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1.
Doping is an efficient approach to narrow the band gap of TiO 2 and enhance its photocatalytic activity. Here, we perform generalized gradient approximation (GGA)+U calculations to narrow the band gap of TiO 2 by codoping of X (F, N) with transition metals (TM = Fe, Co) to extend the absorption edge to longer visible‐light wavelengths. Our results show that all the codoped systems can narrow the band gap significantly, in particular, (F+Fe)‐codoped system could serve as remarkably better photocatalysts with both narrowing of the band gap and relatively smaller formation energies than those of (F+Co) and (N+TM)‐codoped systems. Our results provide useful guidance for codoped TiO 2 efficient for photocatalytic activity. © 2013 Wiley Periodicals, Inc. 相似文献
2.
As a promising two‐dimensional conjugated polymer, graphitic carbon nitride (g‐C 3N 4) has been utilized as a low‐cost, robust, metal‐free, and visible‐light‐active photocatalyst in the field of solar energy conversion. This Review mainly describes the latest advances in g‐C 3N 4 photocatalysts for water splitting. Their application in CO 2 conversion, organosynthesis, and environmental purification is also briefly discussed. The methods to modify the electronic structure, nanostructure, crystal structure, and heterostructure of g‐C 3N 4, together with correlations between its structure and performance are illustrated. Perspectives on the challenges and opportunities for the future exploration of g‐C 3N 4 photocatalysts are provided. This Review will promote the utilization of g‐C 3N 4 materials in the fields of photocatalysis, energy conversion, environmental remediation, and sensors. 相似文献
3.
Herein, for the first time, a direct Z‐scheme g‐C 3N 4/NiFe 2O 4 nanocomposite photocatalyst was prepared using facile one‐pot hydrothermal method and characterized using XRD, FT‐IR, DRS, PL, SEM, EDS, TEM, HRTEM, XPS, BET and VSM characterized techniques. The result reveals that the NiFe 2O 4 nanoparticles are loaded on the g‐C 3N 4 sheets successfully. The photocatalytic activities of the as‐prepared photocatalysts were evaluated for the degradation of methyl orange (MO) under visible light irradiation. It was shown that the photocatalytic activity of the g‐C 3N 4/NiFe 2O 4 nanocomposite is about 4.4 and 3 times higher than those of the pristine NiFe 2O 4 and g‐C 3N 4 respectively. The enhanced photocatalytic activity could be ascribed to the formation of g‐C 3N 4/NiFe 2O 4 direct Z‐scheme photocatalyst, which results in efficient space separation of photogenerated charge carriers. More importantly, the as‐prepared Z‐scheme photocatalyst can be recoverable easily from the solution by an external magnetic field and it shows almost the same activity for three consecutive cycles. Considering the simplicity of preparation method, this work will provide new insights into the design of high‐performance magnetic Z‐scheme photocatalysts for organic contaminate removal. 相似文献
4.
As a metal‐free nitrogen reduction reaction (NRR) photocatalyst, g‐C 3N 4 is available from a scalable synthesis at low cost. Importantly, it can be readily functionalized to enhance photocatalytic activities. However, the use of g‐C 3N 4‐based photocatalysts for the NRR has been questioned because of the elusive mechanism and the involvement of N defects. This work reports the synthesis of a g‐C 3N 4 photocatalyst modified with cyano groups and intercalated K + ( mCNN), possessing extended visible‐light harvesting capacity and superior photocatalytic NRR activity (NH 3 yield: 3.42 mmol g ?1 h ?1). Experimental and theoretical studies suggest that the ‐C≡N in mCNN can be regenerated through a pathway analogous to Mars van Krevelen process with the aid of the intercalated K +. The results confirm that the regeneration of the cyano group not only enhances photocatalytic activity and sustains the catalytic cycle, but also stabilizes the photocatalyst. 相似文献
5.
Z-scheme heterojunction photocatalysts based on g-C3N4 generally need to recombine g-C3N4 and a wide bandgap semiconductor. This structure is limited by the large bandgap of the constituent material, which can effectively suppress carrier recombination while limiting the absorption of visible light. Due to the superior up-conversion photoluminescence properties of the carbon quantum dots (CQDs), this dilemma can be solved ingeniously by adding CQDs to the composite. Moreover, the charge reservoirs of CQDs are conducive to the charge carrier separation effect. In this work, a novel CQDs-modified Z-type photocatalyst is constructed and the successful implantation of CQDs is demonstrated. The composite catalyst exhibits broad-spectrum response to visible light and the overall performance is obviously superior to that of the binary MoO3/g-C3N4 heterojunction. The high efficiency and versatility of the degradation imply that the newly prepared CQDs/g-C3N4/MoO3 is a versatile photocatalyst for the removal of various target pollutants in the environment. 相似文献
6.
Doping is an effective strategy to improve the photocatalytic performances of semiconductor photocatalyst for water splitting. In this work, we perform extensive hybrid density functional calculations to investigate perovskite NaNbO 3 with anionic monodoping with N, C, P, and S dopants as well as with (N + N), (C + S), and (N + P) codoping pairs. Theoretical results clearly reveal that the band structures of NaNbO 3 can be effectively tailored by introducing double-hole-mediated coupling of anion-anion pairs. Compared with the monodoping cases, the anion-anion codoped NaNbO 3 systems not only have substantially narrowed band gaps, but also can eliminate the unoccupied localized states appearing above the Fermi level, which are disastrous for photocatalysis as they may trap the photogenerated carriers. Optical absorption curves further convince that the codoped NaNbO 3 can effectively harvest visible light. The band edge positions with respect to the redox potentials of water demonstrate that the (N + N) codoped NaNbO 3 are desirable for efficient solar water splitting. 相似文献
7.
Herein, a novel broken case‐like carbon‐doped g‐C 3N 4 photocatalyst was obtained via a facile one‐pot pyrolysis and cost‐effective method using glyoxal‐modified melamine as a precursor. The obtained carbon/g‐C 3N 4 photocatalyst showed remarkable enhanced photocatalytic activity in the degradation of gaseous benzene compared with that of pristine g‐C 3N 4 under visible light. The pseudo‐first‐order rate constant for gaseous benzene degradation on carbon/g‐C 3N 4 was 0.186 hr ?1, 5.81 times as large as that of pristine g‐C 3N 4. Furthermore, a possible photocatalytic mechanism for the improved photocatalytic performance over carbon/g‐C 3N 4 nanocomposites was proposed. 相似文献
8.
A novel visible‐light‐driven g‐C 3N 4/MIL‐53(Al) composite photocatalyst was successfully prepared using a facile stirring method at room temperature. The g‐C 3N 4/MIL‐53(Al) composites were characterized and their effects on the photocatalytic activities for rhodamine B degradation were investigated. The g‐C 3N 4(20 wt%)/MIL‐53(Al) photocatalyst displayed optimal photocatalytic degradation efficiency, which was about five times higher than the photocatalytic activity of pure g‐C 3N 4. The improved photocatalytic performance of the g‐C 3N 4/MIL‐53(Al) photocatalyst was predominantly attributed to the efficient separation of electron–hole pairs and the low charge‐transfer resistance. g‐C 3N 4/MIL‐53(Al) also exhibited excellent stability and reusability. A proposed mechanism for the enhanced photocatalytic activity is also discussed based on the experimental results. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
9.
Exploiting advanced photocatalysts under visible light is of primary significance for the development of environmentally relevant photocatalytic decontamination processes. In this study, the ionic liquid (IL), 1‐butyl‐3‐methylimidazolium tetrafluoroborate, was employed for the first time as both a structure‐directing agent and a dopant for the synthesis of novel fluorinated B/C‐codoped anatase TiO 2 nanocrystals (T IL) through hydrothermal hydrolysis of tetrabutyl titanate. These T IL nanocrystals feature uniform crystallite and pore sizes and are stable with respect to phase transitions, crystal ripening, and pore collapse upon calcination treatment. More significantly, these nanocrystals possess abundant localized states and strong visible‐light absorption in a wide range of wavelengths. Because of synergic interactions between titania and codopants, the calcined T IL samples exhibited high visible‐light photocatalytic activity in the presence of oxidizing Rhodamine B (RhB). In particular, 300 °C‐calcined T IL was most photocatalytically active; its activity was much higher than that of TiO 1.98N 0.02 and reference samples (T W) obtained under identical conditions in the absence of ionic liquid. Furthermore, the possible photocatalytic oxidation mechanism and the active species involved in the RhB degradation photocatalyzed by the T IL samples were primarily investigated experimentally by using different scavengers. It was found that both holes and electrons, as well as their derived active species, such as .OH, contributed to the RhB degradation occurring on the fluorinated B/C‐codoped TiO 2 photocatalyst, in terms of both the photocatalytic reaction dynamics and the reaction pathway. The synthesis of the aforementioned novel photocatalyst and the identification of specific active species involved in the photodegradation of dyes could shed new light on the design and synthesis of semiconductor materials with enhanced photocatalytic activity towards organic pollutants. 相似文献
10.
N-F codoped TiO 2 (TONF) photocatalysts were prepared using acid catalyzed hydrolysis method from mixed aqueous solution of TiCl 4 and NH 4F. The photocatalytic activity of the TONF was evaluated through the degradation of phenol under both visible and UV light irradiation. X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), scanning electron microscope (SEM), and N 2 adsorption isotherm were used to characterize the obtained powders. The results showed that N-F codoped TiO 2 exhibited significant improvement of visible light catalytic activity. N-F codoping could improve dispersion of TiO 2, inhibit particle size agglomeration, and retard phase transformation. Doped N could extend the light response of TiO 2 to visible light region. In addition, narrower band gap formed by F-doping was beneficial to the high visible light photocatalytic activity. 相似文献
11.
采用研磨煅烧法,以硫脲(TU)作为氮源和硫源,H2TiO3(HT)为TiO2的前驱体,制备了不同TU/HT比例的N,S共掺杂TiO2光催化剂(NS/TiO2);利用X射线衍射仪、透射电镜、X射线光电子能谱仪、拉曼光谱仪、紫外-可见吸收光谱仪等分析了NS/TiO2的晶体结构、显微形貌、典型元素的化学状态以及光谱性质;利用BET法测定了NS/TiO2的比表面积,同时测定了其在可见光照下催化降解罗丹明B的活性.结果表明,当TU/HT质量比为0.5时,NS/TiO2的光催化活性最佳,光照70min时的罗丹明B降解率为44.4%.氮元素以NH3形式吸附在TiO2表面,硫元素以S6+形式存在,部分S6+取代Ti 4+的位置.与此同时N,S共掺杂使得TiO2的禁带宽度减小,可见光催化活性提高. 相似文献
12.
A novel graphene‐like MoS 2/C 3N 4 (GL‐MoS 2/C 3N 4) composite photocatalyst has been synthesized by a facile ethylene glycol (EG)‐assisted solvothermal method. The structure and morphology of this GL‐MoS 2/C 3N 4 photocatalyst have been investigated by a wide range of characterization methods. The results showed that GL‐MoS 2 was uniformly distributed on the surface of GL‐C 3N 4 forming a heterostructure. The obtained composite exhibited strong absorbing ability in the ultraviolet (UV) and visible regions. When irradiated with visible light, the composite photocatalyst showed high activity superior to those of the respective individual components GL‐MoS 2 and GL‐C 3N 4 in the degradation of methyl orange. The enhanced photocatalytic activity of the composite may be attributed to the efficient separation of electron–hole pairs as a result of the matching band potentials between GL‐MoS 2 and GL‐C 3N 4. Furthermore, a photocatalytic mechanism for the composite material has been proposed, and the photocatalytic reaction kinetics has been measured. Moreover, GL‐MoS 2/C 3N 4 could serve as a novel sensor for trace amounts of Cu 2+ since it exhibited good selectivity for Cu 2+ detection in water. 相似文献
13.
From previous reports, graphitic carbon nitride (g‐C 3N 4) can be used as a photocatalyst, although the low efficiency of solar energy utilization, small specific surface area and high recombination rate of photogenerated electron–hole pairs limit its practical application. For the purpose of increasing photocatalytic activity, especially under irradiation of visible light, we successfully synthesized a new composite, namely porous g‐C 3N 4/Ag/Cu 2O, through chemical adsorption of Ag‐doped Cu 2O on porous g‐C 3N 4, which has not been investigated carefully worldwide. The composition, morphology and optical properties of the composite were investigated through methods including X‐ray diffraction, energy‐dispersive X‐ray, Fourier transform infrared, UV–visible and photoluminescence spectroscopies and transmission electron microscopy. Using rhodamine B as organic pollutant to be degraded under the irradiation of visible light, different mass ratios of Ag/Cu 2O doped on porous g‐C 3N 4 led to enhanced photocatalytic performance of the composite compared to pure porous g‐C 3N 4. When the mass ratio of Ag/Cu 2O is 15%, porous g‐C 3N 4/Ag/Cu 2O exhibits a degradation rate 2.015 times higher than that of pure porous g‐C 3N 4. The reasons for this phenomenon may be attributed to the increased utilization efficiency of visible light, high‐speed separation of photogenerated electron–hole pairs, accelerated interfacial transfer process of electrons and increased surface area of the composite. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
14.
In this work, alcian blue 8GX (AB), a copper(II) phthalocyanine derivative, was employed to functionalize graphitic carbon nitride (g‐C 3N 4) for the preparation of a highly efficient photocatalyst. The approach relies on a facile AB‐assisted ethanol/water mixed‐solvent exfoliation of bulk g‐C 3N 4. The as‐prepared g‐C 3N 4/AB hybrid possesses significantly enhanced solution dispersibility and photoelectrochemical performance resulting from the synergistic effect between g‐C 3N 4 and AB, which involves the optimization of intimate interfacial contact, extension of light absorption range, and enhancement of charge‐transfer efficiency. This synergy contributes enormously to the photocatalytic degradation of rhodamine 6G (R6G) under light irradiation. 相似文献
15.
In this study, the photocatalytic activity of graphitic carbon nitride (g‐C 3N 4) synthesized via different precursors (urea, thiourea, and dicyandiamide) is investigated in the degradation process of tetracycline. Owing to the efficient charge separation and transfer, prolonged radiative lifetime of charge, large surface area, and nanosheet morphology, the urea‐derived g‐C 3N 4 exhibits superior photocatalytic activity for tetracycline degradation under visible‐light irradiation. This performance can compare with that of most reported g‐C 3N 4‐based composite photocatalysts. Through the time‐circle degradation experiment, the urea‐derived g‐C 3N 4 is found to have an excellent photocatalytic stability. The presence of NO 3?, CH 3COO ?, Cl ? and SO 42? ions with the concentration of 10 mm inhibits the photocatalytic activity of urea‐derived g‐C 3N 4, where this inhibitory effect is more obvious for Cl ? and SO 42? ions. For the coexisting Cu 2+, Ca 2+, and Zn 2+ ions, the Cu 2+ ion exhibits a significantly higher inhibitory effect than Ca 2+ and Zn 2+ ions for tetracycline degradation. However, both the inhibitory and facilitating effects are observed in the presence of Fe 3+ ion with different concentration. The h +, .OH and .O 2? radicals are confirmed as major oxidation species and a possible photocatalytic mechanism is proposed in a urea‐derived g‐C 3N 4 reaction system. This study is of important significance to promote the large‐scale application of g‐C 3N 4 photocatalysts in antibiotic wastewater purification. 相似文献
16.
A heterogeneous photocatalyst system that consists of a ruthenium complex and carbon nitride (C 3N 4), which act as the catalytic and light‐harvesting units, respectively, was developed for the reduction of CO 2 into formic acid. Promoting the injection of electrons from C 3N 4 into the ruthenium unit as well as strengthening the electronic interactions between the two units enhanced its activity. The use of a suitable solvent further improved the performance, resulting in a turnover number of greater than 1000 and an apparent quantum yield of 5.7 % at 400 nm. These are the best values that have been reported for heterogeneous photocatalysts for CO 2 reduction under visible‐light irradiation to date. 相似文献
17.
Facile and direct synthesis of porous nanorod‐type graphitic carbon nitride/CuO composite ( CuO‐ g‐C 3N 4 ) has been achieved by using a Cu–melamine supramolecular framework as a precursor. The CuO‐ g‐C 3N 4 nanocomposite demonstrated improved visible‐light‐driven photocatalytic activities. The results indicate that metal–melamine supramolecular frameworks can be promising precursors for the preparation of efficient g ‐C 3N 4 nanocomposite photocatalysts. 相似文献
18.
Graphitic carbon nitride (g‐C 3N 4) has been widely used in fields related to energy and materials science. However, nanostructured g‐C 3N 4 photocatalysts synthesized by traditional thermal polycondensation methods have the disadvantage of small specific surface areas and wide band gaps; these limit the catalytic activity and application range of g‐C 3N 4. Based on the unique nanostructure of g‐C 3N 4, it is a feasible method to modify g‐C 3N 4 with metals to design novel metal–semiconductor composites. Metals alter the photochemical properties of g‐C 3N 4, in particular, narrow the band gap and expand photoabsorption into the visible range, which improves the photocatalytic performance. This review covers recent progress in metal/g‐C 3N 4 nanocomposites for photocatalysts, organic systems, biosensors, and so on. The aim is to summarize the synthetic methods, nanostructures, and applications of metal/g‐C 3N 4 nanocomposite materials, as well as discuss future research directions in these areas. 相似文献
19.
The photocatalytic activity of graphite‐like carbon nitride (g‐C 3N 4) could be enhanced by heterojunction strategies through increasing the charge‐separation efficiency. As a surface‐based process, the heterogeneous photocatalytic process would become more efficient if a larger contact region existed in the heterojunction interface. In this work, ultrathin g‐C 3N 4 nanosheets (g‐C 3N 4‐NS) with much larger specific surface areas are employed instead of bulk g‐C 3N 4 (g‐C 3N 4‐B) to prepare AgIO 3/g‐C 3N 4‐NS nanocomposite photocatalysts. By taking advantage of this feature, the as‐prepared composites exhibit remarkable performances for photocatalytic wastewater treatment under visible‐light irradiation. Notably, the optimum photocatalytic activity of AgIO 3/g‐C 3N 4‐NS composites is almost 80.59 and 55.09 times higher than that of pure g‐C 3N 4‐B towards the degradation of rhodamine B and methyl orange pollutants, respectively. Finally, the stability and possible photocatalytic mechanism of the AgIO 3/g‐C 3N 4‐NS system are also investigated. 相似文献
20.
Monodoping with Mo, Cr, and N atoms, and codoping with Mo?N and Cr?N atom pairs, are utilized to adjust the band structure of NaNbO 3, so that NaNbO 3 can effectively make use of visible light for the photocatalytic decomposition of water into hydrogen and oxygen, as determined by using the hybrid density functional. Codoping is energetically favorable compared with the corresponding monodoping, due to strong Coulombic interactions between the dopants and other atoms, and the effective band gap and stability for codoped systems increase with decreasing dopant concentration and the distance between dopants. The molybdenum, chromium, and nitrogen monodoped systems, as well as chromium–nitrogen codoped systems, are unsuitable for the photocatalytic decomposition of water by using visible light, because defects introduced by monodoping or the presence of unoccupied states above the Fermi level, which promotes electron–hole recombination processes, suppress their photocatalytic performance. The Mo?N codoped NaNbO 3 sample is a promising photocatalyst for the decomposition of water by using visible light because Mo?N codoping can reduce the band gap to a suitable value with respect to the water redox level without introducing unoccupied states. 相似文献
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