Effect Of Anodization Voltage Research Articles

Photoreduction of Cr(VI) in wastewater by anodic nanoporous Nb2O5 formed at high anodizing voltage and electrolyte temperature.

In this study, nanoporous anodic film was produced by anodization of niobium, Nb in a fluoride ethylene glycol electrolyte. The effect of anodization voltage and electrolyte temperature was studied to find an optimum condition for circular, ordered, and uniform pore formation. The diameter of the pores was found to be larger when the applied voltage was increased from 20 to 80V. The as-anodized porous film was also observed to comprise of nanocrystallites which formed due to high field-induced crystallization. The nanocrystallites grew into orthorhombic Nb2O5 after post-annealing treatment. The Cr(VI) photoreduction property of both the as-anodized and annealed Nb2O5 samples obtained using an optimized condition (anodization voltage: 60V, electrolyte temperature: 70°C) was compared. Interestingly, the as-anodized Nb2O5 film was found to display better photoreduction of Cr(VI) than annealed Nb2O5. However, in terms of stability, the annealed Nb2O5 presented high photocatalytic efficiency for each cycle whereas the as-anodized Nb2O5 showed degradation in photocatalytic performance when used continually.

A Modified Quantitative Method for Regularity Evaluation of Porous AAO and Related Intrinsic Mechanisms

In this paper, a new modified quantitative method for order evaluation of porous AAO (Anodic Aluminum Oxide) was proposed. Using this method, the regional order of structural cells of porous AAO can be defined as a specific value. Based on it, the critical temperature (Tc) and optimum temperature (To), which correspond to the order/disorder critical point and the best order point, have been investigated in detail. The effect of anodization voltage (Ua) and temperature of electrolyte (Te) on the regional order of structural cells of porous AAO has also been studied in 0.3 M oxalic acid electrolyte (Ua: 40–50 V, Te: 5–50°C). Moreover, the influence of current density (Ja), growth rate of porous AAO (va), and the internal stress in AAO on the self-ordering of porous AAO has been systematically investigated. The new modified quantitative method can also be used to evaluate other close-packed patterns, and the above mentioned mechanism findings may also be applicable to other valve metal anodization processes.

Hierarchical Co3O4/Co(OH)2 Nanoflakes as a Supercapacitor Electrode: Experimental and Semi-Empirical Model.

In this research, facile and low cost synthesis methods, electrodeposition at constant current density and anodization at various applied voltages, were used to produce hierarchical cobalt oxide/hydroxide nanoflakes on top of porous anodized cobalt layer. The maximum electrochemical capacitance of 601 mF cm(-2) at scan rate of 2 mV s(-1) was achieved for 30 V optimized anodization applied voltage with high stability. Morphology and surface chemical composition were determined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. The size, thickness, and density of nanoflakes, as well as length of the porous anodized Co layer were measured about 460±45 nm, 52±5 nm, 22±3 μm(-2), and 3.4±0.3 μm for the optimized anodization voltage, respectively. Moreover, the effect of anodization voltage on the resulting supercapacitance was modeled by using the Butler-Volmer formalism. The behavior of the modeled capacitance in different anodization voltages was in good agreement with the measured experimental data, and it was found that the role and contribution of the porous morphology was more decisive than structure of nanoflakes in the supercapacitance application.

Effect of anodization voltage on performance of TiO2 nanotube arrays for hydrogen generation in a two-compartment photoelectrochemical cell

Highly ordered TiO2 nanotube arrays were prepared by anodic oxidation of Ti foil under different anodization voltages in ethylene glycol electrolyte. The morphology and photoelectrochemical performance of the TiO2 nanotubes (NTs) samples were characterized by FESEM and electrochemical working station. Hydrogen production was measured by splitting water in the two-compartment photoelectrochemical (PEC) cell without any external applied voltage or sacrificial agent. The results indicated that anodization voltage significantly affects morphology structures, photoelectrochemical properties and hydrogen production of TiO2 NTs. The pore diameter and layer thickness of TiO2 samples increased linearly with the anodization voltage, which led to the enhancement of active surface area. Accordingly, the photocurrent response, photoconversion efficiency and hydrogen production of TiO2 nanotubes were also linearly correlated with the anodization voltage.

The effect of anodization voltage and surface morphology on the capacitance properties of Al–Al2O3–Al nanocapacitors

Al–Al2O3–Al nanocapacitors are fabricated using hard and mild anodization methods which is simple and inexpensive. Samples are prepared with various effective areas and dielectric thicknesses below 10 nm. The experiments are carried out for glass slides and porous anodic alumina as substrates. The capacitance characteristics of the fabricated capacitors were measured and studied. The capacitance of capacitor with a higher ratio of surface to volume has a good stability in high frequencies. The higher traps on a surface are responsible for this effect. The breakdown electric fields of all capacitors are close to each other. The capacitor with a smaller ratio of surface to volume has a lesser leakage current density. Capacitance densities ranged between 0.623 and 1.659 μF/cm2 at 1 kHz, with a low leakage current. The highest value of the capacitance density was obtained for the sample anodized at 3.5 V on the porous anodic alumina substrate.

Highly Conductive Nanostructured C-TiO2 Electrodes with Enhanced Electrochemical Stability and Double Layer Charge Storage Capacitance

The present work reports the structural and electrochemical properties of carbon-modified nanostructured TiO(2) electrodes (C-TiO(2)) prepared by anodizing titanium in a fluoride-based electrolyte followed by thermal annealing in an atmosphere of methane and hydrogen in the presence of Fe precursors. The C-TiO(2) nanostructured electrodes are highly conductive and contain more than 1 × 10(10) /cm(2) of nanowires or nanotubes to enhance their double layer charge capacitance and electrochemical stability. Electrogenerated chemiluminescence (ECL) study shows that a C-TiO(2) electrode can replace noble metal electrodes for ultrasensitive ECL detection. Dynamic potential control experiments of redox reactions show that the C-TiO(2) electrode has a broad potential window for a redox reaction. Double layer charging capacitance of the C-TiO(2) electrode is found to be 3 orders of magnitude higher than an ideal planar electrode because of its high surface area and efficient charge collection capability from the nanowire structured surface. The effect of anodization voltage, surface treatment with Fe precursors for carbon modification, the barrier layer between the Ti substrate, and anodized layer on the double layer charging capacitance is studied. Ferrocene carboxylic acid binds covalently to the anodized Ti surface forming a self-assembled monolayer, serving as an ideal precursor layer to yield C-TiO(2) electrodes with better double layer charging performance than the other precursors.

Effect of Anodization Voltage on Electron Field Emission from Carbon Nanotubes in Anodized Alumina Template

In this work, electron field emission from AAO-CNT structure is studied as a function of anodizing voltage. It is found that the turn-on electric field of AAO-CNTs reduces from 5 V/microm to 4 V/microm as anodization voltage increase from 20 to 30 V. On the other hand, CNTs the turn-on electric field of AAO-CNTs increases from 4 V/microm to 6 V/microm as anodization voltage increase from 30 to 40 V. Thus, anodization voltage of 30 V provides an optimal AAO-CNTs structure for electron field emission. The emission data have been analyzed based on the Fowler Nordhiem (F-N) model. AAO template prepared with 30 V anodization voltage is found to yield CNT nanoarray with optimum alignment and spacing that increase field enhancement factor by the lowering of field screening effect without significant lowering of CNTs density.

Effect of anodization voltage on the formation of phase pure anatase nanotubes with doped carbon

Carbon doped titania nanotubes were prepared by anodization of titanium in a fluoride containing ethylene glycol based electrolyte. Anatase crystallization temperature of the nanotubes varied with respect to anodization voltage. A detailed characterization study and mechanistic analysis of formation and stability of anatase phase of the nanotubes is reported. The findings suggest useful heat treatment parameters for obtaining pure anatase phases of the carbon doped titania nanotubes synthesized by anodization at 40 and 60 V.