Photocatalytic Activity Of TiO2 Nanofibers Research Articles

Examination of the doping effects of samarium (Sm3+) and zirconium (Zr4+) on the photocatalytic activity of TiO2 nanofibers

Pure and samarium (Sm3+) - or zirconium (Zr4+)-doped TiO2 nanofibers were synthesized by electrospinning method followed by calcination at 500 °C for 1 h. As-spun fibers were smooth, straight and continuous, whilst EDS analysis confirmed the fiber composition and incorporation of dopants in the fibers. Doping with Sm3+ and Zr4+ greatly inhibited the phase transformation of anatase to rutile, by surrounding of Sm3+ ions through formation of Ti-O-Sm bonds and by replacement of Ti4+ ions with larger Zr4+ ions. This was confirmed by HRTEM and SAED analysis. The size of nanofibers was determined to be 133 nm, 175 nm and 155 nm for pure, (0.5%)Sm3+:TiO2 and (1%)Zr4+:TiO2, respectively. After calcination, TiO2 crystal lattice with interplanar spacing of 0.353 nm of (101) crystal plane was not significantly disturbed by Sm doping whilst crystal lattice spacing of 0.357 nm of (101) planes of anatase phase in case TiO2:1.0%Zr4+, significantly differs from the value of pure TiO2 (0.352 nm), thus implying that Zr was doped into substitutional sites of the TiO2 lattice. The indirect band gaps were calculated to be in the range 3.07–3.24 eV. TiO2:0.5%Sm3+ and TiO2:1.0%Zr4+ exhibited higher specific surface area, of 47.1 and 59.4 m2/g, respectively, than pure TiO2 fibers (19.7 m2/g). Effects of Sm3+ and Zr4+ dopant content on the photodegradation efficiency of methylene blue (MB) were studied. TiO2:0.5%Sm3+ and TiO2:1.0%Zr4+ nanofibers have shown the highest photocatalytic activity of 97% and 98% with constant rates 0.01768 min−1 and 0.01939 min−1, respectively, within180 min irradiation under visible light.

Examination of the Doping Effects of Samarium (Sm3+) and Zirconium (Zr4+) on the Photocatalytic Activity of Tio2 Nanofibers

Examination of the Doping Effects of Samarium (Sm3+) and Zirconium (Zr4+) on the Photocatalytic Activity of Tio2 Nanofibers

Photocatalytic Activity of TiO₂ Nanofibers: The Surface Crystalline Phase Matters.

The crystal phases and surface states of TiO2 can intrinsically determine its performance in the applications of photocatalysis. Here, we prepared TiO2 nanofibers with different crystal phase contents by electrospinning followed via calcination at different temperatures. The TiO2 nanofibers were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectrometry, transmission electron microscopy (TEM), and photocatalytic performance testing. The results showed that the phases of TiO2 nanofibers were layered, that surface crystal phase transition rate was faster than that of internal layers contributed the difference in the ratio of anatase and rutile in the outer and inner layer of TiO2 nanofibers. The TiO2 nanofibers obtained at 575 °C had the best photocatalytic activity, taking only 25 min to degrade Rhodamine B. At 575 °C, the rutile content of the sample surface was about 80 wt.%, while the internal rutile content was only about 40 wt.%. Subsequently, we prepared two different structures of anatase–rutile core-shell TiO2 nanofibers. The core-shell structure can be clearly seen by TEM characterization. The photocatalytic activity of two kinds of core-shell TiO2 nanofibers was tested. The results showed that the photocatalytic activity was close to that of the pure phase TiO2 nanofibers, which corresponded with the surface phase. This further proves that the photocatalytic activity of the material is mainly affected by its surface structure.

Efficient removal of oil from oil contaminated water by superhydrophilic and underwater superoleophobic nano/micro structured TiO2 nanofibers coated mesh

In this report, we investigated the TiO2 nanofibers coated stainless steel mesh as a novel underwater superoleophobic membrane for the effective separation of contaminated oil-water mixtures. The membrane was fabricated by spray deposition of hydrothermally synthesized TiO2 nanofibers on stainless steel mesh. The fabricated membrane exhibits superhydrophilicity and supereleophobicity properties in air and underwater respectively allowing the separation of oil-water efficiently. Randomly deposited TiO2 nanofibers on mesh exhibit rough surface property and hence superhydrophilic nature. Water oil separation efficiencies of ∼90 and ∼99% were achieved with this filter for less viscous and highly viscous oil respectively. Additionally, the TiO2 nanofibers coated mesh can degrade immiscible organic molecules due to photocatalytic activity of TiO2 nanofibers under UV light. As a result of self-cleaning property of TiO2 nanofibers coated mesh, the durability of the filter membrane is enhanced.

Enhancement in the photocatalytic activity of TiO2 nanofibers hybridized with g-C3N4 via electrospinning

TiO2/g-C3N4 nanofibers with diameter of 100–200 nm were prepared by electrospinning method after calcination at high temperature, using polyvinylpyrrolidone (PVP), Melamine (C3H6N6), Ti(OC4H9)4 as raw materials. The composite nanofibers were characterized by XRD, FT-IR, SEM, UV–vis and PL respectively. The effects of different g-C3N4 contents on structure and photocatalytic degradation of the composite nanofibers were investigated. The results indicated that with increasing g-C3N4 content, the diameter of the composite fibers increased and the morphology changed from uniform structure to a nonuniform one, containing beads. The composite nanofibers displayed the best photocatalytic degradation on RhB, when the g-C3N4 content was 0.8 wt%. The degree of degradation was up to 99% at the optimal conditions of 40 min. The degradation activity of the composite nanofibers on RhB, MB and MO was found to be higher than that of the TiO2 nanofibers.

Erratum to: The effects of atmosphere and calcined temperature on photocatalytic activity of TiO2 nanofibers prepared by electrospinning

[This corrects the article DOI: 10.1186/1556-276X-8-548.].

Super effective Zn-Fe-doped TiO2 nanofibers as photocatalyst for ammonia borane hydrolysis

ABSTRACTIn this study, the photocatalytic activity of TiO2 nanofibers toward ammonia borane hydrolysis has been strongly modified by doping the nanostructure by ZnO and Fe2O3 oxides. Due to the differences in the work function and band gap energy among the three semiconductors (TiO2, ZnO and Fe2O3), illumination of TiO2 leads to accumulate the electrons and holes on the conduction and valance bands of Fe2O3 and ZnO, respectively. Accordingly, the experimental results indicated that the surface of the obtained nanofibers is very active which results in an instant hydrolysis of ammonia borane molecules reaching the active zone surrounding the nanofibers. Moreover, negative activation energy was determined as increasing the temperature led to decrease the photocatalytic performance. Furthermore, kinetic studies indicated that the heterogeneous catalytic reaction describing the ammonia borane hydrolysis process is zero order which additionally supports the super activity of the introduced nanofibers. It was also observed that Fe2O3 content in the introduced nanofibers has distinct influence as the best performance was obtained at 1 wt%. The modified TiO2 nanofibers were prepared by calcination of electrospun nanofibers composed of titanium isopropoxide, zinc acetate and iron acetate in air at 700 °C for 1 h. Overall, the present study opens a new avenue to overcome the fast electrons/holes recombination dilemma facing TiO2-based nanostructures.

The effects of atmosphere and calcined temperature on photocatalytic activity of TiO2 nanofibers prepared by electrospinning

TiO2-based nanofibers were synthesized using a sol–gel method and electrospinning technique. The as-spun composite fibers were heat-treated at different temperatures (500°C, 550°C, 600°C, and 650°C) and atmospheres (ammonia and nitrogen) for 4 h. The fibers had diameters of 50 to 200 nm and mainly featured anatase and rutile phases. The anatase phase decreased and the rutile phase increased with increasing temperature. Different nitrogen conditions exerted minimal effects on the TiO2 crystalline phase. Different nitriding atmospheres during preservation heating yielded various effects on fibers. The effect of nitrogen in ammonia atmosphere is better than that in nitrogen atmosphere. The fibers heat-treated at 600°C and subjected to preservation heating in NH3 showed high photocatalytic activity.

Photocatalytic activity of TiO2 nanofibers sensitized with ZnS quantum dots

ZnS–TiO2 hetero-nanostructured photocatalysts were synthesized by the impregnation of ZnS quantum dots (QDs) on the surface of TiO2 nanofibers. Samples were characterized by X-ray diffraction (XRD), field emission gun scanning electron microscopy (FEG-SEM), X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance spectroscopy. The photocatalytic activity of the prepared nanostructures was assessed by the photodegradation of methylene blue in an aqueous solution under UV irradiation. It was found that titanium dioxide impregnated with ZnS QDs increased photocatalytic activity. We demonstrated that methylene blue was more efficiently photodegraded by UV irradiation using ZnS-TiO2 heterogeneous photocatalysts than using pristine TiO2 nanofibers.

Effect of silver-doping on the crystal structure, morphology and photocatalytic activity of TiO2 nanofibers

In this study, effect of sliver-doping on the crystal structure, the nanofibrous morphology and the photocatalytic activity of titanium oxide nanofibers have been investigated. Silver-doped TiO2 nanofibers having different silver contents were prepared by calcination of electrospun nanofiber mats consisting of silver nitrate, titanium isopropoxide and poly(vinyl acetate) at 600 °C. The results affirmed formation of silver-doped TiO2 nanofibers composed of anatase and rutile when the silver nitrate content in the original electrospun solution was more than 3 wt%. The rutile phase content was directly proportional with the AgNO3 concentration in the electrospun solution. Negative impact of the silver-doping on the nanofibrous morphology was observed as increase the silver content caused to decrease the aspect ratio, i.e. producing nanorods rather nanofibers. However, silver-doping leads to modify the surface roughness. Study of the photocatalytic degradation of methylene blue dye clarified that increase the silver content strongly enhances the dye oxidation process.

Preparation of TiO2 nanofibers immobilized on quartz substrate by electrospinning for photocatalytic degradation of ranitidine

The photocatalytic activity of TiO2 nanofibers immobilized on quartz substrates was investigated by evaluating the decomposition of organic pollutants. TiO2 nanofibers were synthesized by electrospinning the Ti-precursor/polymer mixture solution, followed by hot-pressing for enhancing the adhesion of TiO2-nanofiber films to the substrates. TiO2 started to crystalize in the anatase form at 500 °C and reached the optimal photocatalytic anatase/rutile phase ratio of 70:30 at a calcination temperature of 600 °C. The TiO2-nanofiber film was demonstrated to be an efficient photocatalyst by ranitidine decomposition under UV illumination and was proven to have a comparable photocatalytic activity with the well-known Degussa P25 nanoparticulate photocatalyst and excellent recyclability during 10 cycles of photocatalytic operation, indicating no loss of TiO2 nanofibers during photocatalytic operations.

Enhanced Photocatalytic Activity of Electrospun TiO2 Nanofibers with Optimal Anatase/Rutile Ratio

By way of electrospinning followed by annealing at different temperatures, TiO2 nanofibers with different phases have been successfully fabricated. The corresponding ultraviolet photocatalytic activity was evaluated using rhodamine B degradation as a probe reaction. The photocatalytic activity of TiO2 nanofibers is found to be enhanced when annealed at higher temperatures with amount of anatase phase transformed to rutile. An optimal annealing temperature exists on the photocatalytic activity of TiO2 nanofibers, which increases with the increasing of the calcination temperature up to 600°C and then decreases. According to their phase transformations monitored by X‐ray diffraction, the different crystalline structures could be the reason for the enhanced photocatalytic activity of these electrospun TiO2 nanofibers.

Enhanced photocatalytic activity of TiO2 nanofibers and their flexible composite films: Decomposition of organic dyes and efficient H2 generation from ethanol-water mixtures

TiO2 nanofibers decorated with Pt and Pd nanoparticles have been synthesized and studied in various photocatalytic processes. Excellent photocatalytic behavior in the decomposition of organic dyes in water, degradation of organic stains on the surface of flexible freestanding cellulose/catalyst composite films and in generation of hydrogen from ethanol using both suspended and immobilized catalysts are demonstrated. The performance of the nanofiber-based TiO2 materials is competitive with—and in some cases outperforms—their conventional nanoparticle-based counterparts. In all cases, Pd-decorated TiO2 nanoparticles and nanofibers proved to be more efficient than their Pt-based counterparts, which could be explained on the basis of the formation of nano-sized Schottky interfaces at the contacts between TiO2 and metal nanoparticles. The feasibility of forming cellulose/catalyst composites provides a novel way of utilizing photocatalyst materials in large-area coatings and freestanding films.