| 1. |
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| 2. |
- Jarolimova, Zdenka, et al.
(author)
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All solid state chronopotentiometric ion-selective electrodes based on ferrocene functionalized PVC
- 2013
-
In: Journal of Electroanalytical Chemistry. - : Elsevier. - 0022-0728 .- 1873-2569 .- 1572-6657. ; 709, s. 118-125
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Journal article (peer-reviewed)abstract
- An all solid contact ion-selective electrode based on poly(vinyl chloride) covalently modified with ferrocene moieties allows one to operate the membrane in a chronopotentiometric sensing mode. The membrane is considered as initially non-perm-selective towards anions, and an applied anodic current provokes a defined anion flux in direction of the membrane. With this protocol, a variety of anions can be depleted at the membrane surface. Since this model system does not yet contain an ionophore, their order of preference follows the expected Hofmeister selectivity sequence. The all solid-state configuration tolerates an imposed current density of 1.4 μA mm−2, which translates into an upper detection limit of ca. 1.2 mM. Higher current densities of up to 31.2 μA mm−2are possible with addition of freely dissolved alkyl ferrocene derivative for an expected upper detection limit of 17.0 mM. Numerical simulations are performed in order to establish the fundamental basis of the mechanism that takes place in this all solid-state membrane electrode. The oxidation of bound Fc and the ion-transfer process are considered in the simulation. In view of developing an analytical sensor, different anions are tested. A linear range of two orders of magnitude from 0.01 to 1 mM is found. The membranes are evaluated over several days, displaying practically the same slopes and intercepts, with a RSD of less than 2%. Electrochemical limitations of free Fc and bound Fc are critical evaluated. This approach should allow one to develop a new family of solid-state chronopotentiometric ion sensors that require relatively high current densities.
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| 3. |
- Karlsson, Christoffer, 1986-, et al.
(author)
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Quinone Pendant Group Kinetics in Poly(pyrrol-3-ylhydroquinone)
- 2014
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In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 0022-0728 .- 1873-2569 .- 1572-6657. ; 735, s. 95-98
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Journal article (peer-reviewed)abstract
- Herein, we investigate the kinetics of the redox processes occurring in acidic aqueous electrolyte in electropolymerized poly(pyrrol-3-ylhydroquinone), which has been proposed for electrical energy storage applications. The redox conversion of the pendant groups is found to be limited by the quinone redox kinetics in thin films, rather than by the conduction through the polypyrrole backbone. Rate constants for the elementary steps involved in this 2e−, 2H+ process are reported. As the films are made thicker, a gradual transition to a diffusion limited reaction is observed. The origin of the diffusion process, as well as the elementary reaction steps limiting the pendant group redox conversion is analyzed using DFT computations. The fact that the electron transport through the thin film conducting polymer backbone is not limiting the quinone reaction kinetics should allow for design of battery electrodes with high rate capabilities based on the studied material.
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| 4. |
- Lindberg, Jonas, et al.
(author)
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The effect of O2 concentration on the reaction mechanism in Li-O2 batteries
- 2017
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In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657 .- 0022-0728 .- 1873-2569. ; 797, s. 1-7
-
Journal article (peer-reviewed)abstract
- The promising lithium-oxygen battery chemistry presents a set of challenges that need to be solved if commercialization is ever to be realized. This study focuses on how the O2 reaction path is effected by the O2 concentration in the electrolyte. An electrochemical quartz crystal microbalance system was used to measure current, potential, and change in electrode mass simultaneously. It is concluded that the mass reversibility is O2 concentration dependent while the coulombic efficiency is not. The mass reversibility is higher at low O2 concentration meaning that more of the deposited Li2O2 is removed during oxidation in relation to the amount deposited during reduction. The first step of the reduction is the formation of soluble LiO2, which is then either reacting further at the electrode or being transported away from the electrode resulting in low current efficiency and low deposited mass per electrons transferred. During the oxidation, the first step involves de-lithiation of Li2O2 at low potential followed by bulk oxidation. The oxidation behavior is O2 concentration dependent, and this dependence is likely indirect as the O2 concentration effects the amount of discharge product formed during the reduction. The O2 concentration at different saturation pressures was determined using a mass spectrometer. It was found that the electrolyte follows Henry's law at the pressures used in the study. In conclusion, this study provides insight to the O2 concentration dependence and the preferred path of the O2 electrochemical reactions in lithium-oxygen batteries.
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| 5. |
- Nasef, Hany, et al.
(author)
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Electrochemical molecular beacon DNA biosensor for the detection and discrimination of the DF508 cystic fibrosis mutation
- 2011
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In: Journal of Electroanalytical Chemistry. - : Elsevier. - 0022-0728 .- 1873-2569 .- 1572-6657. ; 662:2, s. 322-327
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Journal article (peer-reviewed)abstract
- Cystic fibrosis is one of the most common genetically inherited diseases in Northern Europe, consisting of a defect of chloride transport in the epithelium, with the DF508 mutation being the most common mutation associated with the disease. In this work the design and characterisation of a reagent-less electrochemical genosensor, based on the use of an electrochemical molecular beacon targeting the DF508 mutation is presented. Different aspects of the sensing platform including molecular beacon design and surface chemistry of the sensor surface were evaluated. Operational parameters such as assay buffer and assay time were also optimised. Using the optimised molecular beacon designs a clear differentiation between the targeted sequence (i.e. mutant) and potential interferent (i.e. wild type) was demonstrated, with a total required assay time of 20 min. The major advantage of the proposed reagent-less sensing platform is the fact that this only required, as intervention of the end-user, the addition of the sample.
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| 6. |
- Tripachev, Oleg, et al.
(author)
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Gold autodeactivation during oxygen electroreduction studied by electrochemical impedance spectroscopy
- 2012
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In: Journal of Electroanalytical Chemistry. - : Elsevier. - 0022-0728 .- 1873-2569 .- 1572-6657. ; 683, s. 21-24
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Journal article (peer-reviewed)abstract
- The deactivation of a polycryst. Au electrode is obsd. during O electroredn. reaction (ORR) in basic medium. At that, the cause of the process is chem. decompn. of the ORR intermediate and blocking of active sites of the electrode surface by hydroxyl radical-like species. The deactivation mechanism is discussed.
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| 7. |
- Zyoud, Ahed, et al.
(author)
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Combined electrochemical/chemical bath depositions to prepare CdS film electrodes with enhanced PEC characteristics
- 2013
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In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 0022-0728 .- 1873-2569 .- 1572-6657. ; 707, s. 117-121
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Journal article (peer-reviewed)abstract
- A new method to prepare CdS film electrodes, based on electrochemical deposition (ECD), followed by chemical bath deposition (CBD), is described. The ECD/CBD-CdS film electrodes combine the advantages of both ECD-CdS film (good adherence to FTO/glass substrate) and CBD-CdS film (suitable film thickness) together. The new ECD/CBD electrode showed higher photo-electrochemical (PEC) efficiency and stability than either ECD- or CBD-CdS film electrodes, especially after annealing. Inter-particle connection and uniformity of the ECD/CBD-CdS film were further enhanced by annealing. Consequently, the electrode PEC conversion efficiency and stability were enhanced. The combined preparation technique, followed by annealing, is potentially useful for future manufacturing of CdS and other film electrode systems. (C) 2013 Elsevier B.V. All rights reserved.
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| 8. |
- Böhme, Solveig, 1987-, et al.
(author)
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Overlapping and rate controlling electrochemical reactions for tin(IV) oxide electrodes in lithiu-ion batteries
- 2017
-
In: Journal of Electroanalytical Chemistry. - 0022-0728 .- 1873-2569. ; 797, s. 47-60
-
Journal article (peer-reviewed)abstract
- The results of this extensive electrochemical study of the electrochemical reactions of SnO2 electrodes in lithium-ion batteries demonstrate that the different reduction and oxidation reactions overlap significantly during the cycling and that the rates of the redox reactions are limited by the mass transport through the layers of oxidation or reduction products formed on the electrodes. The experiments, which were carried out in the absence and presence of the lithium alloy reactions, show that the capacity losses seen on the first cycles mainly can be explained by an incomplete oxidation of the lithium tin alloy and an incomplete reformation of SnO2. The latter can be explained by the formation of thin tin oxide layers (i.e., SnO and SnO2), protecting the remaining tin, as the oxidation current then becomes limited by the Li+ diffusion rate though these layers. The results, also show that the first cycle SnO2 reduction was incomplete for the about 20 μm thick electrodes containing 1 to 6 μm large SnO2 particles. This can be ascribed to the formation of a layer of tin and Li2O (protecting the remaining SnO2) during the reduction process. Although the regeneration of the SnO2 always was slower than the reduction of the SnO2, the results clearly show that the SnO2 conversion reaction is far from irreversible, particularly at low scan rates and increased temperatures. Electrochemical cycling at 60 °C hence gave rise to increased capacities, but also a faster capacity loss, compared to at room temperature. These new findings indicate that a full utilization of SnO2 based electrodes at a given cycling rate only can be reached with sufficiently small particles since the allowed particle size is given by the time available for the mass transport through the formed surface layers. The present results consequently provide important insights into the phenomena limiting the use of SnO2 electrodes in lithium-ion batteries.
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| 9. |
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| 10. |
- Hussain, Mushtaque, et al.
(author)
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Effect of anions on the morphology of Co3O4 nanostructures grown by hydrothermal method and their pH sensing application
- 2014
-
In: Journal of Electroanalytical Chemistry. - : Elsevier. - 1572-6657 .- 1873-2569. ; 717-718, s. 78-82
-
Journal article (peer-reviewed)abstract
- A fast, reliable, accurate, precise and sensitive pH sensor device is highly demanding for the monitoring of pH in biological, clinical and food industry samples. In this research work, the effect of anions on the morphology of cobalt oxide (Co3O4) nanostructures is investigated using low temperature chemical approach for the growth. Different anions have shown visible effect on the morphology of Co3O4 nanostructures. Scanning electron microscopy, X-ray diffraction and transmission electron microscopy techniques were used for the material characterization. This study has shown highly dense, uniform and good crystal quality of fabricated Co3O4 nanostructures. The nanostructures obtained from the cobalt chloride were used for the development of potentiometric pH sensor electrode. The pH sensor electrode showed excellent linearity and close to Nernstian response for the pH range of 3-13 with a sensitivity of -58.45 mV/pH. Moreover, the proposed sensor showed a fast response time of 53 s, and acceptable reducibility and repeatability. The highly sensitive and a fast time response of the proposed sensor device indicate its potential application for the monitoring of pH from real samples including biological fluids.
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| 11. |
- Larses, Patrik, et al.
(author)
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Hydrogen evolution at mixed α-Fe1 − xCrxOOH
- 2018
-
In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657 .- 0022-0728. ; 819, s. 114-122
-
Journal article (peer-reviewed)abstract
- The activity of mixed α-Fe 1 − x Cr x OOH oxides towards hydrogen evolution in alkaline solution is discussed based on Density Functional Theory (DFT) calculations, cyclic voltammetry and steady state measurements. Thermogravimetric and XRD measurements indicate an isomorphic substitution of Fe by Cr. Electrochemical characterization shows increasingly sluggish hydrogen evolution reaction (HER) kinetics with increased Cr loadings. This decrease in activity is accompanied by the inhibition of the reduction of iron in α-Fe 1 − x Cr x OOH. To investigate the origin of this decrease in activity, DFT calculations were performed for mixtures of Fe and Cr placed at Fe(OH) 2 . Based on phase diagrams, the most stable structures under HER conditions are identified and used to estimate the theoretical overpotential. In contrast to experiment, no decrease in HER activity is observed. Instead, mixed FeCr sites display an overpotential comparable to that of Pt. Taking into account the inhibition of the bulk reduction in the presence of Cr, the activity decreases in agreement with experiment. These results are very important in the search for cathodes in the chlorate process that are active also in the absence of chromate in solution and may offer a new route for Pt free HER catalysts in alkaline solution.
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| 12. |
- Phal, Sereilakhena, et al.
(author)
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Covalently electrografted carboxyphenyl layers onto gold surface serving as a platform for the construction of an immunosensor for detection of methotrexate
- 2018
-
In: Journal of Electroanalytical Chemistry. - : Elsevier. - 1572-6657 .- 1873-2569. ; 812, s. 235-243
-
Journal article (peer-reviewed)abstract
- Abstract The classical way to modify a gold electrode surface for immunosensor development is through self-assembly of functionalised thiols for subsequent attachment of antibodies. Here is described a new pathway for surface modification using a diazonium salt-based immunosensor for detection of methotrexate (MTX) with electrochemical immittance spectroscopy (EIS). The diazonium salt, 4-carboxybenzenediazonium tetrafluoroborate was synthesized using a diazotization reaction and characterized by IR and cyclic voltammetry (CV). The Au electrode was electrografted with diazonium and used for anti-MTX antibody immobilization. The EIS detection of MTX was studied with and without application of redox probe; Fe(CN)63−/4−. MTX could not be detected using Fe(CN)63−/4−as redox probe, whereas EIS measurements without redox probe and analysis of the data with singular decomposition (SVD) gave good results. A multivariate calibration model showed good linear behavior on a logarithmic scale with a detection limit for MTX of 7×10−12molL−1.
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| 13. |
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| 14. |
- Wreland Lindström, Rakel, et al.
(author)
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Electrocatalysis and transport effects on nanostructured Pt/GC electrodes
- 2010
-
In: J ELECTROANAL CHEM. - : Elsevier BV. - 1572-6657 .- 0022-0728. ; 644:2, s. 90-102
-
Journal article (peer-reviewed)abstract
- The role and contribution of transport processes in electrocatalytic reactions was investigated in model studies of the oxidation of CO (single-product reaction) and formaldehyde (dual-product reaction), using nanostructured Pt/glassy carbon electrodes with variable Pt loading and defined reactant transport conditions. Nanostructured electrodes with monodispersed, uniformly distributed Pt nanostructures (100-140 nm diameter) supported on planar glassy carbon (GC) electrodes with different densities were prepared by Colloidal Lithography (CL) or Hole-Mask Colloidal Lithography (HCL). Transport effects were evaluated by varying the density of the nanostructures and the electrolyte flow. The resulting changes in the transport limited reaction current (CO oxidation - transition from planar to spherical diffusion with decreasing Pt nanostructure density) and in the distribution of the reaction products HCOOH and CO2 (HCHO oxidation), which is probed by differential electrochemical mass spectrometry (DEMS), are discussed focusing on transport effects. The increasing amount of CO2 with decreasing space velocity (higher nanostructure density, lower electrolyte flow) is explained by increasing re-adsorption and further reaction of desorbing reaction intermediates. (C) 2009 Elsevier B.V. All rights reserved.
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| 15. |
- Alexiadis, Alessio, et al.
(author)
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Comparison between CFD calculations of the flow in a rotating disk cell and the Cochran/Levich equations
- 2012
-
In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 669, s. 55-66
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Journal article (peer-reviewed)abstract
- Three CFD (Computational Fluid Dynamics) models (single-phase. VOF and Euler-Euler) are employed to simulate the flow in a finite, rotating electrode cell under different operative conditions. The main dimensionless groups are derived and their effect on the flow is investigated. Except very close to the rotating electrode (i.e. in the hydrodynamic layer), the results show a flow pattern considerably different from Cochran's approximate analytical solution often used in electrochemistry. Historically, the Cochran equation was used to derive the Levich equation, which permits the calculation of the limiting current density on a rotating electrode. Despite the general inadequacy of Cochran's analytical solution, however, we show that the Levich equation often retains its validity because, in many practical situations, the concentration boundary layer is considerably smaller than the hydrodynamic boundary layer. When bubbles are generated on the electrode and a certain critical void fraction is exceeded, however, the Levich equation also becomes inaccurate. We propose, therefore, an amended version of this equation, which provides results closer to the CFD calculations.
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| 16. |
- Evertsson, Jonas, et al.
(author)
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Anodization of Al(100), Al(111) and Al Alloy 6063 studied in situ with X-ray reflectivity and electrochemical impedance spectroscopy
- 2017
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In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 799, s. 556-562
-
Journal article (peer-reviewed)abstract
- We present results from the anodization of single crystal Al(100) and Al(111) surfaces and the aluminum alloy AA 6063 studied in situ by X-ray reflectivity and electrochemical impedance spectroscopy. We observe that the anodic oxide layer grows linearly with the anodization potential and that the thicknesses are similar for all samples. However, the thicknesses obtained from X-ray reflectivity are higher than that obtained from electrochemical impedance spectroscopy. We attribute the higher thicknesses to an outer porous oxide layer, which is not detected by electrochemical impedance spectroscopy. Both, electrochemical impedance spectroscopy and X-ray reflectivity suggests that a more heterogeneous and rough oxide is formed on AA 6063 due to the influence of the alloying elements and intermetallic particles during the growth.
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| 17. |
- Gonzalez-Arribas, Elena, et al.
(author)
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A conventional symmetric biosupercapacitor based on rusticyanin modified gold electrodes
- 2018
-
In: Journal of Electroanalytical Chemistry. - : Elsevier. - 1572-6657. ; 816, s. 253-258
-
Journal article (peer-reviewed)abstract
- Here we report on an entirely new kind of bioelectronic device - a conventional biosupercapacitor, which is built from copper containing redox proteins. Prior to biodevice fabrication, detailed spectroelectrochemical studies of the protein, viz. Acidithiobacillus ferrooxidcats rusticyanin, in solution and in adsorbed state, were performed, including estimation of the redox potential of the T1 site (0.62 V vs. NHE), protein midpoint potential when adsorbed on a self-assembled monolayer (0.34 V vs. NHE), as well as biocapacitance of rusticyanin modified gold electrodes (115 mu F cm(-2)). The symmetrical biosupercapacitor based on two identical gold electrodes modified with rusticyanin is able to capacitively store electricity and deliver electric power accumulated mostly in the form of biopseudocapacitance, when charged and discharged externally. When charged during Just 5 s, the biosupercapacitor with a total capacitance of about 73 mu F cm(-2) provided a maximum of 4 mu A cm(-2) peak current at 0.40 V. The biodevice, which can be charged and discharged at least 50 times without a significant loss of ability to store electric energy, had a low leakage current below 50 nA cm(-2).
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| 18. |
- Kanso, Hussein, et al.
(author)
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Sunlight photocurrent generation from thylakoid membranes on gold nanoparticle modified screen-printed electrodes
- 2018
-
In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 816, s. 259-264
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Journal article (peer-reviewed)abstract
- In this work we report on the increase in photocurrent obtained by using thylakoid membranes “wired” with an osmium redox polymer (OsRP) immobilized onto screen-printed carbon and gold electrodes (SPCEs and SPAuEs), modified with gold microparticles (AuMPs) and gold nanoparticles (AuNPs). Both AuMPs and AuNPs were electrodeposited by using the same electrodeposition method in order to study the influence of different electrode surface morphologies, namely AuMPs and AuNPs, on the photocurrent generated when illuminated ΔΔΔ with light with an intensity equivalent to that of sunlight (400 W m−2). AuMPs/SPCEs showed the highest current density (62.5 μA cm−2) upon illumination probably due to a higher capacitive current directly related to the enhanced electroactive area (AEA) and roughness factor (ρ). Finally, the so modified electrodes AuMPs/SPCE and AuNPs/SPAuE were characterized by using scanning electron microscopy (SEM) showing a different surface morphology, resulting in a higher surface roughness for AuMPs/SPCE compared to AuNPs/SPAuE therefore an intimate interaction between the large thylakoid membrane and the AuNPs. A high photocurrent density of 62.5 μA cm−2 was generated at a light intensity of 400 W m−2.
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| 19. |
- Li, Xianchan, 1982, et al.
(author)
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Single cell amperometry reveals curcuminoids modulate the release of neurotransmitters during exocytosis from PC12 cells
- 2016
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In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 781, s. 30-35
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Journal article (peer-reviewed)abstract
- We used single cell amperometry to examine whether curcumin and bisdemethoxycurcumin (BDMC), substances that are suggested to affect learning and memory, can modulate monoamine release from PC12 cells. Our results indicate both curcumin and BDMC need long-term treatment (72 h in this study) to influence exocytosis effectively. By analyzing the parameters calculated from single exocytosis events, it can be concluded that curcumin and BDMC affect exocytosis through different mechanisms. Curcumin accelerates the event dynamics with no significant change of the monoamine amount released from single exocytotic events, whereas BDMC attenuates the amount from single exocytotic event with no significant change of the event dynamics. This comparison of the effect of curcumin and BDMC on exocytosis at the single cell level brings insight into their different mechanisms, which might lead to different biological actions. The effect of curcumin and BDMC on the opening and closing of the exocytotic fusion pore were also investigated. These results might be helpful for understanding the improvement of learning and memory and the anti-depression properties of curcuminoids.
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| 20. |
- Loupe, Neili, et al.
(author)
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DFT - experimental IR spectroscopy of lithiated single ion conducting perfluorinated sulfonated ionomers: Ion induced polarization band broadening
- 2017
-
In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 800, s. 176-183
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Journal article (peer-reviewed)abstract
- The impact of state of hydration and ion exchange on the exchange site local symmetry of Aquivion and Nafion perfluorinated sulfonated ionomers (PFSI) are probed by transmission IR spectroscopy.Hydrated PFSI-H membranes exhibit a pair of bands corresponding to a dissociated sulfonate exchange site with a local 3-fold axis of symmetry (C3V). C3V bands are supplanted by C1 bands (no local symmetry) corresponding to the sulfonic acid form of the exchange site. At intermediate states of hydration C3V and C1 bands co-exist. Hydrated PFSI-Li exhibits C3V bands. In contrast to PFSI-H, the PFSI-Li C3V bands persist throughout dehydration, with a final aggregate structure where each Li+ provides 1/3 of a charge per sulfonate oxygen with an overall C3V motif. The C3V band FWHM values progressively increase (hydrated PFSI-H
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| 21. |
- Momodu, Damilola, et al.
(author)
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Stable ionic-liquid-based symmetric supercapacitors from Capsicum seed-porous carbons
- 2019
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In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 838, s. 119-128
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Journal article (peer-reviewed)abstract
- In this study, a symmetric ionic-liquid based supercapacitor was assembled with porous carbon derived from Capsicum (bell pepper) seeds. The “peppered”-activated carbon (ppAC) was synthesized using varying amounts of KHCO 3 activating agent (AA) at 850 °C carbonization temperature. The best device performance reported was recorded with optimum amounts of AA to raw material. The need for less amount of AA is crucial if the entire activation/carbonization process is to be scaled-up with the cost and final product yield also being important for a viable synthesis. A mechanism of saturation of pores with unreacted AA which leads to lower porosity metrics in the samples with increasing the amount of AA during carbonization/activation was also proposed. Using an ionic liquid electrolyte, 1-ethyl-3-methylimidazolium bistrifluorosulfonylimide (EMIM-TFSI), the ppAC-based supercapacitor operated up to a maximum cell voltage of 3.20 V. A specific energy of 37 Wh kg −1 was obtainable with a corresponding practical power density of 0.6 kW kg −1 at 0.5 A g −1 . A specific energy of ∼26 Wh kg −1 was still achievable when the applied current was doubled to 1.0 A g −1 and a high cyclic stability (approx. 99% coulombic efficiency) was proven over 25,000 cycles. Further ageing test performed on the device revealed a remarkable improvement in the electrochemical performance after a 180 h (ca. 1 week) floating time. The obtained results also confirmed a uniquely distributed porous carbon in which the complete utilization of the entire less-corrosive KHCO 3 AA for optimal pore activation at elevated carbonization temperatures. Thus, the efficient design combinations for stable, high-energy and power ionic liquid-based supercapacitors with cheaper biomass-based materials are demonstrated.
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| 22. |
- Munktell, Sara, et al.
(author)
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Towards high throughput corrosion screening using arrays of bipolar electrodes
- 2015
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In: JOURNAL OF ELECTROANALYTICAL CHEMISTRY. - : Elsevier BV. - 1572-6657. ; 747, s. 77-82
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Journal article (peer-reviewed)abstract
- In this work we demonstrate the possibility of combining bipolar electrochemistry with arrays of samples as a fast and versatile method for comparing their corrosion resistances at a wide range of potentials. Several steel samples of different grades were arranged in a bipolar electrochemical cell and exposed to an electric field by applying a constant current. The gradient in electrochemical potential difference across each sample resulted in a pitting corrosion gradient on the anodic parts which was used as a simple, straightforward and qualitative method of screening the corrosion properties of several samples in one single experiment. In the cell, all samples acted as individual bipolar electrodes but interestingly, the current density for each sample was also found to be influenced by the corrosion resistances of its neighbours. Results from the bipolar array were also compared with standard polarisation curves and the pitting resistance equivalent number (PREN) for each steel type.
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| 23. |
- Nazarov, Andrej P., et al.
(author)
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Electrochemical and corrosion properties of ZnO/Zn electrode in atmospheric environments
- 2015
-
In: Journal of Electroanalytical Chemistry. - : Elsevier B.V.. - 1572-6657. ; 737, s. 129-140
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Journal article (peer-reviewed)abstract
- ZnO films of different thicknesses were prepared by thermal oxidation of zinc. The oxide covered surfaces were characterized by Scanning Kelvin Probe (SKP) and Scanning Kelvin Probe-Surface Photovoltage (SKP-SPV) techniques, Infrared Reflection Absorption Spectroscopy (IRRAS), contact angle measurements, and dc voltammetry. The influence of the thickness of ZnO on the absorption of the light, water and oxygen was evaluated. SKP and dc electrochemistry were used to estimate the mechanism of electron exchange between the zinc surface and an aqueous solution containing a red-ox system [Fe(CN)6]2-/[Fe(CN)6]3-. It was shown that ZnO/Zn electrodes with a thick ZnO film nobled the Volta potential that enhanced the electron transfer from the bulk zinc to the molecule of the oxidizer- [Fe(CN)6]3-. Atmospheric corrosion of oxidized zinc surface was investigated after deposition of a single droplet of NaCl aqueous electrolyte. Thicker ZnO films promote the oxygen reduction and the spreading area of the cathodic reaction from the local NaCl contamination. It enlarged the area of metal surface participating in the cathodic reaction and consequently accelerated the atmospheric corrosion. The ability to enhance the oxygen reduction was discussed from the point of view of the band structure and the semiconducting properties of the ZnO layer.
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| 24. |
- Nissfolk, Jarl, et al.
(author)
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Interpretation of small-modulation photocurrent transients in dye-sensitized solar cells : A film thickness study
- 2010
-
In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 646:1-2, s. 91-99
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Journal article (peer-reviewed)abstract
- Electron transport in dye-sensitized solar cells with varying mesoporous TiO2 film thicknesses was investigated using experimental and computational methods. More specifically, photocurrent transients resulting from small-amplitude square-wave modulation of the incident light were recorded for a series of solar cells, whereby the dependence of the wavelength and direction of the illumination was investigated. The responses were compared to simulations using different models for diffusional charge transport and analyzed in detail. The photocurrent transients are composed of two components: an initial fast response in case of illumination from the working electrode side, or an initial apparent delay of photocurrent decay for illumination from the counter electrode side, followed by a single exponential decay at longer times, with a time constant that is identified as the electron transport time. The initial response depends on the thickness and the absorption coefficient of the film. Transport times for different films were compared at equal short-circuit current density, rather than at equal light intensity. Experimentally, the transport time showed a power-law dependence on the film thickness with an exponent of about 1.5. Analysis using the quasi-static multiple trapping (MT) formulation demonstrates that this behavior originates from differences in quasi-Fermi level in the TiO2 films of different thickness when equal photocurrents are generated. The Fokker-Planck relation was used to derive expressions for the electrons flux in porous TiO2 films with a position-dependent diffusion coefficient.
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| 25. |
- Shao, Cairu, et al.
(author)
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Influence of Cr doping on the oxygen evolution potential of SnO2/Ti and Sb-SnO2/Ti electrodes
- 2019
-
In: JOURNAL OF ELECTROANALYTICAL CHEMISTRY. - : ELSEVIER SCIENCE SA. - 1572-6657. ; 832, s. 436-443
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Journal article (peer-reviewed)abstract
- Oxygen evolution potential is the determining factor affecting the anode efficiency of the wastewater treatment process. In this study, we focus on increasing oxygen evolution potential of Cr-SnO2/Ti and Cr-Sb-SnO2/Ti electrodes with the pyrolytic method. XRD, SEM and XPS techniques had been applied to characterize the microstructures and chemical compositions of the samples. Electrochemical measurements had been performed to evaluate the oxygen evolution potential as a criterion of the wastewater treatment efficiency. The results show that co-doping of Sb and Cr improved the crystallinity and grain size of SnO2 coating, and Cr existed in the form of Cr(III) valence states. The Cr doping treatment improved the electronic conductivity and the electrocatalytic activity of the electrodes. DFT calculation of the band-structure indicates Cr doped SnO2 had a superior electrical conductivity, where Cr atom acts as an acceptor providing vacancies for electron transportation. The DOS diagrams reveal the Cr doped SnO2 showing a p-type conductivity which would subsequently influence the built-in potential on metal-semiconductor interface. We proposed the mechanism of the increase of oxygen evolution potential is the doping of Cr expands the built-in potential.
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| 26. |
- Steegstra, Patrick, 1978, et al.
(author)
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In situ pH measurements with hydrous iridium oxide in a rotating ring disc configuration
- 2012
-
In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 685, s. 1-7
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Journal article (peer-reviewed)abstract
- Many chemical reactions are pH dependent and for electrochemical reactions taking place at an electrode surface, changes in the near surface pH can be decisive for their outcome. Near surface pH changes have successfully been utilised for formation of oxide films and to control the shape and morphology of the deposit. The mechanistic insight into such processes is hampered by the difficulty to measure the local pH in situ. In the present paper the rotating ring disc electrode (RRDE) configuration is used to measure the near surface pH for two model reactions, hydrogen evolution and oxygen reduction. Iridium oxide is electrodeposited on the titanium ring and used as the pH sensing material. At low current densities and therefore low hydroxide ion concentrations, the pH response is rather slow, limiting the applicability of potentiodynamic sweep experiments under such conditions. At higher current densities a linear relationship between the logarithm of the current and pH is found. Tracking of small pH changes can be made by step experiments where the response is measured as a function of time and steady state conditions can be assured. Key issues for successful use of the RRDE configuration with iridium oxide as the pH sensing material are pre-conditioning of the ring electrode to obtain well defined redox properties of the film and choice of ring substrate onto which the iridium oxide is deposited. (C) 2012 Elsevier B.V. All rights reserved.
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| 27. |
- Tavahodi, Mojtaba, et al.
(author)
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Interaction of polymer-coated gold nanoparticles with cellobiose dehydrogenase : The role of surface charges
- 2018
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In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 819, s. 226-233
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Journal article (peer-reviewed)abstract
- Studying the interaction of functional proteins such as enzymes and nanoparticles (NPs) includes the important topic of investigating any possible changes in stability and function of enzymes in nanostructured environments. The effects of NPs on the enzyme activity and stability are governed by their physical and chemical properties such as structure, shape, size, surface chemistry and their surface charges. In this study, the influence of negatively and positively charged AuNPs are investigated on the activity of immobilized Myriococcum thermophilum cellobiose dehydrogenase (MtCDH) and its electron transfer rate with graphite electrodes modified with positively and negatively AuNPs. The MtCDH modified graphite electrode premodified with positively charged AuNPs showed an alkaline shift in the pH of maximum activity from pH5.5 to 8. No change in the pH of maximum activity was observed when MtCDH graphite electrodes were premodified with negatively charged AuNPs. The results clearly demonstrated the effect of surface charge of AuNPs on the activity of the enzyme. The catalytic current density and the KM app value for MtCDH graphite electrode premodified with positively charged AuNPs were enhanced with up to 66 and 8 times, respectively. Two spectroscopic assays were also performed in solution to investigate the influence of the presence of positively or negatively charged AuNPs on the activity of MtCDH in homogeneous solution. The results clearly demonstrated that not only the rate of the heterogeneous electron transfer between the immobilized MtCDH and the electrode but also the rate of the homogeneous electron transfer between soluble MtCDH and the acceptor was highly dependent on the type of surface charge of the AuNPs.
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| 28. |
- Ye, Chen-Qing, et al.
(author)
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EIS analysis on chloride-induced corrosion behavior of reinforcement steel in simulated carbonated concrete pore solutions
- 2013
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In: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 688, s. 275-281
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Journal article (peer-reviewed)abstract
- The corrosion behavior of reinforcement steel in simulated carbonated concrete pore (SCCP) solution containing different concentrations of chloride was studied by electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) measurements simultaneously, and the topographies of the steel specimens and the elemental distribution at corrosion area were examined by scanning electron microscope (SEM)/electron microprobe analysis (EMPA). The results showed the capacitive loop and polarization resistance decreased with chloride increasing. Furthermore, when the chloride concentration reached a critical value, the Bode plots obviously exhibited two phase angle peaks indicating two time constants. However, when the chloride content exceeded a critical value, the phase angle peaks decreased to one phenomenal peak. An equivalent circuit with two RC loops was used to characterize the corrosion behavior of reinforcement steel in SCCP solution according to the measurements of EIS. Based on the dependence of the equivalent circuit elements on chloride content and immersion time, the formation, growth and breakdown of passive film of the steel were discussed. It was found that the EIS evaluation of corrosion behavior for reinforcement steel in SCCP solution was good agreement with the LPR and SEM measurements. The EMPA mapping revealed MnS inclusions at steel surface play a leading role in the initiation of pitting corrosion.
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| 29. |
- Žalnėravičius, Rokas, et al.
(author)
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Nanoplatelet MoS2 arrays decorated with Pt nanoparticles for non-enzymatic detection of hydrogen peroxide
- 2019
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In: Journal of Electroanalytical Chemistry. - : Elsevier. - 1572-6657. ; 839, s. 274-282
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Journal article (peer-reviewed)abstract
- An electrochemical detection platform for monitoring of hydrogen peroxide was designed based on molybdenum disulphide nanocomposites. Bulk MoS2 as well as flower-like MoS2 sheets on Ti substrate were synthesized via a hydrothermal approach. Monodispersed MoS2 nanoparticles with average size less than 2 nm were fabricated by simple and low-cost ultrasonication and gradient centrifugation method. The MoS2/Ti structures were further assessed for amperometric H2O2 detection. The nanoflower MoS2/Ti electrode were electrochemically designed with highly dense Pt nanoparticles. The structure and surface morphology were subsequently characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. The electrochemical behaviours and sensing performances of the MoS2/GC, MoS2/Ti and Pt/MoS2/Ti electrodes were studied by cyclic voltammetry (CV) and chronoamperometry. The MoS2 nanoparticle modified GC electrode displayed excellent sensitivity towards H2O2 at applied voltage of -0.6 V and the best sensitivity of 1.93 mu A mu M-1 cm(-2) was reached with Pt/MoS2/Ti electrodes. The electrodes prepared by using novel hybrid MoS2 nanomaterials showed high sensitivity, selectivity and long-term stability (at least 10 days) for monitoring of H2O2 and, thus, deserve further studies of their application in development of sensors and biosensors.
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| 30. |
- Zaman, Siama, et al.
(author)
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CuO nanoflowers as an electrochemical pH sensor and the effect of pH on the growth
- 2011
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In: JOURNAL OF ELECTROANALYTICAL CHEMISTRY. - : Elsevier. - 1572-6657. ; 662:2, s. 421-425
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Journal article (peer-reviewed)abstract
- Well-crystallized flower-shaped cupric oxide (CuO) nanostructures composed of thin leaves have been synthesized by simple low-temperature chemical bath method and used to fabricate pH sensor. We examined the effect of the pH on the growth of the CuO nanostructures, by changing the pH of the precursor solutions different morphologies of the CuO nanostructures were obtained. CuO nanoflowers have recently become important as a material that provides an effective surface for electrochemical activities with enhanced sensing characteristics. The proposed sensor exhibited a linear electrochemical response within a wide pH range of (2-11). The experimental results (time response, electrochemical activity, reproducibility, absorption spectra, and XRD) indicate that the CuO nanoflowers can be used in pH sensor applications with enhanced properties.
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