Anodic Synthesis Research Articles

A novel approach towards multivariate optimization of graphite/PbO2 anode synthesis conditions: Insight into its enhanced oxidation ability and physicochemical characteristics

Electrochemical oxidation has drawn great interest for its potential application in degrading persistent organic pollutants (POPs) through electrogenerated hydroxyl radical at the surface of anode. This study aims at the preparation of an inexpensive graphite/PbO2 anode. For enhancing oxidation performance, preparation process parameters viz. Pb(NO3)2 concentration, potential, and time of electrodeposition of a graphite/PbO2 anode, electrodeposited from acidic electrolyte bath, were optimized targeting a POP, 2,4-dinitrophenol removal. The changes in morphological properties of the developed oxide films were analyzed using scanning electron microscopy (SEM) which manifested significant impacts of selected anode preparation process parameters. Furthermore, PbO2 film prepared at optimum conditions were characterized using SEM, atomic force microscopy (AFM), energy dispersive X-ray spectroscope (ESD) elemental mapping, and X-ray diffraction (XRD) for thorough investigation of crystal structures, elemental distribution over surface, and phase of PbO2. Angular structures in both SEM and AFM analysis and appearance of β-PbO2 characteristic peaks in XRD analysis confirmed formation of electrocatalytically active phase of PbO2. For further enhancing the oxidation ability, influencing experimental parameters viz. current intensity, pH, and NaCl concentration were optimized. After 2 h of electrolysis at optimum experimental conditions, COD and total organic carbon removal efficiency of 93.6 ± 0.63% and 71.7 ± 1.52% were obtained respectively.

Oxidative transformation of N-substituted 3-aminopyrazoles to azopyrazoles using electrogenerated bromine as a mediator

The one-pot process of anodic transformation of N-alkyl-3-aminopyrazoles into azopyrazoles under conditions of membraneless electrolysis in an aqueous solution of NaBr was studied for the first time. It was found that under these conditions the aminopyrazoles, which do not have a substituent at position 4, transform into the corresponding 4,4´-dibromoazopyrazoles. The corresponding yield was in the interval of 28—80%, depending on the structure of the products. The transformation of 4-substituted aminopyrazoles resulted in the formation of azopyrazoles in the yields lying within 62—86% when this process was implemented under conditions with the anodically generated Br2 acting as a mediator. A convenient method of anodic synthesis of azopyrazoles in an aqueous medium without the use of additives of chemical oxidants was proposed. The process is environmentally sound and is characterized by a high atom efficiency (>85%).

Anodic Synthesis of New Benzofuran Derivatives Using Active Methylene Group at Platinum Electrode

A facile and Eco-compatible synthesis of benzofuran derivatives (4a–4h) has been carried out at platinum electrode by electrochemical oxidation of catechol in the presence of active methylene groups. Electro- organic synthesis has been performed in an undivided cell at ambient conditions. The products of electrolysis have been purified and characterized by FTIR, 1H NMR and 13C NMR and mechanism was deduced by voltammetric studies.

One‐Step Cathodic and Anodic Synthesis of Hydrophilic Carbon Nanomaterials

AbstractIt was demonstrated that the galvanostatic polarization of graphite electrodes in a cell with two separated compartments generates simultaneously and straightforwardly, without further separation and functionalization, two distinct sets of hydrophilic carbon nanomaterials [electrogenerated hydrophilic carbon (EHC)], in the anodic and cathodic compartments, respectively. The synthesized products comprise an amorphous carbonaceous material with aromatic sp2 carbon clusters, differing mainly in their oxidation degree. Surprisingly, it was found that nitrogen is incorporated in the carbon‐based material during the electrolysis, which is provided by the N2 gas present in the air and/or aqueous medium. This phenomenon is explained on the basis that very reactive carbonaceous species are formed during the electrodes polarization, owing to an anomalous high electric field generated along the galvanostatic polarization. In addition, it was also evidenced that ECH materials display a negative charge, counterbalanced by sodium ions and unique optical properties, exhibiting deep ultraviolet emission (ca. 4.1 eV), as well as blue luminescence. It is foreseen that these carbon materials will have important repercussions in optoelectronics devices, energy technology (supercapacitors, batteries, and fuel cells), and biomedicine.

Self-Organized TiO2 Nanotubes: Influence of the Ti Microstructure on the Nanotube Growth

The synthesis of highly-ordered nanostructures of valve metal oxides has recently attracted huge scientific and technological interest motivated by their possible use in many applications. The most established member of this group of materials is nanoporous Al2O3, which has been prepared two decades ago by anodic oxidation of Al into perfectly ordered, honeycomb-like porous structures employing suitable electrochemical conditions [1]. Owing to the flexibility of the pore diameter/length and the relative ease of the Al2O3 dissolution, its porous membranes have been since than widely used as template material of choice for a range of materials [2-4]. Recently, TiO2 has received the highest attention after Al2O3 motivated by its range of applications, including photocatalysis, water splitting, solar cells and biomedical uses. Very significant research efforts have led to reproducible synthesis of self-organized TiO2 nanotube layers by means of anodic oxidation, during which the starting Ti substrate is converted into a highly-ordered nanotubular layer by anodization in suitable electrolytes [5-7]. Although advancements in the anodic synthesis of self-organized TiO2 nanotube layers have been presented over the past years [8], the degree of ordering has not reached so far the level known from porous alumina [1]. Numerous factors influence the ordering and the homogeneity of the TiO2 nanotube layers. In the presentation, we demonstrate significant advancements in the understanding of the influence of Ti substrates on the TiO2 nanotube growth compared to the recent state-of-art. Using SEM, AFM, GDOES and optical measurements we will show how to obtain a high degree of ordering, uniformity and homogeneity in the nanotube structure of TiO2 by tailoring the anodization protocol [9, 10]. Furthermore, based on SEM, EBSD and TEM measurements, we will demonstrate how the Ti grain structure influences the lateral uniformity of the nanotube layers [11].

The anodization synthesis of copper oxide nanosheet arrays and their photoelectrochemical properties

We studied the growth of copper oxide nanosheet arrays on copper foil via a simple anodization method. The structures, morphologies, and elemental compositions of the specimens were characterized with an X-ray diffractometer, scanning electron microscope, high resolution transmission electron microscope, and X-ray photoelectron spectrometer. The copper oxide (Cu2O and CuO) nanosheet arrays were comprised of 30-nm-thick nanosheets that stand vertically on the Cu substrate. The anodizing parameters, such as the current density, temperature, and polyethylene glycol concentration, were optimized to obtain the regular nanosheet arrays. The optical absorption properties of the anodized products were evaluated using a diffuse reflectance spectrometer, and broad and strong optical absorption bands arising from the UV to visible region were observed. The photoelectrochemical performance of the nanosheet arrays was measured with chronoamperometry and cyclic voltammetry on an electrochemical workstation equipped with a Xe lamp (wavelength >400nm). A negative photocurrent was obtained due to the p-type semiconductor of the copper oxides. The copper oxide nanosheet arrays achieve the highest photocurrent of 0.4mA/cm2 at the current density of 1.0A/dm2, temperature of 70°C, and polyethylene glycol concentration of 0.5g/L.

Life cycle assessment of high capacity molybdenum disulfide lithium-ion battery for electric vehicles

This study presents a comprehensive life cycle assessment (LCA) on a potential next-generation lithium ion battery (LIB) with molybdenum disulfide (MoS2) anode and Nickel-Cobalt-Manganese oxide (NMC) cathode. The NMC-MoS2 battery is configured with 49.4 kWh capacity enabling a 320 km driving range for a mid-sized EV. In this study, the MoS2 anode synthesis is modeled based on our lab-scale experimentation and the battery design is based on the electrochemical parameters obtained from our lab results. The life cycle impact assessment is conducted using the ReCiPe method. The freshwater ecotoxicity impact is assessed through the modified USEtox™ method, based on the characterization factor of the CNT (carbon nanotubes) is derived. The obtained impact results of the NMC-MoS2 battery are benchmarked with those of a conventional NMC-Graphite battery under the same driving distance per charge. The results show that the NMC-MoS2 battery has higher environmental impacts in most impact categories compared to a conventional NMC-Graphite battery. Impacts on global warming potential and fossil depletion potential are 6%–7% higher while impacts in freshwater ecotoxicity, freshwater eutrophication, human toxicity, marine toxicity, marine eutrophication and terrestrial ecotoxicity are 141%–271% higher. Finally, a sensitivity analysis is performed to investigate the robustness and reliability of the LCA results.

Anodic Synthesis of β-Ni(OH)2 Thin Films on Si(100)

In this work is described the synthesis of Ni(OH)2 thin films on top of monocrystalline n-type silicon (100) via anodic electrodeposition assisted by light. As electrolyte was employed an aqueous solution of NiSO4.6H2O. The Ni(OH)2 electrodeposition was carried out at two NiSO4.6H2O concentrations, 0.50 and 0.75 M, and at constant electrolyte temperatures ranging from 10 to 25°C. Potentiostatic current density transients, obtained during Ni(OH)2 deposition, pointed out that the Ni(OH)2 nucleation dynamics depend on the tested electrolyte conditions. The Ni(OH)2 films were investigated by contact profilometry, field emission scanning electron microscopy, Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The results showed that the as-deposited films correspond to α-Ni(OH)2 unstable phase, which is progressively converted, by environment aging in air atmosphere, to β-Ni(OH)2 after ∼10 days. The β-Ni(OH)2 film is stable and its surface presents a uniform and shiny coloring in the entire film. Its surface has a uniform porous nanostructure, which characteristics depends on the synthesis parameters, salt concentration and electrolyte temperature.

Recent Progress in Synthesis and Application of Low-Dimensional Silicon Based Anode Material for Lithium Ion Battery

Silicon is regarded as the next generation anode material for LIBs with its ultra-high theoretical capacity and abundance. Nevertheless, the severe capacity degradation resulting from the huge volume change and accumulative solid-electrolyte interphase (SEI) formation hinders the silicon based anode material for further practical applications. Hence, a variety of methods have been applied to enhance electrochemical performances in terms of the electrochemical stability and rate performance of the silicon anodes such as designing nanostructured Si, combining with carbonaceous material, exploring multifunctional polymer binders, and developing artificial SEI layers. Silicon anodes with low-dimensional structures (0D, 1D, and 2D), compared with bulky silicon anodes, are strongly believed to have several advanced characteristics including larger surface area, fast electron transfer, and shortened lithium diffusion pathway as well as better accommodation with volume changes, which leads to improved electrochemical behaviors. In this review, recent progress of silicon anode synthesis methodologies generating low-dimensional structures for lithium ion batteries (LIBs) applications is listed and discussed.

Self-Organized TiO2 Nanotube Arrays: Towards Improved Ordering

Synthesis of highly-ordered nanostructures of valve metal oxides has recently attracted huge scientific and technological interest motivated by their possible use in many applications. The nanoporous Al2O3 – most established member of this group of materials – has been prepared by anodic oxidation of Al under suitable electrochemical conditions two decades ago into perfectly ordered, honeycomb-like porous structures (1). Owing to the flexibility of the pore diameter/length and the relative ease of the Al2O3 dissolution, its porous membranes have been since than widely used as template material of the choice for a range of materials (2-4). It is the TiO2 that has received the highest attention after Al2O3 motivated by its range of applications, including photocatalysis, water splitting, solar cells and biomedical uses. Very significant research efforts have led to reproducible synthesis of self-organized TiO2 nanotube layers by means of anodic oxidation, during which the starting Ti substrate is converted into highly-ordered nanotubular layer by anodization in suitable electrolytes (5-7). Although advancements in the anodic synthesis of self-organized TiO2 nanotube layers have been presented over past years (8), the degree of ordering has not reached so far the level known from porous alumina (1). Numerous factors influence the ordering and the homogeneity of the TiO2nanotube layers. In the presentation, we aim to demonstrate significant advancements in the ordering of anodic TiO2nanotubes compared to known state-of-art. In particular, we will show recent results on the extremely ordered nanotube arrays. In addition, utilizing AFM, SEM and optical measurements, we will show how to obtain via tailored anodization protocols a very decent degree of uniformity and homogeneity of the nanotube layers. Moreover, based on SEM, EBSD and TEM measurements, we will demonstrate how the Ti grain structure influences the lateral uniformity of the nanotube layers (9-11).

Short-Step Anodic Synthesis of Color-Tunable Emissive Nucleoside Analogues

Since natural nucleobases are not emissive, emissive nucleoside analogues have been widely used to monitor fundamental biochemical transformations directly. Nowadays, useful libraries of synthetic emissive nucleoside analogues have been constructed and researchers have a wide variety of choices. A typical approach to prepare these synthetic probes is “pre-formed” manner, namely, a glycosylation is carried out using emissive nucleobases under carefully selected conditions to control both stereoselectivity at the anomeric position and regioselectivity of the aglycon attack. Such a glycosylation usually requires a time-consuming trial-and-error procedure, because the reaction selectivities are affected by the interaction of the protected groups of both the sugar and aglycon. On the other hand, the preparation approach based on “post-forming” manner would be effective since a cumbersome glycosylation could be done in an early synthesis stage. We have been developing anodic intermolecular cycloadditions in lithium perchlorate/nitromethane electrolyte solution. In this electrolyte solution, unactivated alkenes can function as effective carbon nucleophiles to trap anodically generated cations or radical cations, leading to the formation of corresponding ring systems. Especially, we previously reported that the anodic oxidation of methoxyphenols in the presence of alkene nucleophiles was able to give highly emissive dihydrobenzofuran derivatives through formal [3 + 2] cycloadditions. These results in hand, we herein demonstrate a short-step “post-forming” synthesis of novel emissive nucleoside analogues based on the anodic cycloadditions. Initially, we tried to attach a methallyl moiety to a ribose scaffold as an alkene nucleophile. After the numerous optimizations, we finally accomplished the stereoselective allylation at the anomeric position to obtain both a- and b-methallyl ribose and we were able to use each corresponding pure form for further transformations. The anomeric stereochemistry was successfully fixed at the first synthesis stage. Methoxyphenols were then anodically oxidized in the presence of the methallyl ribose and we found that emissive dihydrobenzofuran structures were able to be constructed on the sugar moiety in one step. The emission color was significantly affected by the carbonyl substituent, ranging roughly from 400 nm to 500 nm with long stokes shift values. In the presentation, the synthesis details and photophysical properties will be discussed.

On the electrochemical deposition of metal–organic frameworks

In this paper we study and compare the anodic and cathodic electrodeposition of Metal–Organic Frameworks (MOFs) and suggest guidelines for the electrodeposition of new MOFs with this technique. KHUST-1 was electrodeposited both anodically and cathodically and a four step mechanism is proposed to explain the anodic synthesis.

In situ metal doping during modified anodization synthesis of Nb2O5 with enhanced photoelectrochemical water splitting

SignificanceA new technique of in situ doping of alkali metal (Li+, Na+, K+, Rb+, and Cs+) in Nb2O5 was showcased by the modified anodization of Nb foils at high frequency, negative‐to‐positive pulsed voltage. At the optimized dopant concentration and synthesis condition, the doped‐Nb2O5 shows twofold enhancement in photoelectrochemical water splitting efficiencies compared with the undoped Nb2O5 electrode, as a result of improved charge carrier density and enhanced surface charge transfer. © 2015 American Institute of Chemical Engineers AIChE J, 62: 352–358, 2016

Electrochemical synthesis of nanosized TiO2 nanopowder involving choline chloride based ionic liquids

Abstract The paper presents some experimental results regarding the electrochemical synthesis of TiO2 nanopowders through anodic dissolution of Ti metal in choline chloride based eutectic mixtures (DES). A detailed characterization of the obtained titania has been performed, using various techniques, including XRD, Raman spectroscopy, XPS, SEM associated with EDX analysis, BET and UV–vis diffuse reflectance spectra. The anodic behavior of Ti electrode in DES has been also investigated. The photoreactivity of the synthesized materials was evaluated for the degradation of Orange II dye under UV (λ = 365 nm) and visible light irradiation. An anodic synthesis efficiency of minimum 92% has been determined. The as-synthesized TiO2 showed amorphous structure and a calcination post-treatment at temperatures between 400 and 600 °C yielded anatase. The anodically obtained nanocrystalline oxides have crystallite sizes of 8–18 nm, a high surface area and enhanced photocatalytic effect.

Oxide nanofilms on copper and silver: anodic synthesis and semiconducting properties

Structure-sensitive properties of oxide nanofilms anodically formed on single crystals and polycrystalline silver and copper were determined by photoelectrochemical methods and scanning electron microscopy. At transition from polycrystalline substrate to single crystals the structural disordering decreases for Ag(I) oxide and increases for Cu(I) oxide in accordance with morphological modification.

Effect of NaBF4 addition on the anodic synthesis of TiO2 nanotube arrays photocatalyst for production of hydrogen from glycerol–water solution

Addition of NaBF4 during anodic synthesis of TiO2 nanotube arrays (TNTAs) photocatalyst and its application for generating hydrogen from glycerol–water solution has been investigated. The TNTAs were synthesized by anodic oxidation of titanium metal in glycerol electrolyte solution containing NH4F. During the process, the NaBF4 with different concentrations were added to the solution. Annealing of the formatted TNTAs were performed at 500 °C for 3 h under 20% H2 in argon atmosphere, to produce crystalline phase photocatalyst. FESEM analysis showed that self-organized and well ordered TNTAs have range of inner diameters, wall thicknesses and lengths approximately 62–130 nm, 27 nm and 1.53 μm, respectively. FTIR analysis indicated that carbon, nitrogen and boron were incorporated into the TNTAs lattice. Refer to UV–Vis DRS and XRD analysis, the TNTAs photocatalysts prepared have the band gap range of 2.70–3.10 eV, with mostly have anatase phase. The NaBF4 addition during synthesis, resulted modified TNTAs that can reduce the recombination of photo-induced electrons-holes. Photocatalytic hydrogen production test, from glycerol–water solution, indicated that TNTAs with the addition of NaBF4 during anodic synthesis process showed higher hydrogen production comparing to the one without NaBF4 addition. Among them the TNTAs,b (with the addition 5 mM of NaBF4) showed up to 32% improvement in the hydrogen production and can be considered as the optimum condition.

Self-Ordered Titanium Dioxide Nanotube Arrays: Anodic Synthesis and Their Photo/Electro-Catalytic Applications.

Metal oxide nanotubes have become a widely investigated material, more specifically, self-organized titania nanotube arrays synthesized by electrochemical anodization. As a highly investigated material with a wide gamut of applications, the majority of published literature focuses on the solar-based applications of this material. The scope of this review summarizes some of the recent advances made using metal oxide nanotube arrays formed via anodization in solar-based applications. A general methodology for theoretical modeling of titania surfaces in solar applications is also presented.

Anodic synthesis of Np(VII) compounds from acetate solutions

A procedure was suggested for the synthesis of Np(VII) compounds by electrochemical oxidation in acetate solutions. The conditions for preparing compounds of type MNpO4·nH2O, where M is a single-charged cation of alkali metals, ammonium, silver, guanidinium, or tetraalkylammonium, and of Np(VII) compounds with double-charged cations of alkaline-earth metals, Cu, Cd, and Zn were studied in detail. The compounds were characterized by chemical analysis and by IR and electronic spectroscopy.

Electrosynthesis of Electrochromic Poly-3,4-ethylenedioxythiophene – Polyaniline Hybrid Layers

The poly-3,4-ethylenedioxythiophene (PEDOT) – polyaniline (PANI) electrochromic films are obtained by the electrochemical polymerization of EDOT on the indium tin oxide (ITO) surfaces modified by a thin film of PANI. It is shown that the anode synthesis of PEDOT on the ITO electrode modified by PANI leads to a significant improvement of the contrast ratio and changes a potential limit of the electrooptical activity of the obtained layer as compared with the individual polymer films.

ChemInform Abstract: Synthesis of 12-Oxophytodienoic Acid (12-OxoPDA) and the Compounds of Its Enzymic Degradation Cascade in Plants, OPC-8:0, -6:0, -4:0 and -2: 0 (epi-Jasmonic Acid), as Their Methyl Esters.

The synthesis of 12-Oxophytodienoic acid, and the compounds of its enzymic degradation sequence, OPC-8:0, -6:0, -4:0 and -2:0, important plant metabolites derived from linolenic acid, is reported. The syntheses use the known cyclopent-3-ene-1,2-diacetic acid as an early intermediate, and this is derived from the Cope rearrangement of 5-vinyltrinorborn-2-ene via bicyclo[4.3.0]nona-3,7-diene. lodolactonisation and tributyltin hydride reduction provides the key intermediate (3-oxo-2-oxabicyclo[3.3.0]octan-6-yl)acetic acid for the OPC series, whilst phenylselenolactonisation and elimination provides the necessary unsaturated lactone (7-oxo-8-oxabicyclo[3.3.0]oct-2-en-4-yl)acetic acid for 12-oxoPDA. Members of the OPC-series were made by chain extending the saturated oxabicyclooctane acid: that for the OPC-4:0 involved double Arndt–Eistert reaction, whilst the intermediates for OPC-6:0 and -8:0 were made by Kolbe anodic crossed coupling. The lactones were then converted via their lactols, Wittig reaction, esterification and oxidation, into the compounds of the OPC ester series, including OPC-2:0 (methyl epi-jasmonate).The unsaturated lactone 8-(7-oxo-8-oxabicyclo[3.3.0]oct-2-en-4-yl)octanoic acid required for 12-oxoPDA synthesis could also be prepared by anodic synthesis either from (7-oxo-8-oxabicyclo[3.3.0]oct-2-en-4-yl)acetic acid, or from its 2-phenylseleno-2, 3-dihydro precursor as elimination occurred concomitantly during the reaction. Since yields were low, the unsaturated acid lactone was converted into its lactol and the (Z)-pent-2-enyl side-chain was inserted first. After TBDMS blocking of the cyclopentene hydroxy group, the side-chain was elaborated to give 5-(pent-2-enyl)cyclopent-2-enylacetaldehyde and chain extension carried out by a Grignard-demesylation procedure. Sequential desilylation and depyranylation, followed by oxidation of the diol, gave 12-oxoPDA, isolated as its methyl ester.