Construction of hierarchical nanostructured TiO2/Bi2MoO6 heterojunction for improved visible light photocatalysis

In this study, Bi2MoO6 hollow microspheres were modified by depositing TiO2 nanoparticles through a simple hydrothermal method. The prepared TiO2/Bi2MoO6 photocatalysts were characterized by scanning and transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The photocatalytic performance of the heterostructured catalysts was evaluated by degradation of methylene blue (MB) under visible-light irradiation (lambda>420 nm). The photocatalysts based on nanostructured Bi2MoO6 and TiO2 exhibit much higher photocatalytic activity than the single-phase Bi2MoO6 or TiO2 and the mechanical mixture of Bi2MoO6 and TiO2 for degradation of MB under the same conditions. The results reported in this study provide insight into constructing other heterostructured photocatalysts.     

(Metal yolk)/(porous ceria shell) nanostructures for high-performance plasmonic photocatalysis under visible light

We describe a route to the preparation of (metal yolk)/(porous ceria shell) nanostructures through the heterogeneous growth of ceria on porous metal nanoparticles followed by the calcination-induced shrinkage of the nanoparticles. The approach allows for the control of the ceria shell thickness, the metal yolk composition and size, which is difficult to realize through common templating approaches. The yolk/shell nanostructures with monometallic Pt and bimetallic PtAg yolks featuring plasmon-induced broadband light absorption in the visible region are rationally designed and constructed. The superior photocatalytic activities of the obtained nanostructures are demonstrated by the selective oxidation of benzyl alcohol under visible light. The excellent activities are ascribed to the synergistic effects of the metal yolk and the ceria shell on the light absorption, electron-hole separation and efficient mass transfer. Our synthesis of the (metal yolk)/(porous ceria shell) nanostructures points out a way to the creation of sophisticated heteronanostructures for high-performance photocatalysis.

     

纳米Bi_2O_3的制备及其可见光催化活性

采用共沉淀法制备纳米Bi_2O_3,并将其应用于光催化,研究不同热处理温度下制备的Bi_2O_3的光催化降解甲基橙的活性。通过扫描电子显微镜、X射线衍射、紫外-可见吸收光谱和荧光光谱表征Bi_2O_3的形貌、结构、光学及光催化活性。结果表明:Bi_2O_3的光催化活性与热处理温度有关,热处理温度为400℃时,合成的Bi_2O_3在可见光照射180 min时,对甲基橙的降解率达到86%。良好的可见光吸收和较低的光生载流子复合是获得优异光催化活性的主要原因。     

Fabrication and enhanced visible light photocatalytic activity of fluorine doped TiO2 by loaded with Ag

F-doped TiO2 loaded with Ag (Ag/F-TiO2) was prepared by sol-gel process combined with photoreduction method. The physical and chemical properties of the prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL). XPS analysis indicated Ag species existed as Ag0 in the structure of Ag/F-TiO2 samples. UV-Vis diffuse reflectance spectra showed that the light absorption of Ag/F-TiO2 in the visible region had a significant enhancement compared with the F-doped TiO2 (F-TiO2). PL analysis indicated that the electron-hole recombination rate had been effectively inhibited when Ag loaded on the surface of F-TiO2. The photocatalytic activities of the samples were evaluated for the degradation of X-3B (Reactive Brilliant Red dye, C.I. reactive red 2) under visible light (lambda > 420 nm) irradiation. Compared with F-TiO2, the sample of 0.50 Ag/F-TiO2 showed the highest photocatalytic activity. The interaction between F species and metallic Ag was responsible for improving the visible light photocatalytic activity.     

One-pot synthesis of oleic acid modified monodispersed mesoporous TiO2 nanospheres with enhanced visible light photocatalytic performance

Herein, we report a facile one-pot solvothermal method to prepare unique oleic acid (OA) modified monodispersed mesoporous TiO₂ nanospheres with carboxylate ligands from the oleic acid in the bidentate chelating linkage mode. The mesoporous OA-TiO₂ nanospheres have a very large specific surface of nearly 510?m²/g. The oleic acid cannot only act as a binding ligand to control the shape of mesoporous TiO₂ nanospheres, but also be benefit to enhance the visible-light absorption. The mesoporous OA-TiO₂ nanospheres exhibit an excellent photocatalytic performance in the degradation of Rhodamine B and phenol under the visible light irradiation and show almost no attenuation after four cycles.     

Sn-doped hematite nanostructures for photoelectrochemical water splitting

We report on the synthesis and characterization of Sn-doped hematite nanowires and nanocorals as well as their implementation as photoanodes for photoelectrochemical water splitting. The hematite nanowires were prepared on a fluorine-doped tin oxide (FTO) substrate by a hydrothermal method, followed by high temperature sintering in air to incorporate Sn, diffused from the FTO substrate, as a dopant. Sn-doped hematite nanocorals were prepared by the same method, by adding tin(IV) chloride as the Sn precursor. X-ray photoelectron spectroscopy analysis confirms Sn(4+) substitution at Fe(3+) sites in hematite, and Sn-dopant levels increase with sintering temperature. Sn dopant serves as an electron donor and increases the carrier density of hematite nanostructures. The hematite nanowires sintered at 800 °C yielded a pronounced photocurrent density of 1.24 mA/cm(2) at 1.23 V vs RHE, which is the highest value observed for hematite nanowires. In comparison to nanowires, Sn-doped hematite nanocorals exhibit smaller feature sizes and increased surface areas. Significantly, they showed a remarkable photocurrent density of 1.86 mA/cm(2) at 1.23 V vs RHE, which is approximately 1.5 times higher than that of the nanowires. Ultrafast spectroscopy studies revealed that there is significant electron-hole recombination within the first few picoseconds, while Sn doping and the change of surface morphology have no major effect on the ultrafast dynamics of the charge carriers on the picosecond time scales. The enhanced photoactivity in Sn-doped hematite nanostructures should be due to the improved electrical conductivity and increased surface area.     

非金属元素掺杂TiO2可见光催化原理的探讨

本文从几篇文献的误解入手,介绍了掺氮二氧化钛(TiO2)具有可见光活性的几种不同观点,在分析后,得出掺氮TiO2具有可见光活性是由于两方面的因素造成的:一是氮的掺杂使TiO2的价带产生变化,这种变化使价带附近的空穴活动性降低、带隙变小;二是掺氮TiO2存在氧空位,并且氧空位在导带边缘,使能带变窄.同时还介绍了掺硫TiO2、掺碳TiO2吸收可见光的原理.     

Construction of novel TiO_2/Bi_4Ti_3O_(12)/MoS_2 core/shell nanofibers for enhanced visible light photocatalysis

TiO2/Bi4 Ti3 O12 hybrids have been widely prepared as promising photocatalysts for decomposing organic contaminations.However,the insufficient visible light absorption and low charge separation efficiency lead to their poor photocatalytic activity.Herein,a robust methodology to construct novel TiO2/Bi4 Ti3 O12/MoS2 core/shell structures as visible light photocatalysts is presented.Homogeneous bismuth oxyiodide(BiOI) nanoplates were immobilized on electrospun TiO2 nanofiber surface by successive ionic layer adsorption and reaction(SILAR) method.TiO2/Bi4 Ti3 O12 core/shell nanofibers were conveniently prepared by partial conversion of TiO2 to high crystallized Bi4 Ti3 O12 shells through a solid-state reaction with BiOI nanoplates,which is accompanied with certain transition of TiO2 from anatase to rutile phase.Afterwards,MoS2 nanosheets with several layers thick were uniform decorated on the TiO2/Bi4 TiO3 O12 fiber surface resulting in TiO2/Bi4 Ti3 O12/MoS2 structures.Significant enhancement of visible light absorption and photo-generated charge separation of TiO2/Bi4 Ti3 O12 were achieved by introduction of MoS2.As a result,the optimized TiO2/Bi4 Ti3 O12/MoS2-2 presents 60% improvement for photodegrading RhB after 120 min irradiation under visible light and 3 times higher of apparent reaction rate constant in compared with the TiO2/Bi4 Ti3 O12.This synthetic method can also be used to establish other photocatalysts simply at low cost,therefore,is suitable for practical applications.     

UV and visible light photodegradation effect on Fe–CNT/TiO2 composite catalysts

Using multi-walled carbon nanotube (CNT) as an one-dimensional support, we have succeeded in uniformly anchoring of TiO₂ and Fe nanoparticles at its surface. The as-prepared Fe–CNT/TiO₂ composite photocatalysts have been investigated by degrading methylene blue (MB) under UV and differently intensified visible light irradiation. The ability of CNT to store and shuttle electrons, and Fe nanoparticles demonstrate its capability to serve as a yield and transfer electrons on demand to separate h^?+?/e^??? pairs. Moreover, the MB photodegradation increase with an increase of visible light intensity can be ascribed to the enhancement MB cationic radical. In addition, chemical oxygen demand (COD) of piggery waste and reduction efficiency of Cr (IV) was done at regular intervals, which gave a good idea about mineralization of wastewater.     

掺氮TiO2的制备及可见光催化研究

实现TiO2 的可见光催化一直是研究的热点 ,通常的方法 ,如过渡金属离子掺杂、染料敏化等有一定的缺陷。而掺氮TiO2 可以克服这些缺陷 ,有希望实现可见光活性TiO2 催化剂的工业化 ,本文详细介绍了氮掺杂TiO2 的制备方法、研究现状和可见光催化的应用情况 ,并对未来的发展趋势作了预测     

NO treated TiO2 as an efficient visible light photocatalyst for NO removal

In this study, we report that nitrogen doped TiO₂ could be achieved via thermal treatment of Degussa P25 TiO₂ in NO atmosphere directly (P25-NO). The samples were characterized with XRD, XPS, and FT-IR. The characterization results suggested that nitrogen species were interstitially doped in P25-NO during the NO thermal treatment process. In comparison with P25, the P25-NO exhibited significantly enhanced photocatalytic activities under visible light irradiation (λ > 420 nm) for gaseous NO removal. On the basis of electronic band structure theory, we proposed a possible mechanism for the enhanced visible light driven photocatalytic oxidation process over the interstitial N doping P25-NO samples. This work could not only deepen understanding of the enhanced photoactivity originated from interstitial N doping in TiO₂, but also provide a facile route to prepare nitrogen doped TiO₂ for environmental and energy applications.     

In-situ synthesis of TiO2 nanostructures on Ti foil for enhanced and stable photocatalytic performance

TiO_2 nanostructures with strong interfacial adhesion and diverse morphologies have been in-situ grown on Ti foil substrate through a multiple-step method based on conventional plasma electrolytic oxidation(PEO) technology, hydrothermal reaction and ion exchange process. The PEO process is critical to the formation of TiO_2 seeding layer for the nucleation of Na_2Ti_3O_7 and H_2Ti_3O_7 mediates that are strongly attached to the Ti foil. An ion exchange reaction can finally lead to the formation of H_2Ti_3O_7 nanostructures with diverse morphologies and the calcination process can turn the H_2Ti_3O_7 nanostructures into TiO_2 nanostructures with enhanced crystallinity. The morphology of the TiO_2 nanostructures including nanoparticles(NP), nanowhiskers(NWK), nanowires(NW) and nanosheets(NS) can be easily tailored by controlling the NaOH concentration and reaction time during hydrothermal process. The morphology, composition and optical properties of TiO_2 photocatalysts were analyzed using scanning electron microscope(SEM), X-ray diffraction(XRD), photoluminescence(PL) spectroscopy and UV–vis absorption spectrum. Photocatalytic tests indicate that the TiO_2 nanosheets calcined at 500?C show good crystallization and the best capability of decomposing organic pollutants. The decoration of Ag cocatalyst can further improve the photocatalytic performance of the TiO_2 nanosheets as a result of the enhanced charger separation efficiency. Cyclic photocatalytic test using TiO_2 nanostructures grown on Ti foil substrate demonstrates the superior stability in the photodegradation of organic pollutant, suggesting the promising potential of in-situ growth technology for industrial application.     

Synthesis and characterization of N-doped TiO2/ZrO2 visible light photocatalysts

Zirconia and nitrogen-doped TiO₂ powder was synthesized using a polymer complex solution method for the preparation of an enhanced visible light photocatalyst. The produced catalysts were characterized via the Brunauer, Emmett, and Teller method (BET), X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectra, and UV–Vis spectrophotometry analyses. The N-doped TiO₂/ZrO₂ photocatalyst showed a high specific surface area and small crystal sizes. The XPS spectra of the N-doped TiO₂/ZrO₂ sample indicated that nitrogen was doped into the TiO₂ lattice and enhanced the photocatalytic activity. The UV–Vis absorption spectra of the N-doped TiO₂/ZrO₂ sample noticeably shifted to the visible light region compared to that of the TiO₂. The photocatalytic activities of the prepared catalysts were evaluated for the decomposition of gaseous NO_x under UV and visible light irradiations. The photocatalytic activities of N-doped TiO₂/ZrO₂ were much greater than those of commercial Degussa P25 in both the UV and visible light regions. The high photocatalytic activity can be attributed to stronger absorption in the visible light region, a greater specific surface area, smaller crystal sizes, more surface OH groups, and to the effect of N-doping, which resulted in a lower band gap energy.     

Enhancement of visible light activity in Ag modified SnO2/TiO2

Ag modified SnO₂/TiO₂ nanoparticles were successfully prepared by a modified sol–gel method, without adding any acid or alkali. The entire preparation differs from the traditional sol–gel synthesis of TiO₂ that the reaction can get controlled by adjusting the flow speed of water vapor. Ultraviolet–visible diffuse reflectance spectra (UV–vis) and spin-trapping electron paramagnetic resonance (EPR) were used to forecast the photocatalytic activity of the samples, and the results were proved by the degradation of methylene blue solution under visible light. Compared with pure TiO₂, as-prepared Ag modified SnO₂/TiO₂ nanoparticles exhibited not only an enhanced photocatalytic activity but also an improved stability. Among all of samples, the composite with 0.5% of Ag and 1% of Sn showed the best photocatalytic performance and stability. Further increasing the Ag proportion will result in the decrease of the photocatalytic activity. A relative mechanism was proposed and discussed in detail.     

Preparation and photocatalytic activity of nanoglued Sn-doped TiO2

In this paper, Sn-doped TiO(2) photocatalyst was prepared and immobilized on a glass substrate using an about-to-gel SiO(2) sol as a nanoglue. The characterization of the Sn-doped TiO(2) by XRD showed that 5% Sn content is formed by anatase and rutile crystallites. Characterization of the nanoglued photocatalyst by the BET measurement, TEM, and SEM showed that the photocatalyst was a nanoporous material with a high-surface area. The Sn-doped TiO(2) was uniformly dispersed within the three-dimensional network of the silica in the form of nanoparticles. The nanoglued photocatalyst showed high photocatalytic activity during the degradation of penicillin under UV light. The effect of different Sn content on the amount of hydroxyl radical was discussed by using salicylic acid as probe molecules. The results show that an appropriate amount of Sn dopant can greatly increase the amount of hydroxyl radicals generated by TiO(2) nanoparticles, which are responsible for the obvious increase of photocatalytic activity.     

Antibacterial effect of visible light reactive TiO2/Ag nanocomposite thin film on the orthodontic appliances

This study evaluated the antibacterial effect of a visible light reactive TiO2/Ag nanocomposite thin film on dental orthodontic wire (STS 304 wire). The growth of S. mutans and A. actinomycetemcomitans was suppressed on the specimens coated with TiO2/Ag compared to the uncoated specimens. The antibacterial effect of the TiO2/Ag nanocomposite thin film was improved under visible light irradiation.     

阴离子掺杂型TiO2可见光活性研究进展

阴离子掺杂改性TiO2光催化材料是目前光催化材料界的一个研究热点.综述了阴离子掺杂改性TiO2可见光活性的研究进展,重点探讨了N、C和S等元素掺杂TiO2材料的原理,实验工艺,效果以及优缺点.并对TiO2光催化材料可见光活性未来发展趋势进行了展望.     

Hierarchical nanostructures of copper(II) phthalocyanine on electrospun TiO(2) nanofibers: controllable solvothermal-fabrication and enhanced visible photocatalytic properties

In the present work, 2,9,16,23-tetranitrophthalocyanine copper(II) (TNCuPc)/TiO(2) hierarchical nanostructures were successfully fabricated by a simple combination method of electrospinning technique and solvothermal processing. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), UV-vis diffuse reflectance (DR), Fourier transform infrared spectrum (FT-IR), X-ray photoelectron spectroscopy (XPS), and thermal gravimetric and differential thermal analysis (TG-DTA) were used to characterize the as-synthesized TNCuPc/TiO(2) hierarchical nanostructures. The results showed that the secondary TNCuPc nanostructures were not only successfully grown on the primary TiO(2) nanofibers substrates but also uniformly distributed without aggregation. By adjusting the solvothermal fabrication parameters, the TNCuPc nanowires or nanoflowers were facilely fabricated, and also the loading amounts of TNCuPc could be controlled on the TNCuPc/TiO(2) hierarchical nanostructural nanofibers. And, there might exist the interaction between TNCuPc and TiO(2). A possible mechanism for the formation of TNCuPc/TiO(2) hierarchical nanostructures was suggested. The photocatalytic studies revealed that the TNCuPc/TiO(2) hierarchical nanostructures exhibited enhanced photocatalytic efficiency of photodegradation of Rhodamine B (RB) compared with the pure TNCuPc or TiO(2) nanofibers under visible-light irradiation.     

Study of chromium modified TiO2 nano catalyst under visible light irradiation

Visible light active photocatalysts were successfully prepared by incorporating chromium into anatase TiO2 at two Cr/Ti atomic ratios (0.03% and 0.11%) by the use of a modified sol-gel process. Results show that the size of the chromium modified TiO2 particles is approximately 14-25 nm. As indicated by diffuse reflectance ultra violet/visible absorption spectra, heavier chromium dosage tends to result in greater absorption in both ultra violet and visible light. The simulation results from Cr K-edge X-ray absorption spectra suggest that Cr(0) and Cr(III), accounting for approximately 25% and 75% of total Cr, respectively, coexist in the TiO2 catalyst doped with 0.11% Cr. Cr dopant is suggested to be responsible for the phenomenon of enhanced light absorption in both ultra violet and visible regions. Further, Cr(0) can act as an electron remover because of the formation of the Schottky barrier between Cr(0) and TiO2, thus reducing the possibility of electron hole recombination. Photo-catalytic degradation of methylene blue under irradiation of blue light (with peak flux at 460 nm wavelength and a small flux near 367 nm) was considerably enhanced under appropriate reaction time (12 and 24 h) as small amount of Cr was doped into anatase titanium dioxide catalyst. After prolonged reaction time, Cr(0) was suggested to be poisoned and/or oxidized by SO4(2-), one of the final products of mineralizing methylene blue, thus loosing the capability of the electron hole separation.