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  • 1.
    Böhme, Solveig
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Edström, Kristina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Strukturkemi.
    Nyholm, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Oorganisk kemi.
    Overlapping and rate controlling electrochemical reactions for tin(IV) oxide electrodes in lithiu-ion batteries2017Ingår i: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 797, s. 47-60Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 2.
    Edwards, M O M
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi I. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektronik.
    Andersson, M
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi I. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektronik.
    Gruszecki, T
    Pettersson, H
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi I. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektronik.
    Thunman, Robert
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Thuraisingham, G
    Vestling, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Hagfeldt, A
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Fysikalisk kemi I. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektronik.
    Charge-discharge kinetics of electric-paint displays2004Ingår i: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 565, nr 2, s. 175-184Artikel i tidskrift (Refereegranskat)
  • 3.
    Eskhult, Jonas
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Oorganisk kemi.
    Herranen, Merja
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Oorganisk kemi.
    Nyholm, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi, Oorganisk kemi.
    On the origin of the spontaneous potential oscillations observed during galvanostatic deposition of layers of Cu and Cu2O in alkaline citrate solutions2006Ingår i: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 594, nr 1, s. 35-49Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Potential oscillations are demonstrated under reducing galvanostatic conditions in alkaline solutions of 0.4 M Cu(II) and 1.2 M citrate at elevated temperatures. The oscillations, which give rise to the deposition of layers of Cu and Cu2O, as verified by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) as well as Raman measurements, originate from local modulations of the pH in the vicinity of the working electrode. A reaction scheme for the oscillations is presented based on the model previously proposed by Leopold et al. [J. Electroanal. Chem., 547 (2003) 45-52] for the Cu(II)-lactate system. It is shown that the oscillations are due to the fact that the rate of the electrodeposition Of Cu2O is modulated by the local pH variations. This causes this reaction to be switched on and off as the local pH increases and decreases, respectively. In analogy with the Cu(II)-lactate case, a local pH increase is obtained during the deposition of copper from the [Cu(2)H(-2)Cit(2)](4-) complex ([Cu(2)H(-2)Cit(2)](4-) + 4e(-) + 2H(2)O = 2Cu + 2[Cit](3-) + 2OH(-)) predominating in the solution. This increase stems from the protonation of the liberated citrate. As a result of this, electrodeposition Of Cu2O ([Cu(2)H(-2)Cit(2)](4-) + 2e(-) + H2O = Cu2O + 2[Cit](3-)) becomes possible at the rate required by the constant current. However, electrochemical quartz crystal microbalance (EQCM) data clearly show that the onset of this reaction is accompanied by an electroless deposition of Cu2O. This reaction, which under oscillating conditions mainly involves a comproportionation reaction ([Cu(2)H(-2)Cit(2),](4-) + 2Cu + 2OH(-) = 2Cu(2)O + 2[Cit](3-)), can give rise to Cu2O deposition at current efficiencies much larger than 100%. As a result of the combined electroless deposition and electrodeposition Of Cu2O, the local pH decreases rapidly, mainly due to the comproportionation reaction. When the local pH drops, the electrodeposition Of Cu2O becomes unable to sustain the current and the potential shifts negatively. This causes the onset of the reduction of the previously deposited Cu2O (i.e. Cu2O + 2e(-) + H2O = 2Cu + 2OH(-)). The EQCM and XRD results, however, clearly show that this reduction is incomplete during the oscillating conditions. This finding, which explains the presence of both copper and Cu2O in the deposits, is ascribed to the formation of a growing layer of copper on top of the remaining Cu2O. It is shown that the extent of the Cu2O reduction (and thus the amount Of Cu2O in the obtained deposits) depends on the Cu(II) concentration in the solution. Finally, the oscillation cycle is completed by a gradual replacement of the reduction Of Cu2O by the reduction of the [Cu(2)H(-2)Cit(2)](4-) complex, which causes the local pH to increase again. The proposed model is discussed in detail with particular emphasis on the reactions taking place in the region of the oscillation potential peak.The requirements for the attainment of oscillations under quiescent and forced convection conditions are discussed as well as the applicability of the model with respect to other Cu(II)complx systems.

  • 4.
    Karlsson, Christoffer
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Nanoteknologi och funktionella material.
    Huang, Hao
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Nanoteknologi och funktionella material.
    Strømme, Maria
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Nanoteknologi och funktionella material.
    Gogoll, Adolf
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Syntetisk organisk kemi.
    Sjödin, Martin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Nanoteknologi och funktionella material.
    Quinone Pendant Group Kinetics in Poly(pyrrol-3-ylhydroquinone)2014Ingår i: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 735, s. 95-98Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 5.
    Nygård, B
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Johansson, E
    Olofsson, J
    An electronic device for automatic precision measurement of polargraphic drop-times on single drops and for recording complete electrocapillary curves1966Ingår i: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 12, s. 564-Artikel i tidskrift (Refereegranskat)
  • 6.
    Waita, S. M.
    et al.
    Department of Physics, University of Nairobi.
    Aduda, B. O.
    Department of Physics, University of Nairobi.
    Mwabora, J. M.
    Department of Physics, University of Nairobi.
    Granqvist, Claes-Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Lindquist, Sten-Eric
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Niklasson, Gunnar A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Hagfeldt, Anders
    KTH, Fysikalisk kemi, Physical Chemistry.
    Boschloo, Gerrit K.
    KTH, Fysikalisk kemi, Physical Chemistry.
    Electron Transport and Recombination in Dye Sensitized Solar Cells Fabricated from Obliquely Sputter Deposited and Thermally Annealed TiO2 Films2007Ingår i: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 605, nr 2, s. 151-156Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dye sensitized solar cells based on annealed titanium dioxide films prepared by oblique reactive DC magnetron sputtering have been investigated in detail. Electron transport and recombination were studied using intensity-modulated photocurrent and photovoltage spectroscopy. Electron transport time as well as lifetime were found to increase upon lowering of the light intensity and to increase upon increasing the thickness of the TiO2 film. The properties are very similar to those observed for solar cells based on colloidal TiO2 films despite the morphologies being very different. In all cases, films are composed of a porous assembly of TiO2 nanocrystals. Grain boundaries with associated trap and/or energy barriers may explain the observed transport properties.

  • 7.
    Waita, Sebastian M.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Aduda, B O
    Mwabora, J M
    Niklasson, Gunnar A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Granqvist, Claes-Göran
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets fysik.
    Boschloo, Gerrit
    Electrochemical Characterization of TiO2 Blocking Layers Prepared by Reactive DC Magnetron Sputtering2009Ingår i: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 637, nr 1-2, s. 79-83Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thin TiO2 (anatase) films were prepared by reactive DC magnetron sputtering and characterized in detail. Specifically, they were tested as compact blocking underlayers in dye-sensitized solar cells. Elastic recoil detection analysis and optical measurement showed some porosity in the sputtered films, but electrochemical measurements demonstrated good blocking characteristics. This suggests the presence of small voids rather than pinholes in the deposited films. In the case of an iodide/iodine redox couple, thin underlayers (similar to 20 nm) improved the fill factor without affecting other properties of the cell. in case of a ferrocene/ferrocenium-based electrolyte, the presence of underlayers was necessary to obtain functional dye-sensitized solar cells.

  • 8.
    Zettersten, Camilla
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Kemiska institutionen, Avdelningen för analytisk kemi.
    Lomoth, Reiner
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    Hammarström, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Fysikalisk-kemiska institutionen.
    Sjöberg, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Kemiska institutionen, Avdelningen för analytisk kemi.
    Nyholm, Leif
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
    The influence of the thin-layer flow cell design on the mass spectra when coupling electrochemistry to electrospray ionisation mass spectrometry2006Ingår i: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 590, nr 1, s. 90-99Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of the flow cell configuration on the mass spectra obtained when coupling an electrochemical thin-layer flow cell to electrospray mass spectrometry (ESI-MS) has been investigated. It is shown that interferences due to the electrochemical reaction on the counter electrode and/or the absence of 100% conversion efficiency can alter the mass spectra when conventional thin-layer flow cells are used in conjunction with ESI-MS. The effects, which affect the intensities and distribution of the peaks in the mass spectra, can result in the inability to detect products formed at the working electrode. Comparisons of mass spectra, generated after the electrochemical oxidation of a dinuclear Mn complex (where bpmp = 2,6-bis[bis(2-pyridylmethyl) amino]methyl-4-methylphenol) using two different thin-layer flow cells clearly show that the potential dependence and appearance of the mass spectra depend on the flow cell configuration used. The use of a modified thin-layer flow cell, in which the counter electrode had been separated from the working electrode, gave rise to significantly increased intensities for the oxidised MnIII,IV state of the complex. With the conventional unmodified cell, the corresponding complex was only seen for considerably higher oxidation potentials. The different results can be explained by the reduced risk of redox cycling and interferences due to species generated at the counter electrode with the modified cell. As interferences due to the counter electrode reactions likewise may be expected with many coulometric flow cells, the electrochemical cell design clearly needs to be considered when using electrochemistry coupled to ESI-MS to study electrochemical reactions.

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