Change search
Refine search result
12 1 - 50 of 51
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Behm, R. J.
    et al.
    University of Ulm.
    Seidel, Y. E.
    University of Ulm.
    Lindström, Rakel Wreland
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Jusys, Z.
    University of Ulm.
    Wiedwald, U.
    University of Ulm.
    Ziemann, P.
    University of Ulm.
    Wickman, B.
    Chalmers.
    Kasemo, B.
    Chalmers.
    Zhang, D.
    Karlsrohe University.
    Deutschmann, O.
    Karlsrohe University.
    Boneberg, J.
    University of Konstanz.
    Leiderer, P.
    University of Konstanz.
    Electrocatalytic Function of Nanostructured Surfaces – Reaction and Mass Transport2010In: Nanotechnology: Fundamentals and Applications of Functional Nanostructures / [ed] T. Schimmel, H. v. Löhneysen, M Barczewski, Eds, Stuttgart: Baden-Württemberg Stiftnung , 2010, p. 281-303Chapter in book (Refereed)
  • 2. Blucher, D. B.
    et al.
    Lindström, Rakel
    Svensson, J. E.
    Johansson, L. G.
    The effect of CO2 on the NaCl-induced atmospheric corrosion of aluminum2001In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 148, no 4, p. B127-B131Article in journal (Refereed)
    Abstract [en]

    A laboratory study of the effect of CO2 and NaCl on the atmospheric corrosion of aluminum is reported. The samples were exposed to pure air with 95% relative humidity and the concentration of CO2 was <1 and 350 ppm, respectively. Sodium chloride was added before exposure (0, 14, and 70 g/cm(2)). The main result is that the NaCl-induced atmospheric corrosion of aluminum is about 10 to 20 times faster in CO2-free humid air compared to air containing ambient levels of CO2. It is suggested that the rapid corrosion of aluminum coated with NaCl in humid CO2-free air is connected to high-pH areas in the surface electrolyte that develop due to the cathodic reduction of oxygen. The anodic dissolution of aluminum is known to be enhanced by high pH. The unexpected corrosion-inhibitive effect of CO2 is explained by the neutralization of the surface electrolyte. In the absence of CO2, bayerite, Al(OH)(3), forms. Only minute amounts of carbonate were found on the surface after exposure to CO2-containing air.

  • 3.
    Carlson, Annika
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Eriksson, Björn
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Olsson, Joel
    Lund University.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Jannasch, Patric
    Lund University.
    Lindström, Rakel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Fuel cell evaluation of anion exchange membranes based on PPO with different cation placementManuscript (preprint) (Other academic)
    Abstract [en]

    Four different poly(phenylene oxide)-based anion exchange membranes were investigated for electrochemical performance, conductivity and water transport properties in an operating fuel cell. The polymers have a 1- or 5-carbon alkyl spacer between the backbone and a trimethylalkylammonium or piperidinium cationic group, and two different levels of ion-exchange capacity. These structural variations result in different water uptake, hydration number (λ, number of H2O molecules per cation) and conductivity. It is shown that the use of a 5-carbon alkyl spacer does not improve performance unless coupled with a large increase in ion-exchange capacity for the membranes with trimethylalkylammonium cations. Introduction of a piperidinium cation results in lower performance regardless of high ion-exchange capacity. The polymer with a 1-carbon alkyl spacer shows higher and more stable performance than expected from previous ex-situ evaluation, which is attributed to a lower λ value and lower dependence on humidification. The overall water flux under load is in the direction from anode to cathode and high flux improves the performance primarily at unsaturated cell conditions and higher current densities. In summary the results showed that the membrane properties: high conductivity, a higher water transport from anode to cathode and a lower dependency on hydration promote the higher electrochemical performance. Further, no loss of functional groups or crosslinking is detected even after stressing the membranes extensively. Therefore, with further electrode development and fine-tuning of the operating conditions these membranes are promising for electrochemical applications.

  • 4.
    Carlson, Annika
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Shapturenka, Pavel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Porous electrode optimization in anion-exchange membrane fuel cells2015In: Proceedings of the 6th European Fuel Cell - Piero Lunghi Conference, EFC 2015, ENEA , 2015, p. 221-222Conference paper (Refereed)
    Abstract [en]

    The performance of anion-exchange membrane fuel cells is highly dependent on electrode preparation. This study has investigated the influence of water content and catalyst to ionomer ratio in the electrode ink on in-situ fuel cell performance and the electrode microstructure using SEM. It has shown that changing the solvent composition affects the electrode properties. Higher water content in ink results in a lower power density. An increase in water content from 40 to 70 vol% shows a 500 mA/cm2 drop in current density. SEM analysis of newly prepared electrodes revealed an observable difference in the microstructure. This indicates that for high water volume the ionomer distribution in the electrode is very uneven. The results also indicate that lower ionomer content in the bulk of the structure lowers the cell performance, which may be explained by limited hydroxide transportation.

  • 5.
    Eriksson, Björn
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Jaouen, F.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Degradation and lifetime evaluation of Fe-N-C based catalyst in PEMFC2015In: Proceedings of the 6th European Fuel Cell - Piero Lunghi Conference, EFC 2015, ENEA , 2015, p. 223-224Conference paper (Refereed)
    Abstract [en]

    The restricted lifetime of Fe-N-C based catalysts is often assumed to be connected to the operating temperature. This study will investigate how the cell performance, electrode structure and composition vary over time, at different cell temperatures. At lower temperature, one may expect an increase in radical's stability, but a decrease in reactivity. Results show that the electrode degenerates over time, and that the electrochemical performance decay is similar for 40, 60, and 80° C. However, the loss of active sites is higher at higher temperature. This suggests that indirect production of radicals via H2O2 production during ORR is higher at higher temperatures and is a key degradation mechanism for this Fe-N-C catalyst.

  • 6.
    Eriksson, Björn
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Montserrat-Sisó, Gerard
    Chalmers University of Technology.
    Brown, Rosemary
    Chalmers University of Technology.
    Lindström, Rakel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Wickman, Björn
    Chalmers University of Technology.
    Lagergren, Carina
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Evaluation of rare earth metal alloy catalysts for the oxygen reduction reaction in proton exchange membrane fuel cellsManuscript (preprint) (Other academic)
    Abstract [en]

    To achieve large scale commercialization of fuel cells more active catalysts need to be developed. In this work highly active alloy catalysts of Pt3Y, Pt5Gd and Pt5Tb are evaluated in a proton exchange membrane fuel cell. The alloys are produced by sputter deposition onto gas diffusion layers. The alloy catalysts show activity increases between 2 and 2.5 times that of pure platinum. EDX and XPS analyses show that after acid cleaning a platinum overlayer is formed. After the electrochemical measurements, each alloy had different amounts of alloying element left, as well as different ratios between metallic and non-metallic rare earth metal, highlighting that the alloys are affected differently by the fuel cell measurements. However, the results show that the tested alloys are highly active and can significantly reduce the amount of platinum required. If the activation procedure is optimized, even higher activities might be achievable.

  • 7. Esmaily, M.
    et al.
    Blücher, D. B.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Svensson, J. -E
    Johansson, L. G.
    The influence of SO2 on the corrosion of Mg and Mg-Al alloys2015In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 162, no 6, p. C260-C269Article in journal (Refereed)
    Abstract [en]

    The SO2-induced atmospheric corrosion of some magnesium-aluminum (Mg-Al) alloys, including Mg alloy AZ91D, and commercially pure Mg (CP Mg) was investigated using well-controlled laboratory exposures and included real-time measurements of SO2 deposition. The influence of SO2 concentration, alloy composition, humidity, and ppb level additions of O-3 or NO2 on the rate of SO2 deposition was investigated. SO2 accelerates the corrosion of Mg and Mg alloys causing localized corrosion, MgSO(3)6H(2)O being the dominant corrosion product. At 60% RH, traces of O-3 or NO2 strongly increased both the SO2 deposition and the corrosion rate. The rate of SO2 deposition was strongly dependent on humidity; at 70% RH and higher the SO2 deposition rate was very rapid and constant in time while it was transient below 50% RH. At 60% RH, a change from transient to rapid, steady-state, SO2 deposition occurred. The sudden activation is explained by the onset of electrochemical corrosion. The activation behavior was shown to depend on SO2 concentration, the thickness of the surface film and by the presence of ambient O-2. (C) The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.

  • 8.
    Fatima, Masoom
    et al.
    KTH, School of Chemical Science and Engineering (CHE).
    Farooq, R.
    Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Saeed, M.
    A review on biocatalytic decomposition of azo dyes and electrons recovery2017In: Journal of Molecular Liquids, ISSN 0167-7322, E-ISSN 1873-3166, Vol. 246, p. 275-281Article in journal (Refereed)
    Abstract [en]

    Discharge of waste water from textile industry during coloring processes contains high concentrations of biologically difficult-to-degrade dye chemicals along with antifouling agents. Azo dyes considered to be the largest class of synthetic dyes used in the textile industries and are present in significant amounts in its effluents. These are highly stable because of its complex aromatic structure and covalent azo bonds. Traditional physico-chemical methods are not considered sufficient because of their high cost, partial degradation and more sludge production. The use of biocatalysts for decolorization is a gaining momentum due to having redox-active molecules. Current review explored techniques for the decomposition of textile dyes, their merits, limitations and recommended the emerging microbial fuel cell technology followed by aerobic treatment for complete degradation of dye intermediate metabolites.

  • 9.
    Kanninen, Petri
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Eriksson, Björn
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Davodi, Fatemeh
    Aalto University.
    Buan, Marthe
    Aalto University.
    Kallio, Tanja
    Aalto University.
    Lindström, Rakel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
    Carbon corrosion properties and performance of multi-walled carbon nanotube support with and without nitrogen-functionalization in fuel cell electrodesManuscript (preprint) (Other academic)
    Abstract [en]

    Pt-supported on multi-walled carbon nanotubes (MWCNT) and N-modified MWCNT (N-MWCNT) catalysts are synthesized by pyrolysis from emeraldine solution and microemulsion. Their electrochemical properties and carbon corrosion resistance in a Proton Exchange Membrane Fuel Cell (PEMFC) are compared with a commercial Pt/Vulcan catalyst through I-V curves, cyclic voltammetry and CO stripping. The initial fuel cell performances of the Pt/(N-)MWCNT catalysts are superior to Pt/Vulcan. The corrosion of the catalysts is quantified by the continuous measure of the CO2 release by online-mass spectrometry during potentiodynamic cycling between 0.1 and 1.6 V at 80°C. The results show that Pt/MWCNT (with the lowest double-layer capacity) is the most stable catalyst followed by Pt/N-MWCNT and Pt/Vulcan, initially losing carbon at a rate of 1.1, 3.4 and 4.7 µgC (mg Ctot)−1 cycle−1 , respectively. After about 30 % carbon loss (50-70 cycles) all catalysts corrode at an approximate rate of 5.5 µgC mg−1 cycle−1. At this stage, all show similar electrochemical surface area and double-layer capacity. However, the substantial diminution of the initially very thick and porous Pt/(N-)MWCNT catalyst layers after corrosion consequences in lower fuel cell performance compared to the structurally less affected Pt/Vulcan electrode. The results clearly reveal that CNT-based catalyst supports are more corrosion resistant compared to state-of-the-art Vulcan. Moreover, the performance of the corroded electrodes envisages the importance of electrode porosity. 

  • 10.
    Klett, Matilda
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Eriksson, Rickard
    Uppsala University.
    Groot, Jens
    Chalmers Technical University.
    Svens, Pontus
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Ciosek Högström, Katarzyna
    Uppsala University.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Berg, Helena
    Gustafson, Torbjörn
    Uppsala University.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Edström, Kristina
    Uppsala University.
    Non-uniform aging of cycled commercial LiFePO4//graphite cylindrical cells revealed by post-mortem analysis2014In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 257, p. 126-137Article in journal (Refereed)
    Abstract [en]

    Aging of power-optimized commercial 2.3 Ah cylindrical LiFePO4//graphite cells to be used in hybrid electric vehicle is investigated and compared for three different aging procedures; (i) using a simulated hybrid electric vehicle cycle within a narrow SOC-range, (ii) using a constant-current cycle over a 100% SOC-range, and (iii) stored during three years at 22 degrees C. Postmortem analysis of the cells is performed after full-cell electrochemical characterization and discharge. EIS and capacity measurements are made on different parts of the disassembled cells. Material characterization includes SEM, EDX, HAXPES/XPS and XRD. The most remarkable result is that both cycled cells displayed highly uneven aging primarily of the graphite electrodes, showing large differences between the central parts of the jellyroll compared to the outer parts. The aging variations are identified as differences in capacity and impedance of the graphite electrode, associated with different SEI characteristics. Loss of cyclable lithium is mirrored by a varying degree of lithiation in the positive electrode and electrode slippage. The spatial variation in negative electrode degradation and utilization observed is most likely connected to gradients in temperature and pressure, that can give rise to current density and potential distributions within the jellyroll during cycling.

  • 11.
    Klett, Matilda
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Giesecke, Marianne
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Nyman, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Hallberg, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Furó, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Quantifying mass transport during polarization in a Li Ion battery electrolyte by in situ 7Li NMR imaging2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 36, p. 14654-14657Article in journal (Refereed)
    Abstract [en]

    Poor mass transport in the electrolyte of Li ion batteries causes large performance losses in high-power applications such as vehicles, and the determination of transport properties under or near operating conditions is therefore important. We demonstrate that in situ 7Li NMR imaging in a battery electrolyte can directly capture the concentration gradients that arise when current is applied. From these, the salt diffusivity and Li + transport number are obtained within an electrochemical transport model. Because of the temporal, spatial, and chemical resolution it can provide, NMR imaging will be a versatile tool for evaluating electrochemical systems and methods.

  • 12.
    Klett, Matilda
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Svens, Pontus
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry. Scania CV AB, Sweden.
    Tengstedt, Carl
    Seyeux, Antoine
    Swiatowska, Jolanta
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Uneven Film Formation across Depth of Porous Graphite Electrodes in Cycled Commercial Li-Ion Batteries2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 1, p. 90-100Article in journal (Refereed)
    Abstract [en]

    A critical aging mechanism in lithium-ion batteries is the decomposition of the electrolyte at the negative electrode forming a solid electrolyte interphase (SEI) layer that increases impedance and consumes cyclable lithium. In contrast to the typical nanometer SEI layer generally discussed, this paper reports on the formation of a micrometer thick film on top of and within the upper part of a porous graphite electrode in a deep-cycled commercial cylindrical LiFePO4/graphite cell. Morphological, chemical, and electrochemical characterizations were performed by means of cross-sectional electron microscopy in combination with energy dispersive X-ray spectroscopy and focused ion-beam milling, time-of-flight secondary ion mass spectrometry, and electrochemical impedance spectroscopy (EIS) to evaluate the properties and impact of the uneven film. It is shown that the film is enriched in PO and carbonate species but is otherwise similar in composition to the thin SEI formed on a calendar-aged electrode and clogs the pores in the electrode closest to the separator. Performance evaluation by physics-based EIS modeling supports a local porosity decrease, impeding the effective electrolyte transport in the electrode. The local variation of electrode properties implies that current distribution in the porous electrode under these cycling conditions causes inefficient material utilization and sustained uneven electrode degradation.

  • 13.
    Klett, Matilda
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Svens, Pontus
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Tengstedt, Carl
    Scania CV AB.
    Swiatowska, Jolanta
    Institute de Recherche de Chimie Paris, CNRS- Chimie ParisTech.
    Seyeux, Antoine
    Institute de Recherche de Chimie Paris, CNRS- Chimie ParisTech.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Uneven film formation across depth of porous graphite electrodes from cycling in commercial Li-ion batteriesManuscript (preprint) (Other academic)
  • 14.
    Klett, Matilda
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Zavalis, Tommy
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Hellqvist Kjell, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Behm, Mårten
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Altered electrode degradation with temperature in LiFePO4/mesocarbon microbead graphite cells diagnosed with impedance spectroscopy2014In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 141, p. 173-181Article in journal (Other academic)
    Abstract [en]

    Electrode degradation in LiFePO4 / mesocarbon microbead graphite (MCMB) pouch cells aged at 55 °C by a synthetic hybrid drive cycle or storage is diagnosed and put into context with previous results of aging at 22 °C. The electrode degradation is evaluated by means of electrochemical impedance spectroscopy (EIS), measured separately on electrodes harvested from the cells, and by using a physics-based impedance model for aging evaluation. Additional capacity measurements, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) are used in the evaluation. At 55 °C the LiFePO4 electrode shows increased particle/electronic conductor resistance, for both stored and cycled electrodes. This differs from results obtained at 22 °C, where the electrode suffered lowered porosity, particle fracture, and loss of active material. For graphite, only cycling gave a sustained effect on electrode performance at 55 °C due to lowered porosity and changes of surface properties, and to greater extent than at low temperature. Furthermore, increased current collector resistance also contributes to a large part of the pouch cell impedance when aged at increased temperatures. The result shows that increased temperature promotes different degradation on the electrode level, and is an important implication for high temperature accelerated aging. In light of the electrode observations, the correlation between full-cell and electrode impedances is discussed.

  • 15.
    Kortsdottir, Katrin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Dominguez Fernandez, Carlota
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Influence of Hydrogen and Operation Conditions on CO2 Adsorption on Pt and PtRu Catalyst in a PEMFC2013In: ECS Electrochemistry Letters, ISSN 2162-8726, Vol. 2, no 5, p. F41-F43Article in journal (Refereed)
    Abstract [en]

    CO2 is a major component in reformate gas and can, as a source of CO, be a catalyst poison in polymer electrolyte membrane fuel cells. The effect of CO2 on cell performance is not fully understood in the presence of hydrogen. This paper addresses the influence of hydrogen on CO2 adsorption on Pt/C and PtRu/C catalysts. The results show that the reduction and adsorption of CO2 is slow but increases if hydrogen is present, especially on PtRu/C. Further, exposure to a CO2 and H-2 mixture at 0.15 V on PtRu/C results in current oscillations, which are dependent on operation conditions.

  • 16.
    Kortsdottir, Katrin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Åkermark, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Influence of toluene contamination at the hydrogen Pt/C anode in a proton exchange membrane fuel cell2010In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 55, no 26, p. 7643-7651Article in journal (Refereed)
    Abstract [en]

    For fuel cells run on hydrogen reformate, traces of hydrocarbon contaminants in the hydrogen gas may be a concern for the performance and lifetime of the fuel cell. This study focuses on the influence of low concentrations of toluene on the adsorption and deactivation chemistry in a proton exchange membrane (PEM) fuel cell. For this purpose cyclic voltammetry and electrochemical impedance spectroscopy (EIS) techniques were employed. Results from adsorption and desorption (by oxidation or reduction) experiments performed in a humidified nitrogen or hydrogen flow in a fuel cell test cell with a mass spectrometer system connected to the outlet are presented. The influence of adsorption potential, temperature, and humidity are discussed. The results show that toluene adsorbs on the catalyst surface in a broad potential window, up to at least 0.85 V versus RHE at 80 degrees C. Adsorbed toluene oxidizes to CO2 with peak potentials above 1.0V for temperatures below 95 degrees C. Some desorption of toluene (or reduced products) may take place at potentials below 0V. In a hydrogen flow, toluene contamination in per mille concentrations leads to a continuous growth of the charge transfer resistance, while a 10-fold dilution of the toluene concentration resulted in a low and constant charge transfer resistance even for longer exposures. This indicates that a competition between toluene and hydrogen may take place on the active platinum surface at the anode.

  • 17.
    Kortsdottir, Katrin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Pérez Ferriz, Francisco Javier
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Reformate Hydrogen Fuel in PEM Fuel Cells: the Effect of Alkene Impurities on Anode Activity2013In: ECS Transactions, Electrochemical Society, 2013, p. 1857-1865Conference paper (Refereed)
    Abstract [en]

    Reformate hydrogen contains many impurities, some are well known while others have been less studied. Hydrocarbons are possible impurities in reformate hydrogen and are among those less studied. This study if aimed at alkenes, with special focus on propene. Adsorption and desorption on the Pt catalyst is studied using stripping cyclic voltammetry combined with mass spectrometry. The results show that although the effect of propene in the presence of hydrogen is expected to be minimal, adsorption and blockage of catalytic sites cannot be ruled out. A small amount of ad-species is formed on Pt at low adsorption potentials, and in the presence of hydrogen, although suppression of the hydrogen desorption peak was minimal if hydrogen was adsorbed on the Pt catalyst prior to exposure.

  • 18.
    Kortsdottir, Katrin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Dominiguez Fernandez, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Hydrogen fuel impurities: The effect of CO2 and hydrocarbons at the anode of a PEM fuel cell2011In: Proceedings of EFC2011, 2011, p. EFC11159-Conference paper (Refereed)
    Abstract [en]

    Hydrogen fuel produced by reforming contains, in addition to hydrogen, CO2, CO, sulphur compounds and small hydrocarbons in varying amount. The effect of CO2 and a few example hydrocarbons has been studied on traditional PEM fuel cell anodes by cyclic voltammetry and constant load experiments. In addition, Electrochemical Impedance Spectroscopy and Mass Spectrometry have been employed to aid in the analysis. The effect of adsorption potential, cell temperature, humidity of the feed gases and concentrations of selected impurities has been studied.

  • 19.
    Kortsdottir, Katrin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    The influence of ethene impurities in the gas feed of a PEM fuel cell2013In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 38, no 1, p. 497-509Article in journal (Refereed)
    Abstract [en]

    Hydrogen produced by reforming may contain traces of hydrocarbon contaminants. These traces may affect the performance and lifetime of a fuel cell run on reformate-hydrogen. This study treats the influence of low concentrations of ethene on the adsorption and deactivation chemistry in a polymer electrolyte membrane (PEM) fuel cell. The study employs mainly cyclic voltammetry accompanied with an on-line mass spectrometer to analyse the outlet gas. Results from adsorption and desorption, by either oxidation or reduction, are presented, and the influence of adsorption potential, temperature and humidity and the presence of hydrogen are discussed. The results show that the adsorption of traces of ethene in a fuel cell is highly dependent on adsorption potential and that ethene adsorbs on Pt catalyst in a limited potential window only. Ethene cannot displace adsorbed H and is oxidised already at potentials of 0.6 V versus RHE at 80°C, where the only detectable product is CO 2. A considerable part of ethene adsorbed at potentials above the hydrogen adsorption/desorption region can be reduced at low potentials and is desorbed as methane or ethene. Overall, the effect of low concentrations of ethene in the hydrogen feed on fuel cell performance is minimal, and no significant loss in cell voltage is found when ethene contaminated hydrogen is fed to a fuel cell running on hydrogen and oxygen at a constant load at 80°C and at highly humidified conditions.

  • 20. Le Van, K.
    et al.
    Groult, H.
    Mantoux, A.
    Perrigaud, L.
    Lantelme, F.
    Lindström, Rakel
    Badour-Hadjean, R.
    Zanna, S.
    Lincot, D.
    Amorphous vanadium oxide films synthesised by ALCVD for lithium rechargeable batteries2006In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 160, no 1, p. 592-601Article in journal (Refereed)
    Abstract [en]

    This study addresses the lithium insertion performances of amorphous vanadium oxide films, synthesized by atomic layer chemical vapour deposition (ALCVD). AFM and SEM investigations showed that the as-deposited films are amorphous, compact and homogeneous. As revealed by XPS and Raman spectroscopy, the ALCVD oxide films after deposition are mainly composed of V2O5, with V4+ surface content (about 10%). The insertion of Li+ into the lattice was investigated in 1 M LiClO4-PC. The results show that the electrochemical performances obtained with amorphous vanadium oxide films, with an optimal thickness of 200 nm (455 mAh g(-1), i.e. composition of Li2.9V2O5), were superior to crystalline V2O5 films. The amorphous films exhibit higher capacity and better cycle ability even for deep lithium insertion ratio compared to crystalline V2O5 films. The chemical diffusion coefficients, deduced from numerical simulation of chronopotentiograms, were comprised between 3 x 10(-12) and 10(-12) cm(2) s(-1) for a lithium insertion ratio comprised between 0 and 2.9. AFM and Raman spectroscopy performed before and after lithiation showed that neither the morphology nor the local order of the amorphous films were significantly affected by the insertion/extraction of lithium. Raman measurements also revealed that a very small amount of lithium are locally trapped in the oxide lattice.

  • 21.
    Lindbergh, Göran
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Teknikbevakning av polymera bränsleceller (PEMFC) 20082008Report (Other (popular science, discussion, etc.))
  • 22.
    Lindström, Rakel
    Göteborg University, Department of Chemistry.
    On the chemistry of atmospheric corrosion: a laboratory study on Zn, Mag and Mg-Al alloys2003Doctoral thesis, comprehensive summary (Other academic)
  • 23. Lindström, Rakel
    et al.
    Johansson, L. G.
    Svensson, J. E.
    The influence of NaCl and CO2 on the atmospheric corrosion of magnesium alloy AZ912003In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 54, no 8, p. 587-594Article in journal (Refereed)
    Abstract [en]

    The influence of NaCl and CO2 on the atmospheric corrosion of magnesium alloy AZ91 is studied in the laboratory. Samples were exposed under carefully controlled air and flow conditions; the relative humidity was 95%, the temperature was 22.0degreesC and the concentration of CO2 was <1 ppm or 350 ppm. Different amounts of sodium chloride (0-70 μg/cm(2)) were added before exposure. The corrosion products were analyzed by gravimetry, ion chromatography, X-ray diffraction and scanning electron microscopy. Mass gain and metal loss results are reported. The combination of high humidity and NaCl is very corrosive towards AZ91. However, the NaCl-induced corrosion is inhibited by ambient concentrations of CO2. Exposure in the absence of CO2 gives rise to heavy pitting, with brucite, Mg(OH)(2), being the dominant corrosion product. In the presence of CO2 a layer of hydrated magnesium hydroxy carbonate, Mg-5(CO3)(4)(OH)(2) &BULL; 5H(2)O forms. A tentative corrosion mechanism is presented that explains the behavior in the two environments.

  • 24. Lindström, Rakel
    et al.
    Johansson, L. G.
    Svensson, J. E.
    The influence of NaNO3 on the atmospheric corrosion of zinc2003In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 150, no 12, p. B583-B588Article in journal (Refereed)
    Abstract [en]

    The influence of NaNO3 salt deposits on the atmospheric corrosion of zinc in humid air has been studied. Comparisons are made with the effects of NaCl and Na2SO4. Also the combined effect of NaNO3 with NaCl or Na2SO4 was investigated. The salts were applied to zinc samples prior to exposure. The samples were exposed to purified humid air with careful control of relative humidity (95%), temperature (22.0degreesC), and flow conditions. The CO2 concentration was 350 ppm and the exposure time was 4 weeks. Mass gain and metal loss results are reported. The corrosion products were analyzed by gravimetry, ion chromatography, and X-ray diffraction. Results show that the corrosion rate in the presence of NaNO3 is only a third of that registered in the presence of NaCl and Na2SO4. Further, a slight inhibitive effect of NaNO3 was found in the presence of NaCl or Na2SO4. The decreased corrosion rate in the presence of NaNO3 was attributed to the reduction of nitrate to nitrite at the zinc surface. Nitrite is suggested to act as a corrosion inhibitor toward zinc.

  • 25. Lindström, Rakel
    et al.
    Johansson, L. G.
    Thompson, G. E.
    Skeldon, P.
    Svensson, J. E.
    Corrosion of magnesium in humid air2004In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 46, no 5, p. 1141-1158Article in journal (Refereed)
    Abstract [en]

    The influence of ambient concentrations of carbon dioxide on the atmospheric corrosion of magnesium has been studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM), revealing the development and growth of corrosion products. The surfaces investigated by AFM were prepared by ultramicrotomy, using a diamond knife, to generate a smooth finish without using water or lubricant. Sputter-deposited Mg films were also studied with mechanically polished samples used to monitor the overall corrosion process. The exposures were performed at 22.0 degreesC in a synthetic environment with precise control of relative humidity (95%) and CO2 (0 or 350 ppm). Corrosion is localized in the absence of CO2 and is related to noble inclusions in the metal matrix. After corrosion product removal, relatively deep pits are evident. In contrast, pitting is inhibited in the presence of CO, with relatively uniform corrosion product development; further, the noble inclusions have no effect on the distribution of corrosion. The inhibitive effect of CO2 is also observed in the long-term exposures, showing that CO2 reduces the average corrosion rate. Mechanisms are introduced to explain the effects of CO2 and the roles of the noble inclusions on the corrosion behaviour.

  • 26.
    Lindström, Rakel
    et al.
    Göteborg University, Department of Inorganic Chemistry.
    Johansson, Lars-Gunnar
    Göteborg University, Department of Inorganic Chemistry .
    Svensson, Jan-Erik
    Chalmers, Inorganic Environmental Chemistry.
    The atmospheric corrosion of magnesium and magnesium alloys, a laboratory study2002In: Proceeding paper, 2002Conference paper (Refereed)
  • 27.
    Lindström, Rakel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Kortsdottir, Katrin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Active area determination for porous Pt-electrodes used in PEM fuel cells: Temperature and humidity effects2009In: Proton Exchange Membrane Fuel Cells 9 / [ed] T. Fuller, C. Hartnig, V. Ramani, H. Uchida, H. Gasteiger, S. Cleghorn, P. Strasser, T. Zawodzinski, D. Jones, P. Shirvanian, T. Jarvi, P. Zelenay, C. Lamy, P. Bele, 2009, p. 1211-1220Conference paper (Refereed)
    Abstract [en]

    This paper aim to discuss a proper measure of the electrochemical active area of carbon supported Pt nanoparticle catalyst used in polymer electrolyte membrane (PEM) fuel cells. The cyclic voltammetric determination of hydrogen under potential deposition (Hupd) and carbon monoxide monolayer oxidation (CO stripping) performed in a fuel cell at fuel cell relevant conditions are compared and the influences of operation temperature (25-80 {degree sign}C) and relative humidity (RH) (40-90% RH) are discussed. The results show that both the shape and the charge of the Hupd are strongly dependent on operating conditions. However, for the CO stripping experiments only a negative shift in potential with increasing temperature or humidity was observed in accordance with results from aqueous electrolytes, whereas the charges for CO monolayer oxidation were almost constant for the temperatures investigated.

  • 28. Lindström, Rakel
    et al.
    Maurice, V.
    Groult, H.
    Perrigaud, L.
    Zanna, S.
    Cohen, C.
    Marcus, P.
    Li-intercalation behaviour of vanadium oxide thin film prepared by thermal oxidation of vanadium metal2006In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 51, no 23, p. 5001-5011Article in journal (Refereed)
    Abstract [en]

    In order to produce thin films of crystalline V2O5, vanadium metal was thermally oxidised at 500 degrees C under oxygen pressures between 250 and 1000 mbar for 1-5 min. The oxide films were characterised by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), X-ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS). The lithium intercalation performance of the oxide films was investigated by cyclic voltammetry (CV), chronopotentiometry and electrochemical impedance spectroscopy (EIS). It was shown that the composition, the crystallinity and the related lithium intercalation properties of the thin oxide films were critically dependent on the oxidation conditions. The formation of crystalline V2O5 films was stimulated by higher oxygen pressure and longer oxidation time. Exposure for 5 min at 750 mbar 02 at 500 degrees C resulted in a surface oxide film composed of V2O5, and consisting of crystallites up to 200 nm in lateral size. The thickness of the layer was about 100 nm. This V2O5 oxide film was found to have good cycling performance in a potential window between 3.8 and 2.8 V, with a stable capacity of 117 +/- 10 mAh/g at an applied current density of 3.4 mu A/cm(2). The diffusion coefficients corresponding to the two plateaus at 3.4 and 3.2V were determined from the impedance measurements to (5.2 and 3.0) x 10(-13) cm(2) s(-1), respectively. Beneath the V2O5 layer, lower oxides (mainly VO2) were found close to the metal. At lower oxygen pressure and shorter exposure times, the oxide films were less crystalline and the amount of V4+ increased in the surface oxide film, as revealed by XPS. At intermediate oxygen pressures and exposure times a mixture of crystalline V2O5 and V6O13 was found in the oxide film.

  • 29. Lindström, Rakel
    et al.
    Maurice, V.
    Zanna, S.
    Klein, L.
    Groult, H.
    Perrigaud, L.
    Cohen, C.
    Marcus, P.
    Thin films of vanadium oxide grown on vanadium metal: oxidation conditions to produce V2O5 films for Li-intercalation applications and characterisation by XPS, AFM, RBS/NRA2006In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 38, no 1, p. 6-18Article in journal (Refereed)
    Abstract [en]

    Thin films of vanadium oxide were grown on vanadium metal surfaces W in air at ambient conditions, (ii) in 5 mm H2SO4 (aq), pH 3, (iii) by thermal oxidation at low oxygen pressure (10(-5) mbar) at temperatures between 350 and 550 degrees C and (iv) at near-atmospheric oxygen pressure (750 mbar) at 500 degrees C. The oxide films were investigated by atomic force microscopy (AIM), X-ray photoelectron spectroscopy (XPS), X-Ray diffraction (XRD) and Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA). The lithium intercalation properties were studied by cyclic voltammetry (CV). The results show that the oxide films formed in air at room temperature (RT), in acidic aqueous solution, and at low oxygen pressure at elevated temperatures are composed Of V2O3. In air and in aqueous solution at RT, the oxide films are ultra-thin and hydroxylated. At 500 degrees C, nearly atmospheric oxygen pressure is required to form crystalline V2O5 films. The oxide films grown at pO(2) = 750 mbar for 5 min are about 260-nm thick, and consist of a 115-nm outer layer of crystalline V2O5. The inner oxide is mainly composed Of VO2. For all high temperature oxidations, the oxygen diffusion from the oxide film into the metal matrix was considerable. The oxygen saturation of the metal at 450 degrees C was found, by XPS, to be 27 at.% at the oxide/metal interface. The well-crystallized V2O5 film, formed by oxidation for 5 min at 500 degrees C and 750 mbar O-2, was shown to have good lithium intercalation properties and is a promising candidate as electrode material in lithium batteries.

  • 30. Lindström, Rakel
    et al.
    Maurice, Vincent
    Klein, Lorena
    Marcus, Philippe
    The use of electrochemical scanning tunnelling microscopy (EC-STM) in corrosion analysis: Reference material and procedural guidelines2007Book (Refereed)
  • 31. Lindström, Rakel
    et al.
    Svensson, J. E.
    Johansson, L. G.
    The atmospheric corrosion of zinc in the presence of NaCl the influence of carbon dioxide and temperature2000In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 147, no 5, p. 1751-1757Article in journal (Refereed)
    Abstract [en]

    The atmospheric corrosion of zinc has been studied at 4, 22, and 38 degrees C. The samples were exposed to synthetic air with careful control of CO2 concentration, relative humidity, and flow conditions. The relative humidity was 95%, and the concentrations of CO2 were <1 and 350 ppm, respectively. Sodium chloride was added before the exposures (0, 14. and 70 mu g/cm(2)). Mass gain and metal loss results are reported. As expected, NaCl is corrosive toward zinc, giving rise to heavy pitting. In the absence of CO2, the rare of the NaCl-induced corrosion was found to increase strongly with temperature. However, in the presence of CO2, the corrosion rate of zinc is independent of temperature. In the absence of CO2. zincite, ZnO, is the dominant corrosion prod;ct, while zinc hydroxy carbonates and simonkolleite, Zn-5(OH)(8)Cl-2. H2O, dominate in the presence of CO2. A mechanism is presented that explains the observations.

  • 32. Lindström, Rakel
    et al.
    Svensson, J. E.
    Johansson, L. G.
    The influence of carbon dioxide on the atmospheric corrosion of some magnesium alloys in the presence of NaCl2002In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 149, no 4, p. B103-B107Article in journal (Refereed)
    Abstract [en]

    The influence of ambient concentrations of carbon dioxide on the NaCl-induced atmospheric corrosion of high purity die-cast MgAl alloys (AM20 and AM60) and MgAlZn alloy (AZ91) is reported. Samples were exposed four weeks in a carefully controlled synthetic atmosphere. Relative humidity was 95%, the temperature was 22.0degreesC, and the concentration of CO2 was <1 or 350 ppm. Sodium chloride was added before the exposures (70 μg/cm(2)). The corrosion products were analyzed by gravimetry, ion chromatography, X-ray diffraction, and environmental scanning electron microscopy. Mass gain and metal loss results are reported. As expected, the combination of high humidity and NaCl is very corrosive toward the magnesium alloys investigated. The NaCl-induced corrosion is inhibited by ambient concentrations of CO2. Exposures in the absence of CO2 give rise to heavy pitting; Mg(OH)(2), brucite, is the dominant corrosion product. In the presence of CO2, a uniform layer of hydrated magnesium hydroxy carbonate, Mg-5 (CO3)(4) (OH)(2)&BULL;5H(2)O, forms. In both environments, the corrosion rates increased in the order AZ91, AM60, AM20.

  • 33. Lindström, Rakel
    et al.
    Svensson, J. E.
    Johansson, L. G.
    The influence of salt deposits on the atmospheric corrosion of zinc - The important role of the sodium ion2002In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 149, no 2, p. B57-B64Article in journal (Refereed)
    Abstract [en]

    The influence of salt deposits on the atmospheric corrosion of zinc was studied in the laboratory. Four chloride-containing salts, NaCl, NH4Cl, ZnCl2, and MgCl2, and four sulfate-containing salts, Na2SO4,(NH4)(2)SO4, ZnSO4, and MgSO4, were investigated. The salts were applied by spraying a saturated ethanol/water solution before exposure. The samples were exposed to purified humid air with careful control of relative humidity (95%), temperature (22.0degreesC), and air flow. The concentration of CO2 was 350 ppm and the exposure time was four weeks. The salts formed aqueous solutions on the metal surface. Mass gain and metal loss results are reported. The corrosion products were analyzed by gravimetry, ion chromatography, and X-ray diffraction. It was concluded that zinc corrodes by an electrochemical mechanism. Of the four cations studied, sodium was by far the most corrosive toward zinc. The corrosion of zinc was directly correlated with the amount of sodium ion and did not depend on whether Na2SO4 or NaCl was added. The comparatively rapid corrosion caused by the two sodium salts is suggested to be due to the absence of insoluble sodium compounds. In contrast, the divalent cations precipitate in the cathodic areas due to the high pH values produced, resulting in the blocking of the cathodic sites.

  • 34.
    Mussa, Abdilbari
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Liivat, Anti
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 538, SE-75121 Uppsala, Sweden..
    Marzano, Fernanda
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 538, SE-75121 Uppsala, Sweden.;Scania CV AB, SE-15187 Sodertalje, Sweden..
    Klett, Matilda
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry. Scania CV AB, SE-15187 Sodertalje, Sweden.
    Philippe, Bertrand
    Uppsala Univ, Dept Phys & Astron, Mol & Condensed Matter Phys, Box 516, S-75120 Uppsala, Sweden..
    Tengstedt, Carl
    Scania CV AB, SE-15187 Sodertalje, Sweden..
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Edstrom, Kristina
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 538, SE-75121 Uppsala, Sweden..
    Lindström, Rakel Wreland
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Svens, Pontus
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry. Scania CV AB, SE-15187 Sodertalje, Sweden.
    Fast-charging effects on ageing for energy-optimized automotive LiNi1/3Mn1/3Co1/3O2/graphite prismatic lithium-ion cells2019In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 422, p. 175-184Article in journal (Refereed)
    Abstract [en]

    The reactions in energy-optimized 25 Ah prismatic NMC/graphite lithium-ion cell, as a function of fast charging (1C-4C), are more complex than earlier described. There are no clear charging rate dependent trends but rather different mechanisms dominating at the different charging rates. Ageing processes are faster at 3 and 4C charging. Cycling with 3C-charging results in accelerated lithium plating but the 4C-charging results in extensive gas evolution that contribute significantly to the large cell impedance rise. Graphite exfoliation and accelerated lithium inventory loss point to the graphite electrode as the source of the gas evolution. The results are based on careful post-mortem analyses of electrodes using: scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). SEM results show particle cracking independent of the charging rate used for the cycling. XPS and EIS generally indicate thicker surface film and larger impedance, respectively, towards the edge of the jellyrolls. For the intended application of a battery electric inner-city bus using this type of cell, charging rates of 3C and above are not feasible, considering battery lifetime. However, charging rates of 2C and below are too slow from the point of view of practical charging time.

  • 35.
    Mussa, Abdilbari
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Klett, Matilda
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry. Scania CV AB, SE-151 87 Södertälje, Sweden.
    Gudmundson, Peter
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Svens, P.
    Lindström, Rakel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Inhomogeneous active layer contact loss in a cycled prismatic lithium-ion cell caused by the jelly-roll curvature2018In: Journal of Energy Storage, E-ISSN 2352-152X, Vol. 20, p. 213-217Article in journal (Refereed)
    Abstract [en]

    Internal resistance is a key parameter that affects the power, energy, efficiency, lifetime, and safety of a lithium-ion battery. It grows due to chemical and mechanical battery wear during ageing. In this work, the effect of the jelly-roll winding curvature on impedance rise is investigated. NMC electrode samples, harvested from the curved as well as the flat regions of the jelly-roll from cycle-aged and calendar-aged prismatic cells (25 Ah, hard casing) are investigated by electrochemical impedance spectroscopy. After cycling, larger impedance rise is observed at the outer radius (concave) of the curved region compared to the inner radius (convex) or the flat region of the jelly-roll, and the difference increases with a decrease in the jelly-roll radius of curvature, from the cell skin towards the core. To identify the causes behind the observed difference in the impedance rise, investigations at different external compression (0 and 2.5 MPa) and temperature (5 and 25 °C) are performed. The results show that contact loss between the current collector and the active layer is the main source of the difference in impedance rise. Mechanical mechanisms that may cause the contact loss are discussed and design recommendations to mitigate the rise in impedance are given. 

  • 36.
    Mussa, Abdilbari Shifa
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Klett, Matilda
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Wreland Lindström, Rakel
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Effects of external pressure on the performance and ageing of single-layer lithium-ion pouch cells2018In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 385, p. 18-26Article in journal (Refereed)
    Abstract [en]

    The effects of external compression on the performance and ageing of NMC(1/3)/Graphite single-layer Li-ion pouch cells are investigated using a spring-loaded fixture. The influence of pressure (0.66, 0.99, 1.32, and 1.98 MPa) on impedance is characterized in fresh cells that are subsequently cycled at the given pressure levels. The aged cells are analyzed for capacity fade and impedance rise at the cell and electrode level. The effect of pressure distribution that may occur in large-format cells or in a battery pack is simulated using parallel connected cells. The results show that the kinetic and mass transport resistance increases with pressure in a fresh cell. An optimum pressure around 1.3 MPa is shown to be beneficial to reduce cyclable-lithium loss during cycling. The minor active mass losses observed in the electrodes are independent of the ageing pressure, whereas ageing pressure affects the charge transfer resistance of both NMC and graphite electrodes and the ohmic resistance of the cell. Pressure distribution induces current distribution but the enhanced current throughput at lower pressures cell does not accelerate its ageing. Conclusions from this work can explain some of the discrepancies in non-uniform ageing reported in the literature and indicate coupling between electrochemistry and mechanics.

  • 37.
    Oyarce, Alejandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Gonzalez, Carlos
    Lima, Raquel Bohn
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Direct sorbitol proton exchange membrane fuel cell using moderate catalyst loadings2014In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 116, p. 379-387Article in journal (Refereed)
    Abstract [en]

    Recent progress in biomass hydrolysis has made it interesting to study the use of sorbitol for electricity generation. In this study, sorbitol and glucose are used as fuels in proton exchange membrane fuel cells having 0.9 mg cm(-2) PtRu/C at the anode and 0.3 mg cm(-2) Pt/C at the cathode. The sorbitol oxidation was found to have slower kinetics than glucose oxidation. However, at low temperatures the direct sorbitol fuel cell shows higher performance than the direct glucose fuel cell, attributed to a lower degree of catalyst poisoning. The performance of both fuel cells is considerably improved at higher temperatures. High temperatures lower the poisoning, allowing the direct glucose fuel cell to reach a higher performance than the direct sorbitol fuel cell. The mass specific peak power densities of the direct sorbitol and direct glucose fuel cells at 65 degrees C was 3.2 mW Mg-catalyst(-1) and 3.5 mW Mg-catalyst(-1), respectively. Both of these values are one order of magnitude larger than mass specific peak power densities of earlier reported direct glucose fuel cells using proton exchange membranes. Furthermore, both the fuel cells showed a considerably decrease in performance with time, which is partially attributed to sorbitol and glucose crossover poisoning the Pt/C cathode.

  • 38.
    Rashtchi, Hamed
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Acevedo Gomez, Yasna
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Raeissi, Keyvan
    Shamanian, Morteza
    Eriksson, Björn
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Zhiani, Mohammad
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Performance of a PEM fuel cell using electroplated Ni–Mo and Ni–Mo–P stainless steel bipolar plates2017In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 13, p. F1427-F1436Article in journal (Refereed)
    Abstract [en]

    The performance and durability of 316L stainless steel bipolar plates (BPP) electroplated with Ni–Mo and Ni–Mo–P coatings are investigated in a proton exchange membrane fuel cell (PEMFC), using a commercial Pt/C Nafion membrane electrode assembly (MEA). The effect of the BPP coatings on the electrochemical performance up to 115 h is evaluated from polarization curves, cyclic voltammetry and electrochemical impedance spectroscopy together with interfacial contact resistance (ICR) measurements between the coatings and the gas diffusion layer. The results show that all the coatings decrease the ICR in comparison to that of uncoated 316L BPP. The Ni-Mo coated BPP shows a low and stable ICR and the smallest effects on MEA performance, including catalyst activity/usability, cathode double layer capacitance, and membrane and ionomer resistance build up with time. After electrochemical evaluation, the BPPs as well as the water effluents from the cell are examined by Scanning Electron Microscopy, Energy Dispersive and Inductively Coupled Plasma spectroscopies. No significant degradation of the coated surface or enhancement in metal release is observed. However, phosphorus addition to the coating does not show to improve its properties, as deterioration of the MEA and consequently fuel cell performance losses is observed.

  • 39.
    Rashtchi, Hamed
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Raeissi, K.
    Shamanian, M.
    Acevedo Gomez, Yasna
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Rajaei, V.
    Evaluation of Ni-Mo and Ni-Mo-P Electroplated Coatings on Stainless Steel for PEM Fuel Cells Bipolar Plates2016In: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 16, no 6, p. 784-800Article in journal (Refereed)
    Abstract [en]

    Stainless steel bipolar plates (BPPs) are the preferred choice for proton exchange membrane fuel cells (PEMFCs); however, a surface coating is needed to minimize contact resistance and corrosion. In this paper, Ni–Mo and Ni–Mo–P coatings were electroplated on stainless steel BPPs and investigated by XRD, SEM/EDX, AFM and contact angle measurements. The performance of the BPPs was studied by corrosion and conduction tests and by measuring their interfacial contact resistances (ICRs) ex situ in a PEMFC set-up at varying clamping pressure, applied current and temperature. The results revealed that the applied coatings significantly reduce the ICR and corrosion rate of stainless steel BPP. All the coatings presented stable performance and the coatings electroplated at 100 mA cm−2showed even lower ICR than graphite. The excellent properties of the coatings compared to native oxide film of the bare stainless steel are due to their higher contact angle, crystallinity and roughness, improving hydrophobicity and electrical conductivity. Hence, the electroplated coatings investigated in this study have promising properties for stainless steel BPPs and are potentially good alternatives for the graphite BPP in PEMFC.

  • 40. Seidel, Y. E.
    et al.
    Lindström, Rakel
    Jusys, Z.
    Cai, J.
    Wiedwald, U.
    Ziemann, P.
    Behm, R. J.
    Nanostructured Pt/GC model electrodes prepared by the deposition of metal-salt-loaded micelles2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 10, p. 5795-5801Article in journal (Refereed)
    Abstract [en]

    Novel, nanostructured, carbon-supported Pt model electrodes with homogeneously distributed Pt nanoparticles of uniform size were fabricated and analyzed with respect to their electrochemical properties. For this purpose, Pt-salt-loaded micelles were deposited on a glassy carbon substrate and subsequently exposed to an oxygen plasma and a H-2 atmosphere for removal of the polymer carriers and reduction of the Pt salt. The morphology of the resulting nanoparticles and their electrochemical/electrocatalytic properties were characterized by high-resolution scanning electron microscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, and differential electrochemical mass spectrometry for CO electrooxidation. The data demonstrate that this method is generally suited to the production of nanostructured model electrodes with well-defined and independently adjustable particle size and interparticle distance distributions, which are specifically suited for quantitative studies of transport processes in electrocatalytic reactions.

  • 41. Seidel, Y. E.
    et al.
    Lindström, Rakel
    Jusys, Z.
    Gustavsson, M.
    Hanarp, P.
    Kasemo, B.
    Minkow, A.
    Fecht, H. J.
    Behm, R. J.
    Stability of nanostructured Pt/glassy carbon electrodes prepared by colloidal lithography2008In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 155, no 3, p. K50-K58Article in journal (Refereed)
    Abstract [en]

    The stability of nanostructured Pt/glassy carbon (GC) model electrodes upon exposure to a realistic electrochemical/electrocatalytic reaction environment (continuous reaction, continuous electrolyte flow) was studied by microscopic techniques, X-ray photoelectron spectroscopy, and electrochemical measurements. The model electrodes consist of Pt nanostructures with well-defined sizes and regular spacing on planar GC substrates, and were fabricated using colloidal lithography techniques. Additional plasma treatments of the GC substrates prior to Pt deposition were tested to improve the stability of the resulting Pt/GC model electrodes. Both evaporation and sputter deposition were used for Pt-film fabrication. The model catalysts prepared by Pt evaporation were found to be rather unstable. The stability was significantly improved for sputter-deposited Pt films, and Pt sputter deposition on a GC substrate, pretreated first in oxygen plasma and then in Ar plasma, resulted in stable model electrodes with a fully intact layer of Pt nanostructures after the electrocatalytic experiments.

  • 42. Seidel, Yvonne E.
    et al.
    Jusys, Zenonas
    Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Stenfeldt, Marie
    Kasemo, Bengt
    Krischer, Katharina
    Oscillatory behaviour in Galvanostatic Formaldehyde Oxidation on Nanostructured Pt/Glassy Carbon Model Electrodes2010In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 11, no 7, p. 1405-1415Article in journal (Refereed)
    Abstract [en]

    The electrocatalytic oxidation of formaldehyde, which results in CO, and HCOOH formation, was investigated under galvanostatic conditions on nanostructured Pt/glassy carbon (GC) electrodes fabricated by employing colloidal lithography (CL). The measurements were performed on structurally well-defined model electrodes of different Pt surface coverages under different applied currents (current densities) and at constant electrolyte transport in a thin-layer flow cell connected to a differential electrochemical mass spectrometry (DEMS) setup to monitor the dynamic response of the reaction selectivity under these conditions. Periodic oscillations of the electrode potential and the CO, formation rate appear not only for a continuous Pt film, but also for the nanostructured Pt/GC electrodes when a critical current density is exceeded. The critical current density for achieving regular osillation patterns increased with decreasing Pt nanodisk density. Lower oscillation frequencies of the electrode potential and lower CO2 formation rate for nanostructured Pt/GC electrodes compared to continuous Pt film at similar applied current densities suggest that transport processes play an essential role. Moreover, from the simple periodic response of the nanostructured electrodes it follows that all individual Pt disks in the array oscillate in synchrony. This result is discussed in terms of the different modes of spatial coupling present in the system: global coupling, migration coupling and mass transport of the essential chemical species, and the coverage of corresponding adsorbates.

  • 43.
    Wreland Lindström, Rakel
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Bränsleceller och material: Rapport från arbetsseminarium 16 juni 20112011Report (Other (popular science, discussion, etc.))
  • 44.
    Wreland Lindström, Rakel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Aguinaga, Luis Guerrero
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Oyarce, Alejandro
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Ubeda, Diego
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Ingratta, Mark
    Jannasch, Patric
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Fuel cell performance using a phosphonated polysulphone ionomer (PSUgPVPA) in the PEM cathode electrode2013In: Fuel Cell Membranes, Electrode Binders, And Mea Performance, Electrochemical Society, 2013, no 23, p. 33-45Conference paper (Refereed)
    Abstract [en]

    Inexpensive and environmentally friendly electrolyte polymers that can be operated at higher temperatures and drier conditions are highly interesting for PEM fuel cells for automotive, portable power and stationary electricity generation applications. In this study an ionomer based on polysulfone grafted with poly(vinylphosphonic acid) (PSUgPVPA) in the cathode Pt/C catalyst layer (CL) was electrochemically characterized and compared to Nafion (R). The performance at different levels of humidity at 80 degrees C was evaluated by polarization and cyclic voltammetry. The results show that the performance of the PSUgPVPA-based cathode CL is comparable to that of Nafion (R) at 100% relative humidity (RH) but with some instabilities. However, at drier conditions significant losses of performance for the PSUgPVPA-based cathode was observed, concomitant to a reduced electrochemical surface area. The lower performance at low humidity is concluded to be due to a combination of lower proton conductivity and wettability or interference with oxygen reduction reaction at lower RH.

  • 45.
    Wreland Lindström, Rakel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Hildebrandt, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Polymera bränsleceller (PEMFC): Teknikbevakningsrapport 20092009Report (Other (popular science, discussion, etc.))
  • 46.
    Wreland Lindström, Rakel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Kortsdottir, Katrin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Pérez Ferriz, Francisco Javier
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Conde Lopez, Julio Jose
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    The Effect of Hydrocarbon Impurities in the Hydrogen Fuel on the Anode Activity in PEMFC2013Conference paper (Refereed)
    Abstract [en]

    The reformate fuel cell has recently gained increasing attention both for APUs in vehicles

    operating on diesel and in stationary applications such as micro-CHP operating on natural

    or biogas. In addition to hydrogen gas, reformate contain considerable amounts of CO2,

    nitrogen, water vapour and traces of CO, sulphur species and hydrocarbons. CO and H2S

    are well known poisons to the anode [1] but the influence of hydrocarbon species in the

    fuel cell has not been much investigated. We have previously investigated toluene [2] and

    ethene [3] on the anode Pt/C catalyst in the PEM fuel cell. In this paper we will discuss the

    influences of alkenes and alkanes in the light of some novel results on the effect of

    propene, propane and methane in the PEM fuel cell. We have especially focused on the

    adsorption and deactivation phenomena of low concentrations of contaminant on a Pt/C

    catalyst. In the experiments, in situ stripping voltammetry and on-line mass spectrometer

    were employed. The effects of adsorption potential and temperature are discussed. We

    show that propene is more poisonous to the Pt/C catalyst than ethene as it is adsorbed on

    the catalyst surface within the Hupd region and forms an adlayer that can be oxidized in two

    steps between 0.5-1 V (at 80°C, 90%RH) or be hydrogenated to propane in the Hupd region

    and in the presence of hydrogen.

  • 47.
    Wreland Lindström, Rakel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Kortsdottir, Katrin
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Wesselmark, Maria
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Oyarce, Alejandro
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lagergren, Carina
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Active Area Determination of Porous Pt Electrodes Used in Polymer Electrolyte Fuel Cells: Temperature and Humidity Effects2010In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, no 12, p. B1795-B1801Article in journal (Refereed)
    Abstract [en]

    This paper discusses the proper measure of the electrochemically active area (ECA)of carbon supported Pt catalyst in PEM fuel cells employing in situ cyclic voltammetry. The charges of the hydrogen underpotential deposition (Hupd) and CO stripping peak obtained in situ are compared, and the influence of operation temperature (25–80°C) and relative humidity (40%–90%) is discussed. The results show that the charges of the Hupd decrease with rising temperature, while the corresponding charges of the CO stripping peak are essentially independent of temperature, at least at high relative humidity. The unexpectedly small Hupd charges are explained by the significant overlap with the hydrogen evolution reaction in a fuel cell at elevated temperatures. According to our results, it is proposed that a more reliable value of Pt ECA is estimated from the CO stripping charge. However, with decreasing humidity the charges of both Hupd and CO stripping peaks decrease, which is probably an effect of increasing blockage of Pt active sites by hydrophobic domains in the electrode ionomer. Some implications of varying cell conditions on the estimated Pt ECA and its correlation with fuel cell activity are discussed in an example from a fuel cell degradation test.

  • 48.
    Wreland Lindström, Rakel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Teknikbevakning av polymera bränsleceller (PEFC)2011Report (Other (popular science, discussion, etc.))
  • 49.
    Wreland Lindström, Rakel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Oyarce, Alejandro
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Aguinaga, Luis Guerrero
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Ubeda, Diego
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Ingratta, Mark
    Jannasch, Patric
    Lindbergh, Göran
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Performance of Phosphonated Hydrocarbon Ionomer in the Fuel Cell Cathode Catalyst Layer2013In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 160, no 3, p. F269-F277Article in journal (Refereed)
    Abstract [en]

    Inexpensive and environmentally friendly electrolyte polymers that can be operated at higher temperatures and drier conditions are highly interesting for PEM fuel cells for automotive, portable power and stationary electricity generation applications. In this study an ionomer based on polysulfone grafted with poly(vinylphosphonic acid) (PSUgPVPA) in the cathode Pt/C catalyst layer was electrochemically characterized and compared to Nafion. The performance at different levels of humidity at 80 degrees C was evaluated by polarization measurements, cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The results show that the performance of the PSUgPVPA-based cathode catalyst layer is comparable to that of Nafion-at 100% relative humidity (RH) but with some instabilities. However, at drier conditions significant losses of performance for the PSUgPVPA-based cathode was observed. This could be an effect of catalyst poisoning by the ionomer interfering with ORR. However, the concomitant decrease of the electrochemical surface area, double layer capacitance and increased imaginary impedance, indicate that the poorer performance at low humidity is mainly an effect of reduced catalyst wetting by the ionomer in combination with the decreased proton conduction in the ionomeric phase.

  • 50.
    Wreland Lindström, Rakel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
    Seidel, Y. E.
    Jusys, Z.
    Gustavsson, M.
    Wickman, B.
    Kasemo, B.
    Behm, R. J.
    Electrocatalysis and transport effects on nanostructured Pt/GC electrodes2010In: J ELECTROANAL CHEM, ISSN 1572-6657, Vol. 644, no 2, p. 90-102Article in journal (Refereed)
    Abstract [en]

    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.

12 1 - 50 of 51
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf