Electrochemical Oxidation Method Research Articles

New Ethylenedithio-TTF Containing a 2,2,5,5-Tetramethylpyrrolin-1-yloxyl Radical through a Vinylene Spacer and Its FeCl4− Salt—Synthesis, Physical Properties and Crystal Structure Analyses

To develop novel magnetic conductors exhibiting conducting/magnetic bifunctionalities and peculiar responses to applied magnetic fields, we synthesized new EDT-TTF (ethylenedithiotetrathiafulvalene) donor containing a 2,2,5,5-tetramethylpyrrolin-1-yloxyl radical through a π-conjugated vinylene spacer 1 and examined its electronic and crystal structures, and physical properties. We also prepared its cation radical salts by an electrochemical oxidation method and successfully cleared the crystal structures and magnetic properties of the cation radical salts, 1·FeCl4 and 1·GaCl4. These salts have strongly dimerized one-dimensional arrays of the fully oxidized donor molecules, giving rise to the formation of spin-singlet state of the π cation radical spins in the dimer. On the other hand, the FeCl4- anion locates on the side of the dimers with very short S-Cl contacts and mediates very strong π-d interaction between the donor and anion moieties, resulting in the antiferromagnetic behavior of the Weiss temperature of θ = -3.9 K through its d-π-d interaction.

Theoretical and experimental studies on the anodic oxidation process for synthesis of self-ordering TiO2 nanotubes: Effect of TiO2 nanotube lengths on photocatalytic activity

In this study, TiO2 nanotubes were synthesized via anodic electrochemical oxidation method and the effects of different parameters such as applied voltage, anodization time, electrolyte solution temperature and pH on the outer diameter and length of TiO2 nanotubes in a NH4F/C2H6O2/H2O electrolyte system were investigated. Based on the experiments, length and outer diameter of the synthesized nanotubes were in the range of approximately 9–71μm and 81–171nm respectively which were found by scanning electron microscopy (SEM) analysis technique. Also a generalized theoretical model was developed to predict the morphology (length and outer diameter) of TiO2 nanotubes prepared by anodization method. The collected experimental data based on classic design was used to obtain adjustable parameters in the presented model.Photocatalytic activity of different lengths TiO2 nanotubes were evaluated in terms of the degradation of formic acid in aqueous solution under ultraviolet (UV) light irradiation. Results showed that the optimal tube length would be an important factor to achieve the good photocatalytic performance of TiO2 nanotube arrays. The highest photocatalytic performance was found for the synthesized TiO2 nanotubes with 46μm length.

From graphite-clay composites to graphene electrode materials: In-situ electrochemical oxidation and functionalization

The development of cost- and time-effective methods to synthesize graphene materials is very urgent in order to promote its large-scale application in electrochemical energy storage devices. Herein, graphene materials were synthesized by the electrochemical exfoliation (electrochemical oxidation) of graphite-clay rods with different clay:graphite ratios in aqueous solution and in short reaction time (1h). The dual role of electrochemical oxidation reaction was presented: (1) the electrochemical oxidation reaction facilitates the exfoliation of pencil graphite leads and in-situ forms functional groups on graphene; (2) the electrochemical oxidation reaction enhances the Faradaic reaction in supercapacitor. The in-situ electrochemical oxidation and functionalization methods can transform low purity graphite to high-value graphene electrode materials for supercapacitors and lithium ion batteries. The specific capacitances of exfoliated graphene are 20-time larger than that of graphite-clay composites. This work provided a value-added way that can transform the low-purity graphite resources to high performance graphene electrode materials.

Electrochemical Degradation of Methyldopa on a Fe Doped PbO2 Electrode: Electrode Characterization, Reaction Kinetics and Energy Demands

The electrochemical degradation of methyldopa in aqueous solution using a Fe-PbO2 electrode was systematically investigated. In contract with the traditional undoped PbO2 electrode, the constructed Fe-PbO2 electrode displayed a more compact structure with smaller crystal size, accompanying with larger electrochemically active surface area and higher electrochemical activity. The effects of operational parameters were studied, and according to the degradation efficiency and energy efficiency, the relative optimal experimental conditions were identified as electrolyte concentration 0.1 mol/L, current density 30 mA/cm2, initial methyldopa concentration 800 mg/L and initial pH 3. The EE/O values were calculated among all the experiments, providing the economic evaluation for the treatment of organic pollutants using electrochemical oxidation method. Kinetic investigations demonstrated that the degradation of methyldopa followed the pseudo-first-order kinetic model.

Effect of Glassy Carbon Electrode Surface on Electrosynthesis of Platinum Nanoparticles and Their Catalytic Durability for Formic Acid Oxidation

Effect of glassy carbon electrode (GCE) surface on electrosynthesis of platinum nanoparticles (PtNPs) and their catalytic durability for formic acid oxidation was systemically investigated. GCEs were pretreated by mechanical polishing and two electrochemical oxidation methods. Experimental results showed that newly generated oxygen-containing groups at GCE surfaces were unfavorable for early nucleation reaction of Pt, and nucleation sites were those sp C aromatic domains, whose features would vary with pretreatment procedures; employment of multi-pluses with high deposition overpotential enabled the electrosynthesis of highly dispersive PtNPs on all the GCE surfaces. The durability of as-prepared PtNPs/GCEs was tested and compared by voltammetric method. It was found that the starting surfaces of GCEs also dominated the morphologic variations of PtNPs and the corrosion behaviors of themselves. Just the electrochemically oxidizing GCE surfaces could absorb Pt cations generated in the cyclic test processes, which could block the redeposition of dissolved Pt cations at PtNPs to retard the formation of inter crystal surfaces; PtNPs on the electrochemically oxidizing GCEs thus had more stable catalytic activity than those on the polished one. The results presented in this study revealed that the adsorption property of carbon support should be important to the durability of PtNPs/C.

MODELING AND EXPERIMENTAL STUDY OF ELECTROCHEMICAL OXIDATION OF ORGANICS ON BORON-DOPED DIAMOND ANODE

Electrochemical oxidation on boron-doped diamond (BDD) electrodes is reportedly more effective than conventional chemical or electrochemical oxidation methods for the removal of recalcitrant organic contaminants from aqueous effluents. This work investigated the electrochemical oxidation of acetic acid and nuclear process effluents containing representative recalcitrant chlorinated and nitrogenated organics on a BDD anode using a DiaCell® apparatus. The removal of organic carbon mostly depended on applied current density, mass transfer effects, and the properties of organic compounds. The total organic carbon concentrations in the solutions were reduced to as low as 0.5 g·m−3, achieving mineralization of up to 99% of organic carbon. Dissolved oxygen significantly contributed to the removal of organic carbon at low concentrations. In particular, the BDD anodic oxidation system was capable of mineralizing organic carbon representing a mixture of mineral oil and carboxylic, aromatic, chlorinated, and nitroge...

Cold incineration of sucralose in aqueous solution by electro-Fenton process

The effective removal of artificial sweeteners sucralose (SUC) from water was carried out for the first time by an electrochemical advanced oxidation method. Electro-Fenton process was used to generate hydroxyl radicals, a highly powerful oxidant species that are able to oxidize organic pollutants until their mineralization at room temperature. The effect of catalyst (Fe2+) concentration and applied current on the mineralization of SUC during electro-Fenton treatment was evaluated. Results showed that the electro-Fenton process is capable to mineralize SUC solution effectively. A higher mineralization rate was obtained with BDD than Pt anode. Mineralization current efficiency results pointed out better mineralization efficacy (MCE) at relatively short electrolysis time and low applied current values. The formation and evolution of the concentration of carboxylic acids and released inorganic ions, as a consequence of mineralization process, were followed along the treatment. Finally, the toxicity of SUC and its oxidation intermediates products was assessed along the mineralization process using Microtox method to show the detoxification capacity of the process.

Preparation, Characterization, Redox, and Photoinduced Electron‐Transfer Properties of the NIR‐Absorbing N‐Ferrocenyl‐2‐pyridone BODIPYs

Mono‐ and di‐(N‐ferrocenyl‐2‐pyridone)‐containing BODIPYs were prepared using a set of ferrocene‐enamine cyclization reactions. The target compounds were characterized by UV‐Vis, NMR, and mass spectrometry, while their redox properties were probed by the electrochemical, spectroelectrochemical, and chemical oxidation methods. Redox properties of the di‐(ferrocenyl)‐containing BODIPY are suggestive of a lack of electronic coupling between the two ferrocene groups. Oxidation of the ferrocene(s) in the target BODIPYs results in their observable fluorescence, while transient absorption spectroscopy data indicate fast electron‐transfer from ferrocene donor to the photoexcited BODIPY acceptor. Density functional theory (DFT) and time‐dependent DFT (TDDFT) methods were used to elucidate electronic structures of the organometallic BODIPYs and confirm the presence of the low‐energy metal‐to‐ligand charge‐transfer states in the NIR region.

Electrodeposited three dimensional tin nano wire anode for thin film Li-Ion micro batteries

The tin wire grown over anodic aluminium oxide template is used as anode for Li ion batteries. This work entails porous template formation through double step electrochemical oxidation method optimized by design of experiment and Tafel polarization. The X-ray diffraction results of different anodized specimens show amorphous alumina layer formation. The pores in alumina matrix and the filamentous outward projection of Sn wires are observed from micrographs. The initial discharge capacity of Sn wire and Sn planar thin film is observed to be around 850 and 531 mA h/g respectively. The 50th cycle capacity of Sn wire is observed to be around 494 mA h/g which is very high when compared to theoretical capacity of graphite anodes.

Electrochemically oxidized multiwalled carbon nanotube/glassy carbon electrode as a probe for simultaneous determination of dopamine and doxorubicin in biological samples.

A facile and effective approach of fabricating oxidized multiwalled carbon nanotube/glassy carbon electrode (OMWCNT/GCE) is herein reported. The OMWCNT/GCE was prepared by electrochemical oxidation method in basic media (0.5mol L(-1) NaOH solution) and used as a sensor for simultaneous determination of dopamine (DA) and doxorubicin (DOX). Scanning electron microscopy, energy dispersive X-ray spectroscopy and cyclic voltammetry were used for characterization and performance study of the OMWCNT/GCE. The modified electrode exhibited good electrocatalytic properties toward the oxidation of DA and DOX. Peaks potential difference of 240mV between DA and DOX was large enough to determine DA and DOX individually and simultaneously. Square wave voltammetry (SWV) was used for the simultaneous determination of DA and DOX in their binary mixture. Under the optimum conditions, the linear concentration dependences of SW peak current responses were observed for DA and DOX in the concentration ranges of 0.03-55μmolL(-1) and 0.04-90μmolL(-1), respectively. The detection limits (S/N = 3) were 8.5 × 10(-3)μmolL(-1), and 9.4 × 10(-3)μmolL(-1) for DA and DOX, respectively. The analytical utility of OMWCNT/GCE was also successfully demonstrated for the simultaneous determination of DA and DOX in human blood serum and urine samples. Graphical Abstract Fabrication of new oxidized multiwalled carbon nanotube/glassy carbon electrode for simultaneous determination of dopamine and doxorubicin.

Electrochemical dispersion method for the synthesis of SnO2 as anode material for lithium ion batteries

A method of electrochemical oxidation and dispersion of tin electrodes under alternating pulse current was proposed as a novel approach for the synthesis of SnO2 nanoparticles suitable as an alternative anode for lithium ion batteries. The electrochemically obtained, non-hydrated SnO2 nanopowder was crystalline, having a tetragonal lattice and an average crystallite size of about 11–16 nm. When used as anode in lithium ion batteries, the material delivered around 680 mAh g−1 reversible capacity with 66 % capacity retention over more than 60 cycles.

Fabrication, characterization and biocompatibility of TiO2 nanotubes via anodization of Ti6Al7Nb

Ti6Al7Nb has been used as an implant material because of its good corrosion resistance and high mechanical properties. However, the presence of aluminium (Al), which may lead to ostemalacia, anaemia and nervous system disorders, limited its wide clinical use. In this study, a titanium oxide (TiO2) nanoporous layer was fabricated on a Ti6Al7Nb alloy using an electrochemical anodic oxidation method. The structure of the TiO2 nanoporous layer was examined by scanning electron microscopy. The chemical compositions of the samples were analysed by X-ray photoelectron spectroscopy (XPS). Biocompatibility was evaluated by culturing rat osteoblast cells. The result showed that TiO2 nanoporous layers comprise a mixed oxide containing TiO2 and a small amount of nobium oxides (Nb2O5) and almost no elemental aluminium. The outer layer of the TiO2 nanoporous layer comprises highly ordered nanotubes and the inner layer forms disordered nanopores. The TiO2 nanoporous layer could support the adhesion, proliferation, differentiation and gene expression of osteoblast cells. Therefore, a TiO2 nanoporous layer could enhance the biocompatibility of Ti6Al7Nb alloy and is as a promising candidate for Ti6Al7Nb alloy implants.

Decomposition Studies of Aqueous Phase Ligands Used in Advanced Reprocessing Flowsheets

Two potential methods for decomposing organic ligands in nitric acid have been studied using acetic acid and diethylenetriaminepentaacetic acid (DTPA) as examples; these methods were oxidation by nitric acid at elevated temperatures (70-110°C) and electrochemical oxidation, both direct and mediated electrochemical oxidation. Based on total carbon measurements, acetic acid proved to be rather stable against nitric acid oxidation whereas 60-80% of DTPA was decomposed at 100-110°C. Electrochemical oxidation methods were generally more effective in decomposing acetic acid and DTPA with mediated electrochemical oxidation using Ag(II) ions the most effective method under the conditions tested, with ∼80 and >90% loss of carbon from acetic acid and DTPA solutions respectively, at ambient temperature in 6M HNO3.

Synthesis and characterization of supercapacitive behavior of electrodeposited PANI/Co3O4layered composite electrode

Polyaniline (PANI), cobalt oxide (Co3O4) and PANI/Co3O4 layered thin films are successfully synthesized on stainless steel substrate using electrodeposition technique. The electrochemical oxidation (anodic) method is employed for oxidation of layered composite. The structural and morphological studies of these films are investigated using X-ray diffraction and scanning electron microscope. The electrochemical supercapacitive behavior of the films is studied using cyclic voltammetry and galvanostatic charge–discharge measurements in 0.5M Na2SO4 electrolyte bath. The layered composite PANI/Co3O4 electrode shows almost 50% increase in specific capacitance and remarkable enhancement in specific energy and specific power in comparison with the parent Co3O4 electrode. For layered composite electrode after 500 cycles of charge–discharge, it is observed that specific capacitance retains ∼ 100% compared to the first cycle. The electrochemical impedance spectroscopy is also studied. The simulated values of resistance and capacitance are calculated along with equivalent circuit. Hence, the layered composite PANI/Co3O4 electrode may have great potential application for electrochemical supercapacitors.

Characterization of oxidized carbon foil as a low-cost alternative to carbon felt-based electrodes in bioelectrochemical systems

The recent development of bioelectrochemical systems (BESs) is based on the growth of microorganisms on carbon electrode materials. Carbon felt and cloth are the most widely used electrode materials; however, less expensive alternative materials are required when BESs are used for wastewater treatment. In this work, graphite carbon foil was modified using chemical, thermal, and electrochemical oxidation methods to improve its surface characteristics, and the resulting material was compared with oxidized carbon felt. The materials were physically, chemically, and electrochemically characterized. The isotherms revealed that thermal oxidation increased the surface area of the carbon foil by 39 %, reaching a value of 26.2 m2 g−1. Electrochemical impedance spectroscopy showed that the charge transfer resistance of the untreated carbon foil was 445 Ω, which decreased to 34 Ω after electrochemical oxidation. Additionally, cyclic voltammetry revealed a 100-fold increase in current density for the foil and felt materials following electrochemical oxidation. Based on its large surface area, low charge transfer resistance, remarkable current density under polarization, and comparatively low cost, the graphite carbon foil was identified as a promising alternative that could be used for constructing bioelectrodes.

Probing Electronic Communications in Heterotrinuclear Fe-Ru-Fe Molecular Wires Formed by Ruthenium(II) Tetraphenylporphyrin and Isocyanoferrocene or 1,1'-Diisocyanoferrocene Ligands.

Two new heterotrinuclear Fe-Ru-Fe complexes of ruthenium(II) tetraphenylporphyrin axially coordinated with a pair of isocyanoferrocene ((FcNC)2RuTPP, 1) or 1,1'-diisocyanoferrocene (([C5H4NC]2Fe)2RuTPP, 2) ligands [Fc = ferrocenyl, TPP = 5,10,15,20-tetraphenylporphyrinato(2-) anion] were synthesized and characterized by UV-vis, magnetic circular dichroism, NMR, and FTIR spectroscopies as well as by electrospray ionization mass spectrometry and single-crystal X-ray diffraction. Isolation of insoluble polymeric {([C5H4NC]2Fe)RuTPP}n molecular wires (3) was also achieved for the first time. The redox properties of the new trinuclear complexes 1 and 2 were probed using electrochemical (cyclic voltammetry and differential pulse voltammetry), spectroelectrochemical, and chemical oxidation methods and correlated to those of the bis(tert-butylisocyano)ruthenium(II) tetraphenylporphyrin reference compound, (t-BuNC)2RuTPP (4). In all cases, the first oxidation process was attributed to the reversible oxidation of the Ru(II) center. The second and third reversible oxidation processes in 1 are separated by ∼100 mV and were assigned to two single-electron Fe(II)/Fe(III) couples, suggesting a weak long-range iron-iron coupling in this complex. Electrochemical data acquired for 2 are complicated by the interaction between the axial η(1)-1,1'-diisocyanoferrocene ligand and the electrode surface as well as by axial ligand dissociation in solution. Spectroelectrochemical and chemical oxidation methods were used to elucidate the spectroscopic signatures of the [1](n+), [2](n+), and [4](n+) species in solution. DFT and time-dependent DFT calculations aided in correlating the spectroscopic and redox properties of complexes 1, 2, and 4 with their electronic structures.

Unusually Strong Long-Distance Metal-Metal Coupling in Bis(ferrocene)-Containing BOPHY: An Introduction to Organometallic BOPHYs.

The first organometallic BOPHY (BOPHY=bis(difluoroboron)-1,2-bis{(pyrrol-2-yl)methylene}hydrazine) containing two ferrocene substituents was prepared through a Knoevenagel condensation between tetramethyl substituted BOPHY and ferrocene carboxaldehyde. An unprecedentedly strong long-range (≈17.2 Å) metal-metal coupling in this new complex was investigated using electrochemical, spectroelectrochemical, and chemical oxidation methods. Electrochemical data is indicative of a 200 mV separation between the first and the second ferrocene-centered oxidation processes. Formation of the mixed-valence states and appearance and disappearance of two NIR bands were observed during stepwise oxidation of the first organometallic BOPHY. The electronic structure and the nature of the excited states in this new chromophore were studied by DFT and TDDFT calculations.

Hydrophilic Carbon Nano-Particles; Preparation and Applications

The hydrophilic carbon nanoparticles have been produced from synthetic graphite blocks by the electrochemical oxidation method in pure water. The resulting electrolyzed solution contains colloidal carbon nanoparticles (mean diameter is ca. 400 nm) and shows the pH value of around 2.5. The colloidal state of the solution is maintained more than a several years. After evaporation of water from the solution, carbon powders are obtained, which show a high solubility to water, namely the powder is hydrophilic. The electrolyzed solution containing carbon nanoparticles directly used as the electrical conductivity enhancer for the restoring the deteriorated lead-acid batteries by electrochemical method. The hydrophilic carbon nanoparticles were used as the environmental friendly solid-lubricant for the mechanical cutting coolants. In the case of aqueous coolants, the oily substances are used in the emulsion state in usual. By using the hydrophilic carbon nanoparticle suspension, no surfactants and no oily substances are required to maintain the suspension state. However, the cutting coolants are used in the pH values of alkaline state near 10, so the hydrophilic carbon nanoparticle solution has been neutralized by alkaline substances such as alkanolamines. In the case of oily cutting fluids for heavy duties, carbon mamo-particle powders are used after neutralized by basic barium dinonylnaphthalenesulfonate. The aqueous solutions of hydrophilic carbon nanoparticles exhibit the ability of sanitization effects to the cutting fluids and prolong the life times of them.

A Novel Exfoliation Strategy to Significantly Boost the Energy Storage Capability of Commercial Carbon Cloth.

A facile and efficient electrochemical oxidation method to directly activated carbon cloth as an excellent electrode material for supercapacitors is reported. Flexible asymmetric supercapacitor devices based on activated carbon cloth anodes reach a remarkable energy density and excellent long-term durability.

Valence‐Optimized Vanadium Oxide Supercapacitor Electrodes Exhibit Ultrahigh Capacitance and Super‐Long Cyclic Durability of 100 000 Cycles

Vanadium oxides (VOx) have been intensely investigated as cathode materials for SCs due to the multiple stable oxidation states (III–V) of vanadium in its oxides and typical layered structure. Nevertheless, fast capacity fading is always observed for VOx upon cycling in aqueous electrolyte. Developing an efficient strategy to essentially promote the durability of VOx in mild aqueous electrolyte remains a crucial challenge. Here, an innovative and effective method is reported to significantly boost the durability and capacitance of VOx through tuning the valence state of vanadium. The valence state of vanadium is optimized through a very facile electrochemical oxidation method. A superior electrochemical performance and an ultralong cyclic stability of 100 000 cycles are obtained for these electrodes. An in‐depth study on the variation for the valence state of vanadium during the oxidation process and the cyclic stability test indicates that the long cyclic stability has an important relationship with the distribution of the valence state of vanadium.