| 1. |
- Sjödin, Martin, 1974-, et al.
(författare)
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Proton-coupled electron transfer from an interfacial phenol monolayer
- 2020
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 0022-0728 .- 1873-2569 .- 1572-6657. ; 859
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Tidskriftsartikel (refereegranskat)abstract
- A tert-butyl protected phenol is covalently link to a mixed self-assembled monolayer on a gold or platinum electrode. The phenol reduction potential shows the expected pH-dependence of a one-electron, one-proton couple with a decrease in formal reduction potential of 59 ± 5 mV per pH. A titration of the phenol is observed with a pKa of 13.2 and the reduction potential for the phenolate is 0.11 V . NHE. The kinetic behavior of the proton-coupled oxidation deviates substantially from the commonly used models for a step-wise reaction that assume the proton transfer reactions are in equilibrium throughout the reaction. A novel model for step-wise proton-coupled reactions is presented that fully accounts for the pH dependent kinetics and allows the formal rate constants and the transfer coefficients to be determined.
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| 2. |
- Sjödin, Martin, 1974-, et al.
(författare)
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Reprint of "Proton-coupled electron transfer from an interfacial phenol monolayer"
- 2020
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Ingår i: Journal of Electroanalytical Chemistry. - : ELSEVIER SCIENCE SA. - 0022-0728 .- 1873-2569 .- 1572-6657. ; 875
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Tidskriftsartikel (refereegranskat)abstract
- A tert-butyl protected phenol is covalently link to a mixed self-assembled monolayer on a gold or platinum electrode. The phenol reduction potential shows the expected pH-dependence of a one-electron, one-proton couple with a decrease in formal reduction potential of 59 +/- 5 mV per pH. A titration of the phenol is observed with a pK(a) of 13.2 and the reduction potential for the phenolate is 0.11 V. NHE. The kinetic behavior of the proton-coupled oxidation deviates substantially from the commonly used models for a step-wise reaction that assume the proton transfer reactions are in equilibrium throughout the reaction. A novel model for step-wise proton-coupled reactions is presented that fully accounts for the pH dependent kinetics and allows the formal rate constants and the transfer coefficients to be determined.
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| 3. |
- Hadidi, Hooman, et al.
(författare)
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Numerical investigation of capacitive deionization (CDI) with divergent and convergent channels
- 2023
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 944
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Tidskriftsartikel (refereegranskat)abstract
- This research aims to explore the impact of tilted channel configurations of CDI cells on desalination performance. The results reveal that the titled convergent channels have a faster average salt adsorption rate (ASAR) than the regular straight geometry. For desalination operations that end at a quarter of the equilibrium salt adsorption capacity (SAC), the convergent spacer with a slight slope of 1.5 degrees has a 20 % higher ASAR than the typical straight geometry (0.15 mg/g/min for convergent and 0.12 mg/g/min for straight). This gain increases to about 24, 29.5, and 33%, respectively, for slopes of 3.5, 5.5, and 7 degrees, compared to the straight geometry with the same spacer thickness. By looking at the underlying mechanisms, the spacer geometry is found to shift the location of the initial adsorption. This affects how quickly the device outputs the cleaned water. Interestingly, the geometry angle can also affect the location of the depletion zone, so tilted spacers can also affect the behavior during electrode starvation. Specifically, the convergent geometry has the depletion zone in the middle of the electrode instead of the corner near the outlet, as seen for straight and divergent channels. Together, these findings indicate how to construct tilted spacers to enhance CDI performance.
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| 4. |
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| 5. |
- Molina Osorio, Andres, et al.
(författare)
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Modelling electrochemical modulation of ion release in thin-layer samples
- 2021
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Ingår i: JOURNAL OF ELECTROANALYTICAL CHEMISTRY. - : Elsevier BV. - 1572-6657. ; 903, s. 115851-
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present a model based on the finite element approach to describe the electrochemically controlled release of ions from a redox-active film into a sample confined to a thin-layer spatial domain. The model includes the effect of interfacial charge transfer kinetics and 1D-diffusion treatment for an electron transfer-ion transfer (ET-IT) coupled reaction. More in detail, the oxidation of the redox-active film (ET) involves an ion release to an aqueous phase (IT). The dynamic concentration of the released ion is calculated when the ET-IT reaction proceeds under potentiostatic control, and the effect of the thickness of each phase (i.e., film or aqueous) on the diffusion profile is analyzed. The model is experimentally validated for the particular case in which oxidation of a thin film of polyaniline (PANI, 10 mu m in thickness) is linked to the release of protons from the film into an electrolyte solution. The proton release produces certain pH changes in the electrolyte that are monitored by a pH sensor located at 330 mu m from the PANI film. The charge associated with the proton release is related to the dynamic concentration of protons in the electrolyte through pH-coulograms that agree with the theoretical predictions. Overall, the model can reproduce the general behavior of the experimental proton pump and provides key insights into the functioning mechanism of electrochemical systems where redox and ion transfer reactions are coupled.
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| 6. |
- Mwanza, Daniel, et al.
(författare)
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Capacitive label-free ultrasensitive detection of PSA on a covalently attached monoclonal anti-PSA antibody gold surface
- 2022
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier. - 1572-6657. ; 927
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Tidskriftsartikel (refereegranskat)abstract
- A rapid, low-cost, and accurate point-of-care analytical device for the determination of prostate-specific antigen (PSA) is required for the early diagnosis and prognosis of prostate cancer (PCa). In this work, an electrochemical capacitive immunosensor was developed for the label-free detection of PSA. The immunosensor was based on the covalent immobilization of monoclonal anti-PSA antibody via carbodiimide chemistry onto gold electrode (AuE) pre-modified with a thin monolayer film of isophthalic acid (IPA). A methodology based on the steric hindrance of 1,3-substituted aryldiazonium salt was adopted to control the growth of the IPA thin film on the gold electrode. The non-specific binding sites were blocked with bovine serum albumin (BSA) to afford an AuE-IPA-anti-PSA-mAb|BSA immunosensor. The immunosensor was characterized by X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The analytical performance of the developed sensor was evaluated using the capacitance Nyquist plots generated from the complex impedance data. In addition, complex capacitance was also calculated from the imaginary part of the impedance and plotted against the log of frequency. The double layer capacitance from the circuit fitting (RSC) was also used and compared the sensitive capacitance signals to the changes in PSA concentrations. The LOD values were in fg.mL−1 and distinguishable from the blank (PBS) for the Nyquist plots of capacitance, complex capacitance, and double layer capacitance signals. The developed immunosensor exhibited good stability, selectivity, low detection limits, and a wide linear range which was suitable for screening of prostate cancer using prostate-specific antigen.
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| 7. |
- Papaderakis, Athanasios, et al.
(författare)
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Ternary IrO2-Pt-Ni deposits prepared by galvanic replacement as bifunctional oxygen catalysts
- 2020
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Ingår i: JOURNAL OF ELECTROANALYTICAL CHEMISTRY. - : ELSEVIER SCIENCE SA. - 1572-6657. ; 877
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Tidskriftsartikel (refereegranskat)abstract
- Bifunctional oxygen catalysts with IrO2 and Pt active components have been prepared by means of galvanic partial replacement of Ni layers electrodeposited on glassy carbon substrates (Ni/GC). The resulting IrO2Pt(Ni)/GC electrodes have a homogeneous and compact morphology (SEM), while surface electrochemistry and spectroscopic measurements (EDS, XPS) confirm the ternary bulk structure (EDS: 56.39% Ir- 7.60% Pt - 36.01% Ni atomic ratio) and the existence of a IrO2-Pt thin skin on the outermost layers of the deposits (XPS: Ir+ Pt atomic ratio of 21.7). IrO2Pt (Ni)/GC electrodes were evaluated as bifunctional electrocatalysts for oxygen evolution (OER) and oxygen reduction (ORR) reactions in acid, by means of steady-state current-potential measurements and linear sweep voltanunetry at a Rotating Disc Electrode (RDE) respectively. The OER overpotential required for a current density (per substrate geometric area) of 1 (eta(1)) and 10 mA cm(-2) (eta(10)) on the prepared electrodes was 235 and 302 my respectively, which is in the range of some typical thermally produced IrO2-based DSAs. Their intrinsic OER catalytic activity (as estimated by normalization of the recorded currents at an overpotential of 260 mV by the oxides charge) was found to be 0.29 mA mC(-1) comparable or better to other thermally produced IrO2 and Pt-IrO2 systems. Koutecky-Levich analysis shows that ORR proceeds on the ternary catalysts via the four electrons pathway. The overall ORR catalytic activity (0.4 mA cm(-2) at +0.8 V vs. SIIE) is found to be in the range of that recorded on nanoparticle catalysts, while a suppression of the intrinsic activity compared to bulk Pt is observed most probably due to the presence of IrO2, the latter being in line with similar non-alloyed Pt-IrO2 systems reported in the literature.
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| 8. |
- Rajendra Babu Kalai Arasi, Azega, 1995, et al.
(författare)
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Effect of plasma treatment on electrochemical performance of lignin-based carbon fibers
- 2023
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Ingår i: Journal of Electroanalytical Chemistry. - 1572-6657. ; 946
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Tidskriftsartikel (refereegranskat)abstract
- The abundant and renewable nature of lignin obtained from wood renders it as a sustainable carbon resource for energy storage applications. However, their environmentally unfavorable processing conditions and limited energy storage performance prohibit the use of lignin-based carbon materials' use as supercapacitor electrodes. The material's properties require advancement to overcome the limitation of low specific capacitances. In this study, we report on the impact on the electrochemical performance of inherently hydrophobic lignin-based carbon fibers (LCF) by subjecting them to a mild plasma treatment. The electrode’s capacitance was thus increased by 20%, with better rate capability and energy-power performance (11 Wh/kg and 0.8 kW/kg) in the KOH electrolyte. The quantified improvements were attributed to the capacitive functional groups, and enhanced surface wettability, which increased ion accessibility to active surface area improving charge-transfer ability to the surface with more additional functional groups. Remarkably, the selected plasma conditions introduced mostly desirable functional groups that limited any parasitic faradaic reactions prone to affect the device's long-term cycling stability and self-discharge characteristics. Furthermore, the impact of different inherent and introduced oxygen surface functional groups, including COO−, COH, CO, and CO, on the capacitive performance of these fibers at different device conditions (such as cycling and electrochemical activation) was investigated in different aqueous electrolytes. To ensure environmental favorability, the electrospinning of lignin fibers was conducted using a high molecular fraction of lignin without the inclusion of any fossil-based co-spinning polymers.
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| 9. |
- Wiberg, Cedrik, 1989, et al.
(författare)
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Naphthalene diimides (NDI) in highly stable pH-neutral aqueous organic redox flow batteries
- 2021
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Ingår i: Journal of Electroanalytical Chemistry. - : Elsevier BV. - 1572-6657. ; 896
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Tidskriftsartikel (refereegranskat)abstract
- In the pursuit of environmentally friendly energy storage, aqueous organic redox flow batteries (AORFBs) that use naphthalene diimide hold promise for successful application. In the present article, two different naphthalene diimides (NDI) are studied as negative electrolyte materials for pH-neutral aqueous organic/ organometallic redox flow batteries. The two molecules, one core-unsubstituted NDI (2H-NDI) and one coredimethylamino substituted NDI (2DMA-NDI) are coupled with a solubilized ferrocene (BTMAP-Fc) at a concentration of 50 mM in phosphate buffered potassium chloride. High energy efficiencies and coulombic efficiencies were obtained for both batteries, but a gradual capacity fade was observed while cycling. However, when changing the cation of the supporting electrolyte from potassium to ammonium, similar energy and coulombic efficiencies were obtained, but with undetectable capacity losses over 320 cycles. Finally, 2H-NDI and BTMAPFc at 500 mM were tested in the ammonium-based electrolyte, and while obtaining high coulombic efficiency, the energy efficiency and cycling stability decreased compared to the same system at lower concentration. It is concluded that loss of activity is mainly due to formation of electrochemically inactive compounds and that the electrolyte cation is of great importance for the outcome. Important design strategies for AORFB molecules include using supporting salts that prevent self-association and introducing sterically hindering substituents to the structures.
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