Insight into highly efficient simultaneous photocatalytic removal of Cr(VI) and 2,4-diclorophenol under visible light irradiation by phosphorus doped porous ultrathin g-C3N4 nanosheets from aqueous media: Performance and reaction mechanism
TL;DR: In this article, a phosphorus doped porous ultrathin carbon nitride nanosheets (PCN-S) was prepared successfully via the element doping and thermal exfoliation method.
Abstract: Carbon nitride (g-C3N4) has attracted great attention for its wide applications in hydrogen evolution and photocatalytic degradation. In this study, phosphorus doped porous ultrathin carbon nitride nanosheets (PCN-S) were prepared successfully via the element doping and thermal exfoliation method. The prepared PCN-S was characterized by XRD, SEM, TEM, N2-adsorption-desorption measurement, FT-IR, XPS, UV–vis diffuse reflectance spectra, photoluminescence (PL), photocurrent response (I-t) and EIS. The results show that PCN-S owns regular crystal structure of g-C3N4, large specific surface areas and nanosheet structure with lots of in-plane pores on its surface, excellent chemical stability, and broad light response to the whole visible light region, which was attributed to the doping of phosphorus element. Under visible light irradiation, the photocatalytic reduction of Cr(VI) over different samples indicated that the P doping and porous nanosheet structure play an important role for the enhanced performance of PCN-S. The reason was that P element doping can broaden the visible light response region, and large specific surface areas from the porous nanosheet structure can provide quantities of active sites for the photocatalytic reaction. Then the detailed study on the PCN-S for simultaneous photocatalytic reduction of Cr(VI) and oxidation of 2,4-diclorophenol (2,4-DCP) was conducted. The experiments results show that low pH value and enough dissolved oxygen were found to promote Cr(VI) reduction and 2,4-DCP oxidation. The detailed photocatalytic mechanism was proposed. The strategies used in this study could provide new insight into the design of g-C3N4 based materials with high photocatalytic activity, and present potential for the treatment of Cr(VI)/2,4-DCP or other mixed pollutants in wastewater.
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TL;DR: In this article, a review summarizes the recent progress in the development of efficient and low cost doped graphitic carbon nitride (g-C3N4) systems in various realms such as photocatalytic hydrogen evolution, reduction of carbon dioxide, and removal of contaminants in wastewater and gas phase.
Abstract: As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has been the hotspot in the materials science as a metal-free and visible-light-responsive photocatalyst. Pure g-C3N4 suffers from the insufficient sunlight absorption, low surface area and the fast recombination of photo-induced electron-hole pairs, resulting in low photocatalytic activity. Element doping is known to be an efficient method to tune the unique electronic structure and band gap of g-C3N4, which considerably broaden the light responsive range and enhance the charge separation. This review summarizes the recent progress in the development of efficient and low cost doped g-C3N4 systems in various realms such as photocatalytic hydrogen evolution, reduction of carbon dioxide, photocatalytic removal of contaminants in wastewater and gas phase. Typically, metal doping, nonmetal doping, co-doping and heterojunction based on doped g-C3N4 have been explored to simultaneously tune the crystallographic, textural and electronic structures for improving photocatalytic activity by enhancing the light absorption, facilitating the charge separation and transportation and prolonging the charge carrier lifetime. Finally, the current challenges and the crucial issues of element doped g-C3N4 photocatalysts that need to be addressed in future research are presented. This review presented herein can pave a novel avenue and add invaluable knowledge to the family of element doped g-C3N4 for the develop of more effective visible-light-driven photocatalysts.
1,078 citations
TL;DR: In this paper, a metal-free heterostructure photocatalyst constructed by boron nitride quantum dots (BNQDs) and ultrathin porous g-C3N4 (UPCN) was successfully developed for overcoming these defects.
Abstract: Graphitic carbon nitride (g-C3N4) has enormous potential for photocatalysis, but only possesses moderate activity because of excitonic effects and sluggish charge transfer. Herein, metal-free heterostructure photocatalyst constructed by boron nitride quantum dots (BNQDs) and ultrathin porous g-C3N4 (UPCN) was successfully developed for overcoming these defects. Results showed that the BNQDs loaded UPCN can simultaneously promote the dissociation of excitons and accelerate the transfer of charges owing to the negatively charged functional groups on the surface of BNQDs as well as the ultrathin and porous nanostructure of g-C3N4. Benefiting from the intensified exciton dissociation and charge transfer, the BNQDs/UPCN (BU) photocatalyst presented superior visible-light-driven molecular oxygen activation ability, such as superoxide radical ( O2−) generation and hydrogen peroxide (H2O2) production. The average O2− generation rate of the optimal sample (BU-3) was estimated to be 0.25 μmol L−1 min−1, which was about 2.3 and 1.6 times than that of bulk g-C3N4 and UPCN. Moreover, the H2O2 production by BU-3 was also higher than that of bulk g-C3N4 (22.77 μmol L−1) and UPCN (36.13 μmol L−1), and reached 72.30 μmol L−1 over 60 min. This work reveals how rational combination of g-C3N4 with BNQDs can endow it with improved photocatalytic activity for molecular oxygen activation, and provides a novel metal-free and highly efficient photocatalyst for environmental remediation and energy conversion.
512 citations
TL;DR: In this paper, a metal-free carbon doping-carbon nitride (BCM-C 3 N 4 ) nanocomposite was synthesized by introducing barbituric acid and cyanuric acids during the polymerization of melamine.
Abstract: Many organic and inorganic compounds have been developed as visible light driven photocatalysts for environment and energy application. In this work, a metal-free carbon doping–carbon nitride (BCM-C 3 N 4 ) nanocomposite was synthesized by introducing barbituric acid and cyanuric acid during the polymerization of melamine. The BCM-C 3 N 4 was characterized by structure, porosity, optical performance, and photoelectrochemical properties. Results demonstrated that BCM-C 3 N 4 sample exhibited higher surface area, lower fluorescence intensity, better photocurrent signals and more efficient charge transfer in comparison to pure C 3 N 4 . The BCM-C 3 N 4 exhibits excellent photocatalytic degradation ability of sulfamethazine (SMZ) under visible light irradiation. Much superior photocatalytic activity and high pollutant mineralization rate was achieved by BCM-C 3 N 4 , where it was 5 times than that of pristine C 3 N 4 . The effect of initial SMZ concentrations on photocatalyst was also investigated. Additionally, the trapping experiments and electron spin resonance tests demonstrated that the main active species, such as O 2 − and h + , could be produced under light irradiation. This work might provide an effective approach to the design of low-cost and highly efficient photocatalysis degradation systems for water treatment.
458 citations
TL;DR: This review focuses on bioavailability mechanisms of POPs in terms of sorption, transport and microbial adaptation, which is particularly novel.
388 citations
Cites background from "Insight into highly efficient simul..."
...Most of those compounds are toxic to human health even at low concentrations (Deng et al., 2017b; Tang et al., 2016; Tang et al., 2014; Tang et al., 2008)....
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...For montmorillonite, an expandable phase, the interlayer microporosity provide additional adsorption site for benzene, while for kaolinite, the nonexpendable mineral, only external surface was available for benzene (Deng et al., 2017a)....
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...In addition to surface adsorption, microstructures of minerals are also important in retention of POPs (Deng et al., 2017a; Diagboya et al., 2016)....
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...They are constructed by silicon oxygen tetrahedral sheets and aluminum oxygenhydroxyl octahedral sheet with the proportion of 1:1 or 2:1 (Deng et al., 2017a)....
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TL;DR: In this paper, a review of noble metal free doped graphitic carbon nitride (g-C3N4) photocatalysts for water purification is presented.
353 citations
Cites background from "Insight into highly efficient simul..."
...7 m(2)/g for bulk g-C3N4 and P doped g-C3N4, respectively [117]....
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References
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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
TL;DR: Graphitic carbon nitride nanosheets are extracted via simple liquid-phase exfoliation of a layered bulk material, g-C3N4, to exhibit excellent photocatalytic activity for hydrogen evolution under visible light.
Abstract: Graphitic carbon nitride nanosheets are extracted, produced via simple liquid-phase exfoliation of a layered bulk material, g-C3N4. The resulting nanosheets, having ≈2 nm thickness and N/C atomic ratio of 1.31, show an optical bandgap of 2.65 eV. The carbon nitride nanosheets are demonstrated to exhibit excellent photocatalytic activity for hydrogen evolution under visible light.
2,137 citations
TL;DR: In this article, a novel P-doped graphitic carbon nitride (g-C3N4) nanosheets were fabricated by combining P doping and thermal exfoliation strategies, which achieved a high visible-light photocatalytic H2-production activity of 1596 μmol h−1 g−1 and an apparent quantum efficiency of 3.56% at 420 nm.
Abstract: Novel porous P-doped graphitic carbon nitride (g-C3N4) nanosheets were for the first time fabricated by combining P doping and thermal exfoliation strategies. The as-prepared P-doped g-C3N4 nanosheets show a high visible-light photocatalytic H2-production activity of 1596 μmol h−1 g−1 and an apparent quantum efficiency of 3.56% at 420 nm, representing one of the most highly active metal-free g-C3N4 nanosheet photocatalysts. This outstanding photocatalytic performance originates from the P-doped conjugated system and novel macroporous nanosheet morphology. Particularly, the empty midgap states (−0.16 V vs. standard hydrogen electrode) created by P doping are for the first time found to greatly extend the light-responsive region up to 557 nm by density functional theory and experimental studies, whilst the novel macroporous structure promotes the mass-transfer process and enhances light harvesting. Our study not only demonstrates a facile, eco-friendly and scalable strategy to synthesize highly efficient porous g-C3N4 nanosheet photocatalysts, but also paves a new avenue for the rational design and synthesis of advanced photocatalysts by harnessing the strong synergistic effects through simultaneously tuning and optimizing the electronic, crystallographic, surface and textural structures.
1,070 citations
TL;DR: In this article, a simple chemical exfoliation method was used to obtain single atomic layer nanosheets with a single thickness of 0.4 nm and a lateral size of micrometers.
Abstract: Single atomic layer nanosheet materials show great application potential in many fields due to their enhanced intrinsic properties compared to their counterparts and newly born properties. Herein, g-C3N4 nanosheets with a single atomic layer structure are prepared by a simple chemical exfoliation method. The as-prepared nanosheets show a single atomic thickness of 0.4 nm and a lateral size of micrometers. The structure and photocatalytic properties of the as-prepared single layer g-C3N4 are then studied. Compared with the bulk g-C3N4, single layer g-C3N4 nanosheets show great superiority in photogenerated charge carrier transfer and separation. Accordingly, the photocatalytic H2 production and pollutant decomposition activities and photocurrent generation of single layer g-C3N4 nanosheets are much higher than those of the bulk g-C3N4, indicating the great application potential of single layer g-C3N4 nanosheets in photocatalysis and photosynthesis.
1,023 citations
TL;DR: The prepared MMWCNT adsorbent displayed the main advantage of separation convenience compared to the present adsorption treatment and was well fitted by a pseudo second-order model.
942 citations