reduction, pollutant degradation, organic syntheses, and bacterial disinfection are reviewed, with emphasis on photocatalysis promoted by carbon materials, non-noble-metal cocatalysts, and Z-scheme heterojunctions. Finally, the concluding remarks are presented and some perspectives regarding the future development of g-C3N4 -based photocatalysts are highlighted.

Polymeric Photocatalysts Based on Graphitic Carbon Nitride

A review on g-C3N4-based photocatalysts

Anatase TiO2 microspheres with a high percentage of exposed (001) facets were synthesized by a template-free hydrothermal method without using concentrated hydrofluoric acid. The influence of various experiment conditions, such as hydrothermal temperature, acid condition, reaction time, etc., on the morphology of the final products was investigated in detail. The formation mechanism of the microspheres was deduced according to the XRD, SEM, TEM, and HRTEM characterizations. The as-obtained microspheres exhibited superior photocatalytic activity in the degradation of Acid Red 88 compared to TiO2 without exposed (001) facet.

Facile synthesis of TiO2 microspheres with reactive (001) facets for improved photocatalytic performance.

Visible-light-driven photocatalytic performance of nanohybrid incorporating nickel ions into the tetratitanate interlayer

Molten-salt confined synthesis of nitrogen-doped carbon nanosheets supported Co3O4 nanoparticles as a superior oxygen electrocatalyst for rechargeable Zn-air battery

The magnetically separable ternary polyetherimide/titanate@Fe3O4 (PTF) photocatalysts of special heterostructure between magnetite (Fe3O4) microspheres and titanates nanosheets modified by polyetherimide (PEI) were successfully fabricated via a simple facile hydrothermal deposition method. The as-prepared photocatalysts were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Transmission electron microscopy and UV-vis diffuse reflectance spectroscopy etc. The results showed that the as-fabricated material had a structure of Fe3O4 microspheres coated with titanates nanosheets modified by PEI. The special interfacial contact between 3D microsphere and 2D nanosheets in the nanoarchitectures was formed via electrostatic attraction. Furthermore, the resulted photocatalysts were tested by degradation reaction of methylene blue under visible light irradiation and demonstrated an enhanced performance than the pure Fe3O4 microspheres, and the photocatalytic activity enhanced with the molar ratio of Fe3O4 microspheres and modified titanate gradually, which was attributed to the expansion of the surface area and the different electrostatic contact between the Fe3O4 microspheres and titanate nanosheets. Moreover, the obtained results revealed the high yield magnetic separation and efficient reusability of PTF-5 (96.7%) over 3 times reuse.

Magnetically Recoverable PEI/Titanate@Fe3O4 Photocatalysts: Fabrication and Photocatalytic Properties

Photocatalytic Activity of Fe-Doped Titania Hollow Spheres Prepared by Hydrothermal Precipitation: Photocatalytic Activity of Fe-Doped Titania Hollow Spheres Prepared by Hydrothermal Precipitation

Bizhou Lin

Papers

Facile synthesis of TiO2 microspheres with reactive (001) facets for improved photocatalytic performance.

Visible-light-driven photocatalytic performance of nanohybrid incorporating nickel ions into the tetratitanate interlayer

Molten-salt confined synthesis of nitrogen-doped carbon nanosheets supported Co3O4 nanoparticles as a superior oxygen electrocatalyst for rechargeable Zn-air battery

Magnetically Recoverable PEI/Titanate@Fe3O4 Photocatalysts: Fabrication and Photocatalytic Properties

Photocatalytic Activity of Fe-Doped Titania Hollow Spheres Prepared by Hydrothermal Precipitation: Photocatalytic Activity of Fe-Doped Titania Hollow Spheres Prepared by Hydrothermal Precipitation