Oxygen vacancy-rich 2D/2D BiOCl-g-C3N4 ultrathin heterostructure nanosheets for enhanced visible-light-driven photocatalytic activity in environmental remediation
TL;DR: In this paper, a novel oxygen vacancy-rich two-dimensional/two-dimensional (2D/2D) BiOCl-g-C3N4 ultrathin heterostructure nanosheet (CN-BC) was successfully prepared by a facile solvothermal method for degradation of non-dye organic contaminants.
Abstract: Photocatalytic degradation has been unearthed as a promising strategy for environmental remediation, and the calling is endless for more efficient photocatalytic system. In this study, a novel oxygen vacancy-rich two-dimensional/two-dimensional (2D/2D) BiOCl-g-C3N4 ultrathin heterostructure nanosheet (CN-BC) is successfully prepared by a facile solvothermal method for degradation of non-dye organic contaminants. HRTEM observes the formation of heterojunction, while ESR and XPS unveil the distinct oxygen vacancy concentrations. Density functional calculations reveal that the introduction of oxygen vacancies (OVs) brings a new defect level, resulting in the increased photoabsorption. Under visible light irradiation, the OVs-rich optimum ratio of CN-BC (50CN-50BC) Exhibits 95% removal efficiency of 4-chlorophenol within 2 h, which is about 12.5, 5.3 and 3.4 times as that of pure BiOCl, g-C3N4 and OVs-poor heterostructure, respectively. The photocatalytic mechanism of OVs-rich 50CN-50BC is also revealed, suggesting that the synergistic effect between 2D/2D heterojunction and oxygen vacancies greatly promotes visible-light photoabsorption and photoinduced carrier separation efficiency with a prolonged lifetime, which is confirmed by multiple optical and electrochemical analyses, including DRS, steady-state photoluminescence spectra, electrochemical impedance spectroscopy, photocurrent response and time-resolved fluorescence spectra. This study could bring new opportunities for the rational design of highly efficient photocatalysts by combining 2D/2D heterojunctions with oxygen vacancies in environmental remediation.
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TL;DR: Recently, due to the attractive properties such as appropriate band structure, ultrahigh specific surface area, and more exposed active sites, two-dimensional (2D) photocatalysts have attracted significant attention as discussed by the authors.
Abstract: Hydrogen generation from the direct splitting of water by photocatalysis is regarded as a promising and renewable solution for the energy crisis The key to realize this reaction is to find an efficient and robust photocatalyst that ideally makes use of the energy from sunlight Recently, due to the attractive properties such as appropriate band structure, ultrahigh specific surface area, and more exposed active sites, two-dimensional (2D) photocatalysts have attracted significant attention for photocatalytic water splitting This Review attempts to summarize recent progress in the fabrication and applications of 2D photocatalysts including graphene-based photocatalysts, 2D oxides, 2D chalcogenides, 2D carbon nitride, and some other emerging 2D materials for water splitting The construction strategies and characterization techniques for 2D/2D photocatalysts are summarized Particular attention has been paid to the role of 2D/2D interfaces in these 2D photocatalysts as the interfaces and heterojunctions a
717 citations
TL;DR: In this paper, a review of the latest fabrication strategies of graphitic carbon nitride nanosheets based on conventional strategies and firstly summarizes their photocatalytic properties systematically.
Abstract: Over the past years, two dimensional (2D) graphitic carbon nitride nanosheets (CNNs) have attained increasing interest in the study of graphitic carbon nitride (g-C3N4) due to their superior physical-optical properties as photocatalyst. More and more researchers attempt to design photocatalytic systems based on CNNs to realize the control of photocatalyst morphology for enhancing performance. Hence their combination with zero dimensional (0D) nanomaterials, which frequently serve as guest materials, has witnessed great progress. Therefore this review introduces the latest fabrication strategies of CNNs based on conventional strategies and firstly summarizes their photocatalytic properties systematically. More important, typical advanced examples combining CNNs with 0D nanomaterials like carbon nanodots, noble metal atoms and semiconductor nanoparticles are presented for their characteristic 0D/2D nanostructures, which have never been reported in any previous reviews up to now. Their preparation, photocatalytic mechanisms and performance influence factors are deeply discussed. In addition, three kinds of multicomponent complex systems, which take advantages of 0D nanomaterials/CNNs ingeniously, are elaborated on their charge-transfer pathways in our review. Finally, the current challenges and development ideas of 0D nanomaterials/CNNs systems in photocatalytic applications are proposed. This review enriches the knowledge in the applications of CNNs and paves road to the combination of 0D materials with CNNs and even other 2D materials.
301 citations
TL;DR: The unique and special layered structure of BiOCl, the typical and common synthesis methods that can control the morphology, and the most important part is varies of modification routes ofBiOCl and the application of Bi OCl-based materials for photocatalytic degradation of organic pollutants are introduced.
267 citations
TL;DR: It is demonstrated that the 2D/2D Ti3C2/g-C3N4 composites are promising photocatalysts thanks to the ultrathin MXenes as efficient co-catalysts for photoc atalytic hydrogen production.
Abstract: Photocatalytic hydrogen evolution from water has received enormous attention due to its ability to address a number of global environmental and energy-related issues. Here, we synthesize 2D/2D Ti3C2/g-C3N4 composites by electrostatic self-assembly technique and demonstrate their use as photocatalysts for hydrogen evolution under visible light irradiation. The optimized Ti3C2/g-C3N4 composite exhibited a 10 times higher photocatalytic hydrogen evolution performance (72.3 μmol h-1 gcat-1) than that of pristine g-C3N4 (7.1 μmol h-1 gcat-1). Such enhanced photocatalytic performance was due to the formation of 2D/2D heterojunctions in the Ti3C2/g-C3N4 composites. The intimate contact between the monolayer Ti3C2 and g-C3N4 nanosheets promotes the separation of photogenerated charge carriers at the Ti3C2/g-C3N4 interface. Furthermore, the ultrahigh conductivity of Ti3C2 and the Schottky junction formed between g-C3N4/MXene interfaces facilitate the photoinduced electron transfer and suppress the recombination with photogenerated holes. This work demonstrates that the 2D/2D Ti3C2/g-C3N4 composites are promising photocatalysts thanks to the ultrathin MXenes as efficient co-catalysts for photocatalytic hydrogen production.
266 citations
TL;DR: In this article, the photocatalytic performance of visible-light-responsive, CdI2-type layered SnS2 by employing good conductivity N-doped reduced graphene oxide (NRG) and polyaniline (PANI) as the receptors and transporters of photogenerated electrons and holes, respectively, was investigated.
Abstract: Effective enhancement of the separation and transfer of photogenerated electrons and holes of semiconductor photocatalysts is key to increase their photocatalytic efficiency. This study aims at improving the photocatalytic performance of visible-light-responsive, CdI2-type layered SnS2 by employing good conductivity N-doped reduced graphene oxide (NRG) and polyaniline (PANI) as the receptors and transporters of photogenerated electrons and holes, respectively. PANI/SnS2/NRG ternary composites were prepared by a three-step method, and the optimum conditions for preparing the most efficient product were explored. The photocatalytic experiments demonstrated that the PANI/SnS2/NRG ternary composite prepared under the optimum conditions (PANI/SnS2/NRG-2%) had markedly higher photocatalytic activity than SnS2 nanoplates, SnS2/PANI and SnS2/NRG binary composites in the reduction of aqueous Cr(VI) under the irradiation of visible-light (λ > 420 nm). Based on comparison of the photoabsorption, photoluminescence and electrochemical impedance properties of PANI/SnS2/NRG, SnS2/PANI and SnS2, it was thought that the coupling of SnS2 with both PANI and NRG had synergistic effects in increasing the absorption of visible-light as well as the separation and transfer of photogenerated electrons and holes, which contributed to the exceptionally high photocatalytic activity of PANI/SnS2/NRG ternary composite. Moreover, it was discovered that the photocatalytic reduction of Cr(VI) over PANI/SnS2/NRG-2% was dominantly through the reduction by photogenerated electrons, whereas both photogenerated electron and superoxide anion radical (O2 –) reduction played important roles in the photocatalytic reduction of Cr(VI) over SnS2. Besides, the influences of photocatalytic testing conditions (including starting pH and concentration of Cr(VI) solution, and dosage of photocatalyst) on the efficiency of PANI/SnS2/NRG-2% in treatment of aqueous Cr(VI) were also examined.
261 citations
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TL;DR: It is shown that an abundant material, polymeric carbon nitride, can produce hydrogen from water under visible-light irradiation in the presence of a sacrificial donor.
Abstract: The production of hydrogen from water using a catalyst and solar energy is an ideal future energy source, independent of fossil reserves. For an economical use of water and solar energy, catalysts that are sufficiently efficient, stable, inexpensive and capable of harvesting light are required. Here, we show that an abundant material, polymeric carbon nitride, can produce hydrogen from water under visible-light irradiation in the presence of a sacrificial donor. Contrary to other conducting polymer semiconductors, carbon nitride is chemically and thermally stable and does not rely on complicated device manufacturing. The results represent an important first step towards photosynthesis in general where artificial conjugated polymer semiconductors can be used as energy transducers.
9,751 citations
TL;DR: 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.
Abstract: 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...
5,054 citations
TL;DR: The unique advances on ultrathin 2D nanomaterials are introduced, followed by the description of their composition and crystal structures, and the assortments of their synthetic methods are summarized.
Abstract: Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...
3,628 citations
TL;DR: This review attempts to summarize the recent progress in the rational design and fabrication ofheterojunction photocatalysts, such as the semiconductor-semiconductor heterojunction, the semiconductors-metal heterojunctions, the silicon-carbon heteroj junction and the multicomponent heteroj conjunction.
Abstract: Semiconductor-mediated photocatalysis has received tremendous attention as it holds great promise to address the worldwide energy and environmental issues. To overcome the serious drawbacks of fast charge recombination and the limited visible-light absorption of semiconductor photocatalysts, many strategies have been developed in the past few decades and the most widely used one is to develop photocatalytic heterojunctions. This review attempts to summarize the recent progress in the rational design and fabrication of heterojunction photocatalysts, such as the semiconductor–semiconductor heterojunction, the semiconductor–metal heterojunction, the semiconductor–carbon heterojunction and the multicomponent heterojunction. The photocatalytic properties of the four junction systems are also discussed in relation to the environmental and energy applications, such as degradation of pollutants, hydrogen generation and photocatalytic disinfection. This tutorial review ends with a summary and some perspectives on the challenges and new directions in this exciting and still emerging area of research.
3,013 citations
TL;DR: In this article, a top-down thermal oxidation etching of bulk g-C3N4 in air has been shown to improve the photocatalytic activities of the material in terms of OH radical generation and hydrogen evolution.
Abstract: Graphitic (g)-C3N4 with a layered structure has the potential of forming graphene-like nanosheets with unusual physicochemical properties due to weak van der Waals forces between layers. Herein is shown that g-C3N4 nanosheets with a thickness of around 2 nm can be easily obtained by a simple top-down strategy, namely, thermal oxidation etching of bulk g-C3N4 in air. Compared to the bulk g-C3N4, the highly anisotropic 2D-nanosheets possess a high specific surface area of 306 m2 g-1, a larger bandgap (by 0.2 eV), improved electron transport ability along the in-plane direction, and increased lifetime of photoexcited charge carriers because of the quantum confinement effect. As a consequence, the photocatalytic activities of g-C3N4 nanosheets have been remarkably improved in terms of OH radical generation and photocatalytic hydrogen evolution.
2,900 citations