| 1. |
- Evertsson, Jonas, et al.
(författare)
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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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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 799, s. 556-562
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Gonzalez-Arribas, Elena, et al.
(författare)
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A conventional symmetric biosupercapacitor based on rusticyanin modified gold electrodes
- 2018
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier. - 1572-6657. ; 816, s. 253-258
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Tidskriftsartikel (refereegranskat)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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| 3. |
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| 4. |
- Kanso, Hussein, et al.
(författare)
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Sunlight photocurrent generation from thylakoid membranes on gold nanoparticle modified screen-printed electrodes
- 2018
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 816, s. 259-264
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Tidskriftsartikel (refereegranskat)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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| 5. |
- Larses, Patrik, et al.
(författare)
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Hydrogen evolution at mixed α-Fe1 − xCrxOOH
- 2018
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657 .- 0022-0728. ; 819, s. 114-122
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Li, Xianchan, 1982, et al.
(författare)
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Single cell amperometry reveals curcuminoids modulate the release of neurotransmitters during exocytosis from PC12 cells
- 2016
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 781, s. 30-35
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Tidskriftsartikel (refereegranskat)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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| 7. |
- Lindberg, Jonas, et al.
(författare)
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The effect of O2 concentration on the reaction mechanism in Li-O2 batteries
- 2017
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657 .- 0022-0728 .- 1873-2569. ; 797, s. 1-7
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Tidskriftsartikel (refereegranskat)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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| 8. |
- Loupe, Neili, et al.
(författare)
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DFT - experimental IR spectroscopy of lithiated single ion conducting perfluorinated sulfonated ionomers: Ion induced polarization band broadening
- 2017
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 800, s. 176-183
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Tidskriftsartikel (refereegranskat)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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| 9. |
- Momodu, Damilola, et al.
(författare)
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Stable ionic-liquid-based symmetric supercapacitors from Capsicum seed-porous carbons
- 2019
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 838, s. 119-128
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Tidskriftsartikel (refereegranskat)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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| 10. |
- Munktell, Sara, et al.
(författare)
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Towards high throughput corrosion screening using arrays of bipolar electrodes
- 2015
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Ingår i: JOURNAL OF ELECTROANALYTICAL CHEMISTRY. - : Elsevier BV. - 1572-6657. ; 747, s. 77-82
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Tidskriftsartikel (refereegranskat)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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