Flower-like TiO2 Research Articles

Hierarchical flower-like TiO2 microspheres with improved dye-sensitized solar cell performance

Hierarchical flower-like TiO2 microspheres (FMS) and TiO2 nanorice (NR) were obtained, respectively, by controlling the dosage of Ti precursor via a simple hydrothermal process. Flower-like TiO2 microspheres consist of nanopetals grown from the center radially, the nanopetals are about several nm in average thickness, and each nanopetal has a thinned tip with an average size of 15 nm. The unique hierarchical TiO2 microspheres with large surface area (118.6 m2 g−1) suggested its potential application in dye-sensitized solar cells (DSSCs). The power conversion efficiency of FMS-based DSSCs (9.58%) is much higher than that of NR-based DSSCs (7.13%), which could be ascribed to its excellent light-scattering and dye absorption ability, shorter electron transport pathway and longer electron recombination time derived from the thin thickness and large specific surface area of nanopetals.

CZTS counter electrode in dye-sensitized solar cell: enhancement in photo conversion efficiency with morphology of TiO2 nanostructured thin films

In the present investigation, kesterite phase Cu2ZnSnS4 (CZTS) nanoparticle, and one-dimensional (1D) nanorods and three-dimensional (3D) flower-like rutile phase TiO2 thin films were obtained by the conventional hydrothermal method. The (112) plane–oriented single-phase CZTS nanoparticles with chemical composition Cu/(Zn + Sn) = 0.84, 0.90, 1.05 were obtained by changing the copper concentration of the precursor solution. The CZTS thin films were prepared on fluorine-doped tin oxide (FTO) substrate by the doctor blade coating method. The effect of reaction time on growth of the hydrothermal deposited rutile phase TiO2 nanorod thin films were investigated. The detailed structural properties, phase identification, and morphological developments were investigated using X-ray diffraction (XRD), Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and scanning electron microscopy (SEM) techniques. The dye-sensitized solar cells were fabricated with CZTS counter electrodes (CEs) and hydrothermal deposited nanostructured TiO2 photoanodes. The device formed with three-dimensional TiO2 nanostructured photoanode showed higher efficiency (2.65%) than one-dimensional microstructures (1.74%). The study demonstrates that the nanostructure-based morphologies of TiO2 photoanodes affect the performance of CZTS CEs–based dye-sensitized solar cell.

Photovoltaic and capacitance measurements of solar cells comprise of Al-doped CdS (QD) and hierarchical flower-like TiO2 nanostructured electrode

This work focuses on the performance of Al-doped CdS quantum dot (QD)/TiO2 solar cells. The devices were analyzed through current-voltage and capacitance-voltage measurements. It was observed from the analysis of absorption spectra that TiO2 nanowires improve the absorption of light of Al doped CdS QDs both in visible and near infrared (NIR) range. Current-voltage characteristics curve of Al doped CdS/TiO2 at different illuminations show that decrease in illumination (from 100 to 5 mW/cm2), affects the voltage and current correspondingly. Power-voltage curve at various intensities of light indicates that power of the solar cell increases with the increase of the bias voltage and reaches its maximum value at each value of light illumination intensity. The peak value of power at maximum illumination is 35 µW at 0.20 V and with decreasing illumination the peak value decreases. Capacitance-voltage measurements reveal that by increasing the bias voltage from −2.0 V to 0 V, the capacitance voltage indicates the rising trend. However, at 5 kHz and 10 kHz frequencies, it was observed that a marginal increase of capacitance was noticed with exceeding bias voltage. The results revealed that subsequent addition of the TiO2 nanowires significantly improved the output performance of QDSSC.

Superior de/hydrogenation performances of MgH2 catalyzed by 3D flower-like TiO2@C nanostructures

Abstract Magnesium hydride has been seen as a potential material for solid state hydrogen storage, but the kinetics and thermodynamics obstacles have hindered its development and application. Three-dimensional flower-like TiO2@C and TiO2 were synthesized as the catalyst for MgH2 system and great catalytic activities are acquired in the hydrogen sorption properties. Experiments also show that the flower-like TiO2@C is superior to flower-like TiO2 in improving the hydrogen storage properties of MgH2. The hydrogen desorption onset and peak temperatures of flower-like TiO2 doped MgH2 is reduced to 199.2 °C and 245.4 °C, while the primitive MgH2 starts to release hydrogen at 294.6 °C and the rapid dehydrogenation temperature is even as high as 362.6 °C. The onset and peak temperatures of flower-like TiO2@C doped MgH2 are further reduced to 180.3 °C and 233.0 °C. The flower-like TiO2@C doped MgH2 composite can release 6.0 wt% hydrogen at 250 °C within 7 min, and 4.86 wt% hydrogen at 225 °C within 60 min, while flower-like TiO2 doped MgH2 can release 6.0 wt% hydrogen at 250 °C within 8 min, and 3.89 wt% hydrogen at 225 °C within 60 min. Hydrogen absorption kinetics is also improved dramatically. Moreover, compared with primitive MgH2 and the flower-like TiO2 doped MgH2, the activation energy of flower-like TiO2@C doped MgH2 is significantly decreased to 67.10 kJ/mol. All the improvement of hydrogen sorption properties can be ascribed to the flower-like structure and the two-phase coexistence of TiO2 and amorphous carbon. Such phase composition and unique structure are proved to be the critical factor to improve the hydrogen sorption properties of MgH2, which can be considered as the new prospect for improving the kinetics of light-metal hydrogen storage materials.

Spatially confined growth of Bi2O4 into hierarchical TiO2 spheres for improved visible light photocatalytic activity

Bi2O4 is a promising visible light responsive photocatalyst but its application is limited by the large particle size and fast recombination rate of charge carriers. Herein, the flower-like hierarchical TiO2 sphere with rich mesorpores and macropores was used as the framework for the space-confined growth of nanosized Bi2O4, creating enormous Bi2O4/TiO2 type II heterojunctions and enlarging the interfacial contract areas between Bi2O4 and TiO2. Benefitting from these outstanding features, the photocatalytic activity of Bi2O4/TiO2 heterojunction for the degradation of methyl orange is much higher than that of pure Bi2O4 under visible light. The greatly improved separation efficiency of charge carriers that derived from the heterojunction and the shortened transfer distance of photogenerated charges from interior to surface of nanoscaled Bi2O4 are responsible for the enhanced photocatalytic performance. In addition, radical capture experimental results imply that hole is the dominant reactive species for the degradation of methyl orange.

Palladium nanoparticles uniformly and firmly supported on hierarchical flower-like TiO2 nanospheres as a highly active and reusable catalyst for detoxification of Cr(VI)-contaminated water

The rational design of highly active and stable nanocatalysts towards the detoxification of Cr(VI)-contaminated water is of great importance for environmental remediation. In the present work, a novel Pd-based hybrid nanomaterial, composed of Pd nanoparticles (Pd NPs) supported on three-dimensional hierarchical titania nanoflowers (fTiO2), was fabricated and systematically investigated as the catalyst of chromium detoxification. Pd NPs with diameter of ~ 2.8 nm were found to be uniformly and firmly supported onto the crystalline nanosheets of fTiO2. More importantly, the highly open porous flower-like architecture of Pd NPs/fTiO2 could not only endow the catalyst with high surface area (237.5 m2 g−1) and large pore volume (0.86 cm3 g−1), but also facilitate reactant diffusion and exposure of active sites. Benefitting from these remarkable features, the Pd NPs/fTiO2 exhibited superior catalytic performance for reduction of Cr(VI) in the presence of formic acid. The TOF reached up to 633.0 h−1, which was several and even more than one hundred times as high as those obtained by previously reported supported Pd-based catalysts. Moreover, the catalytic activity of Pd NPs/fTiO2 could remain almost unchanged after being recycled several times, demonstrating its long-term stability. Therefore, the Pd NPs/fTiO2 would be promising for practical wastewater treatment.

What happens if anodic TiO2 nanotubes are soaked in H3PO4 at room temperature for a long time?

We have found that anodized amorphous TiO2 nanotubes can be transformed into rutile phase TiO2, resulting in the formation of a flower-like structure, when soaked in H3PO4 solution at room temperature for 2–4 days. The presence of PO43− ions in the soaking solution is believed to play a key role in the formation of the flower-like TiO2 structure. The resulting TiO2 flower-like material can be used as a binder-free electrode and exhibits obvious redox activity in AlCl3 solution and superior supercapacitive performance compared to conventional TiO2 nanotubes. The presented technique offers a simple, scalable, energy-saving, and cost-effective way to tailor the morphology and properties of anodized TiO2 nanotubes for different applications.

Ag nanoparticle-modified double-layer composite film based on P25/NaLuF4:Yb3+/Er3+ and flower TiO2 for highly efficient dye-sensitized solar cells

A composite film was prepared by mixing NaLuF 4 :Yb 3+ /Er 3+ up-conversion luminescent material with commercial P25, and a scattering layer composed of flower-like TiO 2 was added on to the composite film (UC/P25) to form a double-layer composite film (UC/P25 + FT). An AgNO 3 solution was irradiated by ultraviolet light to deposit nano-Ag particles on the prepared double-layer film, and a nano-Ag modified double-layer film (UC/P25 + FT + Ag) was finally obtained. The synergistic effect of the three improved methods conferred the UC/P25 + FT + Ag film with a wide spectral absorption range, strong light-scattering ability, and strong light absorption capability, which greatly improved the photoelectric performance of the film. The maximum photoelectron conversion efficiency of dye-sensitized solar cells with the UC/P25 + FT + Ag photoanode reached up to 8.14%, which increased by 32.36% compared with that of the pure P25 film photoelectrode. • The NaLuF 4 :Yb 3+ /Er 3+ was mixed with commercial P25 to broaden the spectral absorption range. • The flower TiO 2 was used as light-scattering layer to increase the light-scattering ability. • The plasmon resonance effect of the Ag nanoparticle enhanced the absorption of visible light.

TiO2 Nano Flowers Based EGFET Sensor for pH Sensing

In this study, pH sensors were successfully fabricated on a fluorine-doped tin oxide substrate and grown via hydrothermal methods for 8 h for pH sensing characteristics. The morphology was obtained by high-resolution scanning electron microscopy and showed randomly oriented flower-like nanostructures. The TiO2 nanoflower pH sensors were measured over a pH range of 2–12. Results showed a high sensitivity of the TiO2 nano-flowers pH sensor, 2.7 (μA)1/2/pH, and a linear relationship between IDS and pH (regression of 0.9991). The relationship between voltage reference and pH displayed a sensitivity of a 46 mV/pH and a linear regression of 0.9989. The experimental result indicated that a flower-like TiO2 nanostructure extended gate field effect transistor (EGFET) pH sensor effectively detected the pH value.

Facile Hydrothermal Preparation of Flower-Like Tio2 Nanostructure With Enhanced Photocatalytic Activity

This paper demonstrated the preparation of flower-like TiO2 nanostructures by low temperature hydrothermal process from TiO2 nanoparticles. The as-synthesized TiO2 nanoparticles and flower-like TiO2 nanostructures were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2 adsorption-desorption measurements. The flower-like TiO2 nanostructures possessed good crystallinity, showed fairly large surface area of 220 m2/g and exhibited better photocatalytic degradation of rhodamine B than TiO2 nanoparticles under simulated solar radiation.

Self-cleaning properties of polyester fabrics coated with flower-like TiO2 particles and trimethoxy (octadecyl)silane

The presented work reported the growth of 3D-shaped TiO2 flower particles on the surface of polyester fabrics using two step approaches of sol–gel technology and hydrothermal method. The scanning electron microscopy, EDS analysis, Raman spectroscopy, and X-ray diffraction techniques were employed to study the effect of titanium isopropoxide (TTIP) concentration on the growth of flower-like TiO2 microstructures. Later, a layer of trimethoxy(octadecyl)silane was applied on TiO2-coated polyester fabrics to fabricate the self-cleaning textiles. The physical self-cleaning properties were examined based on superhydrophobicity and contact angle measurements, where maximum static contact angle of 160.1o and minimum roll off angle of 3° was found for 2 mL TTIP concentration. The degradation of methyl orange dyes under UV light irradiation was observed to confirm the photocatalytic chemical self-cleaning behavior, where the samples coated with 2 mL TTIP decolorized the dye solution in 150 min, whereas the samples coated with 1 mL and 1.5 mL TTIP took almost 300 and 210 min, respectively.

Fabrication of flower-like TiO2 on Bucky paper with enhanced photocatalytic activity

The difficulty of recycling and low photocatalytic efficiency in the visible light significantly limit the use of nano-TiO2 in water pollution control. In this work, Bucky papers (BPs), which play a vital role for adsorption of pollutants and transfer of electrons, are introduced as substrates to fabricate and anchor TiO2 nanorods by a facile hydrothermal method. The photocatalytic properties of the TiO2 and BP composites (TiO2@BP) are studied by photodegrading methylene blue in water solutions. It is found that TiO2@BP possesses four times photocatalytic efficiency for methylene blue of TiO2@Si under ultraviolet light irradiation and 10 times under visible light irradiation. This is considered to be attributed to the synergic effect of TiO2@BP system and surface defects of TiO2 nanorods. The TiO2@BP also shows a stable photocatalytic property even after five cyclic photocatalytic degradation. This study indicates that TiO2@BP is a promising candidate for photocatalytic applications, which provides a reference for further research on synthesis of reusable photocatalysts with higher efficiency.

A different wettable Janus material with universal floatability for anti-turnover and lossless transportation of crude oil

Flower-like TiO2 particles were prepared to endow diverse materials with the ability of steady floatability and anti-turnover on different liquids. This strategy was applied in the design of a promising way for lossless transportation of crude oil via sea.

A Study of Controllable Synthesis and Formation Mechanism on Flower-Like TiO2 with Spherical Structure

The development of photocatalytic materials with specific morphologies promises to be a good opportunity to discover geometrically relevant properties. Herein, this paper reported a facile hydrothermal method to directly synthesize TiO2 crystals with flower-like structures using tetrabutyl titanate (TBT) as a titanium source and ethylene glycol as an additive. We also proposed a reasonable growth mechanism by controlling reaction time in detail. The as-prepared samples were analyzed by using X-ray diffraction, scanning electron microscopy and transmission electron microscopy for structure and morphology characterization. The N2 adsorption-desorption isotherm results showed that the surface area of flower-like TiO2 with 10 h reaction time can reach 297 m2/g. We evaluated the photocatalytic performance of samples by using the degradation rate of methylene blue (MB) solution under UV-vis light. The TiO2 with 10 h reaction time exhibited a superior photocatalytic property than other samples in degrading MB under UV-vis light irradiation. More importantly, the catalyst could be reused many times. These results could benefit from the special morphology, high crystallinity and large specific surface area of the samples.

Engineering Bi2S3/BiOI p-n heterojunction to sensitize TiO2 nanotube arrays photoelectrodes for highly efficient solar cells and photocatalysts

To significantly improve the solar harvesting and electron transportation, Bi2S3/BiOI p-n heterojunctions were successfully formed on the surface of TiO2 nanotube arrays (TiO2 NTs/Bi2S3-BiOI) by a simple solvothermal method, and the morphology, composition and photoelectrochemical property of the TiO2 NTs/Bi2S3-BiOI were investigated by adjusting the concentration ratio of sulphur/iodonium. TiO2 NTs/Bi2S3-BiOI nanosheets and nanorods were prepared, and the self-assembled microflowers were also observed. The results indicated that flower-like TiO2 NTs/Bi2S3-BiOI showed high visible light absorption, photocurrent density and rapid photoelectrocatalytic removal of organic dyes and Cr(VI). The growth and photocatalytic mechanism were proposed to illuminate the high photoelectrochemical performances. The excellent photoelectrochemical activities drive the TiO2 NTs/Bi2S3/BiOI being superior environmental and energy materials in the applications of wastewater purification and solar cells.

Fabrication of flower-like mesoporous TiO2 hierarchical spheres with ordered stratified structure as an anode for lithium-ion batteries

In this study, flower-like mesoporous TiO2 hierarchical spheres (FMTHSs) with ordered stratified structure and TiO2 nanoparticles (TNPs) were synthesized via a facile solvothermal route and an etching reaction. Multilamellar vesicles (MTSVs) and unilamellar TiO2/SiO2 vesicles (UTSVs) were prepared using cetyltrimethylammonium bromide and didodecyldimethylammonium bromide as structure-directing agents under different solvothermal conditions. FMTHSs and TNPs were obtained from the etching reactions of MTSVs and UTSVs, respectively, in an alkaline system. FMTHSs display flower-like, ordered stratified structures on each petal. The thickness of the ordered stratified structure is approximately 3–6 nm, and the number of layers is approximately 2–4. The FMTHSs2 electrode exhibits the first discharge capacity of 212.4 mA h g−1 at 0.2 C, which is higher than that of TNPs electrode (167.6 mA h g−1). The discharge specific capacity of FMTHSs2 electrode after 200 cycles at 1 C is 105.9 mA h g−1, which is higher than that of TNPs electrode (52.2 mA h g−1) after the same number of cycles. The outstanding performance of FMTHSs2 electrode is attributed to the advantages of FMTHSs. In particular, their own stratified structure can provide additional active sites for reactions. The hierarchical structure can provide short diffusion length for Li+, large electrolyte–electrode contact area, and superior accommodation of the strain of Li+ intercalation/deintercalation.

Highly stable and sensitive resistive flexible humidity sensors by means of roll-to-roll printed electrodes and flower-like TiO2 nanostructures

Titanium dioxide (TiO2) nanostructure is synthesized and utilized as a sensing material in flexible resistive humidity sensors. The morphology of TiO2 flower-like nanostructure was optimized to possess high surface area by controlling pH value of precursor solution. The electrode was roll-to-roll gravure printed, and synthesized TiO2 nanoflower and protective layer were drop cast on flexible polyimide substrate. The humidity sensor made of TiO2 nanoflower with highest surface area exhibited highest sensitivity of 485.7 RH%−1. Furthermore, it showed comparably good repeatability, little hysteresis, and high degree of chemical stability as well as excellent resistance to random mechanical deformation. High sensitivity and stability of sensors based on TiO2 nanoflower hierarchical structure make them suitable for flexible and/or wearable applications.

Pd nanoparticles on carbon layer wrapped 3D TiO2 as efficient catalyst for selective oxidation of benzyl alcohol

In this work, a uniform thickness of a two-dimensional carbon layer wrapping a three-dimensional flower-like TiO2 (CFT) is used to support Pd nanoparticles (Pd/CFT) as efficient catalyst for selective oxidation of benzyl alcohol in a three-phase reaction system. The results of characterization reveal that the TiOC bond plays a key role in establishing interactions between the CFT and Pd. In comparison to the Pd/AC catalyst, Pd nanoparticles (PdNPs) with active phases can be effectively anchored on the surfaces of CFT without obvious dynamic change under reaction conditions.

Enhanced photocatalytic activity of TiO2 by micrometer-scale flower-like morphology for gaseous elemental mercury removal

A flower-like TiO2 photocatlyst has been fabricated using hydrothermal method with the changing of sodium hydroxide volume to control the morphology so as to enhance the photocataltic activity. The as-prepared photocatalysts has entire anatase phase with numerous nanowires covered on its surface, which structure is conducive to the higher BET surface area (86.7910 m2/g) and lower recombination between holes and photoelectrons. The photocatalytic ability was tested by oxidation of gaseous Hg0 in a lab-scale reactor, and TiO2-5 is found to be the best efficiency and 80 °C is the optimum photocatalytic reaction temperature. The photocatalytic oxidation mechanism has also been proposed.

Study of the structure and lattice distortion on the sensing properties of hierarchical rutile TiO2 nanoarchitectures

In this paper, we report the hydrothermal synthesis of 3D hierarchical rutile TiO2 nanorod microspheres in an acid medium with controlled morphology. Four different controlled hierarchical rutile TiO2 architectures (HRTA) characterized by X-ray diffraction (XRD), Rietveld refinement, scanning electron microscopy (SEM) were tested as an electrochemical sensor to quantify nitrobenzene (NB) in aqueous solution. Based on the characterization results, we found the open hierarchical nanorod microspheres with flower-like appearance showing a higher distortion of the octahedral structure and higher performance as an electrochemical sensor reaching NB concentrations below the parts per billion. The findings of this study have several valuable implications for future studies of volatile organic compound (COV) monitoring in aqueous solution using flower-like hierarchical rutile TiO2 nanorod microspheres clusters.