Performance Of TiO2 Nanotube Arrays Research Articles

Optimization of Photoelectrochemical Response on TiO2 Nanotube Arrays Treated by H3PO4 and Mechanism Analysis of the Slowing Down Effect during Preparation.

The process control of anodization has been a hot topic for a long time. In this study, the addition of phosphoric acid to the traditional electrolyte changed the ion distribution on the reaction interface and the composition of the anion contamination layer so as to achieve the slowing down effect on anodization, the mechanism and theoretical model of which are also given in this paper. TiO2 is a common material in photoelectrocatalysis, but there are few studies on the photoelectrochemical performance of TiO2 nanotube arrays. The stability and rapidity of the photoelectrochemical response of TiO2 nanotube arrays prepared in phosphoric acid containing an electrolyte were effectively optimized in this study.

Ni-TiO2 nanotube arrays for highly sensitive and selective detection of acetone vapor

To further improve the acetone sensing performance of TiO2 nanotube arrays synthesized by an electrochemical anodization method, the Ni dopants in lower variable valences than Ti4+ ions were introduced into TiO2 nanotube arrays via a hydrothermal method. At the prime operating temperature of 420 °C, the Ni-TiO2 nanotube arrays-based sensor showed almost three times higher acetone vapor response (29.5–100 ppm) than the TiO2 sensor, as well as a higher degree of linearity (R2 = 0.99) and sensitivity (slope = 1.03) to 1–500 ppm acetone, faster response/recovery speed (1.8/88.3 s), higher long term stability (29.5 ± 1.9 %), and better selectivity against toluene, alcohol, methoxythanol, methanol, DMF, glycol, hydrogen, and ammonia. As revealed by XRD, SEM, and XPS, the improved acetone sensing performance of Ni-TiO2 nanotube arrays should be contributed by the substitution of the smaller Ni2+/Ni3+ ions for the larger Ti4+ ions in TiO2 lattice which yielded the reduction of nanotube thickness and average crystallite size, as well as the increase in the content of OV on the surface.

Ti3C2Tx MXene functionalization induced enhancement of photoelectrochemical performance of TiO2 nanotube arrays

Due to a unique planar structure, hydrophilic functional groups, and excellent metallic conductivity, recently developed two-dimensional (2D) MXene offers great potential in applications such as energy storage, photothermal conversion, gas sensing, etc. Herein, we have fabricated 2D Ti3C2Tx MXene functionalized TiO2 nanotube arrays (TNTs) to achieve enhanced photoelectrochemical (PEC) water splitting. We have observed ∼30% increase in photocurrent density for MXene functionalized TNTs over that of bare TNTs. Impedance spectroscopy analysis suggests a decrease in charge transfer resistance from ∼11.38 kΩ to ∼2.94 kΩ at an optimal amount of MXene functionalization. Analysis of Mott-Schottky measurement shows that donor density increases in MXene functionalized TNT sample. Under light irradiation, Ti3C2Tx MXene shows a localized surface plasmon resonance (LSPR) effect and injects electrons to the conduction band of TNT thereby increasing the photogenerated charge carriers, which in turn, enhances the PEC performance of bare TNTs. The work provides a pathway to design new plasmonic heterostructure materials based on monolayers MXene flakes for overall water splitting application.

Synergistic Effects of Plasmonic Gold and Perovskite-Type SrTiO3 for Enhanced Photocatalytic Performance of TiO2 Nanotube Arrays

Synergistic Effects of Plasmonic Gold and Perovskite-Type SrTiO₃ for Enhanced Photocatalytic Performance of TiO₂ Nanotube Arrays

Study on supercapacitance performance of TiO2 nanotube arrays modified by non-metal doping and Polyaniline electrodeposition methods

Highly ordered TiO2 nanotube arrays were synthesized by a two-step anodizing method. Although TiO2 nanotubes have excellent electrical and capacitive properties because they provide a unidirectional path for electron transfer. But these properties can be improved by effective methods such as non-metallic doping or by a conductive polymer. For this purpose, nitrogen and hydrogen doping methods and electrical deposition of polyaniline were used simultaneously to prepare the polyaniline-TiO2, polyaniline/N-TiO2, and polyaniline/H-TiO2 nanotube arrays samples. To evaluate the electrochemical and capacitive properties in more detail, cyclic voltammetry, electrochemical impedance spectroscopy, Matt-Schottky, and galvanostatic charge-discharge tests were performed. The results showed that the composite of TiO2 doped with hydrogen and deposited with polyaniline nanowires had the highest capacitance (5666 µF.Cm-2) at the current density of 100 µA/cm2, approximately 4.5 times more than polyaniline/TiO2 sample. It also has the lowest charge transfer resistance (0.008 Ωcm2) and the highest charge carrier density (1.63×1024cm-3). Increasing the density of charge carriers and decreasing the electrical resistance can be attributed to the fact that the hydrogen doping, the presence of oxygen vacancies, and conductive polymer increase the rate of separation of the charge carriers and decrease their recombination rate. Therefore, the electron transfer rate and the electric current increase.

Photoelectrochemical performance of TiO2 nanotube arrays modified with Ni2P Co-catalyst

Solar-driven water splitting to produce hydrogen is an important solution to the problem of energy shortage and environmental pollution. The photolysis of water to produce hydrogen requires highly efficient and stable photocatalysts, and the anode used as catalyst for oxygen evolution is a bottleneck in this process. In this paper, the a-TNTAs/Ni2P composite photo-anode was constructed by electrodeposition to anchor the Ni2P co-catalyst for oxygen evolution at the active site of TiO2 nanotube arrays (TNTAs). The a-TNTAs/Ni2P delivered excellent oxygen evolution at a photocurrent density of 1.058 mA cm-2, an improvement of 2.78 times, 13.2 times, and 15.8 times over a-TNTAs, TNTAs/Ni2P, and TNTAs photo-anodes, respectively. The Mott-Schottky curve showed that Ni2P as co-catalyst for oxygen evolution accelerated the rates of separation and transfer of the photogenerated electrons. This research provides a simple and efficient method to promote the OER performance of optical semiconductors.

Effectiveness of undoped and (Nd, Yb)-doped PbTe nanoparticles deposition on supercapacitor performance of TiO2 nanotube arrays

Undoped and doped PbTe nanoparticles with neodymium (Nd) and ytterbium (Yb) ions were hydrothermally synthesized and deposited on anodized TiO2 nanotube (TNT) arrays to form hybrid binder-free TNT electrodes for supercapacitor. The as-prepared TNT electrodes were characterized by XRD, SEM, and XPS. Besides, BET method was used to confirm the surface area of as-synthesized nanoparticles. Among TNT electrodes, the one with Yb-doped PbTe exhibited enhanced capacitance (0.93 mF/cm2 at 10 mV/s, 2.16 mF/cm2 at 5 µA/cm2) and low resistance (4.68 Ω), along with good stability (~93%). Overall, TNT in combination with Yb-doped PbTe nanoparticles could provide an ideal platform for efficient delivery of capacitance.

Enhanced Photoelectrochemical Water-Splitting Property on TiO2 Nanotubes by Surface Chemical Modification and Wettability Control.

We report a simple method to control the photoelectrochemical (PEC) water-splitting performance of TiO2 nanotube arrays (NTs) by surface chemical modification. Four types of modifier molecules with different surface energy and functional groups, including amine (-NH2), n-alkane (-CnH2n+1), perfluoroalkyl (-F), and polymer molecule (-polymer), were self-assembled to the surface of TiO2 NTs, which could change the surface chemical composition and wettability from superhydrophilicity to hydrophobicity. Interestingly, different from expected results, photoelectrochemical measurement results show that the n-octadecyltrichlorosilane-modified TiO2 nanotube arrays with a contact angle of about 134° present the highest PEC property with doubled photocurrent density and more negative onset potential. And the total PEC performance order of the monolayers-modified TiO2 NTs is (-CnH2n+1) > (-F) > (-NH2) > (-OH, pristine TiO2) > (-polymer), which is due to the molecular monolayers modification being able to suppress the recombination of photogenerated electrons and holes and facilitate water oxidation by regulating the interface electric double layer, whereas a thick polymer layer on the photoelectrode surface would affect the light absorbance and decrease the PEC performance. Further investigation indicates that the surface energy and wettability of the TiO2 photoelectrode adjusted by surface modification also have an important influence on the interface reaction of water oxidation and the adsorption/desorption of newly formed oxygen, which also provides a new method for controlling the surface photocatalytic reactions.

Photoelectrochemical performance of TiO2 nanotube arrays by in situ decoration with different initial states

Here, carbon dots (CDs) only or nanocomposites of CDs and TiO2 (CDs–TiO2) were used to decorate titanium dioxide nanotube arrays (TiO2NTs) in situ by solvothermal method. Two initial states of TiO2NTs were prepared for contrast, including the amorphous TiO2NTs (TiO2NTs-0) just experienced anodic oxidation process and that further calcined TiO2NTs (TiO2NTs-450). It was found that the newborn CDs or CDs–TiO2 were more likely to anchor on TiO2NTs-0 than the calcined TiO2NTs-450, and more Ti–C bonds were found in the composites which were derived from TiO2NTs-0 after the solvothermal treatment. An evident photocurrent could be demonstrated for either CDs or CDs–TiO2 decorated TiO2NTs once exposed to visible light. And CDs–TiO2NTs-0 showed the highest photocurrent density (4.51 µA·cm−2). However, the results of photodegradation measurements revealed that CDs–TiO2 decorated TiO2NTs with different initial states (especially CDs–TiO2–TiO2NTs-0) showed more excellent photocatalytic activity under both ultraviolet (UV) and visible light illumination.

Enhanced the photoelectrocatalytic performance of TiO2 nanotube arrays by the synergistic sensitization of Ag-AgBr nanospheres.

Ag-AgBr nanospheres were synthesized on the tubular surface of TiO2 nanotube arrays (TiO2 NTA/Ag-AgBr) by the one-pot hydrothermal deposition strategy using cetyltrimethyl ammonium bromide (CTAB) as bromine source and morphology controlling agent. The results showed that the TiO2 NTA/Ag-AgBr (0.025) prepared with 0.025 g CTAB had the uniform particle distribution, high visible light absorption, photoelectric conversion activity and photoelectrocatalytic (PEC) removal of organic dyes and heavy metal ions. The high photocatalytic decomposition of organic pollutants in waste water was attributed to the synergistic effect of Ag-AgBr nanospheres with the strong visible light response and effective separation of electron-hole pairs. The active group and photocatalytic mechanism for the rapid pollutant removal were systematically explored. This work will open the window of TiO2 NTA based photoelectrodes for the applications in solar energy conversion and dyeing waste water purification.

Synthesis, surface properties, crystal structure and dye-sensitized solar cell performance of TiO2 nanotube arrays anodized under different parameters

In this paper, TiO2 nanotube arrays were prepared by anodic oxidation method. The effects of water content, anodizing time and sample post-treatment on the morphology and crystal structure of TiO2 nanotube arrays were systematically investigated. We explored the performance of dye-sensitized solar cells (DSSCs) based on dye N-719. The TiO2 nanotube arrays prepared under different water content and different anodizing time conditions were used as photoanodes. The results show that DSSC has best photovoltaic performance when the water content is 2 vol%. With the increase of oxidation time, Jsc increases continuously, open voltage (Voc) and fill factor (FF) increase first and then decrease. The best optoelectronic properties obtained that the short circuit current, open circuit voltage, fill factor and photoelectric conversion efficiency as following, Jsc = 5.2 mA/cm2, Voc = 0.7 V, FF = 0.54, η = 1.96% respectively.

Improving Hydrogen Sensing Performance of TiO2 Nanotube Arrays by ZnO Modification

In this work, anodization was utilized to synthesize highly ordered TiO2 nanotube arrays, and ZnO was successfully decorated onto the surface of as-prepared TiO2 nanotubes via a facile impregnation method. The gas sensing performance of TiO2@ZnO composite was systematically studied. At a working temperature of 300 °C, the response of TiO2@ZnO to 100 ppm H2 was ~340, 2.7 times larger than that of pristine TiO2. A power-law relationship between the response and H2 concentration was observed. In addition, the response time was significantly reduced by four times, and improved selectivity to H2 was achieved. The highly improved sensing performance of TiO2 nanotubes by ZnO decoration may be attributed to the enhanced oxygen adsorption and formation of n-n heterojunctions.

Enostavna metoda priprave množice s CuO modificiranih TIO2 nanocevk za postopek razcepljanja vode ter njihove fotoelektrokemične lastnosti

Enostavna metoda priprave množice s CuO modificiranih TIO2 nanocevk za postopek razcepljanja vode ter njihove fotoelektrokemične lastnosti

Enhanced photoelectrochemical performance of TiO2 nanotube arrays with coexisted Pt nanoparticles and Co-Pi cocatalysts

Highly-ordered TiO2 nanotube arrays (TNTAs) were prepared by electrochemical anodization. Cobalt-phosphate (Co-Pi) film fabricated by electrodeposition and Pt nanoparticles (Pt NPs) fabricated by photochemical reduction were decorated onto TNTAs to enhance the photoelectrochemical (PEC) performance together. The photocurrent density of the TNTAs/Co-Pi/Pt photoelectrode could reach 0.185mA/cm2 at 1.23V versus reversible hydrogen electrode under UV lamp illumination (1mW/cm2), which is 2.65 times compared to that of the pure TNTAs photoelectrode. Electrochemistry impedance spectroscopy and Mott-Schottky analysis were conducted to explore the reasons for the enhancement of the PEC performance. Pt NPs could promote the reduction of Co(Ⅳ)-oxo intermediate to Co(II) or Co(Ⅲ) which facilitated the charge transfer in the PEC performance. The result provides a promising guideline to design a simple and efficient photoelectrode for the PEC water-splitting system.

Synthesis, surface properties, crystal structure and dye sensitized solar cell performance of TiO2 nanotube arrays anodized under different voltages

In this study, anodic TiO2 nanotube (TNT) arrays with average nanotube diameter from 26 nm to 115 nm and length from 1.3 μm to 6.4 μm were grown by electrochemical method. Anodization process were performed under different voltages from 10 to 50 V in ethylene glycol – ammonium fluoride – water electrolyte. Formation mechanism of TNTs was summarized. Surface morphology, crystal structure, roughness, wettability and elasticity of TNT arrays were characterized by using field emission scanning electron microscope (FESEM), X-Ray diffraction (XRD), atomic force microscope (AFM), optical tensiometer and universal mechanical tester, respectively. Water contact angle measurements and nanoindentation tests proved that water contact angle and elastic modulus of TNT arrays decrease with increasing anodization voltage. Photocurrent-photovoltage curves and electrochemical impedance spectroscopy (EIS) measurements of dye sensitized solar cells (DSSC) were made to investigate the effects of anodization voltages on photoanode performance. The light conversion efficiency and photocurrent density of TNT photoanodes was increased with increasing anodization voltage due to larger nanotube length and surface area. The results show that anodization voltage is significant parameter for the surface properties and dye sensitized solar cell (DSSC) performance TNT arrays.

Theoretical and experimental studies on the anodic oxidation process for synthesis of self-ordering TiO2 nanotubes: Effect of TiO2 nanotube lengths on photocatalytic activity

In this study, TiO2 nanotubes were synthesized via anodic electrochemical oxidation method and the effects of different parameters such as applied voltage, anodization time, electrolyte solution temperature and pH on the outer diameter and length of TiO2 nanotubes in a NH4F/C2H6O2/H2O electrolyte system were investigated. Based on the experiments, length and outer diameter of the synthesized nanotubes were in the range of approximately 9–71μm and 81–171nm respectively which were found by scanning electron microscopy (SEM) analysis technique. Also a generalized theoretical model was developed to predict the morphology (length and outer diameter) of TiO2 nanotubes prepared by anodization method. The collected experimental data based on classic design was used to obtain adjustable parameters in the presented model.Photocatalytic activity of different lengths TiO2 nanotubes were evaluated in terms of the degradation of formic acid in aqueous solution under ultraviolet (UV) light irradiation. Results showed that the optimal tube length would be an important factor to achieve the good photocatalytic performance of TiO2 nanotube arrays. The highest photocatalytic performance was found for the synthesized TiO2 nanotubes with 46μm length.

The Effect of the Heating Rate on Anatase Crystal Orientation and Its Impact on the Photoelectrocatalytic Performance of TiO2 Nanotube Arrays

Tuning the degree of anatase crystal orientation in TiO2 nanotube arrays has emerged as a new strategy to control their photoelectrochemical performance, since electron transport through the nanotubular film is favored. However, the existing literature fails to provide an accurate approach to evaluate the impact of anatase crystal orientation, since it is normally studied using TiO2 nanotube films synthesized in different anodizing baths, which in turn affects the properties of the films. In this work, anatase crystal orientation was controlled by changing the heating rate during sample heat-treatment (450°C for 30 min), which resulted in randomly oriented anatase crystals when the film was taken from room temperature to 450°C, to highly crystalline films with preferential anatase crystal orientation when the heating rate was decreased to 5 °C min−1 and 1 °C min−1. Even though the physicochemical properties of the films were almost unaltered, increasing anatase crystal orientation resulted in higher photocurrents and photoelectrocatalytic methyl orange discoloration, showing a maximum for the film treated at a heating rate of 5°C min−1.

Remarkable supercapacitive performance of TiO2 nanotube arrays by introduction of oxygen vacancies

Highly ordered TiO2 nanotube arrays (TNAs) with large specific surface exhibit excellent electrochemical performance but their poor electrical conductivity limits the practical applications in supercapacitor. Here, we present a simple strategy for improving the electrical conductivity of TNAs by introduction of oxygen vacancies in NaBH4 aqueous solution. The reduced TNAs (rTNAs) electrodes exhibit significant improvement on electrical conductivity and carrier density compared to those of the pristine TNAs. Interestingly, the rTNAs electrode obtained from 5M NaBH4 aqueous solution exhibits the highest specific capacitance of 23.24mFcm−2 at a scan rate of 2mVs−1 with outstanding long term cycling stability. Moreover, the reduced MnCo2O4/TNAs electrodes are also prepared by a facile chemical bath deposition method and then reduced in NaBH4 aqueous solution. The reduced MnCo2O4/TNAs electrode prepared in 5M NaBH4 aqueous solution achieves a high specific capacitance of 484.35mFcm−2 at a scan rate of 2mVs−1. The enhancement of capacitance and cycling stability of reduced MnCo2O4/TNAs electrodes can be attributed to the improved electrical conductivity of MnCo2O4/TNAs by introduction of oxygen vacancies and the tubular structure of TNAs that accelerate the electron and ions transport.

Enhancing photoelectrochemical performance of TiO2 nanotube arrays by CdS and Bi2S3 co-sensitization

TiO2 nanotube arrays (TiO2 NTs) were prepared by a two-step anodization of titanium foils in ethylene glycol electrolyte. Then, CdS and Bi2S3 nanoparticles were deposited on TiO2 NTs by an one-pot solvothermal method. The investigations of X-ray diffraction and scanning electron microscopy indicated that CdS and Bi2S3 nanoparticles grew uniformly on the surface of TiO2 NTs. UV–vis absorption and photoelectrochemical measurements proved that the CdS and Bi2S3 co-sensitization significantly improved the visible light absorption, photocurrent response and photoelectrocatalytic removal of RhB and Cr(VI). In addition, the influence of Cd2+/Bi3+ concentration ratios on the photoelectrochemical performance of TiO2 NTs-CdS/Bi2S3 was investigated in detail. The TiO2 NTs-CdS/Bi2S3 (1:1) showed an optimal photoelectrochemical activity which could be attributed to the improvement of visible light response and charge separation derived from the coupling effect of CdS/Bi2S3 nanoparticles.

Nanoindentation study of the mechanical behavior of TiO2 nanotube arrays

Titanium dioxide (TiO2) nanotube arrays are attracting increasing attention for use in solar cells, lithium-ion batteries, and biomedical implants. To take full advantage of their unique physical properties, such arrays need to maintain adequate mechanical integrity in applications. However, the mechanical performance of TiO2 nanotube arrays is not well understood. In this work, we investigate the deformation and failure of TiO2 nanotube arrays using the nanoindentation technique. We found that the load–displacement response of the arrays strongly depends on the indentation depth and indenter shape. Substrate-independent elastic modulus and hardness can be obtained when the indentation depth is less than 2.5% of the array height. The deformation mechanisms of TiO2 nanotube arrays by Berkovich and conical indenters are closely associated with the densification of TiO2 nanotubes under compression. A theoretical model for deformation of the arrays under a large-radius conical indenter is also proposed.