Electrochemical Anodization Method Research Articles

Synthesis of TiO2 nanotubes/nickel-gallium layered double hydroxide heterostructure for highly-efficient photocathodic anticorrosion of 304 stainless steel

The corrosion of 304 stainless steel (304SS) is a major global issue in the context of ships and marine engineering constructions. The photocathode anticorrosion system, composed of semiconductor material in the form of photoanode and 304SS in the form of cathode, is an effective method to solve 304SS corrosion of large components. Owing to the rapidly photoinduced charge-transfer at the semiconductor interface that supplies photogenerated electrons to the electrically connected 304SS and shifts the coupled potential to much more negative values, constructing a photoanode heterostructure material promotes charge separation and thus improves the photocathodic anticorrosion of 304SS. Herein, we fabricated TiO2 nanotubes/nickel‑gallium layered double hydroxide (TiO2/NiGa-LDH) heterostructure material by the electrochemical anodization and hydrothermal method for highly-efficient photocathodic anticorrosion of 304SS. Owing to the modulated band structure and enhanced photogenerated carriers separation and transfer, TiO2/NiGa-LDH heterostructure material gave rise to largely reduced open circuit potential (OCP, −690 mV), which facilitated the transfer of electrons from the TiO2/NiGa-LDH heterostructure material to the 304SS to improve the photocathodic anticorrosion of 304SS, along with good stability after the OCP test for 72 h. This work provides a strategy for exploring LDH-based photoanodes materials toward highly-efficient photocathodic anticorrosion of 304SS.

Preparation of CuO/Ag rough nanostructures as SERS-active substrates

In this paper, CuO nanostructures with nanometer roughness were firstly prepared by electrochemical anodic oxidation method, and then CuO/Ag composite nanostructures were prepared by magnetron sputtering method on the surface of CuO substrate. The successful deposition of Ag films on CuO was confirmed by XRD, UV-Vis and SEM. In addition, the effects of different Ag sputtering time on substrate morphology and SERS properties were studied. Due to the many gaps between the rough CuO/Ag nanomorphology, the substrate has many “hot spots” and adsorption sites, which can effectively improve the SERS performance of the substrate. We selected R6G dye molecule as the probe molecule to evaluate the SERS performance of the substrate. The final experimental results show that the preparation method of CuO/Ag rough nanostructure is simple, and it has significant SERS performance improvement. The substrate’s detection limit for R6G can even reach 10-11M.

One step immobilization of glucose oxidase on TiO2 nanotubes towards glucose biosensing

Biocatalysts of redox enzymes have fascinated escalating attention for development of electronic biomaterials and devices for industrial, clinical and environmental applications. Enzyme immobilization leads to more stable, repetitive and better activity. Including of immobilization substrate or materials; the different kinds of nanostructured TiO2 have often been used to immobilize enzymes on their surface for fabricating electrochemical biosensors, because of their unique physico-chemical properties constitute novel and interesting matrices. Glucose oxidase (GOx) is one of the typical enzymes which are being extensively used especially in glucose diagnosis. In this study, titanium dioxide nanotubes (TNT) were synthesized by electrochemical anodizing method and used as GOx immobilization substrate for glucose detection. The morphology, structure and electrochemical performance of TNT are characterized by field emission scanning electron microscope (FE-SEM), Energy-dispersive X-ray (EDX), X-ray Diffraction (XRD), Atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Our results show that the TNT electrode provides an excellent matrix for the GOx immobilization and exhibits a very low detection limit (8.5 µM), linearly range from 0.0 to 1.0 mM, with high stability and good reproducibility. These findings demonstrate a promising strategy to integrate enzymes and TNT, which could provide an analytical access to a large group of enzymes for bioelectrochemical applications.

Mechanical and Electrical Interaction of Biological Membranes with Nanoparticles and Nanostructured Surfaces.

In this review paper, we theoretically explain the origin of electrostatic interactions between lipid bilayers and charged solid surfaces using a statistical mechanics approach, where the orientational degree of freedom of lipid head groups and the orientational ordering of the water dipoles are considered. Within the modified Langevin Poisson–Boltzmann model of an electric double layer, we derived an analytical expression for the osmotic pressure between the planar zwitterionic lipid bilayer and charged solid planar surface. We also show that the electrostatic interaction between the zwitterionic lipid head groups of the proximal leaflet and the negatively charged solid surface is accompanied with a more perpendicular average orientation of the lipid head-groups. We further highlight the important role of the surfaces’ nanostructured topography in their interactions with biological material. As an example of nanostructured surfaces, we describe the synthesis of TiO2 nanotubular and octahedral surfaces by using the electrochemical anodization method and hydrothermal method, respectively. The physical and chemical properties of these nanostructured surfaces are described in order to elucidate the influence of the surface topography and other physical properties on the behavior of human cells adhered to TiO2 nanostructured surfaces. In the last part of the paper, we theoretically explain the interplay of elastic and adhesive contributions to the adsorption of lipid vesicles on the solid surfaces. We show the numerically predicted shapes of adhered lipid vesicles corresponding to the minimum of the membrane free energy to describe the influence of the vesicle size, bending modulus, and adhesion strength on the adhesion of lipid vesicles on solid charged surfaces.

A novel CaIn2S4/TiO2 NTAs heterojunction photoanode for highly efficient photocathodic protection performance of 316 SS under visible light

Designing heterojunction photocatalysts with matched band structure and good interface contact is an effective method to improve the photoelectrochemical activity. Herein, novel CaIn2S4/TiO2 nanotube arrays (NTAs) heterojunction photoanodes were successfully prepared by electrochemical anodization and hydrothermal method. The microstructures, compositions, crystal structures, chemical valence states and light absorption performances of the composites were evaluated by field emission scanning electron microscopy, energy dispersive x-ray spectroscopy transmission electron microscope, high-resolution transmission electron microscope, x-ray diffractometer, x-ray photoelectron spectroscopy and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), respectively. The photocathodic protection performances of CaIn2S4/TiO2 composites for 316 stainless steel (SS) and the influences of the CaIn2S4 content on the performances were studied. The microstructural examination revealed the uniform doping of CaIn2S4 nanofragments on the TiO2 NTAs, and the composite was made up cubic CaIn2S4 and anatase TiO2. The photogenerated electrons were transferred from the TiO2 to CaIn2S4 at the interface of the composite. Compared with pure TiO2 NTAs, CaIn2S4/TiO2 NTAs exhibited better photocathodic protection performance for 316 SS under visible light. Potential drop reached 0.78 V versus saturated calomel electrode for the 316 SS coupled with CaIn2S4/TiO2 NTAs. The photocurrent density of the 316 SS coupled with the composite photoanode (235.4 μA cm–2) was 17.4 times that of TiO2. The improved photocathodic protection property of CaIn2S4/TiO2 NTAs was ascribed to the enhanced separation efficiency of the photogenerated carriers and the strong visible light absorption of the material. The CaIn2S4/TiO2 NTAs exhibited continuous protection of the 316 SS for more than 12 h even in the dark. Therefore, the CaIn2S4/TiO2 NTAs heterojunction composite is an outstanding and efficient photoanode for the photocathodic protection of metals.

Fabrication of titanium dioxide nanotubes with reduced bandgaps by varying electrolytic concentrations

The main objective of this work is to fabricate titanium dioxide nanotubes of reduced bandgaps for hydrogen generation. Nano scaled material has many peculiar properties than the bulk ones and has led to great break in various fields of science and technology. Titanium dioxide nanotubes have great potential because of its functional properties such as large surface to volume ratio. The TiO2 nanotubes are grown by electrochemical anodization method at constant DC voltage of 12V for 1 hour. For sample A 0.25 wt% of potassium fluoride dissolved in 99% of ethylene glycol with molarity 0.004M is used as electrolyte. For samples B,C and D the electrolytic solution was prepared by the dissolution of 0.004M of ethylene glycol with copper nitrate(Cu(NO3)23H2O) solution of different concentration (0.002mM,0.003M,0.004M).Titanium dioxide nanotubes formed were studied by Field Emission Scanning Microscope and Photoluminescence Spectroscopy and the results were discussed.

Thermal Ramping Rate during Annealing of TiO2 Nanotubes Greatly Affects Performance of Photoanodes

Herein, highly ordered TiO2 nanotube (NT) arrays on a Ti substrate is synthesized in a fluoride‐containing electrolyte, using the electrochemical anodization method, which yields amorphous oxide tubes. The effects of different thermal annealing profiles for the crystallization of the amorphous TiO2 NTs are studied. It is found that the temperature ramping rate has a significant impact on the magnitude of the resulting photocurrents (incident photon‐to‐current conversion efficiency [IPCE]) from the tubes. No appreciable changes are observed in the crystal structure and morphology of the TiO2 NTs for different annealing profiles (to a constant temperature of 450 °C). The electrochemical properties of the annealed TiO2 NTs are investigated using intensity‐modulated photocurrent spectroscopy (IMPS), open‐circuit potential decay, and Mott–Schottky analysis. The results clearly show that the annealing ramping rate of 1 °C s−1 leads to the highest IPCE performance. This beneficial effect can be ascribed to a most effective charge separation and electron transport (indicating the least amount of trapping states in the tubes). Therefore, the results suggest that controlling the annealing ramping rate is not only a key factor affecting the defect structure but also a powerful tool to tailor the physical properties, and photocurrent activity of TiO2 NTs.

Preparation of FeS2/TiO2 nanocomposite films and study on the performance of photoelectrochemistry cathodic protection

FeS2/TiO2 nanotube array composite films with clean, high efficiency, low cost and low consumption were prepared by electrochemical anodization and hydrothermal methods. The modification of FeS2 nanoparticles on the surface of TiO2 nanotube array film not only broadens the light absorption range of TiO2, but also improves the utilization ratio of visible light and the separation rate of photogenerated electron–hole pairs, which greatly improves the photoelectrochemical cathodic protection performance of TiO2 for 304 stainless steel (304SS). Under visible light irradiation, the open circuit potential of 304SS coupled with the FeS2/TiO2 nanocomposite films decreased from − 170 to − 700 mV, and the electrode potential can still maintained at − 400 mV after the light was turned off. Compared with pure TiO2 nanotube array film, FeS2/TiO2 nanocomposite film has better photoelectrochemical cathodic protection effect on 304SS in 3.5 wt% NaCl corrosion medium.

Preparation and fabrication of NiCo coated TiO2-NTs for hydrogen evolution

ABSTRACT Hydrogen production via water splitting is a very attractive way using effective electrocatalysts. One of the effective electrocatalysts that are used in water splitting is NiCo alloys. In this study, highly ordered titanium dioxide nanotubes (TiO2-NTs) are firstly prepared by electrochemical anodization method in terms of being a substrate material for NiCo coatings. Hydrogen evolution behaviors of three types of NiCo coated TiO2-NTs are investigated in 1 M KOH solution at room temperature. Coated surfaces are characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), and cyclic voltammetry (CV). HER activities of NiCo coated TiO2-NTs are investigated by cathodic current–potential curves, electrochemical impedance spectroscopy (EIS), and electrolysis process. The stability of NiCo-coated TiO2-NTs is also investigated. Results show that TiO2-NTs surface leads to large surface area and high porosity for NiCo nano-particles and thus, HER performance of coatings increases. NiCo-coated TiO2-NTs improves the catalytic HER activity in terms of current density, hydrogen volume, polarization resistance (Rp), and conductivity. Enhanced HER activity can be based on the boosted surface area, conductivity, and more active sites for hydrogen ion adsorption as well as synergistic effects.

Variation of etching time on formation of porous silicon on p-type Si (111) using electrochemical anodization method

Porous silicon (PSi) has been formed on p-type Si (111) substrates using electrochemical anodization method. Silicon surfaces were anodized in HF (40%) dan ethanol (96%) solution with a ratio of 1:1. Anodization time was varied at 6, 8, 10 and 12 min with current density was maintained constant at 80 mA/cm2. Platinum foil was as a cathode while silicon was as an anode with a distance of 5 cm. The optical reflectance of the sample was determined using UV-Vis Spectrophotometer and surface morphology was observed using AFM. AFM’s images could determine the depth, width and roughness of PSi. The reflectance of PSi on Si (111) decreased with increasing the etching time. It indicated that many photons were trapped inside the porous. AFM images confirmed that the depth, the width, and the roughness of PSi increased with the increasing of the etching time. It is considered that the etching direction worked in the vertical and horizontal ways.

The formation of porous silicon (PSi) on p-type Si (100) substrate via the electrochemical anodization method with varying current density

The porous silicon (PSi) has been successfully formed on the surface of p-type Si (100) using the electrochemical anodization method in which Si was as an anode and Pt was as a cathode etched in the HF ethanoic solution for 12 min. The current densities applied during the anodization process varied from 60 mA/cm2, 70 mA/cm2, 80 mA/cm2, and 90 mA/cm2 to observe its effects on the morphological and optical properties of PSi. The morphology of PSi was tested via AFM instrument while its reflectance was measured using UV-Vis Spectrometry. The AFM images of the surface PSi reveals the pores’ depth, the pores’ size, and the surface roughness of the PSi. The results demonstrate that the increase in the current densities results in the deeper pores’ depth and the bigger pores’ size so that lifts the surface roughness values as well. On the other hand, the increase in the current densities tends to decrease the reflectance intensities of the PSi.

The Synthesis and Characterization of Anodic Alumina Oxide Using Sulfuric Acid and Oxalic Acid

Anodic Alumina Oxide (AAO) is one of the nanomaterials that have developed as a template in the nanowires, nanodots and nanotubes. This research focuses on synthesizing AAO by two different electrolytic solutions which are using sulfuric acid (H2SO4) and oxalic acid (C2H2O4) by electrochemical anodization method. Two parameters were influencing the anodization process in the experiment; the type and the concentration of the electrolytic solution. The effects of the different type of electrolytic solutions produced different size of pores. When the voltage used is 25 V in H2SO4, the optimum reading size of the nanopores is in the range of 16-22 nm, whereas the AAO pores in C2H2O4 are in the range of 100-200 nm. Meanwhile, the concentration of H2SO4 and C2H2O4 is set to be 0.3 M, 0.4 M and 0.5 M., The results in 0.3 M H2SO4 and C2H2O4, show the optimum concentration of electrolytic solutions which is the key parameter affecting the morphological structure of porous membranes in AAO. The optimum value for these two acidic solutions has produced such highly ordered arrangement of nanopores which are from the average size of nanopores that anodized in sulfuric acid is 19 nm while 120 nm in oxalic acid. The morphological structure properties of AAO templates include the diameter of nanopores, the thickness of membrane and density of nanopores would be examined by Field Emission Scanning Electron Microscope (FESEM) and Energy Dispersive X-ray (EDX). Also, Fourier-transmittance infrared spectroscopy (FTIR) detected the chemical functional group of bonds in AAO. In conclusion, AAO templates have a big potential to be the major contributor in the future for the development of new electronic devices.

Highly Ordered Nanotube Arrays as Photo-Anodes for Dye-Sensitized Solar Cells by Electrochemical Method

Symmetrically packed TiO2 nanotubes (TNTs) were fabricated in fluorine free perchloric acid medium by electrochemical anodization method. During anodization interconnected pores developed by forming amorphous/ hydroxides of titanium film. On increasing anodization, thickness of film increased and pores tend to become aligned providing surface layer of nanotubes on the electrode material. The 1-D charge carrier transport property of the tubular geometry have attracted scientists attention in using TNTs for TiO2 photovoltaic and photo catalysis applications. By controlling the anodization process, the length, diameter and wall thickness of TNTs can be tailored. The iron and chromium doped highly ordered 1-D TNTs obtained during anodization are superior photoanodes for dye-sensitized solar cells because of its reduced inter tube connections, vertical electron transport, suppressed electron recombination and enhanced current density, efficiency in power conversion and light scattering. The morphological characteristics and microstructure of TNTs were investigated by SEM and X-ray diffraction analysis. Diffusion electron spectroscopy has been used to analyze the amount absorption of the dye on the surface of the various TNT, which acknowledges the direct co relation between the dye absorption and morphology of the sample.

Formation of porous silicon on N-type Si (1 0 0) and Si (1 1 1) substrates by electrochemical anodization method

Abstract Porous silicon (PSi) was formed on n-type Si (1 0 0) and Si (1 1 1) substrates via the electrochemical anodization method. The samples were anodized in HF: ethanol solution (1:1) and flowed with a varied current density of 10, 20, 30, 40, and 50 mA/cm2 for 30 min. The reflectance, the pores size, and the pores depth of PSi were characterized by UV–Vis spectroscopy, SEM instrument, and Dektak Profilometer, respectively. The higher current density results in lower reflectance of PSi on both Si (1 0 0) and Si (1 1 1) substrates, while SEM images and Dektak tests confirmed that the pore depth and the pore size of PSi increased. It is concluded that PSi could be applied to solar cell devices as an anti-reflective surface. PSi reflectance on Si (1 0 0) is lower than on the Si (1 1 1) substrate. It suggested that in DSSC, PSi on Si (1 0 0) could be considered to have better anti-reflective properties.

Electroless deposition of Pd/Pt nanoparticles on electrochemically grown TiO2 nanotubes for ppb level sensing of ethanol at room temperature.

This work presents a comparative sensing study of three sensors based on pristine TiO2 nanotubes, Pd loaded TiO2 nanotubes, and Pt loaded TiO2 nanotubes. Pristine TiO2 nanotubes were synthesized using an electrochemical anodization method and an electroless plating method was used for the uniform deposition of noble metal nanoparticles of either Pd or Pt over the surface of TiO2 nanotubes. The samples were thoroughly characterized by XRD, FESEM, EDS, TEM, and XPS techniques. The sensitivity of all three sensors was investigated at room temperature (300 K) for different volatile organic compounds like ethanol, methanol, 2-propanol, acetone, and benzene. The results revealed that loading of Pd and Pt nanoparticles improved the response magnitude of the sensor remarkably as these noble metals possess better oxygen dissociation capability than pristine TiO2. The Pd-TiO2 nanotube sensor exhibited a maximum response magnitude of 20-98% towards 100-1000 ppb of ethanol at room temperature. Notably, the formation of Pd/Pt-TiO2 discrete heterojunctions on the surface of TiO2 nanotubes was found to be responsible for enhanced sensitivity of the sensors.

Fabrication of TiO2 nanotubes and PDMS nanopillar by using anodization process to stamping technique

Abstract A great focus is pondered over the electrochemical anodization method, which offers a less intense synthesis process and results in uniform coverage of Titanium foil with titania nanotubes. After the different structural templates were prepared by different techniques, the surface morphology was done by Field Emission Scanning Electron Microscopy. Thereafter, the PDMS thin coating was done on the template by the spin coating method. To prepare a thick pattern of PDMS, the continuous layering of a dilute solution is done after drying it in an interval of time. After that, the sample was heated in an oven for a few hrs. to prepared molds. Then easily the PDMS mold was peeled off. titania template leaves an impression of the pore on the PDMS substrate and the nano impression of PDMS molds work as a top-electrode application.

Highly Ordered of Anatase Titanium Dioxide Nanotube Arrays at Different Calcination Temperatures via Electrochemical Anodization Method

Highly ordered titanium dioxide nanotube arrays (TNTAs) were fabricated via electrochemical anodization of Ti sheet in electrolyte containing aqueous and nonaqueous electrolyte. The formation of highly ordered TNTAs was varied by calcination temperatures (350, 450, 550oC) for 120 minutes to investigate the effect of calcination temperature on surface morphology, roughness, crystallinity and band gap energy. The field emission scanning electron microscopy revealed that the prepared TNTAs grow uniformly with average diameter in the range of 48.23 to 52.14 nm as the temperature increased from 350 to 550oC. The X-ray diffraction pattern showed the TNTAs exhibit anatase phase with prominent (101) peak recorded for the sample calcined at 450oC. The transformation from anatase to rutile phase appeared after calcination at 450oC. The band gap value (~3.24 eV) was obtained for all calcination temperature sample due to homogeneity of the TNTAs structures.

An Accurate Growth Mechanism and Photocatalytic Degradation Rhodamine B of Crystalline Nb2O5 Nanotube Arrays

To effectively improve photocatalytic activity, the morphology and crystallinity of semiconductor photocatalysts must be precisely controlled during the formation process. Self-aligned Nb2O5 nanotube arrays have been successfully fabricated using the electrochemical anodization method. A novel growth mechanism of Nb2O5 nanotubes has been proposed. Starting from the initial oxidation process, the “multi-point” corrosion of fluoride ions is a key factor in the formation of nanotube arrays. The inner diameter and wall thickness of the nanotubes present a gradually increasing trend with increased dissociative fluorine ion concentration and water content in the electrolyte. With dehydroxylation and lattice recombination, the increased crystallinity of Nb2O5 represents a reduction of lattice defects, which effectively facilitates the separation and suppresses the recombination of photo-generated carriers to enhance their catalytic degradation activity.

Low-temperature highly selective and sensitive NO2 gas sensors using CdTe-functionalized ZnO filled porous Si hybrid hierarchical nanostructured thin films

In this report, we present improved NO2 gas sensing properties based on CdTe-functionalized ZnO filled porous Si (PSi) hybrid hierarchical nanostructured thin films (CdTe/ZnO@PSi). The CdTe and ZnO nanostructured thin films were grown on the PSi substrate using a scalable magnetron sputtering technique. The PSi substrate was prepared using the electrochemical anodization method. The proposed CdTe/ZnO@PSi sensor was characterized in terms of structural, morphological, and compositional properties. The sensing performance and corresponding mechanism of NO2 gas sensor based on CdTe/ZnO@PSi were described comprehensively. In order to compare, the sensing characteristics of both CdTe/ZnO@PSi and pristine ZnO@PSi thin film sensors were tested in different temperature range varied from 30 °C to 180 °C for 1 ppm concentration of NO2 gas. We found that CdTe/ZnO@PSi sensor displays enhanced NO2 sensing characteristics (∼3.5-fold greater sensor response ∼19.82 %, fast response/recovery time ∼13 s/54 s) at the relatively low working temperature of 90 °C towards 1 ppm NO2 gas in comparison to the pristine ZnO@PSi sensor (sensor response ∼5.72 % and response/recovery time ∼41 s/124 s at an operating temperature of 150 °C). Further, the fabricated NO2 gas sensor demonstrated excellent reversibility and good stability, and enabling CdTe/ZnO@PSi a promising candidate for its practical use in IoT sensing devices.

Development of α-Fe2O3/TiO2 3D hierarchical nanostructured photocatalysts through electrochemical anodization and sol–gel methods

Titanium dioxide (TiO2) nanotubes have attracted much attention due to their formation, properties, and functionality in recent years. Many methods have been used to obtain the nanotubes, such as template synthesis, hydrothermal, sol–gel, and electrochemical anodization. Compared to others, the electrochemical anodization method makes it possible to grow dense and well-aligned nanotube layers on pure and/or alloyed titanium surfaces. However, for enhanced photocatalytic activities, the parameters of the anodization process such as applied potential, time, and electrolyte composition should be tightly controlled to obtain regular, well-aligned, and continuous nanotube arrays. Alternatively, by the formation of heterojunctions such as α-Fe2O3/TiO2, the performances of the photocatalysts can be boosted due to the shifts of absorption range into the visible region and narrower band gaps of the hierarchical structures. In this study, TiO2 nanotubes were obtained by electrochemical anodization on Ti foil in ethylene glycol, ammonium fluoride and distilled water-based electrolyte under constant voltage and varying anodization durations. Herein, it was aimed to observe the effects of the anodization time on the length and diameter of the nanotubes, which have significant roles on the photocatalytic activity. Besides the investigation of the anodization parameters, the heterogeneous structure, α-Fe2O3/TiO2, was formed on anodized surfaces to scrutinize the improvement of the photocatalytic properties. The TiO2 nanotubes were characterized through XRD and SEM to determine the phase structure and morphology, respectively. The variation of optical bandgap values of α-Fe2O3/TiO2 samples depending on the processing parameters was determined by using a UV–Vis spectrophotometer. The photocatalytic performances of the α-Fe2O3/TiO2 photocatalysts were revealed using an aqueous solution of methylene blue. Photocatalytic degradation rates and kinetic study of α-Fe2O3/TiO2 photocatalysts were evaluated by a comparative approach. The highest degradation efficiency was achieved as 85% using the α-Fe2O3 coated photocatalyst with the anodization time of 30 min and anodization voltage of 30 V.