This work is focused on the characterization of series of solid nanocomposite polymer electrolytes consisting of poly(ethylene oxide) (PEO), aminopropyl hepta isobutyl polyhedral oligomeric ...silsesquioxane (POSS) and lithium bis(oxalato)borate (LiBOB). Nanocomposites were prepared by melt intercalation method with different ether oxygen to lithium ions molar ratios (EO/Li) and different POSS loadings. Differential scanning calorimetry shows that an addition of LiBOB and POSS causes an important decrease in the crystallinity and melting temperatures of PEO, while the glass transition temperatures shift to higher values. The influence of LiBOB and POSS on the PEO crystallinity was also confirmed by Fourier transform infrared spectroscopy. Thermal stability as one of the key issues of the polymer electrolytes was investigated by the non-isothermal thermogravimetry. Thermogravimetric analysis showed a more complex degradation of the prepared samples compared to pure PEO. However, polymer electrolytes remain thermally stable enough for their suitable applications in the electrochemical devices. Electrochemical impedance spectroscopy reveals that LiBOB and POSS incorporation has positive influence on the ionic conductivity of PEO at room temperature. Considering the ionic conductivity of nanocomposites, the optimized system was determined.
Istraživan je utjecaj natrijeva alginata (NaAlg) na strukturu i svojstva filmova poli(etilen-oksida) (PEO) izlivenih iz vodenih otopina primjenom infracrvene spektroskopije s Fourierovom ...transformacijom (FT-IR), diferencijalne pretražne kalorimetrije (DSC), neizotermne termogravimetrije (TG) i elektrokemijske impedancijske spektroskopije (EIS). Cilj istraživanja je pronalaženje optimalne mješavine za pripravu filma čvrstog polimernog elektrolita (SPE) za litij-ionske baterije (LIB). U filmovima mješavina PEO/NaAlg stvaraju se vodikove veze između PEO-a i NaAlg-a te nastaju mješljive mješavine s manjim udjelom kristalne faze u odnosu na film čistog PEO-a. Filmovi mješavina toplinski su nestabilniji od filma čistog PEO-a i pokazuju dielektrična svojstva. Zbog najmanjeg udjela kristalne faze PEO-a mješavina 80PEO/20NaAlg može biti polimerna matrica koja bi dodatkom litijeve soli tvorila pogodan SPE.
Investigation of the influence of sodium alginate (NaAlg) on the structure and properties of poly(ethylene oxide) (PEO) films cast from aqueous solutions was performed by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), non-isothermal thermogravimetry (TG), and electrochemical impedance spectroscopy (EIS). The research aimed to find the optimal blend for the preparation of a solid polymer electrolyte (SPE) film for lithium-ion batteries (LIB). In PEO/NaAlg blend films, hydrogen bonds are formed between PEO and NaAlg, the blends are miscible, and have a lower content of crystalline phase compared to pure PEO film. The films of the blends are more thermally unstable than the film of pure PEO, and show dielectric properties, but the blend 80PEO/20NaAlg is suitable for the preparation of SPE by addition of lithium salt due to the lowest content of PEO crystalline phase.
Od utemeljenja Zavoda, akademske godine 1961./62., njegova znanstveno-istraživačka djelatnost bila je usmjerena na elektrokemijska istraživanja metala, pojavu pasiviteta i inhibiciju korozije. ...Kasnije, ponajprije primjenom elektrokemijskih metoda, proučavaju se fenomeni na granici faza metal│anodni sloj│elektrolitna otopina koji su od značaja za kemijske izvore struje i poluvodičke sustave. Tijekom posljednjih deset godina istraživanja se usmjeravaju u dva smjera: i) ispitivanje utjecaja legirajućih elemenata na dizajn otpornih materijala i biofunkcionalizacija površine biorazgradljivih i biokompatibilnih metalnih implantata; ii) modifikaciju elektroda i njihovih površina u svrhu razvoja novih elektroanalitičkih metoda za određivanje teških metala i biomolekula.
Since the establishment of the Department of General and Inorganic Chemistry in 1961, at the Faculty of Chemistry and Technology, University of Split, its scientific interest and investigations were focused toward electrochemical research. Consequently, electrochemistry became the backbone of the scientific research and development of the Department. In the last 10 years, scientific interest has been focused on the influence of alloying elements on design of corrosion resistance materials, as well as biofunctionalisation of biodegradable and biocompatible metal-based implants. In addition, development of various electroanalytical methods based on modified electrodes as sensing part of sensors, have been in focus in the recent period. The developed sensors were used for determination of heavy metals or biomolecules.
By employing model semiconductor composite system n-type Bi2S3/n-type Bi2O3, and the concept of semiconductor electrochemistry, basic principles for the design of (photo)catalyst materials with ...application in energy conversion and advanced wastewater treatment processes, were analyzed and discussed. Absolute energy values of conduction band edge, ECB, and valence band edge, EVB, were correlated with the semiconductor's stability against decomposition and competitive redox reactions of free radical species formation. The energy-band diagrams were constructed for the proposed photocatalytic system. The ECB position was determined from the flatband potential, EFB, derived from Mott-Schottky analysis taking into account an additional potential drop in the Helmholtz layer due to the adsorption of potential determining ions on the semiconductor surface. Special attention was given to the accuracy of EFB calculation due to the frequency dispersion of the capacitance.
•Electropolymerization of pyrrole on Mg-alloy surface in presence of salicylate.•Salicylate dual role in PPy deposition: passivation and electron transfer mediation.•Redox potential of salicylate ...corresponds to potential of PPy nucleation.•EIS and polarization corrosion studies of PPy coated Mg-alloy in Hanks’ solution.•Polypyrrole significantly slowdown Mg alloy corrosion in Hanks’ solution.
In the present study the reactive surface of Mg alloy was coated with the nontoxic biocompatible polypyrrole (PPy) film synthesized by electrochemical oxidation from an aqueous salicylate solution. Salicylate ions prevent Mg dissolution and act as an electron transfer mediator during the PPy film nucleation, formation and growth on the alloy surface. Kinetics of the pyrrole polymerization as well as corrosion resistance of the PPy coated Mg alloy in the Hanks’ solution were investigated using dc electrochemical methods and electrochemical impedance spectroscopy (EIS). Characterization of the surface film was performed by optical and Fourier transform infrared spectroscopy (FTIR).
The similarity of mechanical properties of Mg and human bones makes Mg and Mg-alloys a potential material for biodegradable implants. However, Mg and Mg alloys corrode too quickly in the tissue ...fluids, thereby losing mechanical integrity before the tissues have sufficient time to heal. In order to reduce the corrosion rate and enhance the biocompatibility of the (AZ91D), alloy surface was modified with the hydroxyapatite (HAp) coatings. Hydroxyapatite (HAp) coating on AZ91D alloy substrate was prepared by an electrodeposition method and via chemical deposition by an alternative immersion method (AIM). The as-electrodeposited alloy specimen was post-treated with hot alkali solution to convert the electrodeposited calcium hydrogenphosphate coatings into the bone-like hydroxyapatite coatings. The barrier properties of the HAp coatings were studied using the cyclic voltammetry and electrochemical impedance spectroscopy. The protectiveness of the coatings with different treatment times was investigated by a polarization test in a Hanks' solution. The results revealed that hydroxyapatite coating significantly reduced the localized corrosion of the alloy, which is critical for better in-service mechanical integrity. Fourier transform infrared spectroscopy (FTIR) was used to verify the existence of the HAp coating and its morphology on AZ91D alloy surface.
The hydrogen evolution reaction (HER) on Ni57.3Co42.7 alloy and its main components, polycrystalline nickel and cobalt was investigated in 1.0 mol L–1 NaOH solution at 20 °C using cyclic voltammetry, ...pseudo-steady-state linear polarization and electrochemical impedance spectroscopy methods. The purpose of investigation was to evaluate the effect of cobalt on the intrinsic catalytic activity of nickel. Cyclic voltammetry measurements, performed in a wide potential range from hydrogen to oxygen evolution, clearly showed the potential range of formation and reduction metal oxides / hydroxides. Electrocatalytic activity of the investigated electrodes was derived from pseudo-steady-state linear polarization curves, Tafel plots and electrochemical impedance spectroscopy (EIS). Electrochemical impedance spectra obtained in potential range of hydrogen evolution were modeled with modified Randles electric equivalent circuit. Kinetic parameters (the exchange current density and the cathodic Tafel slope), determined from linear polarization measurements and electrochemical impedance measurements, were compared for all three electrode materials. Ni57.3Co42.7 catalyst has shown better electrocatalytic activity compared with pure Co. The main pathway for the HER at investigated electrode materials is Volmer Heyrovski with Heyrovsky as the rate determining step.
This work is licensed under a Creative Commons Attribution 4.0 International License .
The electrochemically-assisted modification of the N-austenitic stainless
steel (ASS N25) surface was successfully employed to improve barrier
properties of the passive film in a chloride containing ...solution. The
chemical composition, electronic and barrier properties of the surface film
before and after the electrochemical treatment were examined using X-ray
photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy
(EIS). Electrochemical measurements were carried out in a corrosion testing
solution. The excellent corrosion resistance (both pitting and general) of
the N-steel?s modified surface was discussed according to the Mott-Schottky
analysis of the interfacial capacitance of the space charge layer and EIS
results. The conductivity change of the surface film from an n- to a p-type
in the pitting susceptible region was explained using the XPS analysis and
semiconducting properties of the film.
nema
The bismuth film formation from acid nitrate solution on glassy carbon electrode (GCE), graphite electrode (GPE) and on an assembly of carbon fiber microelectrodes (CFME) were studied utilizing ...cyclic voltammetry (CV) and chronoamperometry (CA). Voltamemetric data obtained with all three electrodes indicate that bismuth electrodeposition is controlled by diffusion of Bi3+. In the case of GCE and GPE Bi3+ diffusion coefficient was calculated using Randles-Sevcik equation. Analysis of the experimental current transients, obtained with GCE and GPE, revealed that increment of Bi3+ concentration changes nucleation mechanism from three-dimensional (3D) progressive nucleation toward instantaneous. Transients obtained with CFME, at different Bi3+ concentrations, suggesting only 3D instantaneous nucleation mechanism. Obtained data were used for preparation of appropriate Bi layer on CFME (Bi-film/CFME) for electroanalytical determination of cysteine by using square wave cathodic stripping voltammetry (SWCSV). Optimization of the SWCSV parameters have resulted in good linearity over examined concentration range of 1.0 μmol dm-3 to 10.0 μmol dm-3, with detection limit of 0.028 μmol dm-3 and sensitivity of 398 nA μmol-1 dm3.
PDF
