Strongly Coupled g-C ₃ N ₄ Nanosheets-Co ₃ O ₄ Quantum Dots as 2D/0D Heterostructure Composite for Peroxymonosulfate Activation

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 construction and characteristics of each classification of the heterojunction system will be critically reviewed, namely metal-g-C3N4, semiconductor-g-C3N4, isotype g-C3N4/g-C3N4, graphitic carbon-g-C3N4, conducting polymer-g-C3N4, sensitizer-g-C3N4, and multicomponent heterojunctions. The band structures, electronic properties, optical absorption, and interfacial charge transfer of g-C3N4-based heterostructured nanohybrids will also be theoretically discussed based on the first-principles density functional theory (DFT) calculations to provide insightful outlooks on the charge carrier dynamics. Apart from that, the advancement of the versatile photoredox applications toward artificial photosynthesis (water splitting and photofixation of CO2), environmental decontamination, and bacteria disinfection will be presented in detail. Last but not least, this comprehensive review will conclude with a summary and some invigorating perspectives on the challenges and future directions at the forefront of this research platform. It is anticipated that this review can stimulate a new research doorway to facilitate the next generation of g-C3N4-based photocatalysts with ameliorated performances by harnessing the outstanding structural, electronic, and optical properties for the development of a sustainable future without environmental detriment. Show more

The production of H(2) by photocatalytic water splitting has attracted a lot attention as a clean and renewable solar H(2) generation system. Despite tremendous efforts, the present great challenge in materials science is to develop highly active photocatalysts for splitting of water at low cost. Here we report a new composite material consisting of TiO(2) nanocrystals grown in the presence of a layered MoS(2)/graphene hybrid as a high-performance photocatalyst for H(2) evolution. This composite material was prepared by a two-step simple hydrothermal process using sodium molybdate, thiourea, and graphene oxide as precursors of the MoS(2)/graphene hybrid and tetrabutylorthotitanate as the titanium precursor. Even without a noble-metal cocatalyst, the TiO(2)/MoS(2)/graphene composite reaches a high H(2) production rate of 165.3 μmol h(-1) when the content of the MoS(2)/graphene cocatalyst is 0.5 wt % and the content of graphene in this cocatalyst is 5.0 wt %, and the apparent quantum efficiency reaches 9.7% at 365 nm. This unusual photocatalytic activity arises from the positive synergetic effect between the MoS(2) and graphene components in this hybrid cocatalyst, which serve as an electron collector and a source of active adsorption sites, respectively. This study presents an inexpensive photocatalyst for energy conversion to achieve highly efficient H(2) evolution without noble metals. © 2012 American Chemical Society Show more