1D TiO2 Nanostructures Research Articles

The Role of Cerium Valence in the Conversion Temperature of H2Ti3O7 Nanoribbons to TiO2-B and Anatase Nanoribbons, and Further to Rutile.

CeO2-TiO2 is an important mixed oxide due to its catalytic properties, particularly in heterogeneous photocatalysis. This study presents a straightforward method to obtain 1D TiO2 nanostructures decorated with CeO2 nanoparticles at the surface. As the precursor, we used H2Ti3O7 nanoribbons prepared from sodium titanate nanoribbons by ion exchange. Two cerium sources with an oxidation state of +3 and +4 were used to obtain mixed oxides. HAADF-STEM mapping of the Ce4+-modified nanoribbons revealed a thin continuous layer at the surface of the H2Ti3O7 nanoribbons, while Ce3+ cerium ions intercalated partially between the titanate layers. The phase composition and morphology changes were monitored during calcination between 620 °C and 960 °C. Thermal treatment led to the formation of CeO2 nanoparticles on the surface of the TiO2 nanoribbons, whose size increased with the calcination temperature. The use of Ce4+ raised the temperature required for converting H2Ti3O7 to TiO2-B by approximately 200 °C, and the temperature for the formation of anatase. For the Ce3+ batch, the presence of cerium inhibited the conversion to rutile. Analysis of cerium oxidation states revealed the existence of both +4 and +3 in all calcined samples, regardless of the initial cerium oxidation state.

Electron transport engineering with different types of titanium dioxide nanostructures in perovskite solar cells

The light-harvesting effects and electron transport engineering could be achieved by manipulating electron transport layer (ETL) morphology. In This research, three variant nanostructures (NSs) of titanium dioxide (TiO2) have been applied as the ETL in conventional structure of perovskite solar cells (PSCs). Device structures of FTO/TiO2 compact layer/TiO2 NS layer/Perovskite/Spiro-OMeTAD/Au are used for the fabrication of PSCs in ambient conditions. Zero and one-dimensional structures of TiO2 including TiO2 nanocrystals (NCs) with the dominant size of 25 nm, TiO2 nanorods (NRs) with diameters and lengths about 80 nm and 1–2 µm, and TiO2 nanofibers (NFs) with the same dimensional parameters of 100 nm and 2–12 µm were prepared through the hydrothermal method. Then the effects of ETL morphology on the electron transporting process, interfacial engineering, surface quality and cell performance have been investigated. Triple Cation Cs0.05(MA0.17-FA0.83)0.95Pb(I0.83Br0.17)3 perovskite is also used as the light harvester layer in PSCs due to its proper band gap energy, crystalline quality and longtime stability. According to the results, one-dimensional (1D) TiO2 nanostructures with medium size released the best current density of 21.9 mA/cm2 and maximum filling factor of 0.7. That is while the incomplete pore filling of the sublayer and lower open circuit voltage (VOC) 0.905 V had negative impacts on the power conversion efficiency of TiO2 NRs included perovskite solar cells. Remarkable results were achieved for the PSC with zero-dimensional (0D) TiO2 nanostructures as the compact ETL and highest VOC of 1.02 V led to the maximum power conversion efficiency of 14.88 % in ambient conditions.

Growth of 1D TiO2 nanostructures on Ti substrates incorporated with residual stress through humid oxidation and their characterizations

Different Ti substrates, such as particles (as-received and ball milled), plate and TEM grid were oxidized for the growth of one dimensional (1D) TiO2 nanostructures. The Ti substrates were oxidized for 4 h at temperatures of 700 °C–750 °C in humid and dry Ar containing 5 ppm of O2. The effects of residual stress on the growth of 1D TiO2 nanostructures were investigated. The residual stress inside the Ti particles was measured by XRD-sin2 ψ technique. The oxidized Ti substrates were characterized using field emission scanning electron microscope equipped with energy dispersive x-ray spectroscope, transmission electron microscope, x-ray diffractometer and x-ray photoelectron spectroscope. Results revealed that humid environment enhances the growth of 1D TiO2 nanostructures. Four different types of 1D morphologies obtained during humid oxidation, e.g. stacked, ribbon, plateau and lamp-post shaped nanostructures. The presence of residual stress significantly enhances the density and coverage of 1D nanostructures. The as-grown TiO2 nanostructures possess tetragonal rutile structure having length up to 10 μm along the 〈1 0 1〉 directions. During initial stage of oxidation, a TiO2 layer is formed on Ti substrate. Lower valence oxides (Ti3O5, Ti2O3 and TiO) then form underneath the TiO2 layer and induce stress at the interface of oxide layers. The induced stress plays significant role on the growth of 1D TiO2 nanostructures. The induced stress is relaxed by creating new surfaces in the form of 1D TiO2 nanostructures. A diffusion based model is proposed to explain the mechanism of 1D TiO2 growth during humid oxidation of Ti. The 1D TiO2 nanostructures and TiO2 layer is formed by the interstitial diffusion of Ti4+ ions to the surface and reacts with the surface adsorbed hydroxide ions (OH−). Lower valence oxides are formed at the metal-oxide interface by the reaction between diffused oxygen ions and Ti ions.

Promoting the photo-induced charge separation and photoelectrocatalytic hydrogen generation: Z-scheme configuration of WO3 quantum nanodots-decorated immobilized Ti/TiO2 nanorods

The photoelectrocatalytic hydrogen production, especially using 1D TiO2 nanostructures, has been considered as a clean and sustainable approach to cope with energy crisis. Nevertheless, the large band gap energy of TiO2 and the rapid photo-induced charges recombination have limited its practical application. Therefore, in this study, WO3 quantum nanodots were employed with immobilized TiO2 nanorod arrays (TNRs-WQNDs) to tackle these drawbacks. Based on the results, the incorporation of WQNDs ameliorated both the optical and photoelectrochemical properties of TNRs. In this relation, the introduction of WQNDs into TNRs lattice using 10 mg WCL4 (TNRs-WQNDs (10)), as the optimum amount of tungsten precursor, not only made band gap energy much narrower (from 3 to 2.1 eV), but also significantly improved the photocurrent density from 0.92 to 1.67 mA/cm2 (at 1.23 V vs. RHE). In addition, both the STH and photoconversion efficiencies of TNRs-WQNDs (10) were about 1.7 and 1.5 times more than those of pure TNRs, respectively. As a result of these enchantments, the coupling of WQNDs with TNRs was able to increase the photoelectrocatalytic hydrogen production from 1.4 to 2.4 mmol under UV irradiation. An acceptable photoelectrocatalytic performance was further observed under visible light irradiation, where TNRs-WQNDs (10) could generate almost 1.5 mmol of hydrogen. Meanwhile, by investigating the mechanism of photoelectrocatalytic hydrogen production, it was revealed that the reaction pathways over TNRs-WQNDs (10) conformed to the Z-scheme theory. Finally, the fifth incessant cycled test indicated that TNRs-WQNDs (10) photoanode had excellent chemical stability and low photo-corrosion ability.

Rational Regulation of Surface Free Radicals on TiO2 Nanotube Arrays via Ag2O-AgBiO3 towards Enhanced Selective Photoelectrochemical Detection.

Due to integrated advances in photoelectrochemical (PEC) functionalities for environment detection applications, one-dimensional (1D) TiO2 nanostructures provide a new strategy (PEC sensors) towards organics detection in wastewater. However, the unidealized selectivity to the oxidation of water and organics limits the PEC detection performance. Herein, we designed a ternary photoanode consisting of Ag2O–AgBiO3/TiO2 nanotube arrays (NTAs) to solve this issue by using a facile one-step precipitation reaction. High oxidation capacity for organics is achieved by regulating the surface free radicals properly through the heterostructure formed between the interface of TiO2 and AgBiO3. More importantly, as a trap for electron capture, Ag2O in this ternary system could not only further improve the separation efficiency of charge carriers, but also capture electrons transferred to the TiO2 conduction band, thus reducing the electrons transferred to the external circuit and the corresponding background photocurrent when detecting organics. As a result, the reconstructed TiO2 NTAs decrease their photocurrent response to water and enhance their response to organics, thus presenting lower oxidation activity to water and higher activity to organics, that is, highly selective oxidation characteristics. This work provides more insights into the impact of charge transfer and surface free radicals on developing promising and efficient PEC sensors for organics.

Enhanced photocatalytic activity in TiO2 mixed phase nanostructures

Titanium dioxide (TiO2) is one of the most effective n-type semiconductors for photocatalytic applications. Compared with the bulk TiO2 nanostructures, the one-dimensional (1D) TiO2 nanostructures have elicited great interest due to its various advantageous properties such as high surface-volume ratio, high chemical stability, strong oxidizing power, nontoxicity and low cost. TiO2exists mainly in two crystalline phases namely anatase and rutile. When different phases of TiO2are combined, they have better charge transport and light absorption properties than pristine nanotubes and nanorods. In reference to that, mixed phases play an important role in the modification of the photocatalytic properties.In the present work, three different nanostructures (TiO2 nanotubes, nanorods and mixed phase nanohybrids) are fabricated by electrochemical anodization and hydrothermal processes, respectively. TiO2 nanotubes are synthesized by electrochemical anodization of highly pure titanium foil in a solution containing ethylene glycol, ammonium fluoride and distilled water, TiO2 nanorods are grown on fluorine-doped tin oxide (FTO) using a hydrothermal method and hybrid TiO2 nanostructures consisting of rutile TiO2 nanorods synthesized by hydrothermal method on anodized TiO2 nanotubes in a high temperature and high-pressure condition with titanium-n-butoxide as the reaction precursor. The three different morphologies of nanotubes, nanorods and nanohybrids are investigated using scanning electron microscopy (SEM). The crystallinity of the TiO2 nanotubes, nanorods and nanohybrids are studied using Raman spectroscopy and X-ray diffraction (XRD) techniques. TiO2 nanotubes, nanorods and nanohybrids are crystalized in anatase, rutile and mixed phase (anatase and rutile), respectively. The structural transformation of the formed TiO2 nanohybrid is compared with TiO2 nanorods and nanotubes that further be explored for photocatalysis by degradation of methylene blue (10 μM) under xenon lamp in the presence of catalysts. It is observed that overall photocatalytic activity of mixed phase TiO2 nanohybrids is better than TiO2 nanotubes and nanorods owing to better electron hole separation and transportation.

Performance of TiO2 Fibers Prepared by Electrostatic Spinning As Lithium-Ion Battery Anode Material

This paper reports a one-dimensional (1D) TiO2 nanostructure with significantly enhanced conductivity. Anatase TiO2 with a 1D nanostructure was successfully prepared by the electrostatic spinning method, and the effect of calcination temperature on its electrochemical performance was studied. The samples prepared at different calcining temperatures (400, 450, and 480°C) were analyzed by physical and electrochemical methods to identify the optimal heat-treatment conditions. Temperature was found to be another important factor influencing the electrochemical performance of 1D materials besides their structure and morphology. The anatase TiO2 calcined at 450°C had a discharge capacity of 192.8 mA h g–1 at 0.2 C with over 96% capacity retention after 100 cycles. The improved lithium-ion intercalation properties of the rod-shaped TiO2 might be attributed to the relatively large specific surface area, short transport distance of the 1D structure, and freedom for the volume change accompanying lithium-ion intercalation.

Alkaline Hydrothermal Synthesis, Characterization, and Photocatalytic Activity of TiO₂ Nanostructures: The Effect of Initial TiO₂ Phase.

One-dimensional (1D) titanate nanostructures were synthesized by hydrothermal route, using commercially available TiO₂ (P25) and anatase powders as precursor materials and strong NaOH solution as catalyzer. The prepared titanates were calcined, followed by protonation to produce TiO₂ nanostructures having enhanced photocatalytic and photovoltaic properties. The synthesized TiO₂ 1D nanostructures were characterized using field-emission scanning electron microscope, high-resolution electron microscope, X-ray diffraction analysis, and UV-Vis photospectroscopy to understand the effect of initial TiO₂ phase on morphological and crystallographic features, and bandgap. Methylene blue degradation test was applied to evaluate the photoactivity of the products obtained after different stages of the process. The findings indicate that 1D TiO₂ nanostructures form by different mechanisms from dissolved aggregates during hydrothermal process, depending on the crystal structure of the initial precursor used. Photocatalytic test results reveal that protonated titanates have considerable adsorption capability, while photocatalytic degradation depends on TiO₂ transformation.

The influence of the morphology of 1D TiO2 nanostructures on photogeneration of reactive oxygen species and enhanced photocatalytic activity

The influence of morphology in one-dimensional (1D) TiO2 nanostructures—specifically nanotubes (TNT), nanofibers (TNF), nanorods (TNR), and nanowires (TNW)—on the photogeneration of reactive oxygen species (ROS) and the resulting effect on photocatalytic activity were investigated. 1D TiO2 nanostructures were obtained by hydrothermal route, by employing changes in the crystalline phase of TiO2 precursor and reaction temperature as the morphology-controlling factors. Morphological, structural, textural, and optical properties were studied using scanning and transmission electron microscopy, X-ray diffraction, BET surface area analysis, diffuse reflectance and photoluminescence spectroscopy. The photochemical behaviour of these 1D TiO2 nanostructures was evaluated through ROS quantification including 1O2 and OH, and it was found that TNF exhibits the highest amount of generated ROS, the following tendency was observed: TNF > TNT > TNR > TNW. In addition, the photocatalytic activity for degrading methyl orange (MO) under visible light was studied, and a similar tendency was found. The results showed a more intense photoluminescence emission spectra signal for TNF, suggesting a higher concentration of superficial defects associated with oxygen vacancies (Ov), the same trend on the resulting Ov amount was established. Finally, a correlation between 1D morphology, ROS photogeneration as well as photocatalytic properties was determined. The results suggest the amount of Ov on each material act as active sites that improve the production of ROS as well as the photocatalytic activity. These results unveiled that generation of ROS is mainly dependent on the morphology type of 1D TiO2 nanostructures, significantly affecting the photocatalytic activity of nanomaterial.

One-dimension TiO2 nanostructures with enhanced activity for CO2 photocatalytic reduction

The one dimension (1D) TiO2 nanotubes and nanorods were successfully prepared via a one-step hydrothermal method. The structure and properties of the catalysts were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), Electron paramagnetic resonance (EPR), N2 adsorption-desorption, UV–vis diffuse reflectance and photoluminescence (PL) spectroscopy. Meanwhile, the photoelectrochemical properties were recorded through Mott-Schottky, transient photo-current responses and electrochemical impedance spectroscopy curves (EIS). The results showed that 1D TiO2 nanostructures catalysts had a high specific surface area, enhanced visible light response and superior electron transport properties. The photocatalytic activities of catalysts for reduction CO2 were investigated under 9 h irradiation of a 300 W Xe arc lamp equipped with UV 420 nm bandpass filter. The maximum yields of CH4 over the TiO2 nanotubes (TNT) and TiO2 nanorods (TNR) were 19.16 μmol/g.cat and 12.71 μmol/g.cat, respectively, which were approximately 2.33 folds and 1.48 folds higher than TiO2 nanoparticles (TNP). The enhanced photocatalytic activity of TiO2 nanotubes and nanorods could be ascribed to the presence of oxygen vacancies and defects formed during the calcination process and its special structures, which accelerates the transfer of electrons. Besides, the better activity of TNT than TNR may be ascribed to its unique hollow tubular structure and larger surface area.

Hydrothermally grown 3D hierarchical TiO2 based on electrochemically anodized 1D TiO2 nanostructure for supercapacitor

In the present study, the simple facile chemical approaches have been used to grow one dimensional (1D) titanium dioxide (TiO2) nanotubes and three dimensional (3D) microflowers over 1D (3D–1D) TiO2 hierarchical for supercapacitor. Here, 1D TiO2 nanotubes are synthesized by electrochemical anodization and 3D–1D TiO2 microflowers have been successfully synthesized by hydrothermally grown 3D microflowers on predeposited 1D TiO2 nanotubes. Furthermore, TiO2 films have been characterized by X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectrometry, contact angle measurements and electrochemical properties. The specific capacitance (Cs) values of 1D TiO2 and 3D–1D TiO2 have been calculated by cyclic voltammetry and charge discharge measurements. The improvement in Cs for 3D–1D nanostructure has been observed around 66.50 Fg−1, which is greater than that of 1D nanostructure 54.09 Fg−1 at 5 mV S−1 scan rate. Stability study revealed ~ 67% capacitance retention for 1D TiO2 nanotubes and 76% capacitance retention for 3D–1D TiO2 microflowers after 2000 cycles. These results indicate that the growth of 3D–1D TiO2 microflowers showed better performance than 1D TiO2 nanotubes for supercapacitor application.

Morphological control of 1D and 3D TiO2 nanostructures with ammonium hydroxide and TiO2 compact layer on FTO coated glass in hydrothermal synthesis

The effects of ammonium hydroxide (AH) concentration in the hydrothermal reaction precursors and time on growth, morphological, optical and spectroscopic properties of TiO2 nanostructures have been investigated in detail. The dandelion nanostructures were also observed on the top surface of vertically aligned nanorods whose density increases with increase in AH concentration and reaction time. Dandelion nanostructures were also observed on top of vertically aligned nanorods surface whose density increases with increase in AH concentration and reaction time. The average nanorod length increases with an enhancement in the second generation of nanorods with AH addition. In the case where C-layer was deposited on FTO, the dandelion structures grown via hydrothermal technique were denser exhibiting transformation to flower like morphology. Hence, with AH addition, the formation of 1D/3D (aligned nanorods/dandelion structures) structure has been observed. AH plays crucial role by facilitating second generation crystallite growth and significantly effects resultant morphology. Specifically, the structures grown with AH addition; i.e. primary, first generation and second generation crystals have been observed to be different. Both Raman and XRD studies revealed that nanorods were crystalline (rutile phase) while the C-layer exhibited anatase phase and no extra phase appeared in the spectra. The reflectance increase has been observed with increasing concentration of AH and temperature which is attributed to the increased scattering by dandelion-like structures.

Nano-Heteroarchitectures of Two-Dimensional MoS2@ One-Dimensional Brookite TiO2 Nanorods: Prominent Electron Emitters for Displays.

We report comparative field electron emission (FE) studies on a large-area array of two-dimensional MoS2-coated @ one-dimensional (1D) brookite (β) TiO2 nanorods synthesized on Si substrate utilizing hot-filament metal vapor deposition technique and pulsed laser deposition method, independently. The 10 nm wide and 760 nm long 1D β-TiO2 nanorods were coated with MoS2 layers of thickness ∼4 (±2), 20 (±3), and 40 (±3) nm. The turn-on field (Eon) of 2.5 V/μm required to a draw current density of 10 μA/cm2 observed for MoS2-coated 1D β-TiO2 nanorods emitters is significantly lower than that of doped/undoped 1D TiO2 nanostructures, pristine MoS2 sheets, MoS2@SnO2, and TiO2@MoS2 heterostructure-based field emitters. The orthodoxy test confirms the viability of the field emission measurements, specifically field enhancement factor (βFE) of the MoS2@TiO2/Si emitters. The enhanced FE behavior of the MoS2@TiO2/Si emitter can be attributed to the modulation of the electronic properties due to heterostructure and interface effects, in addition to the high aspect ratio of the vertically aligned TiO2 nanorods. Furthermore, these MoS2@TiO2/Si emitters exhibit better emission stability. The results obtained herein suggest that the heteroarchitecture of MoS2@β-TiO2 nanorods holds the potential for their applications in FE-based nanoelectronic devices such as displays and electron sources. Moreover, the strategy employed here to enhance the FE behavior via rational design of heteroarchitecture structure can be further extended to improve other functionalities of various nanomaterials.

Photocatalytic Properties of 1D TiO2 Nanostructures Prepared from Polyacrylamide Gel–TiO2 Nanopowders by Hydrothermal Synthesis

In the present study, the polyacrylamide gel (PAG) route was employed to synthesize a nanosized TiO2 powder (PAG–TiO2). The resultant PAG–TiO2 and commercial TiO2 (P25‐TiO2) nanopowders were then used as the starting materials to hydrothermally synthesize one‐dimensional (1D) TiO2 nanostructures (nanotubes and nanorods). Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) analysis, X‐ray diffraction (XRD), and thermogravimetric analysis (TGA) were used to characterize the synthesized TiO2 nanostructures. The TiO2 nanopowders, calcined at 400 °C, were further examined for their photocatalytic performance in the decomposition of formic acid as an organic pollutant. The results demonstrate a superior quality of nanotubes synthesized from the PAG–TiO2 nanoparticles as well as enhanced photocatalytic activity compared to the nanotubes synthesized from commercial P25‐TiO2. For the first time, the effect of PAG–TiO2 nanoparticles as starting material of the hydrothermal reaction on morphology and photocatalytic performance of the resulting nanostructures was investigated.

One-Dimensional TiO2 Nanostructured Photoanodes: From Dye-Sensitised Solar Cells to Perovskite Solar Cells

This review presents one dimensional (1D) TiO2 nanostructured photoanodes for next generation solar cells such as dye-sensitised solar cells (DSCs) and perovskite solar cells (PSCs). Due to the unique morphological properties, 1D TiO2 nanostructures can act as express electron channels as well as light scattering layer, leading to improved charge transport properties, such as charge separation, electron injection, and electron lifetime, and light harvesting efficiency. As 1D TiO2 nanostructures are applied to solar cells, 1D TiO2 nanostructures should be further modified to overcome some drawbacks. In this review, we have described some solutions by introducing various 1D TiO2 synthetic methods and device fabrication processes for solar cell applications, where we have described some important surface engineering and hierarchical device design strategies that facilitate charge transport and light utilisation in 1D TiO2 nanostructured photoanode system.

Photoelectrochemical and structural properties of TiO2 nanotubes and nanorods grown on FTO substrate: Comparative study between electrochemical anodization and hydrothermal method used for the nanostructures fabrication

Titanium dioxide in the form of one-dimensional (1D) nanostructure arrays represent widely studied morphological arrangement for light harvesting and charge transfer applications such as photocatalysis and photoelectrochemistry (PEC). Here we report a comparative structural and PEC study of variously grown 1D TiO2 nanostructures including i) nanorod arrays prepared by a hydrothermal method (TNR), ii) nanotube arrays fabricated by a two-step hydrothermal method using a ZnO nanorod array film as a template (THNT) and finally iii) nanotubes grown by self-organized electrochemical anodization of Ti films deposited on the FTO substrate (TNT). These nanostructures are assumed to be utilized as photoanodes in PEC water splitting devices. Field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), TEM images and UV–vis absorption spectra were used to characterize TiO2 nanostructures. The SEM and TEM morphology images revealed that the main difference among the nanostructures grown on the FTO are the shape and diameter of the individual nanotubes/nanorods and also the array’s density in the range of TNR>THNT>TNT and the degree of organization in the range of TNT>TNR>THNT. The obtained photocurrents at 0V vs. Ag/AgCl increased in the order of THNT (110μAcm−2)<TNT (185μAcm−2)<TNR (630μAcm−2). Extended electron lifetime and light absorption shifted to the longer wavelengths were attributed to the enhanced PEC performance of TNR.

Strategy for enhancing the solar-driven water splitting performance of TiO2 nanorod arrays with thin Zn(O,S) passivated layer by atomic layer deposition

An array of one dimensional (1D) TiO2 nanorods (TONRs) has been regarded as an attractive candidate for electrochemical energy conversion and as storage device due to its large surface area, effiective light scattering, and undisturbed charge transport pathway. However, the high defect/trap densities on surface of the nanostructured morphology and architecture may generally hinder the performance enhancement by providing electron-hole recombination sites. Hence, the surface passivation of nanoarchitectures based photoelectrodes has recently received much attention as an effective strategy to enhance the charge-separation and charge-transfer processes in photoelectrochemical (PEC) water splitting devices. In particular, a coating layer with narrowing band gap materials can promote enhanced light harvesting in the UV–vis region as well as surface passivation, directly supplying a driving force for charge separation and charge transfer due to band alignment. In this paper, the surface of TONRs were passivated by 10 and 30nm thick Zn(O,S) layers with a relatively narrow band gap using an atomic layer deposition technique to modulate the thickness exactly. The 10nm Zn(O,S)/TONR array exhibits a significantly enhanced photocurrent density (Jsc) of 5.94mA/cm2 at 1.23eV vs NHE and an incident photon-to-electron conversion efficiency (IPCE) of 49% at 374nm compared with that of TONR arrays (Jsc of 1.99mA/cm2 at 1.23eV vs NHE and an IPCE of 20% at 380nm). However, the PEC performance is worse in the 30nm Zn(O,S)/TONR arrays, showing a Jsc of 3.09mA/cm2 at 1.23eV vs NHE and an IPCE of 29% at 374nm. To clearly demonstrate these PEC behaviors, the TONR and Zn(O,S)/TONR arrays were characterized by electrochemical impedance spectroscopy (EIS), open circuit voltage decay (OCV) measurement, and X-ray photoelectron spectroscopy (XPS). The above mentioned characterizations indicate that the enhanced PEC performance of the 10nm Zn(O,S)/TONR array resulted from the (i) increased light harvesting in the UV–vis region, (ii) lower charge transfer resistance and (iii) high value of valence band offset (VBO, −1.44eV) and conduction band offset (CBO, −1.2eV) than those of the TONR. However, the deterioration of Jsc in the 30nm Zn(O,S)/TONR array is attributed to the negative value of VBO (-0.13eV) and positive value of CBO (+0.27eV), as well as the higher charge transfer resistance to the electrolyte than that of the TONR arrays, despite of the improved light absorption in the visible region. The photocurrent densities of 10nm Zn(O,S)/TONR and 30nm Zn(O,S)/TONR photocathodes decay to 4.718mA/cm2 (5.90mA/cm2 at 0min) and 2.212mA/cm2 (3.03mA/cm2 at 0min) after 90min, respectively, they retain of about∼80% and 70% of its original values. These experimental results and discussions not only provide the physical insights into the surface passivation effect and band alignment but also can open a promising route to design the thin passivation layer having the narrowing band gap energy (1.0eV∼2.5eV) on the 1D TiO2 nanostructure for further enhanced performance and realization of a TiO2 based PEC system.

A review of one-dimensional TiO2nanostructured materials for environmental and energy applications

State-of-the-art development of fabrication methods and surface engineering strategies of 1D TiO2nanostructures is reviewed, and an overview given of their potential applications including pollutant degradation/CO2photoreduction photocatalysts, water splitting, solar cells, lithium-ion batteries and supercapacitors.

Ru nanoparticles decorated TiO2 nanobelts: A heterostructure towards enhanced photocatalytic activity and gas-phase selective oxidation of benzyl alcohol

One-dimensional (1D) TiO2 nanostructures can be used as the support of metal particles to form the heterostructures, which can prevent the metal agglomeration and enhance the activity of metal in various applications. Here, well-dispersed Ru nanoparticles (NPs) supported on 1D TiO2 nanobelts (NBs) are firstly synthesized by a facile photo-reduction method. The as-synthesized Ru/TiO2 NB heterostructures exhibit an improved photocatalytic performance compared with P25 and TiO2 under both UV and visible light irradiation. Our mechanistic investigation reveals that the enhanced photocatalytic activity can be attributed to the Schottky barrier effect of Ru NPs, which efficiently harvest the electrons of TiO2 and enhance the separation of photogenerated electron–hole pairs. Moreover, the Ru/TiO2 NB heterostructures are assembled into the porous nanopaper via a modified paper-making process, which can be applied in heterogeneous catalysis. The formed Ru/TiO2 NB heterostructure nanopapers exhibit enhanced activity and selectivity for catalyzing aerobic oxidation of benzyl alcohol. Ru NPs are well dispersed with the average size of about 1.5nm on the TiO2 NBs support, which could contribute to the high catalytic activity of Ru/TiO2 catalyst.

Stable and Efficient Perovskite Solar Cells Based on Titania Nanotube Arrays.

Highly ordered 1D TiO2 nanotube arrays are fabricated and applied as nanocontainers and electron transporting material in CH3 NH3 PbI3 perovskite solar cells. The optimized device shows a power conversion efficiency of 14.8%, and improved stability under an illumination of 100 mW cm(-2). This is the best result based on 1D TiO2 nanostructures so far.