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1.
Oxygen Vacancy (OVs) and carbon doping of the photocatalyst body will significantly enhance the photocatalytic efficiency. However, synchronous regulation of these two aspects is challenging. In this paper, a novel C@TiO 2-x photocatalyst was designed by coupling the surface defect and doping engineering of titania, which can effectively remove rhodamine B (RhB) and has a relatively high performance with wide pH range, high photocatalytic activity and good stability. Within 90 minutes, the photocatalytic degradation rate of RhB by C@TiO 2-x (94.1 % at 20 mg/L) is 28 times higher than that of pure TiO 2. Free radical trapping experiments and electron spin resonance techniques reveal that superoxide radicals (⋅O 2−) and photogenerated holes (h +) play key roles in the photocatalytic degradation of RhB. This study demonstrates the possibility of regulating photocatalysts to degrade pollutants in wastewater based on an integrated strategy. 相似文献
2.
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
3.
Binary BiOI/TiO 2 hybrid material was synthesized via a sol-gel method combined with chemical etching. The as-prepared powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (DRS), photoluminescence spectra (PLS) and photocurrent response tests. Under visible light (λ > 420 nm), BiOI/TiO 2 degraded methyl orange (MO) efficiently and displayed much higher photocatalytic activity than that of pure BiOI. Moreover, BiOI/TiO 2 can effectively promote photooxidation of other organic dyes like rhodamine B (RhB), crystal violet (CV) and methylene blue (MB). In addition, the quenching effects of different scavengers proved that reactive O 2 ? and h + played the major role in the MO degradation. The photocatalytic activity enhancement of BiOI/TiO 2 is closely related to the strong absorption in the visible region, and the efficient charge separation derived from the matching band potentials between BiOI and TiO 2, as well as the low recombination rate of the electron-hole pairs due to the heterojunction formed between BiOI and TiO 2. 相似文献
4.
Bi2WO6/UiO-66-NH2 photocatalysts were fabricated through solvothermal method using acetic acid as template. The photocatalytic performance of as-fabricated composites was highly improved under simulated visible light due to the addition of UiO-66-NH2. The structural and chemical properties of the composites were characterized through FTIR, XRD, XPS, SEM, BET, UV–vis DRS and PL. After 90 min of visible light irradiation, the RhB at an initial concentration of 10 mg·L?1 in the solution was degraded by 99.4% due to the addition of 10 mg of the composite. There was no significant decrease in the photocatalytic activity even after four rounds of cycles. The free radical capture experiments indicate that the photogenerated holes (h+) were the main active sites. The possible photocatalytic degradation mechanism was proposed as the specific surface area of the composite was enlarged due to the uniform distribution of UiO-66-NH2 on the surface of Bi2WO6. The electron–hole pairs recombination rate was decreased due to the photogenerated electrons (e?) on the CB of Bi2WO6 which can be rapidly transferred to the CB of UiO-66-NH2 and the photogenerated holes of UiO-66-NH2 transferred to the VB of Bi2WO6. Meanwhile, the RhB was directly oxidized to H2O and CO2 by h+ to achieve the purification effect. 相似文献
5.
Europium and nitrogen co-doped TiO 2 was successfully synthesized by the precipitation–peptization method. The structure and properties of the catalysts were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectra. The photocatalytic efficiency was evaluated by monitoring the photocatalytic degradation of salicylic acid under visible light irradiation. It was verified that TiO 2 co-doped with nitrogen and 1% europium showed the highest photocatalytic activity. The adsorption isotherms were obtained by measuring the salicylic acid concentration before and after the dark adsorption at different original solution concentrations. The results illustrated that the doping of Eu was beneficial to the adsorption of salicylic acid. The probable degradation mechanism of salicylic acid was examined by the addition of NaF, Na 2S 2O 3, and K 2S 2O 8 as the probe molecules. It was verified that salicylic acid was first adsorbed on the surface of the catalysts, followed by the degradation by the photogenerated holes ( h vb + ). 相似文献
6.
运用溶胶-凝胶法同步获得了LaCoO 3钙钛矿晶格结构内Mg 2+的掺杂改性及晶格结构外MgO的异质结复合改性。观察到了同步改性后LaCoO 3催化剂上水体罗丹明B(RhB)光催化降解活性的显著提升,相同实验条件下最适Mg含量改性LaCoO 3上RhB的降解率从原始LaCoO 3的58%显著提升至98%,表观一级动力学常数为改性前催化剂的4.5倍。运用X射线衍射(XRD)、氮气低温吸附-脱附(BET法)、扫描及透射电子显微镜(SEM,TEM)、傅里叶变换红外光谱(FT-IR)、X光电子能谱(XPS)、紫外-可见漫反射(DRS)及光致发光光谱(PL)等分析和表征系统探讨了改性前后催化剂的理化特征。结果表明,约10% Co 3+晶格结点可为Mg 2+掺杂取代而LaCoO 3钙钛矿结构基本保持不变,适量Mg 2+对Co 3+的掺杂取代可形成晶格畸变和杂质能级、衍生Co 4+及促进溶氧吸附从而有利于RhB的光催化降解,过量掺杂的Mg则可能成为光生载流子复合中心从而不利于RhB的去除。适量MgO异质结复合改性LaCoO 3一方面赋予复合催化剂较大表面积,利于RhB富集,也赋予丰富的表面羟基利于光生电子的捕获并衍生活性羟基自由基;另一方面还可能通过LaCoO 3与MgO异质结间电子的跃迁和流动以及晶格氧空位抑制光生载流子的复合,提高复合催化剂的光量子效率。 相似文献
7.
In this work, TiO 2/CdS nanocomposites with co-exposed {101}/[111]-facets (NH4F-TiO2/CdS), {101}/{010} facets (FMA-TiO2/CdS), and {101}/{010}/[111]-facets (HF-TiO2/CdS and Urea-TiO2/CdS) were successfully synthesized through a one-pot solvothermal method by using [Ti 4O 9] 2− colloidal solution containing CdS crystals as the precursor. The crystal structure, morphology, specific surface area, pore size distribution, separation, and recombination of photogenerated electrons/holes of the TiO 2/CdS nanocomposites were characterized. The photocatalytic activity and cycling performance of the TiO 2/CdS nanocomposites were also investigated. The results showed that as-prepared FMA-TiO 2/CdS with co-exposed {101}/{010} facets exhibited the highest photocatalytic activity in the process of photocatalytic degradation of methyl orange (MO), and its degradation efficiency was 88.4%. The rate constants of FMA-TiO 2/CdS was 0.0167 min −1, which was 55.7, 4.0, 3.7, 3.5, 3.3, and 1.9 times of No catalyst, CdS, HF-TiO 2/CdS, NH 4F-TiO 2/CdS, CM-TiO 2, Urea-TiO 2/CdS, respectively. The highest photocatalytic activity of FMA-TiO 2/CdS could be attributed to the synergistic effects of the largest surface energy, co-exposed {101}/{010} facets, the lowest photoluminescence intensity, lower charge-transfer resistance, and a higher charge-transfer efficiency. 相似文献
8.
以双氰胺和氢氧化钾为原料制备了能带可控的钾离子掺杂石墨型氮化碳(g-C3N4)光催化剂,并与碱处理的g-C3N4及g-C3N4/KOH复合催化剂进行了对比。采用X射线衍射(XRD)光谱、紫外-可见(UV-Vis)光谱、傅里叶变换红外(FTIR)光谱、N2吸附、电感耦合等离子体-原子发射光谱(ICP-AES)、荧光(PL)光谱、X 光电子能谱(XPS)等分析手段对制备的催化剂进行了表征。结果表明,钾离子含量对氮化碳催化剂的价带及导带位置有显著影响。此外,钾离子的引入抑制了氮化碳晶粒的生长,提高了氮化碳的比表面积以及对可见光的吸收,降低了光生电子-空穴对的复合几率。以染料罗丹明B的降解为探针反应系统研究了钾离子掺杂对g-C3N4在可见光下催化性能的影响,研究了光催化反应机理。结果表明,钾离子掺杂后氮化碳的光催化性能显著提高。制备的钾离子掺杂氮化碳催化剂表现出良好的结构及催化稳定性。 相似文献
9.
运用溶胶-凝胶法同步获得了LaCoO_3钙钛矿晶格结构内Mg~(2+)的掺杂改性及晶格结构外MgO的异质结复合改性。观察到了同步改性后LaCoO_3催化剂上水体罗丹明B(RhB)光催化降解活性的显著提升,相同实验条件下最适Mg含量改性LaCoO_3上RhB的降解率从原始LaCoO_3的58%显著提升至98%,表观一级动力学常数为改性前催化剂的4.5倍。运用X射线衍射(XRD)、氮气低温吸附-脱附(BET法)、扫描及透射电子显微镜(SEM,TEM)、傅里叶变换红外光谱(FT-IR)、X光电子能谱(XPS)、紫外-可见漫反射(DRS)及光致发光光谱(PL)等分析和表征系统探讨了改性前后催化剂的理化特征。结果表明,约10%Co~(3+)晶格结点可为Mg~(2+)掺杂取代而LaCoO_3钙钛矿结构基本保持不变,适量Mg~(2+)对Co~(3+)的掺杂取代可形成晶格畸变和杂质能级、衍生Co~(4+)及促进溶氧吸附从而有利于RhB的光催化降解,过量掺杂的Mg则可能成为光生载流子复合中心从而不利于RhB的去除。适量MgO异质结复合改性LaCoO_3一方面赋予复合催化剂较大表面积,利于RhB富集,也赋予丰富的表面羟基利于光生电子的捕获并衍生活性羟基自由基;另一方面还可能通过LaCoO_3与MgO异质结间电子的跃迁和流动以及晶格氧空位抑制光生载流子的复合,提高复合催化剂的光量子效率。 相似文献
10.
Recently, it has been proven that directional flow of photogenerated charge carriers occurs on specific facets of TiO 2 nanocrystals. Herein, we demonstrate that the photocatalytic activity of anatase TiO 2 nanocrystals in both photoreduction and photooxidation processes can be enhanced by selectively depositing Pt nanoparticles on the {101} facets, which strengthens spontaneously surface‐induced separation between photogenerated electrons and holes in the photocatalysis process. An optimal ratio of the oxidative {001} facets to the reductive {101} facets exists with regard to the photocatalysis of the faceted TiO 2 nanocrystals, and this is crucial for balancing the recombination and redox reaction rates of photogenerated electrons and holes. The present work might help us gain deeper insight into the relation between the specific surface of semiconductor photocatalysts and their photocatalytic activities and provides us with a new route to design photocatalysts with high photocatalytic activity. 相似文献
11.
Photocatalytic reactions are governed by photogenerated charge carriers upon band gap excitation. Therefore, for better understanding of the mechanism, the dynamics of photocarriers should be studied. One of the attractive materials is TiO 2, which has been extensively investigated in the field of photocatalysis. This review article summarizes our recent works of time-resolved visible to mid-IR absorption measurements to elucidate the difference of anatase, rutile, and brookite TiO 2 powders. The distinctive photocatalytic activities of these polymorphs are determined by the electron-trapping processes at the defects on powders. Powders are rich in defects and these defects capture photogenerated electrons. The depth of the trap is crystal phase dependent, and they are estimated to be < 0.1 eV, ∼0.4 eV and ∼0.9 eV for anatase, brookite, and rutile, respectively. Electron trapping reduces probability to meet with holes and then elongate the lifetime of holes. Therefore, it works negatively for the reaction of electrons but positively works for the reaction of holes. In the steady-state reactions, both electrons and holes should be consumed. Hence, the balance between the positive and negative effects of defects determines the distinctive photocatalytic activities of anatase, rutile, and brookite TiO 2 powders. 相似文献
12.
This study investigated the positive effect of surface modification with ozone on the photocatalytic performance of anatase TiO 2 with dominated (001) facets for toluene degradation. The performance of photocatalyst was tested on a home-made volatile organic compounds degradation system. The ozone modi cation, toluene adsorption and degradation mechanism were established by a combination of various characterization methods, in situ diffuse reflectance infrared fourier transform spectroscopy, and density functional theory calculation. The surface modi cation with ozone can significantly enhance the photocatalytic degradation performance for toluene. The abundant unsaturated coordinated 5c-Ti sites on (001) facets act as the adsorption sites for ozone. The formed Ti-O bonds reacted with H 2O to generate a large amount of isolated Ti 5c-OH which act as the adsorption sites for toluene, and thus significantly increase the adsorption capacity for toluene. The outstanding photocatalytic performance of ozone-modified TiO 2 is due to its high adsorption ability for toluene and the abundant surface hydroxyl groups, which produce very reactive OH radicals under irradiation. Furthermore, the O 2 generated via ozone dissociation could combine with the photogenerated electrons to form superoxide radicals which are also conductive to the toluene degradation. 相似文献
13.
采用溶剂热法制备了三维花状CeO 2/TiO 2异质结光催化剂,然后以甲基橙(MO)为模拟有机污染物,在氙灯照射下考察了其光催化活性。结果表明,花状结构由纳米片和纳米颗粒复合而成,纳米片上均匀地附着CeO 2颗粒。Ce/Ti的物质的量之比(n Ce/n Ti)和溶剂热时间影响异质结的光催化性能,当n Ce/n Ti=0.1、溶剂热时间为6 h时,CeO 2/TiO 2的光催化活性达到最佳,氙灯照射50 min的降解率达95%,光催化活性优于纯TiO 2,这主要是CeO 2和TiO 2形成了异质结,有利于光生电子和空穴的分离。 相似文献
14.
采用简单的沉积方法制备了不同碘化氧铋含量的BiOI/Bi 2WO 6光催化剂,通过X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HR-TEM)、紫外-可见漫反射光谱(UV-VisDRS)和BET比表面积测量对其进行了表征。在紫外和可见光的照射下,使用甲基橙和苯酚的光催化降解评价了BiOI/Bi 2WO 6催化剂的光催化性能。结果表明:与商业P 25和纯Bi 2WO 6相比,13.2%BiOI/Bi 2WO 6光催化剂具有更高的紫外和可见光催化性能。这明显增加的光催化活性主要归功于光生电子和空穴在Bi 2WO 6和BiOI界面上的有效转移,降低了电子-空穴对的复合。基于BiOI和Bi 2WO 6的能带结构,提出了光生载流子的一种转移过程。自由基清除剂的实验表明,OH,h +,O 2和H 2O 2,特别是h +,共同支配了甲基橙和苯酚的光催化降解过程。 相似文献
15.
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
16.
采用简易离子交换法制备可见光驱动Ag3PO4光催化剂.通过X射线衍射、场发射扫描电子显微镜、N2吸附-脱附、紫外-可见漫反射光谱及傅里叶变换红外光谱对所制备的Ag3PO4催化剂进行表征.结果表明,在可见光照射下,Ag3PO4催化剂对罗丹明B降解表现出优越的光催化活性,但对甲基橙的降解活性低,这归因于Ag3PO4催化剂对甲基橙分子吸附量低.可见光照Ag3PO4反应体系中,空穴和超氧自由基共同发挥作用导致罗丹明B和甲基橙光催化降解.在罗丹明B的协助作用下,Ag3PO4催化剂对甲基橙的可见光催化降解活性大大增强,这是由于罗丹明B的存在可产生更多的超氧自由基,从而使甲基橙进一步降解. 相似文献
17.
TiO 2 microspheres were synthesized by the sol–gel method using the ionic liquid (IL) 1-vinyl-3-propylimidazolium iodide (VPIM +I ?) as a reaction medium, then calcined at 500 °C. The samples were characterized by X-ray diffraction, scanning electron microscopy, and ultraviolet–visible (UV–Vis) diffuse reflectance spectroscopy. The phase of TiO 2 microspheres is anatase, and VPIM +I ? is able to favor the growth of anatase phase and prevents the collapse of small pores. The photocatalytic activity of TiO 2-IL was tested by degradation of 2-nitrophenol under UV light illumination. The photocatalytic activity of TiO 2-IL was higher than that of samples prepared in the reaction medium without VPIM +I ?. 相似文献
18.
TiO 2 nanoparticles incorporated with CuInS 2 clusters were prepared in a solvothermal process and characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersion X-ray analysis (EDX). Compared with pure TiO 2 nanoparticles, the TiO 2 nanoparticles incorporated with CuInS 2 clusters display higher photocatalytic activity with 99.9% of degradation ratio of 4-nitrophenol after 2 h irradiation. In order to investigate the effect of the CuInS 2 clusters on the photocatalytic activity of TiO 2 nanoparticles, diffuse reflectance UV–Vis spectra (DRS), photoluminescence (PL) spectra, and photocurrent action spectra were measured. The results indicate that the enhanced photocatalytic activity is probably due to the interface between TiO 2 and CuInS 2 as a trap of the photogenerated electrons to decrease the recombination of electrons and holes. 相似文献
19.
CH 3COO (BiO) (denoted as BiOA c) is one of the most easily obtained bismuth compounds and was for the first time proposed by our group as an effective UV light photocatalyst. Herein, BiOC l 1‐x B r x ( x refers to the feeding atomic ratio) were obtained using a facile solid state milling and subsequent water washing. More importantly, all of the as‐prepared BiOC l 1‐x B r x possessed better visible light photocatalytic activity to the corresponding ones obtained by previously reported solution route. Especially at an optimal x value of 0.5, the solid solution showed the highest photodegradation efficiency (~100%) for rhodamine B (RhB) with a concentration of 30 mg L −1, whereas the degradation efficiency was only 63% over that obtained by solution route. Furthermore, the as‐prepared BiOC l 0.5Br 0.5 also exhibited excellent photodegradation activity for malachite green (MG ). The superior photocatalytic performance of the as‐prepared BiOC l 0.5Br 0.5 could be attributed to its thinner sheetlike structures and highly exposed (001) facets, which enable effective separation of the photogenerated electrons and holes along the [001] direction. In addition, the as‐prepared BiOC l 0.5Br 0.5 revealed dramatic adsorption capacity for cationic dyes like MG , RhB and methylene violet (MV ), as well as anion (Cr 2O 7) 2− owing to electrostatic interaction between cationic dyes and negatively charged surface of BiOC l 0.5Br 0.5, and positively charged surface in K 2Cr 2O 7 solution (pH ≈ 3). 相似文献
20.
Constructing a porous structure in photocatalysts is an effective strategy for improving the photocatalytic activity because of its enhanced molecule transfer capability and light capturing efficiency. In this work, a hierarchical macro‐/mesoporous ZnS/TiO 2 composite with macrochannels was successfully synthesized without using templates by the simple dropwise addition of an ethanol solution of tetrabutyl titanate and zinc acetate into a sodium sulfide aqueous solution, which was then calcined at 450°C. Compared with pure TiO 2, the ordered porous ZnS/TiO 2 composite exhibited an enhanced photocatalytic activity on methylene blue removal under UV‐light irradiation. The results indicate that the macro‐/mesoporous structure, the large specific surface area, and the heterostructure combination between ZnS and TiO 2 play a synergistic effect on the enhanced photocatalytic activity via improving the light absorption and the diffusion of organic molecules, providing more reactive sites for the photocatalytic reaction and improving the separation of photogenerated electron–hole pairs, respectively. Radical trapping experiments demonstrated that holes (h +) and superoxide anion radicals (O 2−) play an important role in the photocatalytic oxidation process. 相似文献
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