Modified g-C3N4/TiO2 nanosheets/ZnO ternary facet coupled heterojunction for photocatalytic degradation of p-toluenesulfonic acid (p-TSA) under visible light

Novel ternary nanocomposites with facet coupled structure were synthesized by using modified g-C₃N₄, TiO₂ nanosheets and nano-ZnO. Nanosheet/nanosheet heterojunction structure was investigated by TEM, XPS and XRD. FT–IR and Nitrogen adsorption were illustrated for chemical/physical structure analyses. Solution of p-Toluenesulfonic acid (p-TSA) was chosen as target pollutant for visible light photodegradation and the excellent removal efficiency was achieved by this structurally modified g-C₃N₄/TiO₂/ZnO hybrid. The visible light absorption improvement and quantum efficiency enhancement, which were testified by UV–vis DRS, PL and p-TSA photodegradation measurements, due to the facet coupled structure and appropriate quantity of modified g-C₃N₄ in the nanocomposites.     

Rapid sonochemical synthesis of irregular nanolaminar-like Bi2WO6 as efficient visible-light-active photocatalysts

Irregular Bi₂WO₆ nanolaminars have been successfully synthesized via a rapid sonochemical approach using bismuth nitrate and tungstic acid as precursors in an aqueous solution. The characteristics of them were investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N₂ adsorption, pore value, PL spectroscopy and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). These irregular nanolaminars are of geometric shapes of orthorhombic Bi₂WO₆ with their basal plane being (0 0 1). They possess high crystallinity, lager surface area and pore value, which means fewer traps and stronger photocatalytic activity. The growth mechanism of such special nanolaminar was related to the sonochemical synthesis route, which played a key role in the formation of Bi₂WO₆ nanolaminar. Simultaneously, it was found that the formation of Bi₂WO₆ nanolaminar is a time dependent process. The Bi₂WO₆ nanolaminar has higher photocatalytic activity than bulk Bi₂WO₆ nanoparticle obtained by refluxing method for rhodamine B (Rh.B) degradation under visible light irradiation (λ > 400 nm).     

Flowerlike PtCl4/Bi2WO6 composite photocatalyst with enhanced visible-light-induced photocatalytic activity

Flowerlike PtCl₄/Bi₂WO₆ composite photocatalyst was successfully synthesized through a simple two-step method involving a template-free hydrothermal process and the following impregnation treatment. The samples were fully characterized by the study of X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and UV-Vis absorption spectra. The results indicated that the doping of Pt species did not affect the crystal structure and the morphology of Bi₂WO₆ photocatalyst, but it had great influences on the photocatalytic activity of Bi₂WO₆ towards rhodamine-B (RhB) degradation. Besides, the Pt species was found to be present as PtCl₄ in the composite samples, and also an optimal Pt species content on the surface of Bi₂WO₆ photocatalyst was discovered with the highest photocatalytic ability. The improved photocatalytic performance could be ascribed to the enhanced interfacial charge transfer and the inhibited recombination of electron-hole pairs. Meanwhile, a possible mechanism for RhB photocatalytic degradation over PtCl₄/Bi₂WO₆ catalyst was also proposed.     

g-C3N4 modified Bi2O3 composites with enhanced visible-light photocatalytic activity

Novel g-C₃N₄ modified Bi₂O₃ (g-C₃N₄/Bi₂O₃) composites were synthesized by a mixing-calcination method. The samples were characterized by thermogravimetry (TG), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), UV–vis diffuse reflection spectroscopy (DRS), photoluminescence (PL) and photocurrent-time measurement (PT). The photocatalytic activity of the composites was evaluated by degradation of Rhodamine B (RHB) and 4-chlorophenol (4-CP) under visible light irradiation (>400 nm). The results indicated that the g-C₃N₄/Bi₂O₃ composites showed higher photocatalytic activity than that of Bi₂O₃ and g-C₃N₄. The enhanced photocatalytic activity of the g-C₃N₄/Bi₂O₃ composites could be attributed to the suitable band positions between g-C₃N₄ and Bi₂O₃. This leads to a low recombination between the photogenerated electron–hole pairs. The proposed mechanism for the enhanced visible-light photocatalytic activity of g-C₃N₄/Bi₂O₃ composites was proven by PL and PT analysis.     

A facile preparation strategy for hollow-structured Bi2O3/Bi2WO6 heterojunction with high visible light photocatalytic activity

A hollow-structured heterojunction consisting of Bi₂WO₆ nanoplatelets and Bi₂O₃ nanoparticles was successfully prepared by a facile solvothermal process. Bi₂O₃/Bi₂WO₆ heterojunction is the aggregate of some hollow spheres with diameter ranging from several hundred nanometers to 1.5 μm and is connected to each other by tube-like cavums. On the basis of scanning and transmission electron microscopy observation and X-ray diffraction analysis of the samples synthesized at different reaction stages, a possible growth mechanism was proposed for the growth of hollow-structured Bi₂O₃/Bi₂WO₆ heterojunction. Its photocatalytic activity was evaluated by degradation of rhodamine B under visible-light irradiation (λ>400 nm). The results indicate that the hollow-structured Bi₂O₃/Bi₂WO₆ heterojunction exhibits much higher photocatalytic activity than both pure Bi₂WO₆ and pure Bi₂O₃. The improved photocatalytic performance can be ascribed to the heterojunction of Bi₂O₃ and Bi₂WO₆ in the framework in which the hierarchical hollow structure possesses good permeability and large surface area. More importantly, the hollow-structured Bi₂O₃/Bi₂WO₆ heterojunction is not only highly stable but also easy to be separated by simple sedimentation for recycle.     

圆盘状Bi2WO6-BiPO4异质结的水热合成及光催化性能 (cited: 1)

采用水热法制备Bi₂WO₆-BiPO₄异质结光催化剂．利用模拟太阳光照射下的罗丹明B降解实验评价了Bi₂WO₆-BiPO₄复合物的光催化性能．结果表明,Bi₂WO₆-BiPO₄光催化活性比Bi₂WO₆和BiPO₄高得多．当Bi₂WO₆与BiPO₄的摩尔比为1:1时复合光催化剂对罗丹明B的降解率最高．Bi₂WO₆-BiPO₄催化活性增强主要归结为两者之间形成了有效的异质结结构,其内建电场能够促进光生载流子的分离．同时,Bi₂WO₆的加入增强了其对可见光的吸收．研究表明O₂· ^-和h⁺在光催化降解过程中是主要的活性物种     

Fabrication of g-C3N4/NiO heterostructured nanocomposite modified glassy carbon electrode for quercetin biosensor

Herein, we report a one-pot synthesis of structurally uniform and electrochemically active graphitic carbon nitride/nickel oxide (g-C₃N₄/NiO) nanocomposite and an investigation on the electrocatalytic oxidation of quercetin (QR). The synthesized g-C₃N₄/NiO nanocomposite has uniform surface distribution, which was characterized with scanning electron microscopy (SEM). Moreover, the composition of synthesized g-C₃N₄/NiO nanocomposite was characterized by UV–vis-spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR spectra), BET, SEM and HRTEM. The g-C₃N₄/NiO was electrochemically treated in 0.1 MPBS solution through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The peak current response increases linearly with QR concentration from 0.010 μM to 250 µM with a fast response time of less than 2 s and a detection limit of 0.002 μM. To further evaluate the feasibility of using this sensor for real sample analysis, QR content in various real samples including green tea, green apple, honey suckle were determined and satisfactory results were achieved.     

Ultrasonic irradiation preparation of graphitic-C3N4/polyaniline nanocomposites as counter electrodes for dye-sensitized solar cells

In this research, polyaniline/graphitic carbon nitride (PANI/g-C₃N₄) nanocomposites were synthesized via in-situ electrochemical polymerization of aniline monomer whit different number of cyclic voltammetry scans (10, 20 and 30 cycles) after electrode surface pre-preparation using a potential shock under ultrasonic irradiation. PANI/g-C₃N₄ nanocomposites with two values of g-C₃N₄ (0.010 wt% and 0.015 wt%) were deposited on the surface of the transparent conducting film (FTO glass) by immersing FTO into the aniline solution and g-C₃N₄ during the electro-polymerization. The resulting PANI/g-C₃N₄ films were characterized by Fourier transformed infra-red (FTIR), power X-ray diffraction (PXRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) techniques. The prepared electrodes were applied as counter electrode in dye-sensitized solar cells. Among them, the prepared electrode with 10 cycles and 0.01 wt% g-C₃N₄ showed the best efficiency. These hybrids show good catalytic activity in elevating tri-iodide reduction and due to the synergistic effect of PANI and g-C₃N₄, PANI/g-C₃N₄ nanocomposite electrode shows power conversion efficiency about 1.8%.     

Ultrasound wave assisted adsorption of congo red using gold-magnetic nanocomposite loaded on activated carbon: Optimization of process parameters

In this study, gold-magnetic nanocomposite in the presence of ultrasound wave assisted was synthesized and loaded on activated carbon (Au-Fe₃O₄-NCs-AC) by simple, fast and low-cost process. This novel material was applied for ultrasound assisted adsorption of congo red (CR) as model of toxic and even carcinogenic substance from aqueous solution. The detail of morphology and identity of Au-Fe₃O₄-AC was characterized by SEM and TEM techniques and correlation among response to variables such as pH (2–10), adsorbent mass (0.005–0.025 g), initial CR concentration (10–30 mg L⁻¹) and ultrasound time (2–6 min) was investigated by response surface methodology (RSM) under central composite design (CCD). Analysis of variance (ANOVA) exhibit a high R² value of 0.999 and confirm suitability of constructed second-order regression model for excellent evaluation and prediction of the experimental data. The interaction and main factor and optimum conditions of the under study process were determined from response surface plots based on desirability function. The maximum CR adsorption were achieved at pH of 4, 15 mg L⁻¹ of CR, 0.017 g of Au-Fe₃O₄-AC and 5 min sonication which owing to 99.49% removal efficiency is highly recommended for future CR removal from different matrixes. Adsorption kinetic follow second-order rate expression in combination to inter particle diffusion and equilibrium adsorption data best represented by the Langmuir isotherm with maximum mono-layer adsorption capacity of 43.88 mg g⁻¹.     

Synergistic effect of efficient adsorption g-C3N4/ZnO composite for photocatalytic property

Novel g-C₃N₄/ZnO composite photocatalyst was synthesized from an oxygen-containing precursor by direct thermal decomposition urea in air without any other templates assistance. Different percentages of g-C₃N₄ were hybridized with ZnO via the monolayer-dispersed method. The prepared g-C₃N₄/ZnO composites were characterized by XRD, SEM, UV–vis diffuse reflectance spectra (DRS), FT-IR, TEM and XPS. The composites showed much higher efficiency for degradation of Rhodamine B (RhB) than ZnO under UV and visible light irradiation. Especially, the photocatalytic efficiency was the highest under UV light irradiation when the percentage of g-C₃N₄ was 6%. The improved photocatalytic activity may be due to synergistic effect of photon acquisition and direct contact between organic dyestuff and photocatalyst. Then, effective separation of photogenerated electron–hole pairs at the interface of g-C₃N₄ is an important factor for improvement of photocatalytic activity. This work indicates that g-C₃N₄ hybrid semiconductors photocatalyst is a promising material in pollutants degradation.     

g-C3N4/SnS2异质结构:一类有潜力的光解水催化剂

采用第一性原理方法研究了层间耦合作用对g-C₃N₄/SnS₂异质结构的电子结构和吸光性质的影响.发现g-C₃N₄/SnS₂是一类典型的范德瓦异质结构,能有效吸收可见光,其价带顶和导带底与水的氧化还原势匹配,且由于电荷转移而导致的界面处极化场有利于光生载流子的分离.这些理论研究结果表明g-C₃N₄/SnS₂异质结构是一类非常有潜力的光解水催化材料.     

Preparation and characterization of graphitic carbon nitride through pyrolysis of melamine

Graphitic carbon nitride (g-C₃N₄) has been synthesized via a two-step pyrolysis of melamine (C₃H₆N₆) at 800°C for 2 h under vacuum conditions. X-ray diffraction (XRD) patterns strongly indicate that the synthesized sample is g-C₃N₄. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) morphologies indicate that the product is mainly composed of graphitic carbon nitride. The stoichiometric ratio of C:N is determined to be 0.72 by elemental analysis (EA). Chemical bonding of the sample has been investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Electron energy loss spectroscopy (EELS) verifies the bonding state between carbon and nitrogen atoms. Optical properties of the g-C₃N₄ were investigated by PL (photoluminescence) measurements and UV–Vis (ultraviolet–visible) absorption spectra. We suppose its luminescent properties may have potential application as component of optical nanoscale devices. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were also performed.     

First-principles prediction of an intrinsic half-metallic graphitic hydrogenated carbon nitride

The electronic properties of an experimentally realized graphitic carbon nitride (g-C₃N₃) layer has been studied via first-principles calculations. Unlike the recently reported ferromagnetic g-C₄N₃ structure, the g-C₃N₃ system is nonmagnetic. Based on the two-dimensional g-C₃N₃ structure, we predicts a new graphitic hydrogenated carbon nitride (g-H₃C₃N₃) for the first time, which shows 100% half-metallic property around Fermi energy. It would be a kind of important material in spintronics if it could be synthesized experimentally in the future.     

Impact of Extracellular Polymeric Substance in the Inactivation of Harmful Algae by Ag2O/g-C3N4 under Visible Light

Photocatalysis has attracted much attention as an emerging algae removal technology, but the inactivation performance is inevitably affected by the extracellular polymeric substance (EPS) produced by algae. In this study, a photocatalyst (Ag₂O/g-C₃N₄) with efficient algae inactivation is adopted to investigate the interactions with EPS, and the impact of EPS on photocatalytic algae removal is studied. The results show that EPS can adhere to the surface of Ag₂O/g-C₃N₄ by electrostatic force. The interaction with EPS decreases the surface zeta potential of the Ag₂O/g-C₃N₄ from 7.71 to −22.3 mV with the increase in EPS concentration, and the maximum ratio of particle size increases from 825 to 1281 nm. In addition, the interaction with EPS inhibits the release of Ag⁺ in Ag₂O/g-C₃N₄ by half, thus, the toxicity of metal ions will be alleviated. Meanwhile, EPS can also be degraded by Ag₂O/g-C₃N₄, indicating that EPS can work as a radical scavenger to protect the algae cells. Without the protection of EPS, 97.8% of algae cells are inactivated after 5 h photocatalysis. Therefore, more attention should be given to the interaction between EPS and photocatalyst to promote the design and application of the photocatalytic.     

Synthesis and phonon properties of nanosized Aurivillius phase of Bi2MoO6

Nanosized crystallites Bi₂MoO₆ of a platelet shape were synthesized by a mild hydrothermal crystallization process. The effect of particle size on the structure and properties of Bi₂MoO₆ was studied by X‐ray diffraction, transmission electron microscopy, as well as Raman and infrared (IR) spectroscopies. Moreover, temperature‐dependent Raman spectra were collected for bulk and nanocrystalline Bi₂MoO₆. These studies showed that the thickness of the smallest crystallites is about 8–11 nm. Raman and IR studies have revealed that the damping and the intensity of Raman and IR bands are significantly modified with decreasing particle size and temperature. Moreover, some bands experience significant shifts both towards lower and higher wavenumbers. The obtained results indicate that, similar to the isostructural Bi₂WO₆, the orthorhombic distortion decreases with decreasing particle size. However, the structure of nanocrystalline Bi₂MoO₆ remains orthorhombic and noncentrosymmetric, and the structural changes are not the same as those observed in Bi₂WO₆. Copyright © 2010 John Wiley & Sons, Ltd.     

高比表面积TiO2与g-C3N4复合材料的光催化性能及机理研究

本文通过简单的溶剂热法制备了g-C₃N₄与高比表面积的TiO₂复合材料,该方法操作简单且能耗低. 甲基橙降解实验结果表明,高比表面积的TiO₂有效提高了光催化活性. 光电化学测试结果表明,与g-C₃N₄复合后,TiO₂的电荷载流子迁移速率得到明显改善. g-C₃N₄/高比表面积-TiO₂的光催化活性很强,在100分钟内,6%-g-C₃N₄/高比表面积-TiO₂对甲基橙的降解程度可达92.44%. 6%-g-C₃N₄/高比表面积-TiO₂不仅具有良好的光催化降解性能,还具有较高的稳定性. 本文对6%-g-C₃N₄/高比表面积-TiO₂的光催化机理也进行了系统的研究.     

Preparation of graphitic carbon nitride with large specific surface area and outstanding N2 photofixation ability via a dissolve-regrowth process

Nitrogen fixation is the second most important chemical process in nature next to photosynthesis. Here, we report a convenient dissolve-regrowth method for synthesizing graphitic carbon nitride (g-C₃N₄) with a large surface area and nitrogen vacancies by HCl treatment. XRD, N₂adsorption, SEM, TEM, UV–Vis spectroscopy, EPR, N₂-TPD, Photoluminescence and Photocurrent were used to characterize the prepared catalysts. The results indicate that HCl treatment does not influence the crystal phase of g-C₃N₄ but change the morphology and optical property, leading to the smaller particle size, larger surface area and increased bang gap energy. It is deduced by N₂-TPD, Photoluminescence, Photocurrent and DFT simulations that the nitrogen vacancies formed by the HCl treatment not only serve as active sites to adsorb and activate N₂ molecules but also promote interfacial charge transfer from g-C₃N₄to N₂ molecules. The HCl treated g-C₃N₄ catalyst exhibits outstanding nitrogen photofixation ability under visible light, which is 13.4-fold higher than that of bulk g-C₃N₄ without nitrogen vacancy. The possible reaction mechanism is proposed.     

Solid state synthesis of nonstoichiometric Bi<Subscript>2</Subscript>WO<Subscript>6</Subscript>/Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> composites as visible-light photocatalyst

Nonstoichiometric Bi₂WO₆ photocatalyst with the composition of Bi_2?+?x WO_6?+?1.5x (?0.25 ≤ x ≤ 1) wa synthesized by a facile solid state reaction method. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-vis absorption spectrum. The Bi_2.5WO_6.75 photocatalyst showed excellent visible-light-driven photocatalytic performance; nearly 100 % of RhB (10 ppm, pH?=?3?~?4) was decomposed within 25 min, which demonstrated that nonstoichiometric semiconductors could be an efficient visible-light-driven photocatalyst.     

New template for metal decoration and hydrogen adsorption on graphene-like C3N4

From density functional theory calculations we identify a graphene-like C₃N₄ (g-C₃N₄) as an excellent template for stable and well dispersed decoration of alkali (Li) and 3d transition metal (TM) atoms. The porous sites of g-C₃N₄ accommodate excessive N lone-pair electrons and promote hybridization between the orbitals of N and the metal atoms. The most stable TM decorations (Ti and Sc) on g-C₃N₄ exhibit high capacities of hydrogen adsorption with binding energies suitable for mobile applications. These metal decorated g-C₃N₄ may also prove useful in catalytic and sensing applications for their unique nanoscale structural features unavailable in conventional nano-clusters.     

Synthesis of CuO/g-C3N4 Composite with High Anti-Interference Ability for Enhanced Fenton-Like Catalysis

The combination of semiconductors and transition metal compounds for Fenton-like application has been widely reported. However, there are still some problems that can be further studied such as the optimization of metal species and in-depth research of mechanism. In this paper, using melamine and copper acetate as raw materials, a kind of composite of copper oxide and graphitic carbon nitride (CuO/g-C₃N₄) is synthesized by a facile hydrothermal method. The synthetic conditions such as type of transition metal salt and ratio of raw material are further optimized. With the presence of H₂O₂, the CuO/g-C₃N₄ composite shows exceptional broad-spectrum Fenton-like catalytic performance against the organic dyes in aqueous solution within a wide pH range, and the highest degradation rate of organic dyes can reach 99% within 10 min. After eight times of recycling, the catalytic activity of the composite can still remain more than 85%. More importantly, the CuO/g-C₃N₄ composite presented excellent anti-interference ability toward heavy metal ions and complex pollutants. Finally, the enhanced Fenton-like catalytic mechanism is illustrated in detail.