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The initial corrosion behavior of AZ63 magnesium alloy was investigated in 1, 3, 5 and 7 wt.% NaCl solutions by means of corrosion potential, linear polarization, electrochemical impedance spectroscopy, and polarization measurements, during exposure in the corrosion media. Results show that the increase in chloride concentration provokes an increase in the corrosion rate. Based on the obtained kinetics parameters the mechanisms of anodic dissolution and hydrogen evolution reactions were discussed, and kinetic models were proposed. It is concluded that anodic dissolution proceeds under Temkin conditions and hydrogen evolution reaction depends on the surface coverage of Mg(OH)2 species.

Polypyrrole (PPY) electrode was obtained by electrochemical oxidative polymerization of pyrrole on graphite electrode from aqueous electrolyte containing 0.1 mol dm–3 pyrrole monomer and 1.0 mol dm–3 HCl. Polymerization was achieved at the constant current density of 2 mA cm–2 during 1 h. The estimated active mass of PPY (assuming that the maximal doping degree of 0.33 was achieved and the polymerization efficiency of 100%) was 14 mg. Electrochemical characterization of PPY electrode was performed by galvanostatic experiments of charge (doping) and discharge (dedoping) with different current densities in the range between 0.5 and 1.5 mA cm–2. The experiments were performed in aqueous electrolyte containing 2.0 mol dm–3 NH4Cl and 1.1 mol dm–3 ZnCl2. Based on galvanostatic charge/discharge curves, following parameters of PPY electrode were evaluated: discharge capacity, specific discharge capacity, charge capacity, specific charge capacity, and Columbic efficiency. Both charge and discharge capacities were dependent on charge/discharge currents. The values decreased by increasing charge/discharge current, except for the lowest current density where Columbic efficiency exceeded 100%, which was explained by involvement of cations, from the electrolyte, in the doping process. An electrochemical cell in which PPY electrode served as a cathode and zinc electrode as the anode with an aqueous electrolyte containing 2.0 mol dm–3 NH4Cl and 1.1 mol dm–3 ZnCl2, was formed and relevant electrochemical and electrical parameters of the cell were estimated and discussed. Charge of the Zn|PPY cell was dependent on the charge/discharge current. Charge of the cell started between 0.5 and 0.7 V and proceeded up to 1.5 V, while the open circuit voltage of the fully discharged cell was 1.3 V. Specific discharge capacity of Zn|PPY cell, calculated based on discharge times, ranged from 95 to 70 mA h g–1, decreasing linearly with increasing discharge current density. On the other hand, calculated values of the theoretical capacity of the Zn|PPY cell was 105 mA g–1, meaning that practically 90% of the theoretical capacity can be achieved by discharging the cell with low current densities, while 67% of the theoretical capacity was obtained with the highest used current density. Based on Ragon parameters, the estimated values of specific energy that ranged between 46 and 68 W h kg–1, and the specific power between 125 and 380 W kg–1, Zn|PPY cell might be classified as a “supercapattery”. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. ON172046]

Electroconducting polymers from the group of synthetic metals are extensively investigated due to numerous properties perspective in practical application. These materials may be synthesized by both chemical and electrochemical procedures. Chemical synthesis is suitable when bulk quantities of the polymer are needed and up to date it presents dominant commercial method of producing electroconducting polymers. Nevertheless, electrochemical synthesis has its advantages; it avoids usage of oxidants since conducting polymeric material is obtained at anode upon application of positive potential, leading to increased purity. On the other hand, since the polymer is deposited onto electrode, further electrochemical characterization is facilitated. Owing to actuality of the research in the field this texts aims to describe important aspects of electrochemical synthesis of electroconducting polymers, with special emphasis to polyaniline and polypyrrole. [Projekat Ministarstva nauke Republike Srbije, br. 172046]

The electrochemically synthesized polypyrrole and lead-lead sulfate is examined as a potential electrodes for battery-type hybrid supercapacitors in acidic solution. The device exhibits battery-type behavior at low discharge rate, e.g. lt 0.5 A g(-1), and supercapacitors-type behavior at a higher discharge rate. Discharge in the specific current range of similar to 0.6-2.27 A g(-1) based on the active masses, can deliver capacity of 90-72 Ah kg(-1), energy of 58-40 Wh kg(-1) and power of 40-1350 W kg(-1), with the specific capacitance of the cell in the range of 300-250 F g(-1). The experimentally obtained values are compared with theoretical.

The potential application of electrochemically formed copper sulfide as horseradish peroxidase mediator in the enzymatic biofuel cell and anthraquinone AV109 dye as a fuel is investigated. The open circuit voltage of 0.52 V and short circuit current of similar to 3.6 mu A/cm(2) are obtained, with the maximum specific power of similar to 1 mu W/cm(2). The influence of internal resistance of the cell is discussed. Decolorization is investigated under open circuit potentials, and under external load of 3.31 k Omega conditions. In both cases, 40% of decolorization is achieved, but are three times faster under external load conditions. Specific energy during decolorization in such cell is estimated to 5 mWh/m(2). The possible mechanism of the power generation during decolorization of AV 109 dye is discussed.

This study is concerned with the partitioning of cellulolytic activity in the polyethylene glycol/dextran two-phase systems. In the system of 10% (w/w) polyethylene glycol 1500/5% (w/w) dextran 500,000/80% (w/w) crude enzyme at the pH 5, 100%, yield of cellulolytic activity from Penicillium sp. in the top phase was achieved in a single extraction step. Addition of KH2PO4 to this system at a concentration of 15 mmol/L improved the purification factor in the top phase for cellulolytic activity from crude preparation to a value of 2.6, although it had an adverse effect on the yield in the same phase. U radu je ispitana raspodela celulolitičke aktivnosti u vodenim dvofaznim sistemima polietilenglikol/dekstran. Maksimalno moguć 100% prinos celulolitičke aktivnosti dobijene kultivacijom Penicillium sp. postignut je u dvofaznom sistemu sastava 10% (m/m) polietilenglikol 1500/5% (m/m) dekstran 500000/ 80% (m/m) sirovi enzim na pH 5 u samo jednom koraku ekstrakcije. Dodatak KH2PO4 u koncentraciji 15 mmol/l u ovaj sistem, iako je smanjio raspodelu celulolitičke aktivnosti iz sirovog enzimskog preparata u gornju fazu sistema, poboljšao je faktor prečišćavanja u toj fazi na vrednost 2,6. Razlike u odzivu između celulolitičkih aktivnosti iz dva ispitivana izvora na promene faktora koji utiču na raspodelu mogu se objasniti različitom kompleksošću njihovih matriksa - komercijalnog, delimično prečišćenog, i sirovog neprečišćenog preparata dobijenog kultivacijom. Naime, i prisustvo samih kontaminenata može dodatno uticati na raspodelu enzimske aktivnosti.

The electrochemical synthesis of polyaniline (PANI) on mild steel, aluminum and copper from the sodium benzoate solutions has been investigated. It has been shown that thin, highly adherent, polyaniline films on the investigated metals could be obtained by anodic oxidation with current densities in the range of 0.5 and 1.5 mA cm-2. The corrosion behavior of mild steel, aluminum and copper with polyaniline coating in 0.5 mol dm-3 NaCl (pH 3) solutions, has been investigated by polarization technique. The corrosion current densities, porosity and protection efficiency was determined. It has been shown that polyaniline coating provided corrosion protection of all mentioned metals. U radu je ispitivana elektrohemijska sinteza polianilina (PANI) na mekom čeliku, aluminijumu i bakru iz rastvora natrijum-benzoata i monomera anilina. Ustanovljeno je da se tanki, dobro adherentni, filmovi polianilina mogu formirati na svim ispitivanim metalima pri anodnim gustinama struja od 0,5-1,5 mA cm-2. Ispitivano je koroziono ponašanje metala sa prevlakom polianilina u rastvoru 0,5 mol dm-3 NaCl (3%). Ustanovljeno je da ove prevlake pružaju korozionu zaštitu svim ispitivanim metalima u datoj korozionoj sredini.

The effect of the concentration of the reacting ion on the nature of the control of the electrodeposition process was investigated by digital simulation of the polarization curve using the Newman form of the polarization curve equation and the Levich dependence of the limiting diffusion current density under natural convection conditions. A simple method for the determination of the exchange current density from polarization measurements is also proposed. The agreement with experiments was correct. U radu je ispitivan uticaj koncentracije reagujućeg jona na vrstu kontrole procesa elektrohemijskog taloženja. Primenjena je digitalna simulacija polarizacionih krivih na osnovu Newman-ovog oblika jednačine polarizacione krive i Levich-eve zavisnosti granične difuzione gustine struje u uslovima prirodne konvekcije. Predložen je jednostavan metod određivanja gustine struje izmene na osnovu polarizacionih merenja. Dobijena je zadovoljavajuća saglasnost sa eksperimentalno dobijenim vrednostima.

The corrosion behavior and thermal stability of epoxy coatings electrodeposited on mild steel and on mild steel with electrochemically deposited polyaniline (PANI) film were investigated by electrochemical impedance spectroscopy (EIS) and thermo gravimetric analysis (TGA). The aim of the paper was to present new findings on the corrosion protection of mild steel by a duplex PANI/-epoxy coating in 3% NaCl solution and to determine the effect of thin PANI film on the protective properties of the coating. PANI film was deposited electrochemically on mild steel from an aqueous solution of 0.5 mol dm-3 sodium benzoate and 0.1 mol dm-3 aniline at a constant current density of 1.5 mA cm-2. Non-pigmented epoxy coatings on mild steel and on mild steel with PANI film were obtained by cathodic electrode position at constant voltage and stirring conditions. The resin concentration in the electrode position bath was 10 wt.% solid dispersion in water at pH 5.7. The applied voltage was 250 V, the temperature 26°C and the deposition time 3 min. It was shown that thin PANI film could be used to modify the surface of mild steel prior to epoxy coating deposition, due to the increased corrosion protection of a duplex PANI/epoxy coating comparing to an epoxy coating on mild steel in 3% NaCl solution. Koroziono ponašanje i termička stabilnost epoksidnih kataforetskih prevlaka na mekom čeliku i mekom čeliku sa elektrohemijski taloženim polianilinom (PANI) ispitivani su primenom metoda spektroskopije elektrohemijske impedancije i termogravimetrijske analize. PANI film na mekom čeliku je dobijen elektrohemijskim taloženjem iz vodenog rastvora 0,5 mol dm-3 Na-benzoata I 0,1 mol dm-3 anilina pod galvanostatskim uslovima, gustinom struje od j = 1,5 mA cm-2. Epoksidne prevlake na mekom čeliku I mekom čeliku sa PANI dobijene su elektroforetskim taloženjem u uslovima konstantnog napona uz mešanje. Pokazano je da dvoslojna PANI/epoksidna prevlaka na mekom čeliku ima značajno veću korozionu stabilnosti u 3% rastvoru NaCl u odnosu na epoksidnu prevlaku.

In recent years, great focus has been placed upon polymer thin films. These polymer thin films are important in many technological applications, ranging from coatings and adhesives to organic electronic devices, including sensors and detectors. Electrochemical polymerization is preferable, especially if the polymeric product is intended for use as polymer thin films, because electrogeneration allows fine control over the film thickness, an important parameter for fabrication of devices. Moreover, it was demonstrated that it is possible to modify the material properties by parameter control of the electrodeposition process. Electrochemistry is an excellent tool, not only for synthesis, but also for characterization and application of various types of materials. This book provides a timely overview of a current state of knowledge regarding the use of electropolymerization for new materials preparation, including conducting polymers and various possibilities of applications.

Electrochemical polymerization of polyaniline (PANI) coating on copper electrode was performed galvanostatically in the current density range between 0.50 and 1.25 mA cm(-2), from aqueous solution of 0.3 mol dm(-3) sodium benzoate and 0.2 mol dm(-3) aniline. The corrosion behavior of PANI coated copper and copper electrode exposed to 0.5 mol dm(-3) sodium chloride solution was investigated by potentiodynamic and electrochemical impedance spectroscopy techniques. It was observed that thin PANI (5 mu m) coating had provided efficient protection (similar to 96%) to copper in 0.5 mol dm(-3) sodium chloride solution. Unusual initial impedance behavior to that normally observed with conventional organic coatings was attributed to dedoping of benzoate anions from the polymer coating.

Electrochemical synthesis of polyaniline support for enzyme immobilization provides easier control over the properties of obtained polymer and reduced risk of biocatalyst inactivation with residues of toxic compounds. In the present study, immobilization of lipase from Candida rugosa on electrochemically synthesized PANI (activated with glutaraldehyde) resulted with high lipase loadings up to 93.7 mg of proteins per gram of dry support. The activation of support and immobilization were optimized, with respect to activity yield. The optimum concentration of glutaraldehyde was 2% (w/v) and optimum concentration of enzyme was 4 mg ml −1 . Modification of enzyme surface with carbodiimide and ethylenediamine was performed in order to increase concentration of amino groups. Aminated lipase exhibited higher specific activity (52%) and thermal stability (3 times) after immobilization, compared with non-modified lipase. Also, reusability of immobilized enzyme was significantly increased with amination, especially if immobilization was performed at pH 10, so in such a way obtained derivative retained 91% of activity after 15 reaction cycles.