Tetraethylammonium Perchlorate Research Articles

Influence of Imidazolium Pyrrole-2-Carbonitrile on the Electrochemical Reduction of CO2 on Silver Metal in Acetonitrile

Electrochemical reduction of CO2 into value-added fuels or chemical feedstocks is one of several viable strategies for mitigating carbon dioxide waste. However, CO2 is thermodynamically stable molecule requiring high energy to activate it making this process energy demanding. Therefore, selective catalysts and stable electrolytes with high CO2 solubility are desired. Ionic liquids (ILs) are versatile solvents with tunable properties including high CO2 solubility and electrochemical stability. Literature suggests that ILs co-catalyze the CO2 reduction reaction and can alter the reaction route through its specific interactions with CO2 and reaction intermediates. Therefore, in this study, we examined the influence of 1-ethyl-3-methylimidazolium 2-cyanopyrolide ([EMIM][2-CNpyr]) IL on CO2 reduction in acetonitrile on Ag surface. [EMIM][2-CNpyr] has the carbene, N-heterocyclic, and amine functionalities to complex with CO2. The performed linear sweep voltammetry experiments shows the onset potential of CO2 reduction is -1.82 V (vs. Ag/Ag+) in the presence of the IL. This is confirmed to be due to the presence of the IL when compared to the control experiments with tetraethylammonium perchlorate which is a non-reactive supporting salt. The bulk electrolysis with 1.5 M [EMIM][2-CNpyr] in acetonitrile over Ag cathode showed reduction of CO2 to carbon monoxide (CO) with high selectivity (>80 %) at -2.1 V (vs. Ag/Ag+) and stable current density (~ 6 mA·cm−2) for at least 12 h without any electrolyte decomposition as confirmed by NMR analysis. The fundamental understanding of the interfacial microenvironment is needed and spectro-electrochemical studies are currently underway to probe these interfaces and to develop similarly high performing electrolytes for implementation of combined carbon capture and utilization in the future.

(Digital Presentation) Development of Linear Paired Electrolysis for the Oxidation of Benzyl Alcohol

Electrochemical processes are always coupled reactions, with anodic oxidation and cathodic reduction. Paired electrolysis system can produce valuable products at both anode and cathode, and maximizes the efficient use of applied energy. Especially, the conversion of a single raw material to a single valuable product by paired electrolysis referred to as linear paired electrolysis. Since the electron transfers at both electrodes can produce a single valuable product in the linear paired electrolysis system, a single compound is generated with a current efficiency of 200%, theoretically. The linear paired electrolysis is appearing electrochemical process, however, it remains a challenging topic in organic electrochemical synthesis because it is complicated system. Herein, we develop the synthesis process of benzaldehyde by oxidation of benzyl alcohol using linear paired electrolysis. Electrochemical synthesis of carbonyl compounds by oxidation of alcohol is a challenging topic due to the selectivity and efficiency. We use aqueous media as the electrolyte and oxygen as the terminal oxidant to increase the selectivity and efficiency in the electrochemical transformation.Electrochemical oxidation of benzyl alcohol was performed by following method. A 4.0 mmol of tetraethylammonium perchlorate (Et4NClO4) was dissolved in 20 mL of acetonitrile (CH3CN) and 20 mL of H2O (Milli-Q water). The resultant mixture was used as an electrolyte in this study. The electrolyte was purged with O2 or Ar for 30 min, and then a 0.5 mmol of benzyl alcohol was dissolved in the electrolyte. A 20 mL of cyclohexane was added to the electrolyte to prevent overoxidation of the product. Electrolysis was conducted at room temperature with three electrodes method: a 2 cm2 of carbon felt (CF) anode, a 2 cm2 of various cathode materials, and a Ag/AgCl reference electrode.In the present study, transformation of 4-tert-butyl-benzyl alcohol (peak potential of oxidation: +1.76 V vs. Ag/AgCl) to 4-tert-butyl-benzaldehyde was used as a model reaction for optimization of reaction condition. First, we carried out constant potential electrolysis at +1.8 V vs. Ag/AgCl. Electrolysis using O2-saturated electrolyte resulted in a higher yield of the benzaldehyde (71%) than that using an Ar-saturated electrolyte (45%) when the coulomb amount was 2 F. This result suggested that O2 promoted the desired conversion. Cyclic voltammograms of the electrolyte suggested that reduction of O2 could proceed at cathode. Cathodic reduction of O2 could produce reactive oxygen species (ROS) which have strong oxidizing power. As a result, cathode in our electrochemical cell could have high oxidation potential. Therefore, it was indicated that desired oxidation progressed using ROS in our electrochemical system. In next step, we conducted electrochemical reactions under constant potential electrolysis at −0.7 V vs. Ag/AgCl which was suitable for the reduction of O2. In this condition, benzaldehyde was obtained in 86% yield when the coulomb amount was 2 F, and no byproduct was observed. From this result, we proposed the indirect oxidation pass using ROS generated at cathode. Interestingly, when the cathode (working electrode) was set to −0.7 V vs. Ag/AgCl, the measured potential of the anode (counter electrode) was +1.5 to +1.8 V vs. Ag/AgCl. Therefore, when the reduction of O2 proceeded at cathode, potential of anode reached sufficient value to oxidize the benzyl alcohol. It meant both direct oxidation and indirect oxidation progressed in a single electrochemical cell. It was linear paired electrolysis system of oxidation of benzyl alcohol.We considered the reaction on cathode was important to progress desired oxidation, and the effect of different cathode materials was also investigated. In this investigation, carbon felt, glassy carbon, Pt, and Ni could be used as cathodes in the linear paired electrolysis system. In contrast, a sharp decrease in current was observed immediately after the start of electrolysis using Al as the cathode. Observation and analysis of the used Al electrodes suggested that surface of Al cathodes was passivated. It was indicated that electrochemically generated ROS with high oxidizing power might promote the passivation of the cathode materials. The observed passivation also supported the generation of ROS at cathode in our electrochemical cells.Finally, we demonstrated the versatility of developed linear paired electrolysis with various benzyl alcohols. Especially, 4-Methoxybenzaldehyde was not only obtained in high yields (94%) but also with maximum current efficiencies of 146%. The exceeding 100% current efficiency also supported the linear paired electrolysis system.In summary, we successfully developed a process for oxidation of benzyl alcohols via linear paired electrolysis with high selectivity and efficiency. Since desired reaction progressed both electrodes and aqueous media and O2 were used, this system offered green and sustainable chemical synthesis process. Figure 1

Complexation of U(VI) with BiPDA, DmBiPDA, and PhenDA: Comparison on Structures and Binding Strengths in Aqueous and DMSO/20%(v)H2O Solutions.

The stability constants (log β) of 1:1 uranyl complexes with three N,O-mixed donor ligands (L = 2,2'-dipyridyl-6,6'-dicarboxylate, 3,3'-dimethyl-2,2'-bipyridine-6,6'-dicarboxylate, and 1,10-phenanthroline-2,9-dicarboxylate, denoted as BiPDA, DmBiPDA, and PhenDA, respectively) in aqueous and DMSO/20%(v)H2O solutions were determined by spectrophotometry in 0.1 M tetraethylammonium perchlorate. The effects of ligand preorganization, steric hindrance, and solvation on the binding strength of U(VI) with the three ligands were discussed. In aqueous solution, PhenDA forms stronger complexes with U(VI) than BiPDA due to its well-preorganized structure. In DMSO/20%(v)H2O solution, in contrast, the strong solvation effect of DMSO on the ligands reduces the energy gap between the trans- and cis-conformations of BiPDA, resulting in log β(UO2(BiPDA)) > log β(UO2(PhenDA)). The steric hindrance of methyl groups on DmBiPDA makes the complex UO2(DmBiPDA) of the lowest stability in both aqueous and DMSO/20%(v)H2O solutions. Single-crystal structural data of U(VI) complexes with the three ligands indicate that the ligand coordinates with UO22+ via aromatic nitrogen atoms and carboxylate oxygen atoms. There is no clear correlation between the trend of the stability constants in solutions and the U-N/O bond lengths of the three crystal complexes. Nevertheless, DmBiPDA coordinates to UO22+ in a high-strain fashion as a result of the steric hindrance of methyl groups while BiPDA in a low-strain fashion, which is in accordance with the relative complexation strength of the two respective complexes. The results from this work help us understand the effect of ligand preorganization and solvation on the binding strength of actinides with multidentate N,O-mixed ligands in solid and solutions, which is of importance in designing ligands for the partitioning of actinides from nuclear wastes.

Effect of Calcination Temperature on The Structure and Catalytic Performance of ZrO2 Catalyst in Phenol Degradation

Abstract In this study, tetragonal electrogenerated zirconia nanoparticles (t-EGZrO2) was prepared via simple electrochemical method, and stabilized at a lower calcination temperature without the addition of a dopant in the preparation step. The use of tetraethylammonium perchlorate (TEAP) in the electrolysis system was responsible for the stabilization of t-EGZrO2 by preventing the agglomeration of metal clusters with undesired powders, subsequently decrease in ZrO2 crystal size. The photoactivity of the catalyst was subjected to the degradation of phenol in an aqueous solution. This resulted in 98% degradation of 10 mg/L phenol solution using 0.4 mg/L of catalyst dosage at pH 9 under light irradiation within 1 hour of contact time. The comparison studies were also conducted using monoclinic electrogenerated zirconia (m-EGZrO2), commercial zirconia (c-ZrO2), and photolysis as a control experiment, which gives 45%, 78%, and 3%, respectively. Good photoactivity of t-EGZrO2 toward phenol degradation with simple operation of the system exhibits great potential for improving the quality of wastewater discharge from industries.

Controllable structure of fibrous SiO2–ZSM-5 support decorated with TiO2 catalysts for enhanced photodegradation of paracetamol

Fibrous silica ZSM-5 (FSZ) was synthesized by a microemulsion method, and subsequent incorporation of 5 wt% of TiO2 onto it via electrolysis in varying concentrations of supporting electrolyte tetraethylammonium perchlorate (TEAP) gave TFSZ catalysts. The results verified that the degree of desilication and dealumination, for increasing the insertion of Ti ions into the FSZ framework, was directly proportional to the concentration of TEAP. In parallel, impurity levels of SiOTi bonds, defect sites and oxygen vacancies were formed and enhanced the photodegradation of paracetamol (PCT). However, excess SiOTi interactions, as a consequence of a higher degree of desilication and dealumination, decreased the number of oxygen vacancies and surface defects, resulting in a higher band gap energy. The sequence towards the degradation of PCT was in the following order: 0.2-TFSZ (96%) > 0.1-TFSZ (88%) > 0.3-TFSZ (67%). The kinetics study followed the pseudo-first-order Langmuir–Hinshelwood model. The response surface methodology revealed that the initial concentration of PCT, catalyst dosage and pH were the significant factors in the degradation of PCT. The 0.2-TFSZ maintained the photocatalytic activities after five runs and able to degrade other endocrine disrupting chemicals efficiently, indicating its potential use in the wastewater treatment of those chemicals.

Investigation the Electrochemical Behavior of 5-(4-Dimethylamino-benylidene)-1,3-diethyl-2-thioxodihydro-pyrimidine-4,6-dione using Semi-integration of Current

The electrochemical behavior of 5-(4-Dimethylamino-benylidene)-1,3-diethyl-2-thioxo-dihydro-pyrimidine-4,6-dione at a plat-inum electrode was studied by semi-integration, semi differentiation of current, and digital simulation methods in 0.1 mol/L tetra-ethylammonium perchlorate (TEACl) in acetonitrile solvent. Cyclic voltammetric study revealed that the presence of three oxidative peaks due to the presence of two electron transfer coupled by chemical reaction (EC) and followed by electron transfer (E) step then EC, i.e., the overall process is ECEEC scheme. On going to negative potential there are two unidirectional reductive peaks associated with the oxida-tive peaks. The elucidation of the electrode behavior, the electrochemical and chemical data of the compound under investigation was de-termined using sweep voltammetry, semi integration & semi differentiation of current. The calculated electrochemical parameters and the nature of the electrode reaction were established & confirmed via generation of the theoretical cyclic voltammograms.

Ultrafast Polarization Switching in a Biaxial Molecular Ferroelectric Thin Film: [Hdabco]ClO4.

Molecular ferroelectrics are attracting much attention as valuable complements to conventional ceramic ferroelectrics owing to their solution processability and nontoxicity. Encouragingly, the recent discovery of a multiaxial molecular ferroelectric, tetraethylammonium perchlorate, is expected to be able to solve the problem that in the technologically relevant thin-film form uniaxial molecular ferroelectrics have been found to perform considerably more poorly than in bulk. However, it can show good polarization-electric field (P-E) hysteresis loops only at very low frequency, severely hampering practical applications such as ferroelectric random access memory. Here, we present a biaxial molecular ferroelectric thin film of [Hdabco]ClO4 (dabco = 1,4-diazabicyclo[2.2.2]octane) (1), where a perfect ferroelectric hysteresis loop can be observed even at 10 kHz. It is the first example of a molecular ferroelectric thin film whose polarization can be switched at such a high frequency. Moreover, using piezoresponse force microscopy, we clearly observed the coexistence of 180° and non-180° ferroelectric domains and provided direct experimental proof that 180° ferroelectric switching and non-180° ferroelastic switching are both realized; that is, a flexible alteration of the polarization axis direction can occur in the thin film by applying an electric field. These results open a new avenue for applications of molecular ferroelectrics and will inspire further exploration of high-performance multiaxial molecular ferroelectric thin films.

Molecular Ferroelectric with Most Equivalent Polarization Directions Induced by the Plastic Phase Transition.

Besides the single crystals, ferroelectric materials are actually widely used in the forms of the polycrystals like ceramics. Multiaxial ferroelectrics with multiple equivalent polarization directions are preferable for such applications, because more equivalent ferroelectric axes allow random spontaneous polarization vectors to be oriented along the electric field to achieve a larger polarization after poling. Most of ceramic ferroelectrics like BaTiO3 have equivalent ferroelectric axes no more than three. We herein describe a molecular-ionic ferroelectric with 12 equivalent ferroelectric axes: tetraethylammonium perchlorate, whose number of axes is the most in the known ferroelectrics. Appearance of so many equivalent ferroelectric axes benefits from the plastic phase transition, because the plastic phase usually crystallizes in a highly symmetric cubic system. A perfect macroscopic ferroelectricity can be obtained on the polycrystalline film of this material. This finding opened an avenue constructing multiaxial ferroelectrics for applications as polycrystalline materials.

Rotating Ring-Disc Electrode Investigation of the Aprotic Superoxide Radical Electrochemistry on Multi-Crystalline Surfaces and Correlation with Density Functional Theory Modeling: Implications for Lithium-Air Cells

The realization of a practical Lithium-air cell depends on understanding the oxygen reduction reaction (ORR), identifying a stable electrolyte and finding a suitable cathode. This study investigates the superoxide radical, its side reactions and correlates density functional theory (DFT) predictions of the surface activity to the experimental kinetics. The ORR on glassy carbon (GC), multi-crystalline Pt and multi-crystalline Au substrates in oxygen saturated 0.1 M Tetraethylammonium Perchlorate (TEAClO4) in Dimethyl Sulfoxide (DMSO) was studied using cyclic voltammetery and the rotating ring-disk electrode (RRDE) technique. The RRDE data was analyzed using kinetic models to understand the electrochemistry of the superoxide radical and calculate the surface reaction rate constants. The percentage of the superoxide radicals detected at the ring from GC, Pt and Au surfaces correlated linearly to the modeled activities of the substrates. Further, the modeled activity trend was found to correlate strongly with the ORR onset potential. This study validates the DFT catalyst screening approach. It also shows that side reactions involving the superoxide radical occurs in fresh, anhydrous DMSO based electrolytes.

Synergistic interactions of Cu and N on surface altered amorphous TiO2 nanoparticles for enhanced photocatalytic oxidative desulfurization of dibenzothiophene

Amorphous TiO2 (AT) nanoparticles were prepared by a simple sol–gel method and subsequent incorporation with 5–20 wt% copper via an electrochemical method in the presence of tetraethylammonium perchlorate gave an active CuO/TiO2 (CAT) photocatalyst.

Flavin Mediated Electro-Oxidation of 1,4-Dihydronicotinamides Using Photogalvanic Cell

Much effort has been made to prepare better dye-sensitized photoelectrochemical solar cells and enzymatic biofuel cells to convert sunlight and biofuel into electric energy. Since the last decade, furthermore, hybrids of the solar cells and the enzymatic biofuel cells have also been designed [1]. These hybrid cells possess several advantages over either the solar cells or the biofuel cells operating individually. When the dye-sensitized semiconductors (photoanodes) are irradiated, they oxidize NADH to produce NAD+. Using this NAD+, the corresponding enzymes oxidize the biofuels and NADH is reproduced from NAD+ during the oxidation process. Unfortunately, however, the availability of the sunlight energy in these cells is not high because sunlight is available only on the photoanodes. In other word, the surface areas of the photoanodes limit the amount of the generated NAD+and the available biofuels. If the oxidation of NADH took place in the entire electrolytic solution, the biofuels could be oxidized more frequently than in the hybrid cells, and besides, no photoanodes could be required. As is well-known, direct electrochemical oxidation of NADH requires extremely large overpotential. Although several organic compounds were employed as current mediators such as catechol, their redox potentials still far apart from the formal redox potential of NADH/NAD+ couple. In our previous communication [2], however, we have shown that the redox reaction between NADH model compound (1-benzyl-1,4-dihydronicotinamide, BNAH) and riboflavin (RF) was remarkably accelerated by the light irradiation. Therefore, electrochemical oxidation of NADH is possible at extremely low overpotential (the oxidation potential of reduced flavin) when two different kind of catalysts, flavin and light, are used. In the present study, we tried to utilize a cell reaction instead of using an external power source. The cathodic reaction is the reproduction of hydrogen ion in acidic media. If the photocatalyzed galvanic cell proposed here works well, both electric power and molecular dihydrogen are obtained in the oxidation process of NADH to NAD+. The anode compartment was a quartz tube equipped with a platinum plate (3 x 2 cm) as the anode. Dimethylsulfoxide (DMSO) solution containing both BANH and RF was the anolyte and 0.1 M (1 M=1 mol/dm3) tetraethylammonium perchlorate was added as the supporting electrolyte. The cathodic compartment was a Pyrex glass tube equipped with a platinized platinum plate (0.5 x 2 cm) as the cathode. The catholyte was 2 M sulfuric acid and both compartments were connected with an agar salt bridge. A 150 W tungsten lamp was used as a light source and only the anode compartment was irradiated. The current transient of the galvanic cell was measured under the constant load of 890 Ω. Measurements were done under nitrogen atmosphere at room temperature. The characteristics of a galvanic cell were studied with NADH/flavin model system using RF and BANH. Figure 1 shows the change of cell current with time under the irradiation. The cell current increases steeply by the irradiation and then decreases gradually to reach a steady value. The output current-voltage relationships were measured by changing the external load. Measurements were made after the cell current reached to the steady value. The open-circuit voltage and the short-circuit current was 0.86 V and 300 µA, respectively. The maximum power of 80 µW was obtained when the cell voltage was 0.45 V. The BANH concentration dependence of steady cell currents was examined at 1 hour after irradiation. Although experimental points were rather scattered, the observed steady currents were fairly constant (134 ± 13 µA) when the concentration of BANH was above 2 mM. In addition, the relationship between the quantity of electricity passed and the amount of generated BNA+ (oxidized and deprotonated form of BNAH) showed straight line and the line was almost the same as calculated one assuming 100 % current efficiency. It is obvious that the production of BNA+ from BNAH is quantitative and RF acts as a current mediator. Thus, highly efficient electrochemical conversion of BNAH to BNA+is possible with obtaining both electricity and dihydrogen as by-products. NADH behaves in a similar manner as BNAH does. [1] L. Garza, G. Jeong, P. A. Liddell, T. Sotomura, T. A. Moore, A. L. Moore, D. Gust, J. Phys. Chem. B, 107, 10252 (2003).[2] A. Kitani, M. Yakushidoh, K. Sasaki, Denki Kagaku, 51, 293 (1983). Figure 1

Determination of methylparaben by differential pulse voltammetry using a glassy carbon electrode modified with polypyrrole

A new modified glassy carbon electrode (GCE) based on a synthesized polypyrrole (PPy) was developed for the determination of methylparaben by differential pulse voltammetry (DPV). PPy was covalently immobilized on GCE surface using tetraethyl ammonium perchlorate (TEAP) and acetonitrile (ACN). Methylparaben was oxidized by differential pulse voltammetry and a peak was observed at 1.20 V. The calibration curve obtained with differential pulse voltammetry was linear in the concentration range from 0.01 to 5 mM methylparaben with a limit of detection of 8 ×10−3 mM and RSD of 0.11%. The improved method was applied to the determination of methylparaben in cream samples using the differential pulse voltammetry method.

Low-temperature stabilization of electrosynthesized tetragonal zirconia, its photoactivity toward methylene blue decolorization

AbstractZirconia nanoparticles (ZrO2) were prepared by a simple electrochemical method and characterized using X-ray diffraction, transmission electron microscopy, Brunnauer–Emmett–Teller surface area analysis, and ultraviolet-visible diffuse reflectance spectroscopy. In this study, tetragonal ZrO2 (t-ZrO2) particles were stabilized at a lower calcination temperature without the addition of a dopant in the preparation step. It was suggested that the use of tetraethylammonium perchlorate as the supporting electrolyte was responsible for the stabilization of t-ZrO2 by preventing the agglomeration of metal clusters with undesired powders in the electrolysis system, resulting in a decrease in ZrO2 crystal size. The photoactivity of the catalyst was optimized using central composite design with response surface methodology and the optimum values of the parameters were a solution pH of 11, contact time of 4 h, catalyst dosage of 1.0 g L−1, and calcination temperature of 523 K. This resulted in 84.9% decolorizat...

Effect of Hydration Property of Pore Wall on Performance of Electric Double Layer Capacitors

Electric Double Layer Capacitors (EDLCs) store charges (ions) on electrode-electrolyte interfaces. When using nanoporous electrodes for EDLCs, specific capacitances decrease as the pore size becomes small due to the difficulty in supply of ions from bulk solution into nanopores. In the course of studies in electrodeposition within nanoporous electrodes, we have revealed that metal ions with a relatively large diameter strongly enhance the electrodeposition within hydrophobic nanopores when the solvent of the deposition bath is water [1]. This result indicates that the ion penetration into the pores is enhanced. We have also reported that by choosing an appropriate combination in hydration property of pore wall and ions, a transition phenomenon occurs within nanopores, which results in a high concentration of metal ions compared with the bulk solution [2]. The results reported in the previous studies lead to an idea that the similar enhancement of ion penetration into nanopores is advantageous for further developments of EDLCs using nanoporous electrodes. In this paper, we focus on the effect of hydration property of pore walls on the capacitances with mesoporous silicon electrodes. Secondly, the effect of pore size on the capacitance is discussed. In the present study, mesoporous silicon is utilized as a model electrode. Mesoporous silicon electrodes were prepared by anodization of an n-type Si (100) wafer with a resistivity of less than 0.02 Ω cm in 22 wt% HF solution. After anodization, the electrode was immersed in n-hexane containing propiolic acid or methyl propiolate to make the surfaces hydrophilic and hydrophobic, respectively [3]. Note that we adopted these organic solutes because they have almost the same molecular structure and show opposite hydration properties, i.e., hydrophilic and hydrophobic. Significant differences in pore size are not expected before and after the modification. An aqueous solution containing 0.1 M tetraethylammonium perchlorate was used for the measurement of EDLCs. Cyclic voltammograms (CVs) were measured using the hydrophilic and hydrophobic porous electrodes at a scan rate of 20 mV s–1. The porous silicon electrodes are oxidized above –0.3 V vs. SHE, so that CVs were measured between –0.5 V and –0.3 V. It should be noted that current density in the present study is calculated based on the projected area (0.785 cm2). A clear difference in hydration property of pore wall is observed in Figure 1. The hydrophobic porous electrode yields a much greater capacitance, meaning that more ions were adsorbed (stored) on the hydrophobic electrode-electrolyte interface. This result suggests that the surface hydration property has an important role on the capacitance of the EDLCs. Reference [1] K. Fukami, R. Koda, T. Sakka, T. Urata, K. Aomoto, H. Takada, M. Nakamura, Y. Ogata, and M. Kinoshita, Chem. Phys. Lett., 542, 99 (2012).[2] K. Fukami, R. Koda, T. Sakka, Y. Ogata, and M. Kinoshita, J. Chem. Phys., 138, 094702 (2013).[3] A. Imanishi, S. Yamane, and Y. Nakato, Langmuir, 24, 10755 (2008).

Synthesis and characterization of Fe3O4 nanoparticles by electrodeposition and reduction methods

Magnetite (Fe3O4) nanoparticles have been studied extensively due to their good magnetic, optic and electric properties which offer a great potential of applications in many field especially in removal of heavy metals such as the adsorption of poisonous Cr(VI) ion in water. In addition, Fe3O4 is the only material that has up to now been use in human because it is the only material which is known to be biocompatible, without relevant toxicity in the applied dosage. In this study Fe3O4 nanoparticles were prepared by reduction of ferric oxide (Fe2O3) precursor at 598 K for 10, 20, 30 and 40 min. While, ferric oxide (Fe2O3) precursor was prepared by electrodeposition of iron plate in the N,N-dimethylformamide solvent and tetraethylammonium perchlorate and naphthalene as mediators at 263 K. Reduction of Fe2O3 was carried out with an isothermal heating at 598 K under hydrogen atmosphere. Fe2O3 and Fe3O4 were characterized with XRD, BET Surface area, FTIR, FESEM-EDX and TEM. The surface area of both Fe2O3 and Fe3O4 was 38 - 45 m2/g with the average particle size was 40 - 60 nm. The XRD result showed that the crystallinity of Fe3O4 increased with reduction time. The activity of Fe2O3 and Fe3O4 nanoparticles were tested on the adsorption of chromium (VI) at room temperature in which 30-40 % of Cr(VI) ion was adsorbed on the Fe2O3 and Fe3O4 nanoparticles.

Switching the reaction course of electrochemical CO₂ reduction with ionic liquids.

The ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) offers new ways to modulate the electrochemical reduction of carbon dioxide. [emim][Tf2N], when present as the supporting electrolyte in acetonitrile, decreases the reduction overpotential at a Pb electrode by 0.18 V as compared to tetraethylammonium perchlorate as the supporting electrolyte. More interestingly, the ionic liquid shifts the reaction course during the electrochemical reduction of carbon dioxide by promoting the formation of carbon monoxide instead of oxalate anion. With increasing concentration of [emim][Tf2N], a carboxylate species with reduced CO2 covalently bonded to the imidazolium ring is formed along with carbon monoxide. The results highlight the catalytic effects of the medium in modulating the CO2 reduction products.

A rotating ring disk electrode study of the oxygen reduction reaction in lithium containing non aqueous electrolyte

We show the effect of a very small addition of LiClO4 to tetraethyl ammonium perchlorate (TEAP) in acetonitrile on the electro-reduction of molecular oxygen (ORR) at a rotating ring (Pt) glassy carbon (GC) disk electrode. While TEA+ cations stabilize the first electron reduction product in acetonitrile, superoxide O2−, in the absence of Li+ the ORR proceeds by two one-electron sequential steps to the stabilized peroxide. Addition of 10μM LiClO4 (<1:800 Li+ to TEA+ ratio) strongly affects the ORR mechanism: Both disk (ID) and ring (IR) currents strongly decrease, with less than 0.5% O2− produced at the GC disk reaching the ring electrode, but still IR follows the same potential dependence as ID. On the other hand, addition of DMSO to acetonitrile 0.1M LiClO4 stabilizes soluble O2− detected at the ring since DMSO preferentially solvates Li+ preventing disproportionation of LiO2 into O2 and passivating Li2O2.

Spectrophotometric study of complexation between a series of salophens and some transition metal ions in DMF solvent

The complexation behaviour of some salophen,s derivatives with few transition and heavy metal cations in N , N '-dimethyl formamid as nonaqueous solvent at 25 o C and 0.05 M tetra ethylammonium perchlorate to investigate the effect of structure were studied by spectrophotometric method. The formation of complexes between ligands and metal ions of the types ML, ML 2 or M 2 L was observed. The overall stability constants of such complexes were evaluated by computer refinement of absorption-mole ratio data using the KINFIT program.

Synthesis and Structural Characterization of Copper(I), Silver(I) and Gold(I) Complexes with Pyrimidine‐2‐thionato Ligands and their Adducts with Phosphanes

AbstractHomoleptic copper and silver compounds of a series of pyrimidine‐2‐thionato derivatives (RpymS–; R = 4,6‐Me2,5‐Et; 4‐CF3; 4,6‐CF3,Ph) have been synthesized by electrochemical oxidation of anodic metal (copper or silver) in a cell containing an acetonitrile solution of the appropriate thione and a small amount of tetraethylammonium perchlorate as electrolytic carrier. Subsequent reaction of these pyrimidine‐2‐thionato compounds with triphenylphosphane or bis(diphenylphosphanyl)methane (dppm) in acetonitrile allowed the synthesis of the corresponding heteroleptic complexes. The reaction of [Au(PPh3)Cl] with the corresponding pyrimidine‐2‐thione in ethanol in the presence of triethylamine gave [Au(4,6‐Me2,5‐EtpymS)(PPh3)] and [Au(4‐CF3pymS)(PPh3)] in good yields. The compounds were characterized by microanalysis, IR spectroscopy, FAB‐MS and, when sufficientlysoluble, 1H, 13C and 31P NMR spectroscopy. Compounds [Cu6(4,6‐CF3PhpymS)6] (1), [Ag6(4,6‐Me2,5‐EtpymS)6]·2MeOH·3H2O (2), [Cu2(4‐CF3pymS)2(dppm)2]·2CH3CN (3), [Cu(4‐CF3pymS)(PPh3)2] (4) and [Au(4‐CF3pymS)(PPh3)] (5) were also characterized by X‐ray diffraction.

Large‐volume sample on‐line concentration of angiotensins in non‐aqueous capillary electrophoresis

A single step on-line concentration and separation method for peptides in non-aqueous capillary electrophoresis was developed. ACN containing 50 mM tetraethylammonium perchlorate was used as the electrophoretic medium; angiotensins I-IV were separated as a result of the differences in the magnitudes of their interactions with perchlorate anions. When the sample solution (ACN containing 0.5% trifluoroacetic acid and angiotensins) was injected as a large-volume plug, the analytes were concentrated at the inlet end of the capillary by both sweeping and stacking mechanisms; the separation procedure then started automatically without any operations such as polarity change. It was found that the concentration of analytes, injection period, and concentration of tetraethylammonium perchlorate in the electrophoretic medium were important factors for both separation and concentration efficiencies. The angiotensins were concentrated and separated with the large-volume injection of up to 80% of the effective capillary length.