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1.
Flower-like shaped Bi 12TiO 20 (Bismuth Titanate)/g-C 3N 4 (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 Bi 12TiO 20/g-C 3N 4 heterojunction demonstrates prominent activities for the degradation of rhodamine B and p-nitrophenol, with the introduction of flower-like shaped Bi 12TiO 20 into g-C 3N 4 composites greatly increasing the activity of pure g-C 3N 4. 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 Bi 12TiO 20/g-C 3N 4, •OH also contributed to the degradation of pollutants, which may explain the enhanced photocatalytic activity after the introduction of Bi 12TiO 20, as •OH is inactive in pure g-C 3N 4. Furthermore, 10 wt.% Bi 12TiO 20/g-C 3N 4 showed not only high activity but also good stability for degradation of aqueous organic pollutants, implying potential applications prospect. 相似文献
2.
通过焙烧-超声混合法成功地制备了BiOBr/g-C 3N 4 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Fe 3+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-C 3N 4 S型异质结能原位生成H 2O 2,添加Fe 3+后,H 2O 2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Fe 3+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 3+的加入促进了光生电荷的分离和H 2O 2的活化,超氧阴离子自由基(·O 2-)、空穴和羟基是光-自芬顿催化过程中的主要活性物种,且·O 2-作用更大。 相似文献
3.
通过焙烧-超声混合法成功地制备了BiOBr/g-C 3N 4S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Fe 3+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-C 3N 4S型异质结能原位生成H 2O 2,添加Fe 3+后,H 2O 2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Fe 3+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
4.
Exfoliation of bulk graphitic carbon nitride (g-C 3N 4) into two-dimensional (2D) nanosheets is one of the effective strategies to improve its photocatalytic properties so that the 2D g-C 3N 4 nanosheets (CN) have larger specific surface areas and more reaction sites. In addition, poly- o-phenylenediamine (PoPD) can improve the electrical conductivity and photocatalytic activity of semiconductor materials. Here, the novel efficient composite PoPD/AgCl/g-C 3N 4 nanosheets was first synthesized by a precipitation reaction and the photoinitiated polymerization approach. The obtained photocatalysts have larger specific surface areas and could achieve better visible-light response. However, silver chloride (AgCl) is susceptible to agglomeration and photocorrosion. The PoPD/AgCl/CN composite exhibits an extremely high photocurrent density, which is three times that of CN. Obviously enhanced photocatalytic activities of PoPD/AgCl/g-C 3N 4 are revealed through the photodegradation of tetracycline. The stability of PoPD/AgCl/CN is demonstrated based on four cycles of experiments that reveal that the degradation rate only decreases slightly. Furthermore, ?O 2? and h + are the main active species, which are confirmed through a trapping experiment and ESR spin-trap technique. Therefore, the prepared PoPD/AgCl/CN can be considered as a stable photocatalyst, in which PoPD is added as a charge carrier and acts a photosensitive protective layer on the surface of the AgCl particles. This provides a new technology for preparing highly stable composite photocatalysts that can effectively deal with environmental issues. 相似文献
5.
Ag nanoparticles (NPs) were deposited on the surface of g-C 3N 4 (CN) by an in situ calcination method. NiS was successfully loaded onto the composites by a hydrothermal method. The results showed that the 10 wt%-NiS/1.0 wt%-Ag/CN composite exhibits excellent photocatalytic H 2 generation performance under solar-light irradiation. An H 2 production rate of 9.728 mmol·g ?1·h ?1 was achieved, which is 10.82-, 3.45-, and 2.77-times higher than those of pure g-C 3N 4, 10 wt%-NiS/CN, and 1.0 wt%-Ag/CN composites, respectively. This enhanced photocatalytic H 2 generation can be ascribed to the co-decoration of Ag and NiS on the surface of g-C 3N 4, which efficiently improves light harvesting capacity, photogenerated charge carrier separation, and photocatalytic H 2 production kinetics. Thus, this study demonstrates an effective strategy for constructing excellent g-C 3N 4-related composite photocatalysts for H 2 production by using different co-catalysts. 相似文献
6.
The RP/g-C 3N 4 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-C 3N 4, the 50%-RP/g-C 3N 4 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 O 2– 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 CO 2, H 2O and some intermediates. 相似文献
7.
Exploring noble‐metal‐free, highly active and durable catalysts is vital to get to grips with the energy and environmental issues. Herein, we first dexterously design and synthesize a class of ternary Nb 6/CZS/g‐CN photocatalysts for the removal of hexavalent chromium Cr (VI) and organic dye pollutant (MO) from wastewater under visible‐light irradiation. A heterojunction Nb 6–1/CZS/g‐CN loaded with 0.01 g K 7HNb 6O 19 showed excellent photocatalytic performance, with the MO photodegradation efficiency of 94% in 1 h and the Cr (VI) (150 mg/l) photoreduction efficiency as high as 91% in 2 hr. The main active species were deemed to be O 2.‐. Additionally, the as‐prepared ternary heterojunction exhibits superior hydrogen evolution reaction (HER) rate. A heterojunction Nb 6–4/CZS/g‐CN loaded with 0.5 g K 7HNb 6O 19 exhibited the highest H 2 evolution rate as high as 1777.86 μmol h ?1 g ?1 under visible‐light illumination, which is increased to 5.7 and 2.7 times that of bare CZS and biphase heterojunction CZS/g‐CN . These findings afford a new class of promising low‐cost photocatalyst bodying for its huge potential value in sustainable energy development and wastewater treatment. 相似文献
8.
The unique heterojunction photocatalyst of graphite carbon nitride(g-C 3N 4) modified ultrafine TiO 2(gC 3N 4/Ti O 2) was successfully fabricated by electrochemical etching and co-annealing method. However,the effects of various environmental factors on the degradation of TC by g-C 3N 4/Ti O2and the internal reaction mechanism are still unclear. In this study, the effects of initial p H, anions, and cations on the ph... 相似文献
9.
Forming eco-friendly heterojunction photocatalysts is excellent method to accelerate the separation rate of photogenerated charge carriers, which is attracting more and more attention. In this study, a novel and stable disordered porous g-C 3N 4/SiO 2/SnO 2 (DOP-CSiSn) heterojunction composites was fabricated by a sol-gel hard template method, and the optimal g-C 3N 4 doped ratio was adjusted in DOP-CSiSn. The DOP-CSiSn photocatalyst had the much larger specific surface area and disordered porous structure, which exhibited strong photocatalytic effect to degrade Rhodamine B (RhB), Methylene blue (MB) and Methyl orange (MO) under visible light. When the g-C 3N 4 doping content was 30 wt%, the highest photocatalytic activities were obtained, and the degradation rate of MB and MO were 99.73% and 95.58% after 50 min, respectively. Degradation rate of RhB was 95.10% after 90 min. Photocatalytic degradation rate of organic pollutants were still more than 90% after six time consecutive cycles, the composite had wonderful stability and potential value in environmental purification. 相似文献
10.
Direct Z-scheme g-C 3N 4/TiO 2 nanorod composites were prepared for enhancing photocatalytic activity for pollutant removal. The characterization revealed that the g-C 3N 4/TiO 2 nanorod composite formed a close interface contact between g-C 3N 4 and TiO 2 nanorods, which was of benefit for the charge transfer and resulted in its high photocatalytic activity. The g-C 3N 4/TiO 2 nanorod composites exhibited higher photocatalytic activity for degradation of Rhodamine B (RHB) than bare g-C 3N 4 and TiO 2 nanorods. The high photocatalytic activity of g-C 3N 4/TiO 2 nanorod composites is attributed to the formation of the direct Z-scheme system, in which the electrons from the conduction band (CB) of TiO 2 combine with the holes from the valence band (VB) of C 3N 4 while the electrons from the CB of C 3N 4 and holes from the VB of TiO 2 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 O 2− 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
11.
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. 相似文献
12.
Polypyrrole-modified graphitic carbon nitride composites (PPy/g-C 3N 4) are fabricated using an in-situ polymerization method to improve the visible light photocatalytic activity of g-C 3N 4. The PPy/g-C 3N 4 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-C 3N 4 composites increases upon assembly of the amorphous PPy nanoparticles on the g-C 3N 4 surface. Owing to the strong conductivity, the PPy can be used as a transition channel for electrons to move onto the g-C 3N 4 surface, thus inhibiting the recombination of photogenerated carriers of g-C 3N 4 and improving the photocatalytic performance. The elevated light adsorption of PPy/g-C 3N 4 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-C 3N 4 in 2 h. Moreover, the degradation kinetics follow a pseudo-first-order model. A detailed photocatalytic mechanism is proposed with ·OH and ·O 2? radicals as the main reactive species. The present work provides new insights into the mechanistic understanding of PPy in PPy/g-C 3N 4 composites for environmental applications. 相似文献
13.
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-C 3N 4 (BiOI/ECN hereafter) was synthesized by the combination of thermal exfoliation of g-C 3N 4 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-C 3N 4. 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
14.
以凹凸棒石(简称凹土,ATP)为基体,通过原位化学法一步直接合成g-C_3N_4薄层材料,并将其有效固载于凹土表面(ATP/gC_3N_4),再通过原位沉淀法引入不同比例AgFeO_2纳米颗粒,构筑系列兼具磁分离特性和高效光催化活性的ATP/g-C_3N_4-AgFeO_2-Y复合光催化剂(Y=wATP/g-C_3N_4/(wATP/g-C_3N_4+wAg FeO_2)×100%,表示ATP/g-C_3N_4在ATP/g-C_3N_4-AgFeO_2复合材料中所占的质量百分数)。采用XRD、SEM、BET、UV-Vis、PL和ICP表征其结构和物化性能,以酸性红G(ARG)为目标降解物,研究其光催化性能。研究发现:通过形成Si-O-C键,g-C_3N_4薄层被均匀固定在凹土表面;AgFeO_2纳米颗粒均匀沉积于ATP/g-C_3N_4表面并形成Z型异质结,ATP/gC_3N_4-AgFeO_2-Y具有比ATP/g-C_3N_4和AgFeO_2更优异的可见光光催化性能,且随着ATP/g-C_3N_4含量的增大呈先升高而后下降的趋势;当Y=57%时复合材料的性能最佳,ATP/g-C_3N_4-AgFeO_2-57%对20 mg·L-1酸性红G的降解率可达97.4%,循环4次使用后,降解率仍保持94.2%。通过自由基捕获实验研究了光催化反应机理,发现·O2-是光催化过程的主要活性物种。 相似文献
15.
Bi 2S 3/g-C 3N 4 (BSCN) samples with different mass ratios of CN to BS were prepared by a facile and practicable hydrothermal method with 2D g-C 3N 4 nanosheets (CN). The microscopic morphology and structure of pure CN, BS and BSCN were measured by multiple testing methods. Analysis results show that the BSCN was prepared successfully, and the Bi 2S 3 nanoparticles closely and uniformly adhered to the surface of CN with sheet-like structure. The introduction of Bi 2S 3 did not change the structure of the CN. The results of the ultraviolet–visible spectroscopic analysis, photoluminescence spectra and electrochemical performance indicated that BSCN showed superior visible-light response compared with CN, and the separation and transfer efficiency of photogenerated carriers was significantly improved. With the decrease of mass ratio of CN/BS, the photocatalytic activity of BSCN initially increased and then decreased for 20 ppm of Rhodamine B solution (RhB), and the Bi 2S 3/g-C 3N 4-B with a mass ratio of 8:1 for CN to BS showed optimal photocatalytic performance (98.98%). Furthermore, the Bi 2S 3/g-C 3N 4-B exhibited apparent degradation effects (1.021 x10 -2, 0.879 x10 -2 and 0.793 x10 -2 min ?1) to three kinds of antibiotics (tetracycline, ciprofloxacin, and oxytetracycline). The BSCN samples still maintained higher degradation efficiency after five cycles of degradation to tetracycline. The capture experiments and the electron spin resonance (ESR) spectra analysis indicated that the h + and ·O 2? played a major role, and ·OH played secondary role during the photocatalytic reaction. 相似文献
16.
Numerous approaches have been used to modify graphitic carbon nitride(g-C 3N 4) for improving its photocatalytic activity. In this study, we demonstrated a facial post-calcination method for modified graphitic carbon nitride(g-C 3N 4-Ar/Air) to direct tuning band structure, i.e., bandgap and positions of conduction band(CB)/valence band(VB), through the control of atmospheric condition without involving any additional elements or metals or semiconductors. ... 相似文献
17.
用化学沉淀法制备中空管状g-C 3N 4/Ag 3PO 4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:Ag 3PO 4纳米颗粒均匀地分散在中空管状g-C 3N 4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Ag 3PO 4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
18.
为了进一步提高聚合物半导体类石墨相氮化碳(g-C 3N 4)降解有机物的活性,通过简单的水热法复合得到碳化MoS 2/掺硫g-C 3N 4异质结(MoSC/S-CN),并在可见光下研究其罗丹明B (RhB)的降解性能。结果表明,相较于纯g-C 3N 4,最优化的MoSC/S-CN样品对可见光的吸收范围得到明显拓宽,并且在100 min内对RhB的降解效率为92.5%,比纯g-C 3N 4性能提高68.83%。一系列的结构和光学性质表明,掺硫后再进一步与碳化MoS 2耦合可以协同作用于g-C 3N 4,改善g-C 3N 4的能带结构,加速光生电子空穴对的分离,有效提高光催化活性。 相似文献
19.
Herein, cobalt (Co)-based metal–organic zeolitic imidazole frameworks (ZIF-67) coupled with g-C 3N 4 nanosheets synthesized via a simple microwave irradiation method. SEM, TEM and HR-TEM results showed that ZIF-67 were uniformly dispersed on g-C 3N 4 surfaces and had a rhombic dodecahedron shape. The photocatalytic properties of g-C 3N 4/ZIF-67 nanocomposite were evaluated by photocatalytic dye degradation of crystal violet (CV), 4-chlorophenol (4-CP) and photocatalytic hydrogen (H 2) production. In presence of visible light illumination, the photocatalytic dye results showed that 95% CV degradation and 53% 4-CP degradation within 80 min. The H 2 production of the g-C 3N 4/ZIF-67 composite was 2084 μmol g −1, which is 3.84 folds greater than that of bare g-C 3N 4 (541 μmol g −1). 相似文献
20.
Heterojunction design in a two-dimensional (2D) fashion has been deemed beneficial for improving the photocatalytic activity of g-C 3N 4 because of the promoted interfacial charge transfer, yet still facing challenges. Herein, we construct a novel 2D/2D Cu 3P nanosheet/P-doped g-C 3N 4 (PCN) nanosheet heterojunction photocatalyst (PCN/Cu 3P) through a simple in-situ phosphorization treatment of 2D/2D CuS/g-C 3N 4 composite for photocatalytic H 2 evolution. We demonstrate that the 2D lamellar structure of both CuS and g-C 3N 4 could be well reserved in the phosphorization process, while CuS and g-C 3N 4 in-situ transformed into Cu 3P and PCN, respectively, leading to the formation of PCN/Cu 3P tight 2D/2D heterojunction. Owing to the large contact area provided by intimate face-to-face 2D/2D structure, the PCN/Cu 3P photocatalyst exhibits significantly enhanced charge separation efficiency, thus achieving a boosted visible-light-driven photocatalytic behavior. The highest rate for H 2 evolution reaches 5.12 μmol·h –1, nearly 24 times and 368 times higher than that of pristine PCN and g-C 3N 4, respectively. This work represents an excellent example in elaborately constructing g-C 3N 4-based 2D/2D heterostructure and could be extended to other photocatalyst/co-catalyst system. 相似文献
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