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1.
2D heterojunction based on g-C 3N 4 nanosheets with other semiconductor nanosheets is a promising way to improve photocatalytic hydrogen evolution (PHE) activity over g-C 3N 4. However, current 2D heterojunction based on g-C 3N 4 are unsatisfactory due to their insufficient absorption of visible light and inefficient charge separation. In this work, Ag/TiO 2/g-C 3N 4 nanocomposites based on 2D heterojunction coupling with Ag surface plasmon resonance (SPR) were synthesized by a method combining facile wetness impregnation calcination. The PHE activity of Ag/TiO 2/g-C 3N 4 nanocomposites is attributed to the TiO 2/g-C 3N 4 2D heterojunction and bare g-C 3N 4 nanosheet under visible light irradiation, indicating a cooperative effect between Ag and TiO 2/g-C 3N 4 2D heterojunction. As a result of SPR effect, the composites strongly absorb visible light. In addition, the oscillating hot electrons from Ag can easily transfer to 2D heterojunction. This synergistic effect lead to sufficient visible light absorption and efficient charge separation of 2D heterojunction, which improved the PHE activity of g-C 3N 4. This work indicates that loading metal nanoparticles on 2D heterojunction as metal SPR-2D heterojunction nanocomposites may be a potential method for harvesting visible light for PHE. 相似文献
2.
In this study, the multifunctional carbon nitride based composite graphitic-C 3N 4 (g-C 3N 4)/TiO 2/Ag was prepared through a simple and efficient vacuum freeze-drying route. TiO 2 and Ag nanoparticles were demonstrated to decorate onto the surface of g-C 3N 4 sheet. In the ultraviolet–visible absorption test, a narrower band gap and red-shift of light absorption edge were observed for g-C 3N 4/TiO 2/Ag compared to pristine g-C 3N 4 and single-component modified g-C 3N 4/TiO 2. The photodegradation property of g-C 3N 4/TiO 2/Ag was investigated toward the degradation of methylene blue (abbreviated as MB) under the irradiation of visible light. These results indicated that the degradation performance of organic dyes for g-C 3N 4/TiO 2/Ag was obviously improved compared with g-C 3N 4/TiO 2 and g-C 3N 4. The reaction rate constant of MB degradation for g-C 3N 4/TiO 2/Ag was 4.24 times higher than that of pristine g-C 3N 4. In addition, such rationally constructed nanocomposite presented evidently enhanced antibacterial performance against the Gram-negative Escherichia coli. Concentration dependent antibacterial performance was systematically investigated. And 84% bacterial cell viability loss had been observed at 500 μg/mL g-C 3N 4/TiO 2/Ag within 2 h visible light irradiation. 相似文献
3.
Nitrogen fixation is the second most important chemical process in nature next to photosynthesis. Herein, we report a convenient template-free method for synthesizing sponge-like graphitic carbon nitride (g-C 3N 4) with a large surface area and outstanding nitrogen photofixation ability under visible light. X-ray diffraction (XRD), N 2 adsorption, UV–vis spectroscopy, N 2-Temperature programmed desorption (N 2-TPD), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS), and photocurrent measurements were used to characterize the prepared catalysts. The results indicate that solvent species (alcohols) play the most important role in the formation of the porous structure. Methanol-treated g-C 3N 4 exhibits the highest surface area and nitrogen photofixation ability, which are 15.2-fold and 27.2-fold greater, respectively, than that of untreated g-C 3N 4. Nitrogen vacancies could activate N 2 and promote interfacial electron transfer, thereby significantly improving the nitrogen photofixation ability. 相似文献
4.
BiPO 4/g-C 3N 4 with different amounts of BiPO 4 was prepared through wet impregnation with calcination method. The BiPO 4/g-C 3N 4 showed large surface area (172.9 m 2 g − 1) and the incorporation of BiPO 4 caused a red-shift of g-C 3N 4 in visible light. The photocatalytic degradation of toluene over the samples was investigated. The degradation of toluene could get 82% in BiPO 4/g-C 3N 4 photocatalysts under optimum reaction conditions. The BiPO 4/g-C 3N 4 exhibited a higher photocatalytic activity than pure g-C 3N 4 or BiPO 4. The improved photoactivity of BiPO 4/g-C 3N 4 could be attributed to strong absorption in visible light and effective separation of photo-induced hole-electron pairs between BiPO 4 and g-C 3N 4. 相似文献
5.
In this contribution, a Z-scheme mesoporous BiVO 4/g-C 3N 4 nanocomposite heterojunction with a considerable surface area and high crystallinity was synthesized by a simple soft and hard template-assisted approach. This material demonstrates superior visible light-driven photocatalysis for the photoreduction of Hg(II) ions. TEM and XRD results show that the mesoporous BiVO 4 NPs, with a monoclinic phase and an ellipsoid-like shape, are highly dispersed onto the porous 2D surfaces of g-C 3N 4 nanosheets with a particle size of 5–10 nm. The obtained BiVO 4/g-C 3N 4 nanocomposites with a p-n heterojunction show significantly enhanced Hg(II) photoreduction efficiency compared to the mesoporous BiVO 4 NPs and pristine g-C 3N 4. Among all synthesized photocatalysts, the 1.2% BiVO 4/g-C 3N 4 nanocomposite indicated the highest photoreduction of Hg(II) performance, reaching ~ 100% within 60 min; this result is 3.9 and 4.5 –fold larger than that of the BiVO 4 NPs and pristine g-C 3N 4. The Hg(II) photoreduction rates highly increase to 208.90, 314.95, 411.23 and 418.68 μmol g −1min −1 for the mesoporous 0.4, 0.8, 1.2 and 1.6% BiVO 4/g-C 3N 4 nanocomposites, respectively. The reduction rate of the mesoporous 1.2% BiVO 4/g-C 3N 4 nanocomposite demonstrated a 5.2 and 3.8 times larger increase than that of the pristine g-C 3N 4 nanosheets and pure BiVO 4 NPs. The superior Hg(II) photoreduction efficiency was ascribed to decreased carrier recombination and the improved utilization of visible light by constructing BiVO 4/g-C 3N 4 nanocomposites with a p-n junction. Transient photocurrent measurement and photoluminescence spectra were employed to confirm the possible Hg(II) photoreduction mechanism over these BiVO 4/g-C 3N 4 photocatalysts. This research provides an accessible route for the nanoengineered design of mesoporous BiVO 4/g-C 3N 4 heterostructures that demonstrated unique photocatalytic performance. 相似文献
6.
In this work, cobalt phosphide (CoP) nanoparticles were successfully decorated on an ultrathin g-C 3N 4 nanosheet photocatalysts by in situ chemical deposition. The built-in electric field formed by heterojunction interface of the CoP/g-C 3N 4 composite semiconductor can accelerate the transmission and separation of photogenerated charge-hole pairs and effectively improve the photocatalytic performance. TEM, HRTEM, XPS, and SPV analysis showed that CoP/g-C 3N 4 formed a stable heterogeneous interface and effectively enhanced photogenerated electron-hole separation. UV-vis DRS analysis showed that the composite had enhanced visible light absorption than pure g-C 3N 4 and was a visible light driven photocatalyst. In this process, NaH 2PO 2 and CoCl 2 are used as the source of P and Co, and typical preparation of CoP can be completed within 3 hours. Under visible light irradiation, the optimal H 2 evolution rate of 3.0 mol% CoP/g-C 3N 4 is about 15.1 μmol h −1. The photocatalytic activity and stability of the CoP/g-C 3N 4 materials were evaluated by photocatalytic decomposition of water. The intrinsic relationship between the microstructure of the composite catalyst and the photocatalytic performance was analyzed to reveal the photocatalytic reaction mechanism. 相似文献
7.
We coupled g-C 3N 4 or chlorine modified g-C 3N 4 (Cl/g-C 3N 4) photocatalysis with ozonation for mineralization of oxalic acid (OA) under visible light. g-C 3N 4 and Cl/g-C 3N 4 could trigger a super synergy between photocatalysis and ozonation, with a coupling coefficient at 17.8 and 9.9, respectively. The great gap of redox potential between the conduction band of g-C 3N 4 and ozone greatly benefitted electrons captured by ozone molecules, and thus promoted charge separation and ozone self-decomposition into a growing number of hydroxyl radicals in a photocatalytic ozonation process. Besides, the influence of chlorine modification on g-C 3N 4 to photocatalysis and photocatalytic ozonation was also clearly stated. 相似文献
8.
It is very essential to grow efficient and abundant photocatalysts for overall water cracking to produce hydrogen. Ni 3FeN nanosheets were synthesized by combining simple sol–gel and calcining methods using urea as nitrogen source. A heterostructure was constructed between Ni 3FeN and g-C 3N 4 to enhance the absorption capacity of visible light. The reformed Z-scheme Ni 3FeN/g-C 3N 4 heterojunction exhibited an excellent visible-light photocatalytic activity. The average hydrogen evolution rate of 5 wt% Ni 3FeN/g-C 3N 4 composite is 528.7 μmol h −1 g −1 due to the Z-scheme Ni 3FeN/g-C 3N 4 junction, which promotes the separation of photogenerated e −/h +. Interestingly, the average H 2 production of Ni 3FeN/g-C 3N 4 is nearly 8.3 and 3.6 times higher than that of Fe 4N/g-C 3N 4 and Ni 4N/g-C 3N 4, respectively, indicating that bimetallic nitrides as cocatalysts are more conducive to enhancing the performance of photocatalysts. Importantly, the Ni 3FeN/g-C 3N 4 composite exhibited good cycle stability, and the hydrogen production performance hardly changed after four cycle experiments. Furthermore, photoluminescence, electrochemical impedance spectroscopy, and transient photocurrent response show that Ni 3FeN/g-C 3N 4 heterojunction improves the separation efficiency of photoinduced e −/h +. This work provides a feasibility of the cocatalyst Ni 3FeN for use in photocatalytic hydrogen production. 相似文献
9.
Graphitic carbon nitride (g-C3N4) has received much interest as a visible-light-driven photocatalyst for degrading pollutants such as organic dyes and antibiotics. However, g-C3N4 bulk activity could not meet expectations due to its rapid recombination of photogenerated electron–hole pairs and low specific surface area. In our study, melamine was thermally treated one-step in the presence of NH4Cl to produce g-C3N4 nanosheets. The characterizations of surface morphology and optical properties of all g-C3N4 samples were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrum (XPS), transmission electron microscopy (TEM), and UV–visible diffuse reflectance spectroscopy. Compared to bulk g-C3N4, g-C3N4 nanosheets demonstrated excellent photocatalytic activities, with approximately 98% RhB removal after 210 min of visible light irradiation. Furthermore, the effect of catalyst dosage, pH, and RhB concentration on the removal percentage dye of g-C3N4 nanosheets was also investigated. h+ and ?O2? species were demonstrated as the key reactive species for the RhB. Besides, ECN exposed a tetracycline degradation efficiency of 80.5% under visible-light irradiation for 210 min, which is higher than BCN (60.8%). The improved photocatalytic activity of g-C3N4 nanosheets is due to the restriction of the recombination of photogenerated electrons/hole pairs, as provided by photoluminescence spectra and Nyquist plot. As a result, our research may offer an effective approach to fabricating g-C3N4 nanosheets with high photocatalytic activity and high stability for environmental decontamination. 相似文献
10.
Surface and bandgap engineering of graphitic carbon nitride (g-C 3N 4) could be vital in enhancing photocatalytic performance by suppressing the recombination rate of photogenerated electron-hole pairs. The present report investigated the doping effects of various wt.% (0.2–5.0%) of gold nanoparticles (Au NPs) to g-C 3N 4 (Au/g-C 3N 4) for the enhancement of the photocatalytic efficiency of g-C 3N 4 nanocomposites. A straightforward and cost-effective synthesis methodology has been applied for the desired nanocomposites. Relevant characterization tools such as XRD, XPS, TEM, FTIR, and UV–Vis were utilized to analyze various physicochemical properties. The TEM images clearly show that spherical Au NPs were homogeneously distributed into the thin carbon nitride graphitic layers, confirming the successful doping of Au. The higher-magnification TEM image confirms that the sizes of the Au NPs varied from 15 to 25 nm. The photoactivity of the newly designed Au/g-C 3N 4 nanocomposites has been evaluated for the degradation of both methylene blue dye and the drug gemifloxacin mesylate, and their efficiencies were compared with that of bare g-C 3N 4. Our findings revealed that Au/g-C 3N 4 nanocomposites with various Au contents had superior photocatalytic activity compared to bare g-C 3N 4. However, the 1%Au/g-C 3N 4 nanocomposite could be considered the optimum photocatalyst, producing 95.13% destruction of the target dye molecule in 90 min, in contrast to the 69% achieved with bare g-C3N4, under the clean energy of visible light illumination. Additionally, the photodegradation rate of the 1%Au/g-C 3N 4 nanocomposite is 2.69 times higher than the rate of bare g-C 3N 4. This report might open a new gateway towards a straightforward and cost-effective synthesis approach for Au/g-C 3N 4 nanocomposites and provides a smooth and robust platform for the utilization of this new nanocomposite for environmental remediation processes. 相似文献
11.
Graphitic carbon nitride (g-C 3N 4) and its derivatives are promising candidates as catalysts or supports for photocatalytic applications. Since they are typically produced by polymerization or condensation of monomers under high temperature and high pressure, development of a cost-effective, solution-based, low-temperature method of production is important. Herein, novel hybrid materials composed of g-C 3N 4 and reduced graphene oxide are produced using a simple reaction between graphene oxide and cyanamide using a solution-based process. During the reaction, reduction of graphene oxide and graphene oxide-assisted generation of g-C 3N 4 occurred simultaneously. These hybrids show good photocatalytic performance for the removal of organic dyes under one sun solar light illumination. 相似文献
12.
A novel rice spike-like g-C 3N 4/TiO 2 nanowire heterojunctions are fabricated by hydrothermal treating Na 2Ti 3O 7 ultralong nanotubes in the presence of g-C 3N 4. The presence of g-C 3N 4 promotes the hydrolysis of Na 2Ti 3O 7 ultralong nanotubes. The partially replaced O of TiO 2 by N from g-C 3N 4 leads to the formation of a tight-binding interface between one dimensional TiO 2 and two dimensional g-C 3N 4, which is crucial for fast and effective transfer of photogenerated electrons in heterostructured photocatalysts. As a result, the g-C 3N 4/TiO 2 nanowire heterojunctions exhibit excellent visible-light photocatalytic activity. The kinetic constant (k) of g-C 3N 4/TiO 2 (0.024?min ?1) for degradation of methylene blue under visible light irradiation is 1.85 and 4 times than that of pure g-C 3N 4 and P25, respectively. 相似文献
13.
Molybdenum doped graphitic carbon nitride (g-C 3N 4) catalysts were prepared by a simple pyrolysis method using melamine and ammonium molybdate as precursors. The characterization results indicated that the obtained Mo-doped g-C 3N 4 catalysts had worm-like mesostructures with higher surface area. Introduction of Mo species can effectively extend the spectral response property and reduce the recombination rate of photogenerated electrons and holes. CO 2 photocatalytic reduction tests showed that the Mo-doped g-C 3N 4 catalysts exhibited considerably higher activity (the highest CO and CH 4 yields of 887 and 123 μmol g − 1-cat., respectively, after 8 h of UV irradiation.) compared with pure g-C 3N 4 from melamine. 相似文献
14.
A BiVO 4/2D g-C 3N 4 direct dual semiconductor photocatalytic system has been fabricated via electrostatic self-assembly method of BiVO 4 microparticle and g-C 3N 4 nanosheet. According to experimental measurements and first-principle calculations, the formation of built-in electric field and the opposite band bending around the interface region in BiVO 4/2D g-C 3N 4 as well as the intimate contact between BiVO 4 and 2D g-C 3N 4 will lead to high separation efficiency of charge carriers. More importantly, the intensity of bulid-in electric field is greatly enhanced due to the ultrathin nanosheet structure of 2D g-C 3N 4. As a result, BiVO 4/2D g-C 3N 4 exhibits excellent photocatalytic performance with the 93.0% Rhodamine B (RhB) removal after 40 min visible light irradiation, and the photocatalytic reaction rate is about 22.7 and 10.3 times as high as that of BiVO 4 and 2D g-C 3N 4, respectively. In addition, BiVO 4/2D g-C 3N 4 also displays enhanced photocatalytic performance in the degradation of tetracycline (TC). It is expected that this work may provide insights into the understanding the significant role of built-in electric field in heterostructure and fabricating highly efficient direct dual semiconductor systems. 相似文献
15.
The g-C3N4 nanosheet was prepared by calcination method, the MoS2 nanosheet was prepared by hydrothermal method. The g-C3N4/MoS2 composites were prepared by ultrasonic composite in anhydrous ethanol. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible spectroscopy, and photoluminescence techniques were used to characterize the materials. The photocatalytic degradation of Rhodamine B (Rh B) by g-C3N4/MoS2 composites with different mass ratios was investigated under visible light. The results show that a small amount of MoS2 combined with g-C3N4 can significantly improve photocatalytic activity. The g-C3N4/MoS2 composite with a mass ratio of 1:8 has the highest photocatalytic activity, and the degradation rate of Rh B increases from 50 to 99.6%. The main reason is that MoS2 and g-C3N4 have a matching band structure. The separation rate of photogenerated electron–hole pairs is enhanced. So the g-C3N4/MoS2 composite can improve the photocatalytic activity. Through the active material capture experiment, it is found that the main active material in the photocatalytic reaction process is holes, followed by superoxide radicals. 相似文献
16.
This paper describes the synthesis of a new series of g-C 3N 4/Nb 2O 5 heterostructures and their application in the removal of organic pollutants from water, as a combined strategy of photocatalysis and adsorption processes. The heterostructures were synthesized at different weight ratios through thermal oxidation and hydrothermal treatment, leading to an uniform assembly of Nb 2O 5 nanoparticles onto g-C 3N 4 surface. The heterostructures exhibited improved textural and electronic properties (narrowing in band gap) when compared to pure g-C 3N 4 and Nb 2O 5, respectively. Although adsorption capacities were shown to be influenced by Nb 2O 5 content, g-C 3N 4 was essential to increase the photocatalytic response of the g-C 3N 4/Nb 2O 5 heterostructures, which displayed an enhancement of photocatalytic performance on the degradation of methylene blue and rhodamine B dyes under visible and ultraviolet irradiation. The enhanced photoactivity was explained by the increase in the lifetime of the charge carries due to formation of heterojunctions between Nb 2O 5 and g-C 3N 4. A mechanistic investigation on the photocatalytic process was conducted by using different reactive scavenger species. The superoxide (O 2−•) radical was found to be the main active specie on the dye photodegradation activated by visible radiation. 相似文献
17.
Mesoporous single-crystalline perovskite YFeO3 nanoparticles was synthesized through a soft template-assisted approach. Mesoporous YFeO3 NPs were decorated porous g-C3N4 nanosheets with variation YFeO3 NPs percentages, and the newly synthesized photocatalysts were assessed towards Hg(II) reduction and HCOOH oxidation in aqueous solution upon visible light exposure. XRD and HR-TEM revealed the formation of single-crystalline orthorhombic YFeO3 with uniformly dispersed and the average particle size of 10?±?5 nm, thereby constructing a mesoporous YFeO3/g-C3N4 heterojunctions for the promotion of the photocatalytic performances compared to bare YFeO3 NPs and g-C3N4. 3% YFeO3/g-C3N4 heterostructure revealed the highest and optimum Hg(II) reduction (100%) within 60 min, which determined 3.7 and 5 times larger than of bare YFeO3 NPs and g-C3N4 obeyed by pseudo-first-order kinetics. The YFeO3/g-C3N4 photocatalyst could be recycled five continuous cycles and kept remarkable photostability for long time illumination. The superior Hg(II) reduction over mesoporous YFeO3/g-C3N4 heterojunction is referred to as lower recombination of carriers, the unique electronic structure, higher visible light utilization and high surface area. This work focused on constructing the YFeO3/g-C3N4 heterojunction, indicating outstanding photocatalytic performances in a facile route. 相似文献
18.
The g-C 3N 4/ZnO nanorods were prepared by simple hydrothermal, grinding and calcination methods. The characterization of g-C 3N 4/ZnO nanorods was done by different analytical techniques such as SEM, TEM, XRD, XPS, FT-IR and UV–Vis. g-C 3N 4/ZnO nanorods with heterostructures have been successfully synthesized without changing the structure between the monomers, which broadens the visible light response range and improves several major pollutants in water degradation rate. Photocatalytic studies were done for the degradation of MB, RhB, Cr(VI) and eosin which are almost fully degraded. The experimental results show that the photocatalytic performance of the nanorods is much better than others. The g-C 3N 4/ZnO photocatalyst has excellent stability and repeated cycle performance. Basing on the results of comprehensive free radical trapping test and ESR tests, it is proposed that the main active substance of the catalyst for degrading dyes is ·0 2-, and ·OH played significant roles in the degradation process. A good photocatalytic mechanism has been proven. 相似文献
19.
Excellent charge carrier kinetics and high light absorption capability are key factors in increasing photocatalytic efficiency. Here, novel mesoporous CoTiO 3/g-C 3N 4 heterostructures at varying CoTiO 3 percentages were synthesized utilizing an easy soft and hard template approach for the degradation of acridine orange (AO) under visible light exposure. The TEM images exhibited irregular nanocrystals containing stacked g-C 3N 4 layers with crimped nanosheets, and spherical CoTiO 3 NPs (10 nm) were uniformly distributed throughout the g-C 3N 4 layers. The results indicated that the mesoporous 3%CoTiO 3/g-C 3N 4 heterostructure exhibited the highest degradation of AO dye (100%) within 60 min compared to g-C3N4 (10%) and CoTiO3 (18%). Furthermore, the 3% CoTiO 3/g-C 3N 4 heterostructure had a better degradation rate, approximately 10.75- and 6.93-fold larger than those of g-C 3N 4 and CoTiO 3 NPs, respectively. The enhanced mesoporous CoTiO 3/g-C 3N 4 exhibited effective photoinduced carrier separation, a widened light harvesting range, and synergistic effects. Additionally, the 3% CoTiO 3/g-C 3N 4 heterostructure revealed superior photocatalytic stability in AO dye recycling degradation for long-life regeneration. A direct Z-scheme mechanism was suggested for the degradation of AO dye over mesoporous CoTiO 3/g-C 3N 4, and it was further supported by photoluminescence (PL) spectroscopy and photoelectrochemical responses. The present work demonstrates new insight and an approach to synthesizing mesoporous CoTiO 3/g-C 3N 4 heterostructures for various potential applications. 相似文献
20.
Recently, there has been a significant interest in developing high-performance photocatalysts for removing organic pollutants from water environment. Herein, a ternary graphitic C 3N 4 (g-C 3N 4)/Ag 3PO 4/AgBr composite photocatalyst is synthesized using an in-situ precipitation-anion-exchange process and characterized by several spectroscopic and microscopic techniques. During the photocatalytic reaction, X-ray photoelectron spectroscopy clearly illustrated the formation of metallic Ag on the g-C 3N 4/Ag 3PO 4/AgBr composite surface. The ternary composite photocatalyst demonstrated an increased photoactivity under visible light (>420 nm), achieving a complete decolorization of methyl orange (MO) in 5 min. The ternary g-C 3N 4/Ag 3PO 4/AgBr hybrid was also applied to the 2-chlorophenol degradation under visible light, further confirming its excellent photocatalytic activity. In addition, quenching experiments revealed that holes (h +) and O 2?– were the major attack species in the decolorization of MO. The enhanced photoactivity of g-C 3N 4/Ag 3PO 4/AgBr results from the efficient transfer/separation of photoinduced charges with the dual Z-scheme pathway and the charge recombination sites on the formed Ag particles. 相似文献
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