Showing papers on "Supporting electrolyte published in 2011"

Electrochemical Properties of an All-Organic Redox Flow Battery Using 2,2,6,6-Tetramethyl-1-Piperidinyloxy and N-Methylphthalimide

Abstract: A novel all-organic redox flow battery employing 2,2,6,6-tetramethyl-1-piperidinyloxy/NaClO4/acetonitrile and N-Methyl- phthalimide/NaClO4/acetonitrile as catholyte and anolyte, respectively, is investigated by electrochemical measurements. The quasi-reversible and stable redox reactions are tested by cycle voltammetry. The diffusion coefficient of 0.02 M 2,2,6,6-tetramethyl-1-piperidinyloxy and 0.02 M N-Methylphthalimide in the supporting electrolyte are all in the range of 0.7–1.1× 10−5 cm2s−1 at room temperature. Stable charge-discharge curves and high coulombic efficiency (90%) for the first 20 cycles are obtained through charge-discharge test.

A new redox flow battery using Fe/V redox couples in chloride supporting electrolyte

Abstract: A new redox flow battery using Fe2+/Fe3+ and V2+/V3+ redox couples in chloride-supporting electrolyte was proposed and investigated for potential stationary energy storage applications. The Fe/V redox flow cell using mixed reactant solutions operated within a voltage window of 0.5–1.35 V with a nearly 100% utilization ratio and demonstrated stable cycling with energy efficiency around 80% at room temperature. Stable performance was also achieved in the temperature range between 0 °C and 50 °C. The improved stability and electrochemical activity over a broader temperature range over the current technologies (such as Fe/Cr redox chemistry) potentially eliminate the necessity of external heat management and use of catalysts, making the Fe/V redox flow battery a promising option as a stationary energy storage device to enable renewable integration and stabilization of the electrical grid.

Anodic Dissolution of Pure Aluminum during Electrocoagulation Process: Influence of Supporting Electrolyte, Initial pH, and Current Density

Abstract: In this work, effects of some experimental parameters (supporting electrolyte, initial pH, and current density) on aluminum corrosion and anodic dissolution of aluminum during electrocoagulation process were investigated. Potentiodynamic polarization tests, impedance spectroscopy measurements and potentisotatic current density transients were used to evaluate corrosion parameters and verify effects of supporting electrolyte and initial pH on aluminum corrosion. The presence of NaCl and Na2SO4 shifted the corrosion potential toward more cathodic potentials, indicating that corrosion of aluminum is catalyzed by the presence NaCl and Na2SO4. On the contrary, the presence of NaH2PO4 increased the corrosion potential, which indicates that the presence of NaH2PO4 inhibits the corrosion of aluminum. Galvanostatic electrolyses demonstrated that measured concentrations of aluminum exceeded theoretical values calculated using Faraday’s Law. The excess in dissolved aluminum produced during galvanostatic electrolyses...

Ionic Liquids as Electrolytes for the Development of a Robust Amperometric Oxygen Sensor

Abstract: A simple Clark-type online electrochemical cell design, consisting of a platinum gauze working electrode and incorporating ionic liquids (IL) as electrolytes, has been successfully applied for the amperometric sensing of oxygen. Studying ILs comprising the bis(trifluoromethylsulfonyl)imide anion, the obtained analytical parameters were found to be strongly dependent on the choice of cation. Compared with a conventional Clark cell design based on an aqueous supporting electrolyte, the modified oxygen sensor achieves substantial improvements in performance and stability. A limit of detection for oxygen as low as 0.05 vol %, linearity over an oxygen partial pressure between 0% and 20%, and a steady-state response time of 2 min was demonstrated, with a stable analytical response shown over the examined period of 90 days with no obvious fouling of the electrode surface. Based on the attractive physical attributes of ionic liquids (e.g., thermal stability beyond 150 °C), one can envision intriguing utility in n...

In situ FTIR spectroelectrochemical study on the mechanism of ethylene glycol electrocatalytic oxidation at a Pd electrode

Abstract: The adsorption and electrooxidation pathways of ethylene glycol (EG) on polycrystalline palladium surfaces have been investigated in both alkaline and acidic media by in situFTIR spectroscopy in conjunction with cyclic voltammetry. Palladium exhibits a high electrocatalytic activity in alkaline solution with low onset oxidation potentials and high current densities, depending on the pH, as well as on the supporting electrolyte. Higher potentials are required for EG oxidation in acidic solutions, where the catalytic performance decreases with increasing the pH. The products and intermediates of EG oxidation on Pd are influenced by the pH. In alkaline media, both C2 species (glycolate, glyoxal, glyoxylate and oxalate) and C1 species (formate and carbonate) are formed in mutual concentrations depending on the pH. In contrast, CO2 is selectively produced in acidic aqueous solution.

The mechanism of hydrazine electro-oxidation revealed by platinum microelectrodes: role of residual oxides

Abstract: The electrochemistry of hydrazine at platinum has been re-evaluated by an investigation using microelectrodes. Platinum oxides remaining from preceding oxidative scans results in hydrazine oxidation occurring up to ca. 400 mV more cathodic than at an oxide-free Pt electrode. The observed voltammetry at oxidised or ‘activated’ platinum electrodes was found to be a function of the immersion time (time since ‘activation’) and pH. Differences between phosphate, sulphate and acetate-based electrolytes are noted. The anodic hydrazine oxidation features at ‘activated’ electrodes occurred as a prewave or a prepeak, depending upon the electrolyte and scan rate employed. Although hydrazine is known to react with bulk Pt oxide, the loss of activation with time was found to be independent of hydrazine concentration and was instead a function of pH and supporting electrolyte, therefore the ‘activation’ corresponds to residual rather than bulk platinum oxide. The condition of platinum was examined by X-ray photoelectron spectroscopy (XPS), which demonstrated an increase in oxygen coverage with cycling and the absence of any strongly adsorbed or poisoning species. The facile oxidation of hydrazine has implications with regards to hydrogen storage, generation and fuel cells. The different effects corresponding to insufficient buffering, which has relevance to the electroanalytical detection of hydrazine, was also investigated.

Study of the Ce3+/Ce4+ Redox Couple in Mixed-Acid Media (CH3SO3H and H2SO4) for Redox Flow Battery Application

Abstract: The present paper first reports a kind of supporting electrolyte, mixed-acid media (CH3SO3H and H2SO4), used in redox flow battery (RFB) technology. Experimental work is performed with the aim of e...

Graphite oxide film-modified electrode as an electrochemical sensor for acetaminophen

Abstract: The graphite oxide (GO) was prepared via the chemical oxidation of natural graphite powder, and then used to modify the surface of glassy carbon electrode (GCE). The electrochemical behavior of acetaminophen was examined. In 0.01 mol L −1 HCl, an irreversible oxidation peak is observed for acetaminophen, and the peak current remarkably increases at the GO film-modified GCE. The influences of supporting electrolyte, amount of GO suspension, accumulation potential and time were studied on the oxidation peak current of acetaminophen. As a result, a new electrochemical method was developed for the detection of acetaminophen. The linear range is from 25 μg L −1 to 4 mg L −1 , and the limit of detection is 6 μg L −1 based on three signal–noise ratio. Finally, it was successfully used to detect acetaminophen in tablets.

On the controversial effect of sodium sulphate as supporting electrolyte on electrocoagulation process: A review

Abstract: One of the important factors for electrocoagulation (EC) process is the conductivity of the solution to be treated. Essential mechanisms in EC are charge neutralisation by metal (Fe/Al) hydroxocations and aggregation by van der Waals forces since fl occulation of pollutants with metal is caused by their adsorption on metal hydroxide aggregates. In order to enhance the EC process efficiency in organic wastewater effluents, sodium sulphate (Na2 SO4) has been used as a supporting electrolyte (SE) to increase the electric current diffusion in the EC cell. However, literature has reported controversial effect of sodium sulphate on EC process. This review tries to understand the sulphate effect on the EC reactions. Na2SO4 has been found less efficient than NaCl as SE in EC process for the removal of humic substances, oil-in-water emulsions, and fluoride. However, for unskimmed milk sample and cutting oil emulsion sulphate anions were found to be quite harmful both for electrical consumption and EC efficiency. T...

Development of an empirical model for fluoride removal from photovoltaic wastewater by electrocoagulation process

Abstract: Electrocoagulation experiments were conducted with bipolar aluminium electrodes to determine the optimum conditions for the fluoride removal from synthetic photovoltaic wastewater. A high fluoride concentration in community water supplies can cause fluorosis which has a detrimental effect on human health in particular on teeth and bones. A full 23 factorial design of experiments was used to obtain the best conditions of fluoride removal from water solutions. The three factors considered were initial fluoride concentration, applied potential, and supporting electrolyte dosage. Two levels for each factor were used; supporting electrolyte (0 and 100), applied potential (10 and 30 V), and initial fluoride concentration (20 and 25 mg/L). Results showed that the optimum conditions for fluoride removal from photovoltaic wastewater containing an initial fluoride concentration of 20 mg/L were a supporting electrolyte dose of 100 mg/L and an applied potential of 30 V. These gave a residual fluoride concentration of...

Electrochemical degradation of the dye reactive orange 16 using electrochemical flow-cell

Abstract: Electrochemical removals of color and organic load from solutions containing the dye reactive orange 16 (RO16) were performed in an electrochemical flow-cell, using a platinum working electrode. The influence of the process variables flow-rate, such as NaCl concentration, applied potential and solution pH, were studied. The best color removal achieved was 93% (λ = 493 nm) after 60 min at 2.2 V vs. RHE electrolysis, using 1.00 g L-1 NaCl as supporting electrolyte. The rises in the concentration of NaCl and applied potential increased the color removal rate. The best total organic carbon removal (57%) was obtained at 1.8 V, without the separating membrane, indicating that the ideal conditions for the color removal are not necessarily the same as those to remove the total organic carbon. The degradation efficiency decreased with the solution pH decrease.

Decolorization of levafix brilliant blue E‐B by electrocoagulation method

Abstract: In this study, the decolorization of Levafix Brilliant Blue E-B by electrocoagulation method using aluminum and iron electrodes was investigated. The influence of the operating variables such as current density, initial pH, time of electrolysis, supporting electrolyte concentration on decolorization efficiency, and energy consumption was determined. The results show that aluminum electrode (Al) was more effective than iron (Fe) electrode in terms of decolorization efficiencies and operating costs. When the aluminum electrode was used, 99% decolorization was obtained at current density of 100 A/m2, initial pH of 5.5, electrolyte concentration of 5 mM, and electrolysis time of 20 min. The corresponding energy consumption and operating cost were found as 16.9 kWh/m3 and 2.921 $ per m3, respectively. © 2010 American Institute of Chemical Engineers Environ Prog, 2011

Consistent diffusion coefficients of ferrocene in some non-aqueous solvents: electrochemical simultaneous determination together with electrode sizes and comparison to pulse-gradient spin-echo NMR results

Abstract: Cyclic voltammetry data recorded at disk macro- (millimeter dimension) and microelectrodes (10 and 100 μm) at various scan rates are used to simultaneously determine the diffusion coefficient D of ferrocene (fc) and the electroactive surfaces A and/or radii r of the electrodes. A case study with three electrodes of different sizes in CH3CN- and propylene carbonate (PC)-based electrolytes shows the possibly large effect of incorrect D values. Diffusion coefficients of fc are determined for PC, CH3CN, CH2Cl2, DMF, and DMSO electrolytes and (except for PC) compared to those from pulse-gradient spin-echo nuclear magnetic resonance experiments in the presence of supporting electrolyte in the respective deuterated solvents. The dependence of D fc on solvent viscosity is shown to follow the Stokes–Einstein relation.