Nanotube Array Electrode Research Articles

Porous Dual‐Layered MoOx Nanotube Arrays with Highly Conductive TiN Cores for Supercapacitors

AbstractPorous dual‐layered molybdenum oxide (MoOx) nanotube arrays (NTAs) with highly conductive titanium nitride (TiN) cores (MoOx/TiN/MoOx NTAs) are fabricated by depositing MoOx on porous TiN NTAs produced by nitriding as‐anodized TiO2 NTAs on Ti foils. The highly conductive TiN facilitates electron transfer and the porous MoOx wall allows the electrolyte to permeate the nanotubes readily, maximizing the active sites of the MoOx electroactive material to improve the specific capacitance and rate capability. The coaxial MoOx/TiN/MoOx NTA electrode shows a high specific capacitance of 97 mF cm−2 (323 F g−1) at a current density of 1 mA cm−2, and 60 % capacitance is retained when the current density is increased 20 times. A symmetrical device based on the MoOx/TiN/MoOx NTA electrode exhibits a capacitance as high as 24 F cm−3 (based on the volume of MoOx/TiN/MoOx NTAs) and no significant decay is observed after charging/discharging for 10 000 cycles.

One-step electrochemical growth of a three-dimensional Sn-Ni@PEO nanotube array as a high performance lithium-ion battery anode.

Various well-designed nanostructures have been proposed to optimize the electrode systems of lithium-ion batteries for problems like Li(+) diffusion, electron transport, and large volume changes so as to fulfill effective capacity utilization and increase electrode stability. Here, a novel three-dimensional (3D) hybrid Sn-Ni@PEO nanotube array is synthesized as a high performance anode for a lithium-ion battery through a simple one-step electrodeposition for the first time. Superior to the traditional stepwise synthesis processes of heterostructured nanomaterials, this one-step method is more suitable for practical applications. The electrode morphology is well preserved after repeated Li(+) insertion and extraction, indicating that the positive synergistic effect of the alloy nanotube array and 3D ultrathin PEO coating could authentically optimize the current volume-expansion electrode system. The electrochemistry results further confirm that the superiority of the Sn-Ni@PEO nanotube array electrode could largely boost durable high reversible capacities and superior rate performances compared to a Sn-Ni nanowire array. This proposed ternary hybrid structure is proven to be an ideal candidate for the development of high performance anodes for lithium-ion batteries.

Ni(OH)2/NiO/Ni composite nanotube arrays for high-performance supercapacitors

Transition metal oxide nanostructures are one of current investigation focuses for energy storage applications. We herein report a novel template-free electrochemical approach to fabricate Ni(OH)2/NiO/Ni composite nanotube array films on the nickel substrate. The inner diameter of the composite nanotubes can be effectively tuned by tailoring the concentration of Cu2+ in the precursor solutions. The as-constructed composite nanotube array film electrode, which is fabricated by the electrochemical approach using the 0.1 M Cu2+ containing precursor solution, delivers the specific capacitance of 1070 F g−1 at the current density of 15 A g−1 after 10,000 charge–discharge cycles. The specific capacitance of the cycled electrode at 150 A g−1 is as much as 79.3% of that at 15 A g−1, demonstrating its excellent rate capability. The cycled electrode presents a high specific energy density of 31.4 Wh kg−1 at a larger power density of 11.1 kW kg−1. The excellent pseudocapacitive performance of the Ni(OH)2/NiO/Ni composite nanotube array electrodes can be attributed to their unique structure characteristics.

Efficient quantum dot-sensitized solar cell based on CdSxSe1-x/Mn-CdS/TiO2 nanotube array electrode

Translucent TiO2 nanotube (NT) array film has been used as supporter materials for the fabrication of CdSxSe1-x/Mn-CdS quantum dot sensitized solar cell (QDSSC). The TiO2 NT array electrodes are sensitized with Mn-CdS and CdSxSe1-x QDs by employing a two-stage sensitization strategy combining successive ionic layer adsorption and reaction (SILAR) techniques and hydrothermal process. The photoresponse region of CdSxSe1-x/Mn-CdS/TiO2 NT electrodes could be controlled by the ratio of S and Se. By systematical investigation the optimal composition of CdSxSe1-x, a high power conversion efficiency of 2.41% is obtained with CdS0.47Se0.53/Mn-CdS/TiO2 NT QDSSC prepared with feed molar ratio of S:Se=0:4. After being coated with 3 SILAR cycles of CdSe on the CdS0.47Se0.53/Mn-CdS/TiO2 NT electrode, the power conversion efficiency could be further improved to the highest value of 3.26%. The enhancement of power conversion efficiency is mainly attributed to the significant increase of short-circuit current density (Jsc) which resulted from the improved light harvesting ability caused by expanded light absorption range and efficient electrons collection caused by mid-gap states created by Mn-CdS. These results are well evidenced with the photovoltaic performance studies (J-V behaviors), incident photon to charge carrier generation efficiency (IPCE), and electrochemical impedance spectroscopy (EIS).

Nanotubes array electrodes by Pt evaporation: Half–cell characterization and PEM fuel cell demonstration

A self-standing nanotubes (NTs) array electrode is produced by electron beam evaporation of Pt on porous alumina templates. NTs have a mean diameter ranging from 150 to 300nm, a length of 150nm and a wall thickness of 20nm. The ultrathin electrode has a density ranging between 109 and 4×109 NTscm−2geo with a corresponding catalyst loading of 100μgPtcm−2geo. The NTs are assembled on a Nafion® membrane to obtain a NTs Array based Membrane Electrode Assembly (NTA-MEA) for Polymer Electrolyte Membrane Fuel Cells (PEMFCs) application. Ex-situ half-cell tests are carried out on 0.5cm2geo samples to characterize the electrochemical properties of the NTs array electrode. PEMFC tests are also performed on 17cm2geo samples to demonstrate the great potential of this architecture as fuel cell cathode under real operating conditions. Comparisons with Pt/C dispersions are made to draw conclusions on the advantage of the NTs array on conventional electrodes in terms of catalyst utilization. The NTs array shows improved catalyst accessibility due to the absence of the porous carbon support. Double current density per catalyst unit surface over Pt/C dispersions is measured at 0.6V during PEMFC tests under dry O2 and air with 30%RH humidification.

Plasmon-induced photoelectrocatalytic activity of Au nanoparticles enhanced TiO2 nanotube arrays electrodes for environmental remediation

A pulse electrodeposition (PED) technique was adopted to construct highly dispersed Au nanoparticles (Au-NPs) on TiO2 nanotube arrays (TiO2-NTs) electrodes prepared by electrochemical anodic oxidation. Both the particle size and loading amount were facilely controlled via adjusting electrochemical parameters. The morphology, crystallinity, elemental composition and light absorption capability of as-obtained Au/TiO2-NTs were distinguished based on various characterizations. Compared with pure TiO2-NTs, Au/TiO2-NTs electrodes exhibited much higher photocurrent density and greatly enhanced photoelectrocatalytic (PEC) activity towards the degradation of methyl orange (MO) under visible-light irradiation (λ>420nm). The synergy effect between nanotubular structures of TiO2 and uniformly dispersed Au nanoparticles, as well as the small bias potential and strong interaction between Au and TiO2, facilitated the Au plasmon-induced charge separation and transfer, which lead to highly efficient and stable visible-light PEC activity.

Preparation of β-PbO2/TiO2 Nanotube Array Electrode and Electrocatalysis Degradation of Phenol

Preparation of β-PbO2/TiO2 Nanotube Array Electrode and Electrocatalysis Degradation of Phenol

SnO2 nanoparticle-coated ZnO nanotube arrays for high-performance electrochemical sensors.

Novel 1D nanostructures offer new opportunities for improving the performance of electrochemical sensors. In this study, highly ordered 1D nanostructure array electrodes composed of SnO2 nanoparticle-coated ZnO (SnO2 @ZnO) nanotubes are designed and fabricated. The composite nanotube array architecture not only endows the electrochemical electrodes with large surface areas, but also allows electrons to be quickly transferred along the nanotubes. Modifying the SnO2 @ZnO nanotube arrays with negatively charged polymer film and employing them as a working electrode, sensitive and selective electrochemical detection of an important neurotransmitter, i.e., dopamine, is realized via the cycle voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Interference from ascorbic acid can be successfully eliminated. The oxidative peak currents recorded from CV linearly depend on the dopamine concentrations from 0.1 to 100 μM with a sensitivity of 2.16 × 10(-7) A μM(-1) cm(-2) and detection limit of 45.2 nM. Using the DPV technique, an improved sensitivity and detection limit of 1.94 × 10(-6) A μM(-1) cm(-2) and 17.7 nM are respectively achieved. Moreover, the SnO2 @ZnO nanotube array electrodes can be reused through simple ultrasonical cleaning and no obvious deterioration is observed in the performance.

Enhanced Electrochemiluminescence Performance of Ru(bpy)32+/CuO/TiO2 Nanotube Array Sensor for Detection of Amines

AbstractTripropylamine (TPA) is a highly toxic and carcinogenic compound, therefore, TPA concentration in water must be monitored to protect health and the environment. In this paper, an electrochemiluminescent (ECL) sensor was fabricated by immobilising Ru(bpy)32+‐modified CuO nanoparticles (NPs) on a TiO2 nanotube array (TN) electrode. Compared to an ECL sensor fabricated by immobilising Ru(bpy)32+ on a TN only electrode, the as‐prepared sensor displays a 30 % enhanced ECL signal and a detection limit of 9.6×10−10 M at a signal‐to‐noise ratio=3 with the concentration of TPA in a range 1×10−9 to 1×10−5 M. The results from this study indicated a new approach for the enhancement of performance of ECL sensor in detecting TPA in water.

Enhanced photovoltaic performance of solar cell based on front-side illuminated CdSe/CdS double-sensitized TiO2 nanotube arrays electrode

Free-standing TiO2 nanotube (NT) arrays have been prepared by a two-step anodization method. These translucent TiO2 NT arrays can be transferred to the fluorine-doped tin oxide glass substrates to form front-side illuminated TiO2 NT electrodes. The TiO2 NT electrodes were double-sensitized by CdSe/CdS quantum dots (QDs) through successive ionic layer adsorption and reaction (SILAR) process. The absorption range of the TiO2 NT electrode was extended from ~380 to 700 nm after sensitization with CdSe/CdS QDs. The SILAR cycles were investigated to find out the best combination of CdS and CdSe QDs for photovoltaic performance. The power conversion efficiency of 2.42 % was achieved by the CdSe(10)/CdS(8)/TiO2 NT solar cell. A further improved efficiency of 2.57 % was obtained with two cycles of ZnS overlayer on the CdSe(10)/CdS(8)/TiO2 NT electrode, which is 45.19 % higher than that of back-side illuminated solar cell. Furthermore, the ZnS(2)/CdSe(10)/CdS(8)/TiO2 NT solar cell possesses a higher stability than CdSe(10)/CdS(8)/TiO2 NT solar cell during the same period. The better photovoltaic performance of the ZnS(2)/CdSe(10)/CdS(8)/TiO2 NT solar cell has demonstrated the promising value to design quantum dots-sensitized solar cells with double-sensitized front-side illuminated TiO2 NT arrays strategy.

Oriented TiO2 nanotubes as a lithium metal storage medium

A new strategy for suppressing dendritic lithium growth in rechargeable lithium metal batteries is introduced, in which TiO2 nanotube (NT) array electrodes prepared by anodization are used as a metallic lithium storage medium. During the first charge process, lithium ions are inserted into the crystal structure of the TiO2 NT arrays, and then, lithium metal is deposited on the surfaces of the NT arrays, i.e., in the NT pores and between NT walls. From the second cycle onward, the TiO2 material is used as lithium ion pathways, which results in the effective current distribution for lithium deposition and prevents disintegration of the deposited metallic lithium. Compared to a Li(Cu foil)–LiCoO2 cell, the Li(TiO2 NT)–LiCoO2 cell exhibits enhanced cycling efficiency. This new concept will enable other 3D structured negative active materials to be used as lithium metal storage media for lithium metal batteries.

Infiltration of Spiro-MeOTAD hole transporting material into nanotubular TiO2 electrode for solid-state dye-sensitized solar cells

TiO2 nanotubes grown by anodic oxidation of Ti thin film deposited on conducting transparent fluoride-doped tin oxide (FTO) substrate were used as a unique geometrically organized template to study the infiltration of Spiro-MeOTAD hole transporting material (HTM) inside straight pores. The TiO2 nanotube (TNT) array electrode was compared with a mesoporous one in terms of loading with an organic dye of high extinction coefficient. It was shown that it is possible to build a working solid state dye sensitized solar cell device with such a combination of materials and its performance was compared with a device in which the solid state HTM was replaced by a liquid state electrolyte.

Enhanced capacitive performance of TiO2 nanotubes with molybdenum oxide coating

Alpha-phase MoO3 is electrochemically deposited on well-aligned TiO2 nanotubes which are synthesized by anodic oxidation. The morphology, composition and electrochemical behaviors of MoO3-coated and bare TiO2 nanotubes are studied. The former deliver greatly higher capacitance than the latter and their performance can be readily optimized by varying MoO3 deposition cycles. The large areal capacitance of 209.6mFcm−2 at a scan rate of 5mVs−1 is firstly achieved for TiO2 nanotube array electrode. In addition, the coated TiO2 nanotubes show significantly more capacitance than a dense MoO3 film. For example, they exhibit a capacitance up to 74.9Fg−1 at 5mVs−1 in 1M KCl solution, while the dense film only shows a capacitance of 32.3Fg−1 under same conditions. Such improvement is found ascribed to MoO3 with high pseudocapacity and TiO2 nanotubes with large surface area allowing efficient MoO3 nanoparticle loading and rapid charge transfer. This nanostructured electrode with features of facile synthesis and excellent performance is believed as a potential candidate for supercapacitor applications.

Supportless Platinum Nanotubes Array by Atomic Layer Deposition as PEM Fuel Cell Electrode

This work reports the fabrication and the test of a novel type of electrode for polymer electrolyte fuel cells, based on an array of oriented and self-supported platinum nanotubes. The dense array of nanotubes is produced by coating the surface of a porous Anodized Aluminum Oxide template by Pt using the Atomic Layer Deposition technique. The nanotubes have a length of around 2μm, an external diameter of around 180nm and 20nm thick Pt walls. As a consequence the tubes are stiff and self-standing with no need for a supporting structure. The array of nanotubes has a density of approximately 109 tubes cm−2 and is stuck onto a Nafion® membrane with excellent adhesion. The electrochemical response of the platinum nanotubes array electrode is investigated by means of half-cell tests and it is compared with the response of a conventional electrode based on a Pt/C dispersion. The nanotubes array shows excellent surface utilization and gas accessibility. The surface specific activity of the nanotubes array towards oxygen reduction reaction is comparable to the one of the conventional electrode: 37μA cmPt−2 vs 28μA cmPt−2 of the Pt/C dispersion. Conversely, the mass activity still remains low: 5.5 A/gPt vs 15 A/gPt of the Pt/C dispersion, therefore future actions to decrease the Pt loading and increase the mass activity are outlined. The scale-up of this prototype of supportless nanotubes array electrode from half–cell to fuel cell size is also demonstrated, opening the way to its test under real operating conditions.

Design Hierarchical Electrodes with Highly Conductive NiCo2S4 Nanotube Arrays Grown on Carbon Fiber Paper for High-Performance Pseudocapacitors

We report on the development of highly conductive NiCo2S4 single crystalline nanotube arrays grown on a flexible carbon fiber paper (CFP), which can serve not only as a good pseudocapacitive material but also as a three-dimensional (3D) conductive scaffold for loading additional electroactive materials. The resulting pseudocapacitive electrode is found to be superior to that based on the sibling NiCo2O4 nanorod arrays, which are currently used in supercapacitor research due to the much higher electrical conductivity of NiCo2S4. A series of electroactive metal oxide materials, including CoxNi1-x(OH)2, MnO2, and FeOOH, were deposited on the NiCo2S4 nanotube arrays by facile electrodeposition and their pseudocapacitive properties were explored. Remarkably, the as-formed CoxNi1-x(OH)2/NiCo2S4 nanotube array electrodes showed the highest discharge areal capacitance (2.86 F cm(-2) at 4 mA cm(-2)), good rate capability (still 2.41 F cm(-2) at 20 mA cm(-2)), and excellent cycling stability (∼ 4% loss after the repetitive 2000 cycles at a charge-discharge current density of 10 mA cm(-2)).

One-dimensional copper oxide nanotube arrays: biosensors for glucose detection

One dimensional CuO nanotube (NT) arrays were synthesized by an anodization method and evaluated for glucose detection. The CuO NT arrays electrode showed enhanced activity with a sensitivity of 1.89 mA mM−1 cm−2 and a linear range from 5 μM to 3.0 mM compared with CuO nanorod (NR) arrays due to its larger surface area and faster biomolecule diffusion. Furthermore, the proposed biosensor exhibited excellent stability, high reproducibility and high selectivity for the detection of glucose, and had been successfully applied to determine glucose levels in human plasma samples with satisfactory results. The success of this work indicates the perspective of this kind of CuO electrode for further design and microfabrication of bioelectrochemical nanodevices.

High-performance and renewable supercapacitors based on TiO2 nanotube array electrodes treated by an electrochemical doping approach

Although one-dimensional anodic TiO2 nanotube arrays have shown promise as supercapacitor electrode materials, their poor electronic conductivity embarrasses the practical applications. Here, we develop a simple electrochemical doping method to significantly improve the electronic conductivity and the electrochemical performances of TiO2 nanotube electrodes. These TiO2 nanotube electrodes treated by the electrochemical hydrogenation doping (TiO2-H) exhibit a very high average specific capacitance of 20.08 mF cm−2 at a current density of 0.05mAcm−2, ∼20 times more than the pristine TiO2 nanotube electrodes. The improved electrochemical performances can be attributed to ultrahigh conductivity of TiO2-H due to the introduction of interstitial hydrogen ions and oxygen vacancies by the doping. The supercapacitor device assembled by the doped electrodes delivers a specific capacitance of 5.42 mF cm−2 and power density of 27.66 mW cm−2, on average, at the current density of 0.05mAcm−2. The device also shows an outstanding rate capability with 60% specific capacitance retained when the current density increases from 0.05 to 4.00mAcm−2. More interestingly, the electrochemical performances of the supercapacitor after cycling can be recovered by the same doping process. This strategy boosts the performances of the supercapacitor, especially cycling stability.

A novel self-cleaning, non-enzymatic glucose sensor working under a very low applied potential based on a Pt nanoparticle-decorated TiO2 nanotube array electrode

In this paper, a non-enzymatic amperometric glucose sensor working under a very low applied potential of −0.5V (vs. saturated calomel electrode or SCE) was developed based on a Pt nanoparticle-decorated TiO2 nanotube array (Pt/TiO2 NTA) electrode. A highly ordered TiO2 NTA with a diameter of 200nm was fabricated by anodization of Ti in ethylene glycol containing 0.5wt% NH4F, 10vol% H2O, and 0.9vol% H2SO4. Pt nanoparticles ∼5nm in diameter were uniformly decorated inside the TiO2 nanotubes through ion-exchange reaction with Pt (NH3)4Cl2, followed by reduction with NaBH4. The morphology of the electrode was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The performance of the as-prepared electrode was characterized by cyclic voltammetry and chronoamperometry. The sensor can accurately detect glucose in 0.1M NaOH solution at an applied potential of −0.5V (vs. SCE) in the presence of interferences, such as ascorbic acid and uric acid, with a linear range of 1–15mM and a detection limit of 0.2mM at a signal-to-noise ratio of 3. The Pt/TiO2 synergistic effect shows a good self-cleaning ability. The electrocatalytic ability of the present Pt/TiO2 NTA electrode toward glucose oxidation under a very low applied potential has promising applications in blood glucose measurement and mediator-free anodes for glucose biofuel cells.

Electrodeposition and photoelectrochemical properties of p-type BiOIαCl1-α nanoplatelet thin films

In this paper, a series of BiOIαCl1-α solid solution electrodes were successfully prepared through a simple electrodeposition method. The obtained electrodes were characterized by X-ray diffraction, scanning electron microscopy, UV–vis diffuse reflectance spectroscopy and photocurrent response. We found that all prepared electrodes exhibited p-type conductivity in accordance with reports employing other deposition strategies. What's more, the BiOIαCl1-α solid solution showed the best photoelectrochemical activity at α=0.5 due to the balance between the level of conduction band and the light absorption ability of solid solutions. Finally, wet photovoltaic cells with p-BiOI0.5Cl0.5 and n-TiO2 nanotube array electrodes were also constructed.

TiO2 nanotube arrays via electrochemical anodic oxidation: Prospective electrode for sensing phenyl hydrazine

The TiO2 nanotube (NT) arrays were grown on Ti foil substrate by electrochemical anodic oxidation and utilized as working electrode to fabricate a highly sensitive and reproducible chemical sensor for the detection of harmful phenyl hydrazine chemical. The fabricated chemical sensor based on TiO2 NT arrays electrode exhibited high sensitivity of ∼40.9μA mM−1 cm−2 and detection limit of ∼0.22 μM with short response time (10 s). The enhanced sensing properties were attributed to the presence of depleted oxygen layer on the surface of grown TiO2 NT arrays and its high electron transfer process via good electrocatalytic activity towards phenyl hydrazine chemical.