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1.

Melamine was added to the precursor of TiO2, then TiO2 prepared by hydrothermal, while melamine was modified. Subsequently, a series of Z-scheme TiO2/g-C3N4 heterojunction composites were successfully synthesized by simple calcination. The morphology and structure of samples were characterized by XRD, FT-IR, UV–vis DRS, SEM, TEM, PL and BET. The photocatalytic activity of these samples has been investigated by degradation of Rhodamine B (RhB), and results indicated that photocatalytic activity of the as-prepared samples was greatly influenced by the content of titanium tetrabutoxide in precursors and the hydrothermal time. The degradation rate of TiO2/g-C3N4-1 to RhB was the best, which was 5.05-fold of pure TiO2 (19.61%) and 2.25-fold of bulk g-C3N4 (44.06%), respectively. The trapping experiment results showed that ·O2? and h+ were main active species during degradation of RhB. The photocatalytic activity of the sample did not decrease significantly after 4 cycles. The unique Z-scheme heterojunction between TiO2 and g-C3N4 improved photocatalytic activity of the samples under visible light.

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2.
Antibiotics, once being released into the environment, become recalcitrant organic pollutants, which pose a potential risk to ecological balance and human health. In this study, a Z-scheme heterojunction of bismuth oxyiodide (BiOI)/exfoliated g-C3N4 (BiOI/ECN hereafter) was synthesized by the combination of thermal exfoliation of g-C3N4 and chemical precipitation of BiOI for efficient photocatalytic degradation of tetracycline in aqueous solutions under visible light irradiation. The optimized BiOI/ECN delivered an outstanding degradation rate at circa 0.0705 min?1, which was 10 times higher than that of the bulk g-C3N4. The photocatalytic degradation efficiency of tetracycline remained almost unchanged in a pH range of 3–11, and the BiOI/ECN displayed an excellent photostability upon recycled usage. The photocatalytic mechanism of tetracycline was ascribed to the main reactive oxidation species of photogenerated holes and superoxide radicals. In addition, the possible degradation pathways of tetracycline were investigated by HPLC-MS to identify intermediates. The toxicity of photocatalytic-generated intermediates of tetracycline was found significantly alleviated according to the calculation of quantitative structure–activity relationship prediction. This work not only provides an attractive photocatalyst for the removal of tetracycline but also opens a new avenue for rational design of Z-scheme heterojunction composites for tetracycline degradation.  相似文献   

3.
Flower-like shaped Bi12TiO20 (Bismuth Titanate)/g-C3N4 (graphite-like carbon nitride) heterojunction was prepared through hydrothermal and sonification methods for the degradation of organic pollutants by visible-light irradiation. The preparation process, chemical structures, and the mechanism of photocatalytic enhancement of the heterostructures were studied systematically. Under visible-light irradiation, the novel flower-like shaped Bi12TiO20/g-C3N4 heterojunction demonstrates prominent activities for the degradation of rhodamine B and p-nitrophenol, with the introduction of flower-like shaped Bi12TiO20 into g-C3N4 composites greatly increasing the activity of pure g-C3N4. This activity enhancement for the heterojunction could be mainly attributed to its low recombination speed of electron–hole pairs, high adsorption ability of organic pollutants, and better optical absorption ability. Moreover, in the visible-light system of Bi12TiO20/g-C3N4, OH also contributed to the degradation of pollutants, which may explain the enhanced photocatalytic activity after the introduction of Bi12TiO20, as OH is inactive in pure g-C3N4. Furthermore, 10 wt.% Bi12TiO20/g-C3N4 showed not only high activity but also good stability for degradation of aqueous organic pollutants, implying potential applications prospect.  相似文献   

4.
通过焙烧-超声混合法成功地制备了BiOBr/g-C3N4S型异质结复合光催化剂。采用多种表征手段对样品物理属性进行了表征,包括X射线多晶粉末衍射仪(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UV-Vis DRS)。研究了所制备样品有/无Fe3+的光-自芬顿催化/光催化降解罗丹明B(RhB)性能。通过捕获实验确定了光催化反应中的主要活性物种,提出了光-自芬顿反应的降解机理。研究结果表明,BiOBr/g-C3N4S型异质结能原位生成H2O2,添加Fe3+后,H2O2被原位活化成活性物种且光生电流和载流子分离效率获得显著提高。该光-自芬顿过程能高效降解RhB,其反应速率常数为0.208 min-1,约为无Fe3+光催化反应速率常数的5.3倍,在光-自芬顿循环使用过程中表现出良好的稳定性。Fe...  相似文献   

5.
通过焙烧-超声混合法成功地制备了BiOBr/g-C3N4 S型异质结复合光催化剂。采用多种表征手段对样品物理属性进行了表征,包括X射线多晶粉末衍射仪(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UV-VisDRS)。研究了所制备样品有/无Fe3+的光-自芬顿催化/光催化降解罗丹明B (RhB)性能。通过捕获实验确定了光催化反应中的主要活性物种,提出了光-自芬顿反应的降解机理。研究结果表明,BiOBr/g-C3N4 S型异质结能原位生成H2O2,添加Fe3+后,H2O2被原位活化成活性物种且光生电流和载流子分离效率获得显著提高。该光-自芬顿过程能高效降解RhB,其反应速率常数为0.208 min-1,约为无Fe3+光催化反应速率常数的5.3倍,在光-自芬顿循环使用过程中表现出良好的稳定性。Fe3+的加入促进了光生电荷的分离和H2O2的活化,超氧阴离子自由基(·O2-)、空穴和羟基是光-自芬顿催化过程中的主要活性物种,且·O2-作用更大。  相似文献   

6.
To increase the number of active sites and defects in TiO2 and promote rapid and efficient transfer of photogenerated charges, a g-C3N4@C-TiO2 composite photocatalyst was prepared via in situ deposition of g-C3N4 on a carbon-doped anatase TiO2 surface. The effects of carbon doping state and surface modification of g-C3N4 on the performance of g-C3N4@C-TiO2 composite photocatalysts were studied by X-ray diffraction, X-ray photoelectron spectroscopy, UV-visible diffuse-reflectance spectroscopy, transmission electron microscopy, electrochemical impedance spectroscopy, photoluminescence, and electron paramagnetic resonance. With increasing carbon doping content, the carbon doping state in TiO2 gradually changed from gap to substitution doping. Although the number of oxygen vacancies gradually increased, the degradation efficiency of g-C3N4@C-TiO2 for RhB (phenol) initially increased and subsequently decreased with increasing carbon content. The g-C3N4@10C-TiO2 sample exhibited the highest apparent reaction rate constant of 0.036 min?1 (0.039 min?1) for RhB (phenol) degradation, which was 150 (139), 6.4 (6.8), 2.3 (3), and 1.7 (2.1) times higher than that of pure TiO2, 10C-TiO2, g-C3N4, and g-C3N4@TiO2, respectively. g-C3N4 was grown in situ on the surface of C-TiO2 by surface carbon hybridization and bonding. The resultant novel g-C3N4@C-TiO2 photocatalyst exhibited direct Z-scheme heterojunctions with non-local impurity levels. The high photocatalytic activity can be attributed to the synergistic effects of the improved visible light response ability, higher photogenerated electron transfer efficiency, and redox ability arising from Z-type heterojunctions.  相似文献   

7.
用化学沉淀法制备中空管状g-C3N4/Ag3PO4复合催化剂。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外可见漫反射光谱(UV-Vis DRS)和荧光光谱对其结构、形貌和光学性能进行了表征。结果表明:Ag3PO4纳米颗粒均匀地分散在中空管状g-C3N4表面,两者紧密结合形成异质结。研究复合催化剂在可见光照射下降解盐酸四环素(TC)的光催化活性。结果显示:复合催化剂在80 min内对TC的降解率为98%,其降解反应速率常数是纯相Ag3PO4的3倍。经过5次循环实验后复合催化剂对于TC的降解率仍保持87%,具有优良的循环稳定性。捕获实验表明空穴(h+)和超氧负离子(·O-2)是光催化反应过程中的主要活性物种。根据能带理论,提出了复合催化剂异质结的Z型光催化机理。  相似文献   

8.
As one of the most appealing and attractive technologies, photocatalysis is widely used as a promising method to circumvent the environmental and energy problems. Due to its chemical stability and unique physicochemical, graphitic carbon nitride (g-C3N4) has become research hotspots in the community. However, g-C3N4 photocatalyst still suffers from many problems, resulting in unsatisfactory photocatalytic activity such as low specific surface area, high charge recombination and insufficient visible light utilization. Since 2009, g-C3N4-based heterostructures have attracted the attention of scientists worldwide for their greatly enhanced photocatalytic performance. Overall, this review summarizes the recent advances of g-C3N4-based nanocomposites modified with transition metal sulfide (TMS), including (1) preparation of pristine g-C3N4, (2) modification strategies of g-C3N4, (3) design principles of TMS-modified g-C3N4 heterostructured photocatalysts, and (4) applications in energy conversion. What is more, the characteristics and transfer mechanisms of each classification of the metal sulfide heterojunction system will be critically reviewed, spanning from the following categories: (1) Type I heterojunction, (2) Type II heterojunction, (3) p-n heterojunction, (4) Schottky junction and (5) Z-scheme heterojunction. Apart from that, the application of g-C3N4-based heterostructured photocatalysts in H2 evolution, CO2 reduction, N2 fixation and pollutant degradation will also be systematically presented. Last but not least, this review will conclude with invigorating perspectives, limitations and prospects for further advancing g-C3N4-based heterostructured photocatalysts toward practical benefits for a sustainable future.  相似文献   

9.
In this study, a ternary TiO2/g-C3N4/Bi2WO6 nanocomposite was prepared via a facial approach. The final structure was applied as a new photocatalyst for the removal of brilliant green (BG) dye, as a model of organic pollutants, from the aqueous solution. The results of FESEM, EDS with mapping, XRD, FTIR, UV–vis DRS, PL, and EIS analyses further demonstrate the successful establishment of heterojunction between TiO2, g-C3N4, and Bi2WO6. Integration of g-C3N4 and Bi2WO6 with TiO2 was remarkably decreased the band gap energy of TiO2 to 2.68 eV (from 3.15 eV). The effects of various experimental factors such as TiO2/g-C3N4/Bi2WO6 dosage, initial BG concentration, visible irradiation time, and pH on the photocatalyst behavior of TiO2/g-C3N4/Bi2WO6 were investigated by 2 k-1 factorial design. The results of the analysis of variance demonstrate these experimental factors are effective on the BG degradation efficiency. The response surface methodology was applied to achieve the optimization procedure of BG degradation. According to these results, the complete BG removal efficiency was obtained for the optimal conditions of 15.76 mg of TiO2/g-C3N4/Bi2WO6 nanocomposite, an initial BG concentration of 10 ppm, pH of 9, and time duration of 70 min. The improved photocatalytic performance of ternary TiO2/g-C3N4/Bi2WO6 nanocomposite was related to the formation of heterojunction between TiO2, g-C3N4, and Bi2WO6, significant light adsorption ability, and low recombination of photogenerated carriers.  相似文献   

10.
A series of Z-scheme TiO2/g-C3N4/RGO ternary heterojunction photocatalysts are successfully constructed via a direct electrospinning technique coupled with an annealing process for the first time. They are investigated comprehensively in terms of crystal structure, morphology, composition, specific surface area, photoelectrochemical properties, photodegradation performance, etc. Compared with binary TiO2/g-C3N4 and single-component photocatalysts, ternary heterojunction photocatalysts show the best photodegradation performance for RhB under stimulated sunlight. This can be attributed to the enlarged specific surface area (111.41 m2/g), the formation of Z-scheme heterojunction, and the high separation migration efficiency of photoexcited charge carriers. A potential Z-scheme mechanism for ternary heterojunction photocatalysts is proposed to elucidate the remarkably ameliorated photocatalytic performance based on active species trapping experiments, PL detection test of hydroxyl radicals, and photoelectrochemical properties.  相似文献   

11.
A novel GO modified g-C3N4 nanosheets/flower-like BiOBr hybrid photocatalyst is fabricated by a facile method. The characterization results reveal that wrinkled GO is deposited between g-C3N4 nanosheets and flower-like BiOBr forming a Z-scheme heterojunction. As a mediator, plicate GO plays a positive role in prompting photogenerated electrons transferring through its sizeable 2D/2D contact surface area. The g-C3N4/GO/BiOBr hybrid displays a superior photocatalytic ability to g-C3N4 and BiOBr in photodegrading tetracycline (TC), whose removal efficiency could reach 96% within 2 h. Besides, g-C3N4/GO/BiOBr composite can reduce Cr(VI), and simultaneously treat TC and Cr(VI) combination contaminant under the visible light. The g-C3N4/GO/BiOBr ternary composite also exhibits satisfactory stability and reusability after four cycling experiments. Further, a feasible mechanism related to the photocatalytic process of g-C3N4/GO/BiOBr is put forward. This study offers a ternary hybrid photocatalyst with eco-friendliness and hopeful application in water pollution.  相似文献   

12.
Direct Z-scheme g-C3N4/TiO2 nanorod composites were prepared for enhancing photocatalytic activity for pollutant removal. The characterization revealed that the g-C3N4/TiO2 nanorod composite formed a close interface contact between g-C3N4 and TiO2 nanorods, which was of benefit for the charge transfer and resulted in its high photocatalytic activity. The g-C3N4/TiO2 nanorod composites exhibited higher photocatalytic activity for degradation of Rhodamine B (RHB) than bare g-C3N4 and TiO2 nanorods. The high photocatalytic activity of g-C3N4/TiO2 nanorod composites is attributed to the formation of the direct Z-scheme system, in which the electrons from the conduction band (CB) of TiO2 combine with the holes from the valence band (VB) of C3N4 while the electrons from the CB of C3N4 and holes from the VB of TiO2 with stronger redox ability are used to reduce and oxidize pollutants. Based on the radical-trapping experiments, the main reactive species for RHB degradation are O2 and · OH, which are produced by photoinduced electrons and holes with high redox ability. This work provides insights into the photocatalytic mechanism of composite materials for the photocatalytic removal of organic pollutants.  相似文献   

13.
PtPd bimetallic alloy nanoparticle (NP)-modified graphitic carbon nitride (g-C3N4) nanosheet photocatalysts were synthesized via chemical deposition precipitation. Characterization of the photocatalytic H2 evolution of the g-C3N4 nanosheets shows that it was significantly enhanced when PtPd alloy NPs were introduced as a co-catalyst. The 0.2 wt% PtPd/g-C3N4 composite photocatalyst gave a maximum H2 production rate of 1600.8 μmol g–1 h–1. Furthermore, when K2HPO4 was added to the reaction system, the H2 production rate increased to 2885.0 μmol g–1 h–1. The PtPd/g-C3N4 photocatalyst showed satisfactory photocatalytic stability and was able to maintain most of its photocatalytic activity after four experimental photocatalytic cycles. In addition, a possible mechanism for the enhanced photocatalytic activity was proposed and verified by various photoelectric techniques. These results demonstrate that the synergistic effect between PtPd and g-C3N4 helps to greatly improve the photocatalytic activity of the composite photocatalyst.  相似文献   

14.
The RP/g-C3N4 heterojunction photocatalyst was fabricated by a facile heat treatment strategy. The obtained composite has excellent light harvesting ability and charge separation performance. Compared to single RP and g-C3N4, the 50%-RP/g-C3N4 exhibited enhanced photocatalytic activity for simultaneously removing Cr(VI) and RhB, and the removal rates can reach 92% and 99% in 25 min, respectively. The enhanced mechanism was revealed by active species capturing experiments, showing that electrons can reduce Cr(VI) and produce O2 in air and that holes can directly oxidize the dyes. The coexistence of Cr(VI) and RhB will lead to a synergistic improvement of Cr(VI) reduction and RhB degradation due to rapid surface reactions. This further improves the charge separation except for the heterojunction effect. In addition, the COD analysis demonstrates that organic dyes are mainly degraded into CO2, H2O and some intermediates.  相似文献   

15.
Heterojunction design in a two-dimensional (2D) fashion has been deemed beneficial for improving the photocatalytic activity of g-C3N4 because of the promoted interfacial charge transfer, yet still facing challenges. Herein, we construct a novel 2D/2D Cu3P nanosheet/P-doped g-C3N4 (PCN) nanosheet heterojunction photocatalyst (PCN/Cu3P) through a simple in-situ phosphorization treatment of 2D/2D CuS/g-C3N4 composite for photocatalytic H2 evolution. We demonstrate that the 2D lamellar structure of both CuS and g-C3N4 could be well reserved in the phosphorization process, while CuS and g-C3N4 in-situ transformed into Cu3P and PCN, respectively, leading to the formation of PCN/Cu3P tight 2D/2D heterojunction. Owing to the large contact area provided by intimate face-to-face 2D/2D structure, the PCN/Cu3P photocatalyst exhibits significantly enhanced charge separation efficiency, thus achieving a boosted visible-light-driven photocatalytic behavior. The highest rate for H2 evolution reaches 5.12 μmol·h–1, nearly 24 times and 368 times higher than that of pristine PCN and g-C3N4, respectively. This work represents an excellent example in elaborately constructing g-C3N4-based 2D/2D heterostructure and could be extended to other photocatalyst/co-catalyst system.   相似文献   

16.
《中国化学快报》2022,33(10):4715-4718
The efficiency of photocatalytic pollutant removal largely depends on the ability of the photocatalytic system to produce hydroxyl radicals (?OH). However, the capability of photocatalyst to produce ?OH is not strong at present. Advancing the capacity of photocatalytic system to produce ?OH has always been a tough problem and challenge in the field of environmental science. In this research, it was found that introducing nitric oxide (NO) into the graphitic carbon nitride (g-C3N4) photocatalytic system could memorably enhance the ability of producing ?OH group. This study provides a new idea for improving the capacity of photocatalytic ?OH production.  相似文献   

17.
Polypyrrole-modified graphitic carbon nitride composites (PPy/g-C3N4) are fabricated using an in-situ polymerization method to improve the visible light photocatalytic activity of g-C3N4. The PPy/g-C3N4 is applied to the photocatalytic degradation of methylene blue (MB) under visible light irradiation. Various characterization techniques are employed to investigate the relationship between the structural properties and photoactivities of the as-prepared composites. Results show that the specific surface area of the PPy/g-C3N4 composites increases upon assembly of the amorphous PPy nanoparticles on the g-C3N4 surface. Owing to the strong conductivity, the PPy can be used as a transition channel for electrons to move onto the g-C3N4 surface, thus inhibiting the recombination of photogenerated carriers of g-C3N4 and improving the photocatalytic performance. The elevated light adsorption of PPy/g-C3N4 composites is attributed to the strong absorption coefficient of PPy. The composite containing 0.75 wt% PPy exhibits a photocatalytic efficiency that is 3 times higher than that of g-C3N4 in 2 h. Moreover, the degradation kinetics follow a pseudo-first-order model. A detailed photocatalytic mechanism is proposed with ·OH and ·O2? radicals as the main reactive species. The present work provides new insights into the mechanistic understanding of PPy in PPy/g-C3N4 composites for environmental applications.  相似文献   

18.
《中国化学快报》2020,31(10):2789-2794
In order to efficiently remove tetracycline in wastewater through the synergistic effect of adsorption and photocatalytic degradation, a series of novel composite materials (Cu doped g-C3N4) were synthesized by two-pot hydrothermal method. It was found that the composite materials with optimized ratio (Cu/CN-1) displayed outstanding adsorption and photocatalytic performance as compared with pure g-C3N4 photocatalyst. The removal efficiency of tetracycline (TC, 50 mg/L) reached almost 99% within 30 min by Cu/CN-1 through the synergy of adsorption and photocatalysis under visible-light irradiation, which was the highest removal efficiency ever reported. The adsorption kinetics and isotherms of TC on the Cu/CN-1 were well fitted with the pseudo-second-order kinetic model and Langmuir model, respectively. Moreover, it was confirmed that the main effective reactive groups were O2 and h+ in photocatalytic process. The Cu/CN-1 exhibited high stability and excellent reusability after five cycle experiments. Finally, the mechanism of synergy between Cu and g-C3N4 was proposed: on the one hand, the decoration of Cu particles significantly increased the adsorption sites of Cu/CN-1 to tetracycline, on the other hand, the modification of Cu particles effectively inhibits charge recombination and broadens the visible light absorption range of the photocatalyst.This study provided a promising photocatalyst to be used for TC removal in the actual wastewater.  相似文献   

19.
Using a grinding method, nanocomposites of graphitic carbon nitride (g-C3N4) and magnesium aluminate (MgAl2O4) spinel were successfully synthesized for the photocatalytic degradation of methylene blue (MB) and methyl orange (MO). Variously formulated g-C3N4/MgAl2O4 nanocomposites were characterized by thermal gravimetric analysis (TGA), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy equipped with energy dispersive spectroscopy (SEM/EDS), transmission electron microscopy (TEM) and surface area and micropore analysis (BET surface area). The g-C3N4 powder exhibited a nanosheet structure whereas the MgAl2O4 spinel comprised agglomerated nanoparticles. The optical properties of the g-C3N4/MgAl2O4 nanocomposites were investigated by diffuse reflectance spectroscopy (DRS). As the g-C3N4 loading content increased from 0 to 30%, the optical band gap energy of the nanocomposite decreased from 3.84 to 2.86 eV, the specific surface area decreased from 153.78 to 114.45 m2/g, and the porosity decreased from 0.447 to 0.347 cm3/g. A 20%g-C3N4/MgAl2O4 nanocomposite proved to be the most effective photocatalyst and degraded MB faster and more completely than MO. The degradation rates of both MO (0.0107 min?1) and MB (0.0386 min?1) in a mixed MO-MB system were greater than the degradation rates in their single systems. The key factor that improved the photocatalytic degradation of MO was the synergistic effect whereas the synergistic effect and photosensitization were the key factors that enhanced the photocatalytic degradation of MB. The g-C3N4/MgAl2O4 nanocomposite is suitable for the photocatalytic degradation of mixed dyes because its point of zero charge is neutral and it is stable and recyclable.  相似文献   

20.
《中国化学快报》2022,33(8):3792-3796
Water pollution has become a serious problem owing to the development of society. Photocatalysis is a promising approach to remove various pollutants in water, such as organic pollutants and antibiotic resistance bacteria. Meanwhile, the design of heterojunction between two semiconductors is an effective path to improve photocatalytic properties due to its potential in improving separation and transfer of photoinduced carriers. In this study, Nb2O5/g-C3N4 (NO/CN) composite materials were prepared through a one-step heating method. Characterizations confirmed successful preparation of NO/CN heterojunction structure and better optical properties than pure g-C3N4 and Nb2O5. NO/CN composite materials showed excellent photocatalytic efficiency for Escherichia coli (E. coli) inactivation (95%) compared with the pure Nb2O5 (10%) and g-C3N4 (77%). Meanwhile, NO/CN exhibited better organic pollutants removal (RhB for 94%, methyl orange (MO) for 15% and methylene blue (MB) for 87%) under visible light, which is likely owing to the heterojunction structure between g-C3N4 and Nb2O5 that leads to the good separation of photogenerated electron-hole pair. Free radical scavenging and electron spin resonance (ESR) experiments demonstrated that superoxide radicals (?O2?) and holes (h+) were the dominant radicals. Therefore, the NO/CN was proposed to be a promising material for effective disinfection and removal of organic contaminants in water treatment.  相似文献   

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