TiO2 NTs Electrode Research Articles

Liposome-assisted chemical redox cycling strategy for advanced signal amplification: A proof-of-concept toward sensitive electrochemiluminescence immunoassay

This work presents a novel signal amplification strategy for electrochemiluminescence (ECL) biosensor based on liposome-assisted chemical redox cycling for in situ formation of Au nanoparticles (Au NPs) on TiO2 nanotubes (TiO2 NTs) electrode. The system was exemplified by ascorbic acid (AA)-loaded liposome, the redox cycling of AA utilizing tris (2-carboxyethyl) phosphine (TCEP) as reductant, and the use of Au nanoclusters (Au NCs)/TiO2 NTs as working electrode to implement the ECL detection of prostate specific antigen (PSA). Specifically, the AA-loaded liposomes were used as tags to label the captured PSA through a sandwich immunoreaction. After the lysate of the liposome was transferred onto the interface of Au NCs/TiO2 NTs in the presence of Au3+ and TECP, the chemical redox cycling was triggered. In the cycling, Au3+ was directly reduced in situ by AA to form Au NPs on Au NCs/TiO2 NTs electrode, whereas the oxidation product of AA was reduced by TCEP to regenerate AA. The large loading capacity of the liposome and chemical redox cycling resulted in the incomplete reduction of the Au NCs to Au NPs on the TiO2 NTs electrode, enhancing the ECL intensity greatly. The multiple signal amplification strategy achieved an ultrasensitive detection for PSA with a detection limit down to 6.7 × 10−15 g mL−1 and a wide linear concentration range from 1.0 × 10−14 to 1.0 × 10−8 g mL−1. It is believed that this work is anticipated to extend the employment of advanced chemical redox cycling reaction in the field of ECL bioassays.

Photoelectrocatalytic treatment of recalcitrant compounds and bleach stage pulp and paper mill effluent using Au-TiO2 nanotube electrode

A simple anodization technique has been adopted for the synthesis of Au doped TiO2 nanotubes (Au/TiO2NTs) electrode. The physicochemical properties of Au/TiO2NTs electrodes have been studied using FE-SEM, Raman spectroscopy, FTIR, XRD, and UV–vis DRS analysis techniques and, compared with un-doped TiO2NTs electrodes. The optimization of process parameters has been carried out for the photoelectrocatalytic (PEC) degradation of 4-CG (4-Chloroguaiacol) under batch-mode experiments. Au/TiO2 nanotube electrodes showed 84% degradation efficiency in 6 h under optimized conditions viz. 0.15 mM Au loading, 0.08 g L−1 electrolyte concentration, 0.03 A current and pH 3 under UV light irradiations. The degradation of 4-CG was validated with the quantification of generated •OH and degradation intermediates/by-products during the batch-mode PEC treatment. The PEC process was observed to be more efficient for degrading and mineralizing 4-CG when compared to PC and EC processes, individually. PEC degradation of 4-CG has also been assessed in recirculation mode to study the feasibility of synthesized Au/TiO2NTs electrodes to treat large volume of contaminant polluted wastewater. For the feasibility of industrial scale applications, pulp and paper mill effluent was subjected to the PEC degradation under recirculation mode using Au/TiO2NTs electrodes and significant reduction in COD and TOC values were observed. Overall, the cost of electrical energy consumption was computed for all the batch and recirculation-mode PEC treatment of 4-CG as well as real pulp and paper mill effluent.

Removal of Nitrate Nitrogen by Microbial Photoelectrochemical Cell: PANI/TiO2-NTs as a Photoanode

The use of microbial photoelectrochemical cells (MPECs) for the removal of contaminants is a cost-effective and environment-friendly method. Based on the preparation of polyaniline/titanium dioxide nanotube array (PANI/TiO2-NTs) composite photoelectrodes, an MPEC system comprising PANI/TiO2-NTs photoanode and biocathode was constructed and the removal performance of nitrate nitrogen (NO3--N) was studied. The experimental results showed that the PANI/TiO2-NT electrode exhibited the best photoelectric performance when the PANI loading time was 80 s. Compared with the TiO2-NTs electrode, the photocurrent density doubled. The light-driven MPEC system could realize autotrophic denitrification without an external voltage. The biodegradation of NO3--N conformed to the pseudo first-order kinetics. The higher the photoresponse current density, the better the denitrification performance of the system. When the initial concentration of NO3--N was 25 mg·L-1 and the photoresponse current density increased from 0.17 mA·cm-2 to 0.67 mA·cm-2, the average denitrification rate increased from 0.83 mg·(L·h)-1 to 2.83 mg·(L·h)-1. High-throughput sequencing of the biocathode microbial membranes revealed that Pseudomonas (27.37%) was the dominant bacteria. It was considered that the photogenerated electrons generated by the PANI/TiO2-NTs photoanode were transmitted to the cathode through an external circuit. Pseudomonas and other microorganisms with autotrophic denitrification and electrochemical activity directly used the electrons on the electrode as the sole electron donors for autotrophic denitrification reaction.

Hydrogen evolution behavior of nickel coated TiO2

Nickel modified titanium dioxide nanotubes (TiO2-NTs/Ni) and TiO2-NTs electrodes are investigated for hydrogen evolution reaction (HER). To obtain large surface area, TiO2-NTs are prepared by using anodization method at a constant voltage of 60 V for various anodization times (30 min, 1 h and 2 h). Small amount of Ni is successfully deposited over TiO2-NTs via electrodeposition method. Hydrogen evolution activities of TiO2-NTs/Ni and TiO2-NTs are investigated in 1 M KOH solution at room temperature. Characterizations of prepared nano-structured electrodes are analyzed with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and cyclic voltammetry (CV) and electrochemical-activities are determined through cathodic current-potential curves and electrochemical impedance spectroscopy (EIS). Hydrogen volumes produced from prepared electrodes are also measured under constant voltage of 3 V for 30 min. Obtained results showed that hydrogen evolution activity increased with the modification of TiO2-NTs by nickel. High current density at specific overpotentials, hydrogen volume and small polarization resistance are obtained on TiO2-NTs/Ni. High stability and durability are also obtained on this electrode. So, TiO2-NTs/Ni as an electrocatalyst is suggested to use in water electrolysis systems.

Improving the Performance of All-Solid-State Microbatteries By Conformal Electrodeposition of Polymer Electrolyte into Self-Organized TiO2 Nanotubes

To date, microbatteries are in demand as small power sources to satisfy the market requirements with fast development of microelectronic devices. As more energy is required, a shift to all-solid-state 3D architectures has been proposed as a promising approach to tackle the challenge and achieve both high energy and power densities [1]. Hence, various types of microbatteries have been developed and are under investigation. It has been reported that self-organized TiO2 nanotubes (TiO2nts) can be utilized as anode material for Li-ion microbatteries [2]. The improved electrochemical performance of TiO2nts electrode has been mainly attributed to the larger surface area offered by 3D nanoarchitectured electrodes which is responsible for high reversible capacity, excellent rate capability and long cycle life [3]. To fabricate an all-solid-state Li-ion microbatteries, conventional liquid electrolytes need to be replaced by the solid electrolytes such as polymer electrolyte. We have reported that the electrodeposition of the polymer electrolyte into TiO2nts electrodes through cyclic voltammetry technique leads to the filling of the nanotubes by the thin polymer film [3]. In this work, we report the influence of the conformal electrodeposition on the full microbattery utilizing TiO2nts as anode, LiFePO4 as cathode and a drop-casted layer of methyl ether methacrylate-polyethylene glycol (MA-PEG) acting as electrolyte and separator. Clearly, the polymer-coated TiO2nts vs. LiFePO4 microbattery reaches higher capacity of ~98 mA h g-1 (~48 μAh cm-2 μm-1) compared to the bare TiO2nts vs. LiFePO4 microbattery (~12.5 mA h g-1 , ~6 μAh cm-2 μm-1) over 100 charge-discharge cycles. Galvanostatic charge-discharge profiles revealed the positive influence of electrochemical deposition of the polymer electrolyte into self-organized TiO2nts, as shown in Figure 1(a) and (b). In this communication, we will discuss the fabrication and characterization of all-solid-state microbatteries, as well as the influence of polymer-coated TiO2nts on their electrochemical performance.

Optical and Electrochemical Properties of Self-Organized TiO2 Nanotube Arrays From Anodized Ti-6Al-4V Alloy.

Due to their high specific surface area and advanced properties, TiO2 nanotubes (TiO2 NTs) have a great significance for production and storage of energy. In this paper, TiO2 NTs were synthesized from anodization of Ti-6Al-4V alloy at 60 V for 3 h in fluoride ethylene glycol electrolyte by varying the water content and further annealing treatment. The morphological, structural, optical and electrochemical performances of TiO2 NTs were investigated by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), UV-Visible spectroscopy and electrochemical characterization techniques. By varying the water content in the solution, a honeycomb and porous structure was obtained at low water content and the presence of (α + β) phase in Ti-6Al-4V alloy caused not uniform etching. With an additional increase in water content, a nanotubular structure is formed in the (α + β) phases with different morphological parameters. The anatase TiO2 NTs synthesized with 20 wt% H2O shows an improvement in absorption band that extends into the visible region due the presence of vanadium oxide in the structure and the effective band gap energy (Eg) value of 2.25 eV. The TiO2 NTs electrode also shows a good cycling performance, delivering a reversible capacity of 82 mAh.g−1 (34 μAh.cm−2.μm−1) at 1C rate over 50 cycles.

Co3O4 Nanoparticles Modified TiO2 Nanotube Arrays with Improved Photoelectrochemical Performance

Co3O4 modified TiO2 nanotube arrays (TiO2-NTs) were successfully fabricated by electrodeposition and thermal oxidation process. The prepared samples were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopic (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectroscopy. The photoelectrocatalytic properties of as-prepared samples were investigated under visible light and UV-vis light irradiation. Meanwhile, taking methyl orange aqueous solution as target substrate for photoelectrocatalytic degradation experiments, the degradation rate under UV-vis light irradiation and dark condition were evaluated. The prepared Co3O4/TiO2-NTs exhibited much higher photoelectrochemical activity than TiO2-NTs under visible light irradiation and UV-vis light irradiation. The degradation rate of methyl orange on Co3O4/TiO2-NTs electrode reaches 90.7% under applied potential of 1.3 V and UV-vis light irradiation for 10 h, which is only 53.4% on TiO2-NTs electrode. The improved performance could be attributed to the higher photo-generated carrier concentration and carrier mobility.

Hibiscus sabdariffa L. Anthocyanins Immobilization on TiO2 Nanotubes and Its Electrochemical Characterization as a Hydrogen Peroxide Sensing Electrode

The antioxidant activity of the Hibiscus sabdariffa L. (H.s.) used in the food-processing industry inspired a low cost and environmentally friendly chemical modification for a nanostructured electrode. Titanium dioxide nanotubes (TiO2-Nts) grown by anodic oxidation from Ti foil are well-known for their richness of adsorption sites for organic compounds and also for their great electron mobility allowance, which makes them an excellent choice for modified electrode engineering. This study evidences the complexation of the anthocyanins from H.s. to the TiO2-Nts electrode through FTIR and UV-Vis spectroscopy and electrochemical characterization (cyclic voltammetry). This novel electrode showed remarkable stability and regeneration capability. This research also establishes a new method to quantify hydrogen peroxide in solution with a limit of linearity of 2.50 × 10−4 M and a detection limit of 4.50 × 10−6 M.

Highly Efficient and Visible Light Responsive Heterojunction Composites as Dual Photoelectrodes for Photocatalytic Fuel Cell

In the present work, a novel photocatalytic fuel cell (PFC) system involving a dual heterojunction photoelectrodes, viz. polyaniline/TiO2 nanotubes (PANI/TiO2 NTs) photoanode and CuO/Co3O4 nanorods (CuO/Co3O4 NRs) photocathode, has been designed. Compared to TiO2 NTs electrode of PFC, the present heterojunction design not only enhances the visible light absorption but also offers the higher efficiency in degrading Rhodamine B–a model organic pollutant. The study includes an evaluation of the dual performance of the photoelectrodes as well. Under visible-light irradiation of 3 mW cm−2, the cell composed of the photoanode PANI/TiO2 NTs and CuO/Co3O4 NRs photocathode forms an interior bias of +0.24 V within the PFC system. This interior bias facilitated the transfer of electrons from the photoanode to photocathode across the external circuit and combined with the holes generated therein along with a simultaneous power production. In this manner, the separation of electron/hole pair was achieved in the photoelectrodes by releasing the holes and electrons of PANI/TiO2 NTs photoanode and CuO/Co3O4 NRs photocathode, respectively. Using this PFC system, the degradation of Rhodamine B in aqueous media was achieved to an extent of 68.5% within a reaction duration of a four-hour period besides a simultaneous power generation of 85 μA cm−2.

Influence of anodization mode on the morphology and photocatalytic activity of TiO2-NTs array large size electrodes

Properties of nanotubular titania structures (TiO2-NTs) have been widely evaluated in small electrodes at lab scale. A novel experimental approach to overcome the limitations for the anodization of large size electrodes is presented. Several potentiostatic and galvanostatic anodization procedures have been tested, and their impact on the morphological features of the TiO2-NTs analyzed. A clear relationship between the applied voltage and current density and the NTs length and diameter is confirmed. Photocatalytic activity of the TiO2-NTs structures was evaluated in the methanol oxidation reaction. From these results, it was obtained that kinetic constant for the photocatalytic oxidation of methanol is higher when the reaction is carried out with NTs of higher length/diameter aspect ratio. This is related to a higher TiO2 active surface area available to generate photo-induced electron-hole pairs and for the adsorption of the reactants. This work confirms the viability of formation of photocatalytically active large size TiO2-NTs electrodes when high voltage or current density is applied under controlled conditions. Availability of fluoride in the electrolyte can be ensured by the use of a novel concept of continuous flow anodization reactor allowing the renovation of the electrolyte to keep under control not only the composition but also the temperature of the solution.

Synergistic photoelectrochemical reduction of Cr(VI) and oxidation of organic pollutants by g-C3N4/TiO2-NTs electrodes

The g-C3N4/TiO2-NTs electrodes were synthesized by a dip-coating procedure followed by high-temperature annealing used in photoelectrochemical process. From the results, a simultaneous and rapid reduction of Cr(VI) and degradation of phenol in Cr(VI)/phenol system was observed with photoelectrocatalytic activity under UV–visible light irradiation than photocatalytic and electrocatalytic activities. The different kinds of Cr(VI)/organic pollutants systems were also investigated systematically. In addition, different scavengers were also added in Cr(VI)/phenol and Cr(VI)/benzyl alcohol systems to indicate that the hydroxyl radicals and superoxide radicals were the most major active species for the denomination of Cr(VI) and organic pollutants. The intermediates of phenol and benzyl alcohol were also detected during the reaction in order to deduce the photoelectrocatalysis mechanism underg-C3N4/TiO2-NTs electrodes that the charge separation was improved and subsequently electron-transfer efficiency was higher.

Three-dimensional nanostructures of multiwalled carbon nanotubes/graphene oxide/TiO2 nanotubes for supercapacitor applications

R(fMWCNT-GO)/TiO2NTs/Ti electrodes with three-dimensional nanostructures were prepared by co-electrochemical reduction of functionalized multiwalled carbon nanotubes (fMWCNTs) and graphene oxide (GO) onto TiO2 nanotubes/Ti. SEM studies revealed that the reduced fMWCNT-GO hybrid with highly network structures has been uniformly deposited onto the TiO2NTs arrays. The storage energy performance was investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy techniques in 1.0 M H2SO4 aqueous solution. The R(fMWCNT-GO)/TiO2NTs/Ti electrodes exhibit a high specific capacitance up to 600 F g−1 at 12 A g−1 in 1 M H2SO4 and a long cyclic durability with 90 % capacitance retention over 500 cycling, indicating a potential application in electrode material of supercapacitors. The high capacitance of R(GO-fMWCNT)/TiO2NTs electrode could be attributed to the functional groups of GO-fMWCNT, the 3D structures of the electrode and the highly electrical conductivity fMWCNT.

Effect of different nano-structured Ag doped TiO2-NTs fabricated by electrodeposition on the electrocatalytic hydrogen production

In this study, TiO2-NTs electrode was successfully fabricated by two-step anodization technique. Then, different Nano-structured Ag was loaded on the surface of as prepared TiO2-NTs using electrodeposition method at various deposition times. The morphology, composition and structure of Ag doped TiO2-NTs were determined by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The results showed that nanoparticle and nanodentrict Ag were formed on the TiO2-NTs depending on the deposition time and the particle size of anatase TiO2 increased with increasing Ag doping concentration. To evaluate the electrocatalytic properties of Ag doped TiO2-NTs towards the hydrogen evolution reaction (HER), the cyclic voltammetry, cathodic polarization curves and impedance measurements were recorded in 1 M KOH. The electrochemical data indicated that nanodentrict Ag doped TiO2, having the highest charge carrier density (9.02.1029 cm−3) as revealed by Mott–Schottky analysis, exhibits the most effective electrocatalytic activity towards the HER. In addition, long term stability of TiO2-NTs and Ag–TiO2-NTs electrodes and the energy requirement for the electrolytic hydrogen evolution were examined.

Copper nanoparticles sensitized TiO2 nanotube arrays electrode with enhanced photoelectrocatalytic activity for diclofenac degradation

Copper nanoparticles (NPs) deposited on the surface of self-organized highly ordered TiO2 nanotube arrays (Cu/TiO2 NTs) were synthesized by electrochemical anodization and the successive ionic layer adsorption and reaction technique. The morphology, elemental composition, crystallinity, light absorption ability and photoelectrochemical property of the as-prepared Cu/TiO2 NTs electrode were distinguished based on various characterizations. X-ray photoelectron spectroscopy showed that the Cu NPs existed as Cu(II)O and Cu(I)2O on the TiO2 surface. The current–voltage curve of Cu/TiO2 NTs electrode indicated a rectifying behavior. The surface sensitization of TiO2 NTs by CuO and Cu2O NPs enhanced the absorption of visible light. Meanwhile, the enhanced charge separation was demonstrated by electrochemical impedance spectroscopy, transient photocurrent response and photovoltage measurements. Besides, Cu/TiO2 NTs electrode showed more effective photoconversion efficiency and enhanced photoelectrocatalytic activity towards the degradation of diclofenac than pure TiO2 NTs electrode under simulated solar light irradiation, which was attributed to the synergistic effects between nanotubular structures of TiO2 and uniformly dispersed copper nanoparticles, as well as the small bias potential. Furthermore, the photoelectrocatalytic mechanism was proposed and the possible radical species involved in the photoelectrocatalytic degradation of diclofenac were analyzed by active species trapping. The Cu/TiO2 NTs electrode exhibited high reusability.

Aligned TiO2 nanotube/nanoparticle heterostructures with enhanced electrochemical performance as three-dimensional anode for lithium-ion microbatteries

A novel TiO2 three-dimensional (3D) anode with an aligned TiO2 nanotube/nanoparticle heterostructure (TiO2 NTs/NPs) is developed by simply immersing as-anodized TiO2 NTs into water and further crystallizing the TiO2 NTs by post-annealing. The heterostructure, with its core in a tubular morphology and with both the outer and inner surface consisting of nanoparticles, is confirmed by FESEM and TEM. A reversible areal capacity of 0.126 mAh · cm−2 is retained after 50 cycles for the TiO2 NTs/NPs heterostructure electrode, which is higher than that of the TiO2 NTs electrode (0.102 mAh · cm−2 after 50 cycles). At the current densities of 0.02, 0.04, 0.06, 0.08, 0.10 and 0.20 mA · cm−2, the areal capacities are 0.142, 0.127, 0.117, 0.110, 0.104 and 0.089 mAh · cm−2, respectively, for the TiO2 NTs/NPs heterostructure electrode compared to the areal capacities of 0.123, 0.112, 0.105, 0.101, 0.094 and 0.083 mAh · cm−2, respectively, for the the TiO2 NTs electrode. The enhanced electrochemical performance is attributed to the unique microstructure of the TiO2 NTs/NPs heterostructure electrode with the TiO2 NT core used as a straight pathway for electronic transport and with TiO2 NP offering enhanced surface areas for facile Li+ insertion/extraction. The results described here inspire a facile approach to fabricate a 3D anode with an enhanced electrochemical performance for lithium-ion microbattery applications.

Gold-Metal (Ni, Cu) Deposited on the Titania Nanotubes as Electrocatalysts for Borohydride Oxidation

In the present work the optimization of the preparation of titania nanotube supported Au-Ni and Au-Cu catalysts (denoted as Au(Ni)/TiO2-NTs and Au(Cu)/TiO2-NTs) via the galvanic displacement technique is presented. The catalysts were prepared according the following procedures: i) preparation of TiO2 nanotube arrays by anodization of titanium sheets in an aqueous sulfuric acid solution containing some NH4F; ii) deposition of an electroless Ni or Cu sublayers on the synthesized TiO2 nanotube arrays [1-3] and iii) subsequent immersion of the Ni/TiO2-NTs or Cu/NiTiO2-NTs electrodes into the gold-containing solution for various time periods. The morphology and composition of the catalysts were examined by means of Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, X-ray diffraction and Inductively Coupled Plasma Optical Emission Spectroscopy. The electrochemical behavior and electrocatalytic activity of the fabricated catalysts towards borohydride oxidation were measured by means of cyclic voltammetry. The electroactive area of gold surface created on fabricated catalysts was determined from cyclic voltammograms of Au/TiO2-NTs electrodes recorded in a deaerated 0.5 M H2SO4 solution at a scan rate of 10 mV s-1.The prepared Au(Ni)/TiO2-NTs and Au(Cu)/TiO2-NTs electrodes exhibited a high catalytic efficiency towards the oxidation of borohydride when compared to that of bulk Au electrode. A higher catalytic activity of the prepared Au(Ni)/TiO2-NTs and Au(Cu)/TiO2-NTs catalysts under various conditions may be related to production of smaller gold nanoparticles and their fine and uniform dispersion on the surface.The Au-Ni and Au-Cu catalysts deposited on the titania nanotube surface seem to be a promising anodic material for direct borohydride fuel cells. Acknowledgement This research was funded by a grant (No. ATE-08/2012) from the Research Council of Lithuania.

Enhanced photoelectrocatalytic degradation of an acid dye with boron-doped TiO2 nanotube anodes

The present work evaluates the performance of boron-doped TiO2 nanotubes (B–TiO2 NTs) prepared by electrochemical anodization in the presence of 70, 140, 280 and 560ppm of boron when activated by UV/visible irradiation. The presence of boron was characterized by FEG-MEV, XRD, DRS, XPS and photocurrent curves, where the maximum values were obtained for B–TiO2 NTs. Assessment of the electrodes were conducted in the hair dye degradation (Acid Yellow 1 dye) and the degradation rate was 2 times higher at the doped electrode containing 280ppm of boron, where the maximum electrode activation was obtained under UV/vis irradiation. The best results indicate 100% of discoloration and up to 95% of TOC removal when 100ppm of Acid Yellow 1 dye was treated at B–TiO2 NTs electrode during 120min at Eapp=+1.2V in 0.01molL−1 of Na2SO4 at pH 2. These findings showed that the photoelectrocatalysis is an efficient method to remove hazardous organic compounds from water and B-doped TiO2 electrodes are an important step in the search for efficient and stable catalysts for photo(electro)catalysis.

Fabrication of n-type CuInS2 modified TiO2 nanotube arrays heterostructure photoelectrode with enhanced photoelectrocatalytic properties

A novel n-type CuInS2 modified TiO2 nanotube arrays (NTs) heterostructure photoelectrode was successfully prepared via an ultrasonication-assisted cathodic electrodeposition strategy. CuInS2 particles were uniformly decorated on the inner and external walls of the TiO2 NTs electrode. The stoichiometry measured by XPS and ICP-OES clearly illustrated the excess indium. Mott–Schottky analysis further demonstrated CuInS2 possessed an n-type feature. Optical characterizations indicated that the introduced CuInS2 could extend the visible-light response range and enhance the visible light photoactivity. Moreover, the electrochemical measurements attested to a significant improvement of the interfacial electron-transfer properties. The photoelectrocatalytic (PEC) activity of CuInS2/TiO2 NTs electrode was evaluated by degradation of 2-chlorophenol (2-CP) under visible light irradiation (λ>420nm). The results indicated that the as-prepared CuInS2/TiO2 NTs electrode displayed much higher PEC performance than that of the pure TiO2 NTs electrode.

N-doped TiO2 nanotube array photoelectrode for visible-light-induced photoelectrochemical and photoelectrocatalytic activities

N-doped TiO2 nanotube arrays (TiO2NTs) were prepared by hydrothermal treatment of the crystalline TiO2NTs, and characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (DRS). The highly ordered TiO2NTs with an inner diameter of approximately 80nm and a tube length of about 400nm were obtained. XRD patterns showed that the TiO2 nanotube arrays before and after N doping were anatase. XPS analysis indicated that N was doped into the TiO2 lattice. A shift of the absorption edge to a low energy was observed from DRS. N-doped TiO2NTs electrode exhibited higher photoelectrochemical and photoelectrocatalytic activities than the undoped TiO2NTs electrode. The electrochemical impedance spectroscopy and photoluminescence spectra confirmed that doping N promoted the separation of the photogenerated electrons and holes.

Ni nanoparticles decorated titania nanotube arrays as efficient nonenzymatic glucose sensor

A novel nonenzymatic glucose sensor was developed based on the Ni nanoparticles-loaded TiO2 nanotube arrays (Ni-NPs/TiO2NTs). The Ni-NPs/TiO2NTs nanocomposites were prepared first by anodization of Ti foil, followed by pulsed electrodeposition method (PED) and characterized by SEM, XRD and XPS respectively. The results showed that spherical Ni nanoparticles were well dispersed and embedded in the TiO2NTs. The electrochemical measurements presented that the activated Ni-NPs with a diameter of 40nm displayed high electrocatalytic activity for the oxidation of glucose and a good sensitivity of 700.2μA mM−1cm−2 at applied potential 0.6V, with detection limit of 2μM (S/N=3), and good linear range (from 0.004 to 4.8mM). Such high sensitivity was attributed to the large surface area of the highly dispersed nanoparticles for electrocatalytic reaction and the fast electron transfer in the TiO2NTs electrode. The good analytical performance, low cost and simple preparation method make this novel electrode material promising for the development of effective glucose nonenzymatic glucose sensor.