| 1. |
- Adhikari, Arindam, et al.
(författare)
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Electrochemical behavior and anticorrosion properties of modified polyaniline dispersed in polyvinylacetate coating on carbon steel
- 2008
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 53:12, s. 4239-4247
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Tidskriftsartikel (refereegranskat)abstract
- Conducting polyaniline (Pani) was prepared in the presence of methane sulfonic acid (MeSA) as dopant by chemical oxidative polymerization. The Pani-MeSA polymer was characterized by FT-IR, UV-vis, X-ray diffraction (XRD) and impedance spectroscopy. The polyrner was dispersed in polyvinylacetate and coated oil carbon steel samples by a dipping method. The electrochemical behavior and anticorrosion properties of the coating, oil carbon steel in 3% NaCl were investigated using Open-circuit Potential (OCP) versus time of exposure, and electrochemical techniques including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and cyclic voltammetry (CV). During initial exposure, the OCP dropped about 0.35 V and the interfacial resistance increased several times, indicating I certain reduction of the polymer and oxidation of the steel surface. Later the OCP shifted to the noble direction and remained at a stable value during the exposure up to 60 days. The EIS monitoring also revealed the initial change and later stabilization of the coating. The stable high OCP and low coating impedance Suggest that the conducting polymer maintains its oxidative state and provides corrosion protection for carbon steel through out the investigated period. The polarization curves and CV show that the conducting polymer coating induces a passive-like behavior and greatly reduces the corrosion of carbon steel.
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| 2. |
- Alferov, Sergey, et al.
(författare)
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Electrical communication of cytochrome enriched Escherichia coli JM109 cells with graphite electrodes
- 2009
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 54:22, s. 4979-4984
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Konferensbidrag (refereegranskat)abstract
- In the present study three different strains of Escherichia coli (JM 109 - a native "wild type" strain, JM 109/pBSD 1300 - a strain overproducing the membrane anchor domain of Bacillus subtilis succinate-quinone reductase, SQR, a protein that contains two transmembraneously arranged heme groups and JM109/pLUV 1900 - a strain overproducing cytochrome c(550) from B. subtilis, a protein where the cytochrome domain is anchored to the membrane with a transmembrane helix) were immobilised on the surface of a spectrographic graphite electrode and tested for electrical communication using mediators. Such compounds as ferricyanide, 2,6-dichlorophenolindophenol (DCPIP) and ubiquinone (Q(0)) were used as soluble mediators and two flexible osmium redox polymers; poly(1-vinylimidazole)(12)-[Os-(4,4'-dimethyl-2,2'-di'pyridyl)(2)Cl-2](2 +/+) (osmium redox polymer I) and poly(vinylpyridine)-[Os-(N,N'-methylated-2,2'-biimidazole)(3)](2+/3+) (osmium redox polymer II) were co-immobilised with the bacterial cells onto the electrode surface. The effects of applied potential, buffer pH and different substrates were compared for the different combinations bacterial strains - mediators. Through the introduction of the cytochromes in the bacterial membrane it was established that it had great effect on the ability of the bacterial cells to effectively communicate with artificial mediators. The introduction of the transmembraneously arranged heme groups of B. subtilis made it possible for this strain to communicate with the Os-polymers, whereas the introduction of the cytochrome c(550) had an effect especially increasing ability of Q(0) to act as an efficient e(-) acceptor. (C) 2009 Elsevier Ltd. All rights reserved.
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| 3. |
- Bryngelsson, Hanna, et al.
(författare)
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Electrodeposition and electrochemical characterisation of thick and thin coatings of Sb and Sb/Sb2O3 particles for Li-ion battery anodes
- 2007
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 53:3, s. 1062-1073
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Tidskriftsartikel (refereegranskat)abstract
- The possibilities to electrodeposit thick coatings composed of nanoparticles of Sb and Sb2O3 for use as high-capacity anode materials in Li-ion batteries have been investigated. It is demonstrated that the stability of the coatings depends on their Sb2O3 concentrations as well as microstructure. The electrodeposition reactions in electrolytes with different pH and buffer capacities were studied using chronopotentiometry and electrochemical quartz crystal microbalance measurements. The obtained deposits, which were characterised with XRD and SEM, were also tested as anode materials in Li-ion batteries. The influence of the pH and buffer capacity of the deposition solution on the composition and particle size of the deposits were studied and it is concluded that depositions from a poorly buffered solution of antimony-tartrate give rise to good anode materials due to the inclusion of precipitated Sb2O3 nanoparticles in the Sb coatings. Depositions under conditions yielding pure Sb coatings give rise to deposits composed of large crystalline particles with poor anode stabilities. The presence of a plateau at about 0.8V versus Li+/Li due to SEI forming reactions and the origin of another plateau at about 0.4 V versus Li+/Li seen during the lithiation of thin Sb coatings are also discussed. It is demonstrated that the 0.4 V plateau is present for Sb coatings for which the (0 1 2) peak is the main peak in the XRD diffractogram.
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| 4. |
- Bryngelsson, Hanna, et al.
(författare)
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Thin films of Cu2Sb and Cu9Sb2 as anode materials in Li-ion batteries
- 2008
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 53:24, s. 7226-7234
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Tidskriftsartikel (refereegranskat)abstract
- Thin Cu2Sb films have been prepared by heat-treating Sb films. electrodeposited on Cu substrates. The influence of the electrodeposition conditions and the heat-treatment period on composition and morphology of the films were investigated (SEM and XRD) and the obtained films were tested as anode materials for Li-ion batteries. The Cu2Sb material showed a stable capacity of 290 mAh g(-1) (close to the theoretical capacity of 323 mAh g-1) during more than 60 cycles. The presence of 9-11% (w/w) Sb2O3 in the electrodeposited films resulted in smaller particles but also slowed down formation of Cu2Sb during the heat-treatment step. The presence of Sb2O3 was found to decrease the cycling stability although structural reversibility of Cu2Sb was obtained both with and without Sb2O3. Longer heat-treatment of pure Sb films resulted in the formation of Cu9Sb2 which was shown to be reduced at a lower potential than Cu2Sb. The Cu9Sb2 was converted to Cu2Sb during repeated cycling and the capacity of the latter Cu2Sb material was found to be 230 mAh g(-1). While reduction of the materials was complicated by simultaneous formation of an SEI layer, three plateaus Could be identified during the oxidation of Li3Sb, indicating the presence of three separate one-electron oxidation reactions.
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| 5. |
- Bultel, Yann, et al.
(författare)
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Investigation of mass transport in gas diffusion layer at the air cathode of a PEMFC
- 2005
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 51:3, s. 474-488
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Tidskriftsartikel (refereegranskat)abstract
- In a polymer electrolyte membrane fuel cell (PEMFC), slowdiffusion in the gas diffusion electrode may induce oxygen depletion when using air at the cathode. This work focuses on the behavior of a single PEMFC built with a Nafion® based MEA and an E-TEK gas diffusion layer and fed at the cathode with nitrogen containing 5, 10 and 20% of oxygen and working at different cell temperatures and relative humidities. The purpose is to apply the experimental impedance technique to cells wherein transport limitations at the cathode are significant. In parallel, a model is proposed to interpret the polarization curves and the impedance diagrams of a single PEMFC. The model accounts for mass transport through the gas diffusion electrode. It allows us to qualitatively analyze the experimental polarization curves and the corresponding impedance spectra and highlights the intra-electrode processes and the influence of the gas diffusion layer.
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| 6. |
- Dahbi, Mohammed, et al.
(författare)
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A delithiated LiNi0.65Co0.25Mn0.10O2 electrode material : A structural, magnetic and electrochemical study
- 2009
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Ingår i: Electrochimica Acta. - : Elsevier Ltd. - 0013-4686 .- 1873-3859. ; 54:11, s. 3211-3217
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Tidskriftsartikel (refereegranskat)abstract
- A crystalline LiNi0.65Co0.25Mn0.10O2 electrode material was synthesized by the combustion method at 900 °C for 1 h. Rietveld refinement shows less than 3% of Li/Ni disorder in the structure. Lithium extraction involves only the Ni2+/Ni4+ redox couple while Co3+ and Mn4+ remain electrochemically inactive. No structural transition was detected during cycling in the whole composition range 0 < x < 1.0. Furthermore, the hexagonal cell volume changes by only 3% when all lithium was removed indicating a good mechanical stability of the studied compound. LiNi0.65Co0.25Mn0.10O2 has a discharge capacity of 150 mAh/g in the voltage range 2.5–4.5 V, but the best electrochemical performance was obtained with an upper cut-off potential of 4.3 V. Magnetic measurements reveal competing antiferromagnetic and ferromagnetic interactions – varying in strength as a function of lithium content – yielding a low temperature magnetically frustrated state. The evolution of the magnetic properties with lithium content confirms the preferential oxidation of Ni ions compared to Co3+ and Mn4+ during the delithiation process.
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| 7. |
- Danielsson, Carl-Ola, et al.
(författare)
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A Model for the Enhanced Water Dissociation On Monopolar Membranes
- 2009
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 54:11, s. 2983-2991
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Tidskriftsartikel (refereegranskat)abstract
- A model for the enhanced water dissociation that takes place at the solution/membrane interface in electromembrane processes is presented. The mechanisms behind the enhanced water dissociation are poorly understood and therefore a semi-empirical approach is suggested. The enhanced water dissociation is introduced as a heterogeneous surface reaction similar to the well established Butler–Volmer law for electrode reactions. In the model there are two parameters that need to be determined through experiments. A 1D diffusion boundary layer problem is presented and solved in order to show that a sufficient rate of water dissociation can be obtained with the model. The advantage of the presented model is that it can easily be incorporated into simulations of electromembrane processes such as electrodialysis, electrodeionization and electropermutation. The influence of the enhanced water dissociation on these processes can then be studied.
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| 8. |
- Davoodi, Ali, et al.
(författare)
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Integrated AFM and SECM for in situ studies of localized corrosion of Al alloys
- 2007
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 52:27, s. 7697-7705
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Tidskriftsartikel (refereegranskat)abstract
- Rolled 3xxx series Al alloys, e.g., EN AW-3003, are generally used as fin or tube material in heat exchangers for automobiles. With reducing fin thickness, maintaining fin material integrity is of increasing importance. This study aimed at exploring the differences in intrinsic corrosion properties between EN AW-3003 and a newly developed Al–Mn–Si–Zr fin alloy using state-of-the-art local probing techniques. Volta potential mapping of both alloys by scanning Kelvin probe force microscopy (SKPFM) indicates a cathodic behaviour of constituent intermetallic particles (>0.5 μm) relative to the alloy matrix. Compared to EN AW-3003, the Al–Mn–Si–Zr alloy has a smaller number of particles with large Volta potential difference relative to the matrix. In situ atomic force microscopy (AFM) measurements in slightly corrosive solutions showed extensive localized dissolution and deposition of corrosion products on EN AW-3003, and only a small number of corroding sites and “tunnel-like” pits on Al–Mn–Si–Zr. Probing the ongoing localized corrosion process by integrated AFM and scanning electrochemical microscopy (SECM) revealed more extensive local electrochemical activity on EN AW-3003 than on Al–Mn–Si–Zr. In all, the lower corrosion activity and smaller tunnel-like pits resulted in lower material loss of the Al–Mn–Si–Zr alloy, a beneficial property when striving towards thinner fin material.
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| 9. |
- Dolidze, T. D., et al.
(författare)
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Two-equivalent electrochemical reduction of a cyano-complex Tl-III(CN)(2) (+) and the novel di-nuclear compound (CN)(5)Pt-II-Tl-III (0)
- 2005
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 50:22, s. 4444-4450
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Tidskriftsartikel (refereegranskat)abstract
- Extending our recent insights in two-electron transfer microscopic mechanisms for a Tl-III/Tl-I redox system, the electrochemical response of glassy carbon electrode in acidified solutions of Tl-III (ClO4)(3) containing different concentrations of sodium cyanide has been extensively studied for the first time by use of cyclic voltammetry and the CVSIM curve simulation PC program. The complex [Tl-III(CN)(2)](+) has been thoroughly identified electrochemically and shown to display a single welldefined reduction wave (which has no anodic counterpart), ascribed to the two-equivalent process yielding [Tl-I(aq)](+). This behavior is similar to that of [Tl-III (aq)](3+) ion in the absence of sodium cyanide, disclosed in the previous work, and is compatible with the quasi-simultaneous yet sequential two-electron transfer pattern (with two reduction waves merged in one), implying the rate-determining first electron transfer step (resulting in the formation of a covalently interacting di-thallium complex as a metastable intermediate), and the fast second electron transfer step. Some preliminary studies of the two-equivalent reduction of directly metal-metal bonded stable compound [(CN)(5)Pt-II-Tl-III](0) has been also performed displaying two reduction waves compatible with a true sequential pattern.
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| 10. |
- Ekström, Henrik, et al.
(författare)
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Nanometer-thick films of titanium oxide acting as electrolyte in the polymer electrolyte fuel cell
- 2007
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 52:12, s. 4239-4245
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Tidskriftsartikel (refereegranskat)abstract
- 0–18 nm-thick titanium, zirconium and tantalum oxide films are thermally evaporated on Nafion 117 membranes, and used as thin spacer electrolyte layers between the Nafion and a 3 nm Pt catalyst film. Electrochemical characterisation of the films in terms of oxygen reduction activity, high frequency impedance and cyclic voltammetry in nitrogen is performed in a fuel cell at 80 ◦C and full humidification. Titanium oxide films with thicknesses up to 18 nm are shown to conduct protons, whereas zirconium oxide and tantalum oxide block proton transport already at a thickness of 1.5 nm. The performance for oxygen reduction is higher for a bi-layered film of 3 nm platinum on 1.5 or 18 nm titanium oxide, than for a pure 3 nm platinum film with no spacer layer. The improvement in oxygen reduction performance is ascribed to a higher active surface area of platinum, i.e. no beneficial effect of combining platinum with zirconium, tantalum or titanium oxides on the intrinsic oxygen reduction activityis seen. The results suggest that TiO2 may be used as electrolyte in fuel cell electrodes, and that low-temperature proton exchange fuel cells could be possible using TiO2 as electrolyte.
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