Search

This manuscript reports the electrochemical behaviour of electrochemical energy storage system based on carbon-based electrodes modified with phenanthroline and anthraquinone molecules, respectively. The composite electrodes consist of activated carbon powder modified with phenanthroline or anthraquinone molecules by the diazonium chemistry. The phenanthroline-modified carbon used to prepare the composite electrode was characterized by elemental analysis, X-ray photoelectron spectroscopy, thermogravimetric analysis coupled to infrared spectrometry, and nitrogen gas adsorption. Phenanthroline-modified carbon composite electrode exhibited redox activity in aqueous acidic electrolyte around 0.4 V vs. Ag/AgCl. Consequently, it was used as positive electrode in electrochemical energy storage system with an anthraquinone-modified carbon negative electrode. Pre-polarization of both electrodes was needed to take full advantage of the charge storage properties of the grafted species and to reach the potential range of their redox activity upon charge/discharge cycling. This pre-treatment also enabled an increase of the operating voltage cell to 1.0 V in aqueous 1 M H2SO4 electrolyte.

Superconcentrated electrolytes, including water-in-salt solutions, are currently attracting major interest in the field of rechargeable batteries. These electrolytes could potentially find application in other electrochemical systems. Therefore, it is relevant to investigate the electrochemical behavior of common electrode materials such as platinum, gold and glassy carbon in these electrolytes. Preliminary cyclic voltammetry results revealed that the electrochemical stability window of the electrodes increased by about 0.5 V for platinum and gold and 1 V for glassy carbon when the lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) concentration is increased from 1 to 5 M (mol/L). This increase is mainly due to the shift of the oxygen evolution potential to a more positive value in the more concentrated solution. In the latter, the H2O/Li+ molar ratio of 2.6 is insufficient for full solvation of Li+ cations. The positively charged electrode is therefore compensated mainly by TFSI− anions because the electrolyte contains a negligible amount of free water molecules, leading to an enhancement of the oxidative stability of the electrolyte. Keywords: Superconcentrated electrolytes, “Water-in-salt”, Electrode/electrolyte interface, Electrochemical stability potential window

The self-discharge of hybrid electrochemical capacitors based on the redox activity of electrolyte additives or grafted species to the electrode material is investigated simultaneously for the cell and each individual electrode. Electrochemical capacitors using a redox-active electrolyte consisting in hydroquinone added to the electrolyte solution and a redox-active electrode based on anthraquinone-grafted carbon as a negative electrode are investigated. The results are analyzed by using Conway kinetic models and compared to those of a common electrochemical double layer capacitor. The self-discharge investigation is complemented by charge/discharge cycling and it is shown that processes affecting galvanostatic charge/discharge cycling and the self-discharge rate occurring at each electrode of an electrochemical capacitor are different but related to each other. The electrochemical capacitor containing hydroquinone in the electrolyte exhibits a much quicker self-discharge rate than that using a negative electrode based on grafted anthraquinone with a 50% decay of the cell voltage of the fully charged device in 0.6 and 6 h, respectively. The fast self-discharge of the former is due to the diffusion of benzoquinone molecules (formed at the positive electrode during charging) to the negative electrode, where they are reduced, causing a quick depolarization. The grafting of anthraquinone molecules on the carbon material of the negative electrode led to a much slower self-discharge, which nonetheless occurred, by the reaction of the reduced form of the grafted species with electrolyte species.

The electrochemical behaviour of 1,10-phenanthroline molecules immobilized on a glassy carbon electrode surface by electrochemical reduction of the corresponding in-situ generated diazonium ions in an aqueous solution was investigated. Firstly, the derivatization of glassy carbon electrode was confirmed by the presence of the barrier effect in the solution of a redox probe. Secondly, atomic force microscopy measurements revealed the deposition of thin (

The electrochemical reduction of 1,10-phenanthroline in aqueous acidic electrolyte at a glassy carbon electrode led to the covalent modification of the electrode. Thereafter, the deposited film can be switched to an electroactive form by electrochemical oxidation. An electroactive film can be also generated by alternate reductive and oxidative voltammetric cycling in a 1,10-phenanthroline/aqueous sulfuric acid solution. First, the electrochemical procedure for the formation of a film is presented. Second, the morphology and chemical structure of 1,10-phenanthroline coatings were investigated by atomic force microscopy, time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy, and electrochemical techniques. The ultrathin (15 nm) electrodeposited films consist of oligomeric species. The coatings deposited in alternate and/or continuous reductive and oxidative steps contain oxygen atoms incorporated into the oligomer backbone. The preliminary results point out the formation of a dione derivative that is responsible for the electroactivity of the grafted layer.

The bis(1,10-phenanthroline)-5-amino-1,10-phenanthroline iron (II) complex (Fe2+[Phen]2[Phen-NH2]) was synthesized and characterized before covalent attachment to the surface of acetylene black carbon via diazonium chemistry. The metal complex was characterized by UV–visible spectroscopy and elemental analysis. Elemental analysis revealed a low grafting yield of approximately 3 wt%. Cycling voltammetry of modified-carbon electrode showed an apparent redox potential of 4.1 V (vs. Li) characteristic of the iron complex. The voltammetric charge associated to the redox peak corresponded to approximately 3.3 wt% of grafted groups, in agreement with the value estimated by elemental analysis. The electrochemical performance of LiFePO4 cathodes using modified and unmodified acetylene black carbons as conducting additive were compared through galvanostatic cycling and electrochemical impedance spectroscopy measurements. At a 5C rate, the electrode made with the modified carbon delivered a specific capacity of about 60 mAh.g−1 in comparison to only 25 mAh.g−1 for the composite with unmodified conductive additive. Charge/discharge cycling experiments over 200 cycles at C/2.5 revealed a capacity fade of about 0.2 and 0.14% per cycle for the LiFePO4 electrodes made with the unmodified and modified carbons, respectively. Furthermore, the charge-transfer resistance of LiFePO4 electrode using the grafted-carbon is significantly smaller (150 Ω) than the unmodified acetylene black (300 Ω).

Protic ionic liquid based on 2-methoxypyridine and trifluoroacetic acid was used as electrolyte for the functionalization of a glassy carbon electrode surface by electrochemical reduction of in situ generated 4-chlorobenzene diazonium and 4-nitrobenzene diazonium cations. The diazonium cations were synthesized in an electrochemical cell by reaction of the corresponding amines with NaNO 2 dissolved in protic ionic liquid. The resulting electrografted organic layers exhibit similar properties to those layers obtained by the derivatization from isolated diazonium salts dissolved in protic ionic liquid. Functionalized glassy carbon electrode surfaces were characterized by cyclic voltammetry, Fourier transform infrared and X-ray photoelectron spectroscopies. Atomic force microscopy thickness measurements revealed that, in our experimental conditions, the use of protic ionic liquid led to the formation of film with a thickness of about 1.5 nm. It is also demonstrated that the nitrobenzene chemisorbed on glassy carbon electrode or dissolved in protic ionic liquid undergoes electrochemical conversion to hydroxyaminobenzene.

A new one-step electrochemical approach for the localized generation of diazonium cations in the diffusion layer of an electrode by taking advantage of the electrocatalytic properties of the electrode for the formation of the diazotization agent (nitrite) is proposed. Once nitrite anions are formed by electrocatalytic reduction of nitrate, they immediately react with an arylamine to produce the corresponding diazonium cations, which can be electrochemically readily reduced at the electrode surface. By this method, spontaneous modification of the electrode surface can be avoided. Furthermore, because the potential of the electrochemical nitrate reduction depends strongly on the nature of the electrode material, we also demonstrate that selective grafting can be achieved on a surface, which consists of two different materials: copper-gold or copper-glassy carbon substrates.

The voltammetric response of a bipolar cell is described where the cell is applied to electroless deposition processes. The method is illustrated with copper deposition on gold surfaces, driven by the oxidation of dimethylamine borane. Keywords: Deposition, Electroless, Bipolar, Mechanism

Electroreduction of C60 dissolved in hydrophobic solvent deposited on the electrode surface was studied. A microliter amount of C60 and tetrahexylammonium perchlorate solution in 1,2-dichlorobenzene was deposited on basal plane pyrolytic graphite electrode and this electrode was immersed into an aqueous solution. The voltammetry shows three consecutive reduction–oxidation steps. The redox potential of first electroreduction step is sensitive on anion but not on cation present in the aqueous phase. This parameter also depends on electrolyte concentration in the aqueous and organic phase. It is proposed that electroreduction of C60 is preceded by anion exchange and followed by anion expulsion to the aqueous phase. Similar anion effect on the redox potential is also observed for unsupported deposit indicating importance of initial partitioning of electrolyte into the organic phase. Keywords: Fullerene, 1,2-Dichlorobenzene, Ion transfer, Liquid/liquid interface, Redox reaction

A carbon ceramic electrode (CCE) modified with the redox probe—decamethylferrocene solution in hydrophobic organic solvent—2-nitrophenyloctyl ether and immersed into an aqueous solution was studied by scanning electrochemical microscopy (SECM). After the electrochemical oxidation of decamethylferrocene, its cations were detected near the electrode surface in the aqueous phase. This indicates that some fraction of the redox-active cations electrochemically produced in the organic phase is transferred across the liquid/liquid interface. They are reduced at the SECM tip and form a solid deposit. The amount of deposited decamethylferrocene was estimated by the anodic reaction at the tip. It is affected by the substrate–tip distance, deposition time, and electrolyte concentration. The SECM images of unmodified and modified CCEs are consistent with their heterogeneous structure.

Since 2000, ionic liquids are used for electrode modification. When these ionic liquid modified electrodes are immersed into aqueous solution, a well defined ionic liquid | aqueous electrolyte interface is formed. Here, the papers reporting on ion transfer across this interface are reviewed. This process is generated either by the electrochemical redox reaction within the ionic liquid deposit or it results from selective partitioning between the ionic liquid and the aqueous phase. The papers reporting an accumulation of the redox active ions into a thin film of covalently bonded ionic liquid deposited on the electrode surface are also reviewed. Keywords : Ionic liquid, ion transfer, redox reaction, electrode

A microfluidic double channel device was employed to study reactions at a flowing liquid∣liquid interface in contact with a gold electrode. The rectangular flow cell was calibrated for both single phase liquid flow and biphasic liquid∣liquid flow for the case of the immiscible N-octyl-2-pyrrolidone (NOP)∣aqueous electrolyte system. The influence of flow direction and speed and liquid viscosity on the position of the phase boundary was examined.The Ru(NH3)63+/2+ redox system was employed in aqueous solution to calibrate the flow cell in the absence and in the presence of the organic NOP phase. A significant “undercutting” of the organic phase into the aqueous phase was observed in particular for shorter gold band electrodes. The triple phase boundary reaction zone was visualized with a colour reaction based on the oxidation of N-benzylaniline. An approximate expression can be given to predict the mass transport controlled limiting currents even under two-phase flow conditions. Next, n-butylferrocene in NOP (without intentionally added electrolyte) was employed as the organic redox system with 0.1 M NaClO4 as the adjacent aqueous electrolyte phase. Under these conditions the electrochemical reaction only proceeded at the organic liquid∣aqueous liquid∣solid electrode triple phase boundary reaction zone and significant currents were observed. In contrast to the processes at conventional liquid∣electrode interfaces, these currents decreased with an increasing flow rate. The level of conversion at the triple phase boundary reaction zone can be further enhanced (i) at sufficiently slow flow rates and (ii) at larger electrodes. Bulk electrosynthetic processes are feasible, but the reactor design has to be further improved. Keywords: Phase transfer catalysis, Electrochemistry, Microfluidic, Phase boundary, Hydrodynamic, n-Butylferrocene, Ion extraction, Electrosynthesis

Composite electrodes were prepared from chemical vapor deposition grown carbon nanofibers consisting predominantly of ca. 100 nm diameter fibers. A hydrophobic sol–gel matrix based on a methyl-trimethoxysilane precursor was employed and composites formed with carbon nanofiber or carbon nanofiber—carbon particle mixtures (carbon ceramic electrode). Scanning electron microscopy images and electrochemical measurements show that the composite materials exhibit high surface area with some degree of electrolyte solution penetration into the electrode. These electrodes were modified with redox probe solution in 2-nitrophenyloctylether. A second type of composite electrode was prepared by simple pasting of carbon nanofibers and the same solution (carbon paste electrode). For both types of electrodes it is shown that high surface area carbon nanofibers dominate the electrode process and enhance voltammetric currents for the transfer of anions at liquid|liquid phase boundaries presumably by extending the triple-phase boundary. Both anion insertion and cation expulsion processes were observed driven by the electro-oxidation of decamethylferrocene within the organic phase. A stronger current response is observed for the more hydrophobic anions like ClO 4 − or PF 6 − when compared to that for the more hydrophilic anions like F− and SO 4 2− .

Ion transfer processes across liquid–liquid phase boundaries of the type aqueous solution–polar organic solvent supported on a hydrophobic silica carbon composite are studied by cyclic voltammetry and differential pulse voltammetry. The organic phase consists of a redox probe (ferrocene, t -butylferrocene, or decamethylferrocene) dissolved in a polar hydrophobic solvent (nitrobenzene, o -nitrophenyloctylether, or o -nitrophenylphenylether). The organic phase was immobilised in a ceramic carbon material composed of a hydrophobic silicate prepared via a sol–gel process from a methyltrimethoxysilane based sol and carbon particles. When immersed into aqueous electrolyte, ion transfer processes can be monitored as a function of potential. The contributions of solvent, electrolyte, and redox probe to the transition from anion transfer to cation transfer are discussed. Effects due to the presence of a high surface area microporous solid matrix are considered.

Ion transfer processes across liquid|liquid phase boundary formed at electroactive carbon paste electrode immersed into an aqueous solution were studied by cyclic voltammetry and differential pulse voltammetry. The electrode material consists of graphite particles and redox probe (ferrocene, t-butylferrocene, or decamethylferrocene) solution in polar organic hydrophobic solvent o-nitrophenyloctylether as a binder. The anion transfer from the aqueous solution following electrooxidation of the redox probe or ejection of electrogenerated cation from the organic phase was detected by anion dependence of the redox potential of the redox probe dissolved in an organic phase. The contribution of both processes depends on the hydrophobicity of the redox probe and anion present in the aqueous phase. Keywords: Ion transfer, Liquid–liquid interface, o-Nitrophenyloctylether, Voltammetry, Carbon paste electrode

Ceramic carbon electrodes (CCEs) modified with microphases of diluted and undiluted redox liquids were prepared and studied. The electrodes consisting of graphite powder, homogeneously dispersed in a hydrophobic silica matrix, were prepared by reaction of a methyltrimethoxysilane-based sol and graphite powder following a sol-gel methodology. The electrode surface was modified with different amounts of redox liquids (pure t-butylferrocene, solutions of t-butylferrocene in 2-nitrophenyloctylether, and N,N,N',N'-tetraoctyl-1,4-phenylenediamine) using hexane solutions and a solvent evaporation approach. For comparison, a glassy carbon electrode modified analogously with t-butylferrocene was also prepared and studied. The electrochemical behaviour of the electrodes was examined by cyclic voltammetry in aqueous salt solutions. The electrodes exhibited anticipated electroactivity connected with the presence of redox liquids. The shape of voltammograms and the degree of conversion were very different for processes on CCEs compared to those observed on glassy carbon. Presumably due to the promotion of formation of microphases, the magnitude of the current responses obtained with CCEs modified with t-butylferrocene is substantially larger than that obtained with GC electrodes modified with the same amount of redox liquid. In contrast to CCEs modified with diluted and undiluted t-butylferrocene where after 5-10 scans stable voltammetric curves were obtained, glassy carbon failed to give stable cyclic voltammograms. The results can be explained by the extent of triple interface formation in the CCE silicate network. Due to the electrode microstructure, the voltammetric response of CCEs modified with microphases of N,N,N',N'-tetraoctyl-1,4-phenylenediamine shows similar enhancement effects. (C) 2004 Elsevier Ltd. All rights reserved.

Ceramic carbon electrode modified with redox probe solution in hydrophobic polar solvent was prepared and studied. The electrode consisting of graphite powder, homogeneously dispersed in hydrophobic silicate matrix, was prepared from the mixture of methyltrimethoxysilane based sol and graphite powder by sol-gel method. It was immersed in tbutyloferrocene solution in nitrobenzene. The electrode properties were investigated by cyclic voltammetry and chronoamperometry in KNO3 solution of different concentration. In most cases linear polarization of the electrode towards positive potentials results in peak shaped voltammogram originating from electrooxidation of tbutyloferrocene. Its shape changes with time, but after 5 ± 7 scans stable curve is obtained. In all conditions the anodic to cathodic charge ratio is larger than unity. The peak current is proportional to the concentration of the redox probe in organic phase and salt in aqueous phase, whereas the midpeak potential is almost not affected by these factors. It has been concluded, that the electrooxidation of redox probe within hydrophobic silicate matrix is followed by two simultaneous processes: t-butyloferrocenium cation transfer to the aqueous phase and anion transfer from aqueous phase. Their relative contribution depends on the ratio of concentration of the redox probe in organic phase to concentration of salt in aqueous phase.

Biphasic electrode systems are studied for the case of the oxidation of the water-insoluble liquid N,N-didodecyl-N',N'-diethylphenylenediamine (DDPD) neat and dissolved in bis(2-ethylhexyl) phosphate (HDOP) and immersed in aqueous electrolyte media. The oxidation process in the absence of HDOP is accompanied by transfer of the anion (perchlorate or phosphate) from the water into the organic phase. However, in the presence of HDOP, oxidation is accompanied by proton exchange instead. This electrochemically driven proton exchange process occurs over a wide pH range. Organic microdroplet deposits of DDPD in HDOP at basal plane pyrolytic graphite electrodes are studied by voltammetric techniques and compared in their behavior to organic microphase deposits in mesoporous TiO2 thin films. The mesoporous TiO2 thin film acts as a host for the organic liquid and provides an alternative biphasic electrode system compared to the random microdroplet/graphite system. Two types of mesoporous TiO2 thin-film electrodes, (i) a 300-400-nm film on ITO and (ii) a 300-400-nm film on ITO sputter-coated with a 20-nm porous gold layer, are investigated.

Oxidation of methanol has been investigated on polycrystalline and single crystal gold electrodes: Au(poly), Au(1 1 1) and Au(2 1 0), in acidic, neutral and alkaline solutions. As expected, catalytic activity of gold towards methanol oxidation increases with increasing pH of the solution. It has been found that in all studied solutions methanol is oxidised in two potential regions, prior to gold surface oxide monolayer formation and in more positive potentials, on gold surface oxide after so called “turn over”. Surface structure of the electrode has little influence on the oxidation current, however potentials at which oxidation is observed depends on the crystallographic orientation. The mechanism of electro-oxidation of methanol on gold is discussed.

Solid electrolyte composed of hybrid organic–inorganic silicate matrix functionalised with tetraalkylammonium group, solvated by viscous organic polar solvent (propylene carbonate (PC) or sulpholane (TMS)), was prepared by the sol–gel method under controlled drying conditions. Tetramethoxysilane (TMOS), N-trimethoxysilylpropyl-N,N,N-tributylammonium chloride (TMOSPTBACl) and organic solvent were principal sol components. Gel formed within 2 h and 2 days depending on substrate ratio and the solvent additive. The obtained material was transparent and it loosed about 15% of its mass during first 30 days of ageing. It was characterised by thermogravimetry (TGA), differential scanning calorimetry (DSC), NMR, FT-IR spectroscopy, small angle X-ray scattering (SAXS), and impedance spectroscopy. The transport of redox active molecules was studied by electrochemical methods. The porosity of samples dried in supercritical CO2 was also estimated. The shape of TGA and DSC curve appeared to be similar to that of pure solvent. The IR spectra indicated the silicate network formation with some silanol groups left. The NMR spectrum of the solution used to wash crushed sample indicated that all organic substrate is embedded in silicate matrix. The magnitude of electrical conductivity was close to 10 −4 to 10 −5 Sc m −1 , i.e. least more than one order of magnitude larger than that of TMOS based silicate matrix modified with a pure solvent. This conductivity is high enough for electrochemical experiments. Both conductivity and diffusion coefficient of redox probe-ferrocene (Fc) depended on time elapsed after gelation. Their most substantial decrease was observed during first 10 days after gelation and it correlated with mass loss. © 2003 Elsevier Ltd. All rights reserved.

A kinetic study of the electroless deposition of copper on gold, using dimethylamine borane (DMAB) as a reducing agent, has been carried out. The copper deposition rate in the electroless bath was determined to be 50 nm min(-1), through electrochemical stripping of the copper deposits as well as from direct measurements of the film thickness using atomic force microscopy (AFM). Comparison with a galvanic cell setup, where the two half-reactions were physically separated, yielded a lower deposition rate of 30 nm min(-1). An important kinetic effect of the surface on the oxidation of the reducing agent, and thus on the overall process, was therefore revealed. The efficiency of the process was measured over time, revealing the contribution of side reactions in the cathodic half-cell, particularly during the initial stages of the electroless process.

International audience; The paper reports on the chemical functionalization of glassy carbon electrodes with 4-bromobenzene (4-BBDT) and 4-(4′-nitrophenylazo)benzene diazonium tetrafluoroborate (4-NAB) salts in ionic liquids. The reaction was carried out at room temperature in air without any external electrical bias in either hydrophobic (1-butyl-3-methylimidazolium hexafluorophosphate) or hydrophilic (1-butyl-3-methylimidazolium methyl sulfate) ionic liquids. The resulting surfaces were characterized using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and electrochemical measurements. Electrochemical reduction of the terminal nitro groups allowed the determination of surface coverage and formation of an amine-terminated carbon surfaces. The results were compared to glassy carbon chemically modified in an aqueous solution in the presence of 1% sodium dodecyl sulfate (SDS) with the same diazonium salt. Furthermore, Raman spectroscopy coupled with electrochemical measurements allowed to distinguish between the reduction of -NO2 to -NH2 group and the -N=N- to -NH―NH- bond.

International audience; This paper reports on green chemical functionalization of hydrogen-terminated boron-doped diamond (BDD) surfaces with aryldiazonium salts in the presence of ionic liquids. The reaction takes place at room temperature in air without any external bias in either hydrophobic (1-butyl-3-methylimidazolium hexafluorophosphate) or hydrophilic (1-butyl-3-methylimidazolium methyl sulfate) ionic liquids. The resulting surfaces were characterized using X-ray photoelectron spectroscopy and electrochemical measurements.

The electrochemical reduction of 1,10-phenanthroline in aqueous acidic electrolyte at a glassy carbon electrode led to the covalent modification of the electrode. Thereafter, the deposited film can be switched to an electroactive form by electrochemical oxidation. An electroactive film can be also generated by alternate reductive and oxidative voltammetric cycling in a 1,10-phenanthroline/aqueous sulfuric acid solution. First, the electrochemical procedure for the formation of a film is presented. Second, the morphology and chemical structure of 1,10-phenanthroline coatings were investigated by atomic force microscopy, time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy, and electrochemical techniques. The ultrathin (

Biphasic electrode systems allow electrochemical reactions to be driven in a microphase of organic liquid (typically 1–100 nL), which is coupled via ion transfer processes to the surrounding aqueous electrolyte medium. Microdroplet deposits on basal plane pyrolytic graphite as well as thin film deposits of the organic phase within a mesoporous titanium oxide host film are investigated. Cobalt tetraphenylporphyrin (CoTPP) is dissolved in the organic liquid 4-(3-phenylpropyl)-pyridine (PPP) and deposited in the form of microphases at suitable electrode surfaces. The electrode is immersed in aqueous electrolyte environments. It is shown that two stable and highly reversible one-electron metal-centred redox processes occur consistent with Co(III/II)TPP and Co(II/I)TPP in the presence of axial pyridine ligands. The electrochemical characteristics for both processes are strongly affected by the liquid | liquid ion exchange accompanying the redox processes. The potential for both the Co(III/II)TPP and the Co(II/I)TPP redox processes can be adjusted independently by the choice of the nature and concentration of the aqueous electrolyte. The reversible potential observed for the CoTPP metal complex is dominated by the Gibbs energy of transfer for the ‘spectator ions’. Conditions can be chosen to eliminate ion transfer effects on the potential scale for biphasic oxidation and reduction processes.

The electrode based on silicate carbon composite material was modified with redox probe (t-butylferrocene) solution in ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate or 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide). After immersion into an aqueous solution it was studied by cyclic voltammetry. It exhibits electrochemical signal connected with electrode reaction of the redox probe dissolved in ionic liquid. The heterogeneous structure of electrode material enhances substantially efficiency of the electrode process in comparison to the drop deposited on flat electrode surface. The midpeak potential depends on the hydrophobicity of the anion present in the aqueous solution indicating significant contribution of anion injection into the ionic liquid following the electron transfer. The efficiency of the electrode process is much larger than that of similar electrode modified with the redox probe solution in less viscous organic polar solvent. Keywords: Carbon ceramic electrode, Ionic liquid, Redox reaction, Sol–gel, Cyclic voltammetry

not Available.

The transfer of ions between an aqueous and an organic phase is driven electrochemically at a triple phase junction graphite | 4-(3-phenylpropyl)pyridine | aqueous electrolyte. Tetraphenylporphyrinato (TPP) metal complexes (MnTPP+, FeTPP+, CoTPP) and hemin readily dissolve in the organic 4-(3-phenylpropyl)pyridine phase and undergo oxidation/reduction processes which are coupled to liquid | liquid ion transfer. In order to maintain charge neutrality, each one-electron oxidation (reduction) process is coupled to the transfer of one anion (here PF6−, ClO4−, SCN−, NO3−, OCN−, or CN−) from the aqueous (organic) into the organic (aqueous) phase. The range of anions studied allows effects of hydrophobicity and complex formation (association of the anion to the metal center) to be explored. A preliminary kinetic scheme is developed to quantify complex formation, facilitated anion transfer, and competing cation transfer processes. The effects of the organic solvent on the ion transfer processes are explored. Very strong binding and specific effects are observed for the reversible cyanide transfer process.