Anodic Oxidation Conditions Research Articles

Crystal Structure Regulation of CoSe2 Induced by Fe Dopant for Promoted Surface Reconstitution toward Energetic Oxygen Evolution Reaction.

Most nonoxide catalysts based on transition metal elements will inevitably change their primitive phases under anodic oxidation conditions in alkaline media. Establishing a relationship between the bulk phase and surface evolution is imperative to reveal the intrinsic catalytic active sites. In this work, it is demonstrated that the introduction of Fe facilitates the phase transition of orthorhombic CoSe2 into its cubic counterpart and then accelerates the Co-Fe hydroxide layer generation on the surface during electrocatalytic oxygen evolution reaction (OER). As a result, the Fe-doped cubic CoSe2 catalyst exhibits a significantly enhanced activity with a considerable overpotential decrease of 79.9 and 66.9 mV to deliver 10 mA·cm-2 accompanied by a Tafel slope of 48.0 mV·dec-1 toward OER when compared to orthorhombic CoSe2 and Fe-doped orthorhombic CoSe2, respectively. Density functional theory (DFT) calculations reveal that the introduction of Fe on the surface hydroxide layers will tune electron density around Co atoms and raise the d-band center. These findings will provide deep insights into the surface reconstitution of the OER electrocatalysts based on transition metal elements.

Palladium-catalyzed electrochemical C(sp3)-H acetoxylation of alcohol derivatives with an exo-directing group.

Palladium-catalyzed electrochemical C(sp3)-H acetoxylation to prepare 1,2-diol derivatives was achieved using oxime ethers as exo-directing groups. Various substrates containing alkoxy groups with a methyl branch at the α-position as well as norbornan-2-ol derivative were acetoxylated only using a catalytic amount of Pd(OAc)2 along with NaOAc/Ac2O/AcOH under anodic oxidation conditions.

Preparation of TiO2 Nanotube Arrays with Controllable Morphology and their Superhydrophobic Modification for Photocatalytic Degradation of Water Pollution

TiO2, as a photoactive semiconductor material, where like photocatalysis technology is a hot topic of research in recent years, shows great potential for application in the direction of environmental pollution treatment and solar-chemical energy conversion. In this paper, we prepared titanium dioxide nanotube arrays (TNAs) by a simple one-step anodic oxidation method in an ethylene glycol electrolyte containing ammonium fluoride under optimized conditions. The effects of anodic oxidation voltage, anodic oxidation time and annealing temperature on the growth of TNAs were systematically investigated. It was shown that the sample parameters of TNAs prepared by anodic oxidation were influenced by the anodic oxidation conditions, and the tube diameter and anodic oxidation voltage were positively correlated in a certain range. The TNAs with the best characterization performance were selected for photocatalytic degradation, and methylene blue (MB) was used to simulate the organic pollutants. The results show that TNAs have better photocatalytic activity compared with conventional TiO2. On the basis of this, stearic acid (SA) and TNAs were compounded and modified. The TNAs were made to obtain superhydrophobic properties. The photocatalytic degradation experiments were carried out on them. The results show that the superhydrophobic modification does not affect their photocatalytic activity, so it is possible to achieve photocatalytic degradation of water pollution under the premise of superhydrophobicity, which has greater application prospects in water pollution treatment.

Growth behavior of tantalum oxide nanotubes during constant current anodization

The standard method for growing tantalum oxide (Ta2O5) nanotubes is the constant voltage anodization mode. Although the constant current anodization mode is another feasible approach, the corresponding mechanism is not yet clear. In the present work, Ta2O5 nanotubes have been prepared by constant current anodization in an electrolyte containing HF. The results show that Ta2O5 nanotubes ~ 18 μm in length can be obtained with a very rapid growth rate within 2 min at a current density of 125 mA cm−2. In addition, the effects of current density, anodizing time, concentration of F− ions and electrolyte temperature on the morphology and growth rate of Ta2O5 nanotubes were studied. This work proposes an effective way of preparing tantalum oxide nanotubes under constant current anodic oxidation conditions, and paves the way toward large-scale production of Ta2O5 nanotubes.

Electrochemical Properties of the closo-Decaborate Anion [B10H10]2– and a New Method for Preparation of the [B20H18]2– Anion

The work is devoted to the theoretical and experimental study of the electrochemical characteristics of the closo-decaborate anion. The regions of electrochemical transformations of the [B10H10]2– anion for non-aqueous solvents of different structures (acetonitrile, dichloromethane, and tetrahydrofuran) have been studied by the method of cyclic voltammetry. It has been shown that, under the conditions of anodic oxidation, a dimerization product, the [B20H18]2– anion, is formed. For the synthesis of octadecahydroeicosaborate anion, electrochemical synthesis has been used for the first time.

Electrochemical Synthesis of β‐Ketonitriles from Aryl Methyl Ketones

AbstractA synthesis of β‐ketonitriles by cyanation of aryl methyl ketones with two completely distinct sources of cyanide, namely Me3SiCN and KCN, under metal‐ and oxidant‐free electrochemical anodic oxidation conditions is described. In this approach, a range of β‐ketonitriles can be obtained in good yields. This conversion is facilitated by I2, generated in situ from electrochemical oxidation of iodide ion to afford the β‐ketonitriles. This environmentally benign method is more convenient and practical compared to previous approaches.

Enhanced adhesive strength between SU-8 photoresist and titanium substrate by an improved anodic oxidation method for high aspect-ratio microstructures

This paper presents an anodic oxidation treatment method for improving the adhesive strength between SU-8 photoresist and titanium substrate. The adhesion strengths were measured for the treated titanium substrates by different anodic oxidation techniques, which increased with the enhancement of the surface roughness and thorny structures on the treated substrate. It was found that the adhesion was increased by approximately 86% through anodic oxidation treatment in 3.0 mol l−1 NaOH solution compared to Si wafer substrate. Additionally, the influence of UV dosage and hard bake temperature on the adhesion strength was examined for the anodic oxidation treated substrates. The UV dosage effect, with a range from 0.8 to 2.08 J cm−2, was measured and analyzed for a 300 µm thickness SU-8 cylinder, and the adhesion strength corresponding to the optimal dosage (1.52 J cm−2) was 45.82 ± 3.08 MPa. The adhesion was further strengthened by a hard bake at 110 °C for 60 min and its value was up to 71.64 MPa, which almost approaches the breaking strength of the SU-8 polymer. Using the optimized anodic oxidation and UV lithography conditions, high aspect ratio (24) SU-8 micropillar arrays with 600 µm height were fabricated without any distortion, collapse or delamination. Finally, to evaluate the feasibility of the anodic oxidation treated titanium substrate to serve as a seed layer, the electrochemical properties were measured by polarization curves.

Automated Electrochemical Assembly of the β‐(1,3)‐β‐(1,6)‐Glucan Hexasaccharide Using Thioglucoside Building Blocks

AbstractThis study deals with the design, synthesis, and rational optimization of carbohydrate building blocks of glucosides for automated electrochemical assembly of β‐glucans. Oxidation potentials of building blocks with various types of protecting groups of hydroxyl groups were measured to estimate their reactivity under anodic oxidation conditions. Building blocks for both β‐1,3‐ and β‐1,6‐glycosidic linkages were optimized by an automated electrochemical assembly of disaccharides and trisaccharides. Several synthetic attempts were also made for the synthesis of the hexasaccharide repeating unit in a macrocyclic β‐glucan tridecasaccharide.

Electrochemical Methods as Enabling Tools for Glycosylation

AbstractElectrochemical methods have been widely used for organic synthesis including glycosylation. Electrochemical oxidation via single electron transfer (SET) is a powerful method to activate various types of glycosyl donors. Their oxidation potentials, which reflect the reactivity of glycosyl donors under anodic oxidation conditions are tunable by changing protecting groups and the anomeric leaving groups of glycosyl donors. Not only thioglycosides but also other chalcogenoglycosides have been studied as highly reactive glycosyl donors. Recently, automated electrochemical assembly, which is an automated electrochemical solution‐phase synthesis of oligosaccharides was successfully demonstrated by the rational optimization of thioglycosides as both glycosyl donors and acceptors through electrochemical measurements and DFT calculations.

Palladium-Catalyzed ortho-Selective C-H Chlorination of Benzamide Derivatives under Anodic Oxidation Conditions.

The palladium-catalyzed ortho-selective chlorination of N-quinolinylbenzamide derivatives with hydrochloric acid was achieved under anodic oxidation conditions. The use of 5,7-dichloro-8-quinolinyl group as directing group was effective for the selective chlorination, and the reaction was applicable to benzamide derivatives bearing various functional groups. Synthesis of vismodegib was also completed using the palladium-catalyzed electrochemical C-H chlorination in two different steps.

Transformations of Ferric Chloride-Generated Stilbene Cation Radicals. The Effect of Aromatic Substitution and a Comparison with Anodic Oxidation.

A systematic study on the FeCl3-induced oxidation of 1,2-diarylalkenes was carried out with the focus on the variation of product type as a function of aromatic substitution, as well as to compare the reactivity of stilbene cation radicals generated via Fe(III) oxidation with those generated by anodic oxidation. The aromatic substituents were found to fall into three main categories, namely those that give rise to tetralins and/or dehydrotetralins, those that give products possessing pallidol and ampelopsin F-type carbon skeletons, and last, those that give rise to trimeric products, indanes, and dehydrotetralins/tetralins. The latter are those stilbenes with a para-methoxy substituent in one ring and a para- or meta-EWG (CF3, NO2, Cl, F) in the other, and represent the most prominent departure when compared with the behavior of the same stilbenes under the conditions of anodic oxidation. Reaction pathways to rationalize the formation of the different products are presented.

Structure and transformations of diamantane radical cation: Theory and experiment

Quantum chemical calculations at the DFT (B3LYP-D3, M06-2X, B3PW91) and MP2 levels of theory consistently showed that diamantane radical cation in the gas phase has D 3d symmetry with two elongated apical C-H bonds. Its complexation with a nucleophilic solvent stabilizes alternative C s structure with two elongated medial C-H bonds. This is in agreement with the behavior of diamantane under anodic oxidation conditions, which leads to predominant formation of the medial substitution product.

The influence of the ultrafine-grained structure on passivation of copper

The influence of ultrafine-grained structure on passivation of copper in borate solutions was studied. Ultrafine-grained cooper was prepared by the equal channel angular extrusion. It was shown that, under the conditions of anodic oxidation, an oxide film with improved protective properties is formed on the ultrafine-grained sample. This film is characterized by a small thickness, low roughness, and high content of copper(I) oxide.

Palladium-Catalyzed Regioselective Homocoupling of Arenes Using Anodic Oxidation: Formal Electrolysis of Aromatic Carbon–Hydrogen Bonds

Palladium-catalyzed regioselective homocoupling of arylpyridines under anodic oxidation conditions was achieved in the presence of I2. The dimerization of meta-substituted arylpyridines proceeded selectively at less-sterically congested ortho-positions, and the selectivity is different from that reported for the palladium-catalyzed dimerization using Oxone as an oxidant. The dimerization also proceeds using catalytic amounts of both Pd(OAc)2 and I2 under the electrochemical reaction conditions.

Controlled Directional Water‐Droplet Spreading on a High‐Adhesion Surface

AbstractControlled directional spreading of a droplet on a smart high‐adhesion surface was made possible by simply controlling anodic oxidation. The wettability gradient of the surface was controlled from 0.14 to 3.38° mm−1 by adjusting the anodic oxidation conditions. When a water droplet made contact with the substrate, the droplet immediately spread in the direction of the wettability gradient but did not move in other directions, such as those perpendicular to the gradient direction, even when the surface was turned upside down. The spreading behavior was mainly controlled by the wettability gradient. Surfaces with a V‐ or inverse‐V‐shaped wettability gradient were also formed by the same method, and two droplets on these surfaces spread either toward or away from one another as designed. This method could be used to oxidize many conductive substrates (e.g., copper, aluminum) to form surfaces with variously shaped wettability gradients. It has potential for application in microfluidic devices.

Controlled directional water-droplet spreading on a high-adhesion surface.

Controlled directional spreading of a droplet on a smart high-adhesion surface was made possible by simply controlling anodic oxidation. The wettability gradient of the surface was controlled from 0.14 to 3.38° mm(-1) by adjusting the anodic oxidation conditions. When a water droplet made contact with the substrate, the droplet immediately spread in the direction of the wettability gradient but did not move in other directions, such as those perpendicular to the gradient direction, even when the surface was turned upside down. The spreading behavior was mainly controlled by the wettability gradient. Surfaces with a V- or inverse-V-shaped wettability gradient were also formed by the same method, and two droplets on these surfaces spread either toward or away from one another as designed. This method could be used to oxidize many conductive substrates (e.g., copper, aluminum) to form surfaces with variously shaped wettability gradients. It has potential for application in microfluidic devices.

A kind of double-sided porous anodic alumina membrane fabricated with the three-step anodic oxidation method

The porous anodic alumina membranes (PAAMs) have been successfully used as templates for the fabrication of functional nano-materials due to their outstanding regularity and physicochemical properties. In this paper, a transparent double-sided anodic alumina membrane with ultra-thin aluminum substrate was fabricated with the three-step anodic oxidation method in the oxalic acid electrolyte. The characters such as the top-surface morphology, membrane thickness, and depth of nanopores of this three-layer (Al2O3-Al-Al2O3) sandwiched nano-structure were controllable through regulating the main anodic oxidation conditions, e.g., anodic oxidation time of various steps, coating remove process. The experiments data revealed that the aluminum substrate is exponential declined with the oxidation time when it was approximately reduced by a few micrometers. This new double-sided anodic alumina membrane can be used as the high-quality functional field emission materials and templates.

Degradation of Dipyrone by Electrogenerated H2O2 Combined with Fe2+ Using a Modified Gas Diffusion Electrode

The aim of the present study was to investigate the electrochemical degradation of dipyrone in a single compartment electrochemical cell equipped with a gas diffusion electrode (GDE) modified with cobalt (II) phthalocyanine. Degradations were performed under conditions of anodic oxidation (GDE pressurized with N2) and under conditions promoting the electrogeneration of H2O2 (GDE pressurized with O2) both in the absence and presence of 1 mmol FeSO4.7H2O (electro-Fenton conditions). The efficiency of the electro-Fenton process was satisfactory at all studied potentials, and achieved a maximum reduction of 67% in electrolyte absorbance at 262 nm after 90 min electrolysis at −0.7 V (vs. Ag/AgCl). The reduction in dipyrone concentration attained 95% after 90 min of reaction with electrogenerated H2O2 in the absence or presence of Fe2+ ions at all potentials except −0.5 V (vs. Ag/AgCl). The removal of total organic carbon (TOC) was most efficient under electro-Fenton conditions with a decrease of 54.4% in organic load attained at -0.9 V (vs. Ag/AgCl) and energy consumption (EC) of 270 kWh per kg of TOC removed.

Influence of controlled-charge anodization processes on the morphology of TiO2 nanotubes and their efficiency in dye-sensitized solar cells

Abstract The effect of the electrochemical anodization growth process on the development of self-organized TiO 2 nanotube (NT) films and their efficiency as photoelectrodes in dye sensitized solar cells (DSCs) has been comparatively investigated, by keeping constant the total anodization charge. Slow and rapid potentiostatic anodization processes were accordingly compared to the galvanostatic one, while a two step potentiostatic–galvanostatic technique was applied for the first time for the growth of TiO 2 NT arrays, as a step forward in relation to the existing potentiostatic–potentiostatic (P–P) technique. Scanning electron microscopy and Raman spectroscopy verified the wide diversity in the morphological and structural characteristics of the TiO 2 NTs obtained by the different anodization modes. The novel approach of galvanostatic tube growth on a potentiostatically patterned Ti foil provided the most uniform TiO 2 nanotubular films with clean top surface exempt of nanograss or cracks over extended areas. Evaluation of the TiO 2 NTs performance as photoelectrodes in DSC devices showed distinct differences of their electrical parameters that reflected finely the underlying structure/morphology variations of the different anodic oxidation conditions. Galvanostatic TiO 2 NT films presented the most favorable (open-ordered) structure for DSC photoelectrodes with superior electrical performance, essentially impaired by a relatively low fill factor that requires improvement by appropriate post-treatment. Furthermore, despite the marked differences in morphology, the TiO 2 NT photoelectrodes exhibited comparable overall performance (of the order of 4%), with only exception the P–P samples which presented slightly lower (about 25%) photovoltaic efficiency. These results indicate that the anodization charge is a critical factor that effectively controls the nanotubes behavior when they are used as photoelectrodes in DSCs.

Annealing effects on self-assembled TiO2 nanotubes and their behavior as photoelectrodes in dye-sensitized solar cells

Self-assembled highly ordered TiO2 nanotube arrays were grown on Ti foils in NH4F ethylene glycol electrolyte under mild anodic oxidation conditions. The effect of annealing post-treatment on their structural properties was systematically investigated with respect to their electrical characteristics and photoelectrochemical performance in back-side illuminated dye-sensitized solar cells (DSCs). A variety of parameters was controlled and optimized including the annealing temperature, the heating rate and duration of the thermal treatment. The obtained results confirmed a correlation between the crystalline/structural properties of the TiO2 nanotubes and their electrical characteristics, thus revealing the close interplay of crystal size, grain boundaries and crystallite interconnectivity with the electron dynamics (transport/recombination) governing the DSC operation and efficiency. The high importance of a barrier layer at the interface between the nanotubes and the Ti foil was also highlighted.