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  • 201.
    Rexed, Ivan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    della Pietra, Massimiliano
    University of Perugia.
    McPhail, Stephen
    ENEA.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Molten carbonate fuel cells for CO2 separation and segregation by retrofitting existing plants - An analysis of feasible operating windows and first experimental findings2015Inngår i: International Journal of Greenhouse Gas Control, ISSN 1750-5836, E-ISSN 1878-0148, Vol. 35, s. 120-130Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Molten carbonate fuel cells (MCFC) used as active carbon dioxide concentrator units are a promising solution to reduce greenhouse gas (GHG) emissions from traditional combustion plants. The cell reaction transfers carbonate ions from the cathode to the anode and allows the fuel cell to simultaneously produce power and separate CO2 from a stream of flue gas. Carbon dioxide separation is of high interest for use in natural gas combined cycles and coal gas combustion plants, as a large part of anthropogenic CO2 worldwide originates from such installations. The flue gas from these types of combustion technologies typically contains 3-15% CO2, which is in the lower operational range of the MCFC. The aim of this work was to investigate the possibility to retrofit existing power plants with MCFC to reduce the total release of CO2 without necessarily reducing the power output, and to understand which kind of power plant could have the major benefits with an MCFC retrofitting. The performance of lab scale MCFC fed with simulated flue gas was evaluated, and a number of operational parameters, such as utilization factor and cathode humidification were varied to study the effect on fuel cell performance. The results show that it is feasible to operate the MCFC as a CO2 separator for simulated gas turbine flue gas; however, the voltage drop due to low CO2 concentration may restrict the operating window depending on various operating conditions.

  • 202.
    Rexed, Ivan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Performance of MCFC fed with simulated flue gas2013Inngår i: EFC 2013 - Proceedings of the 5th European Fuel Cell Piero Lunghi Conference, 2013, s. 233-234Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The effect on MCFC performance with CO2 lean oxidant gas, simulating combustion flue gas was evaluated. Furthermore, measurements to test the effect of SO2 in the oxidant gas stream in concentrations up to 24ppm and during 90 min exposure, followed by regeneration with clean gas, was performed. Results show that the performance of the button cell with CO2 lean oxidant gas is acceptable at a base load of 100mA/cm2. The effect on fuel cell performance of short term exposure to SO2 is only clear in the higher range of contaminant concentration (>12ppm). Studying the performance degradation of the fuel cell caused by SO2 in flue gas is important for the use of MCFC as a CCS application.

  • 203.
    Rexed, Ivan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Effect of sulfur contaminants on MCFC performance2014Inngår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 39, nr 23, s. 12242-12250Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Molten carbonate fuel cells (MCFC) used as carbon dioxide separation units in integrated fuel cell and conventional power generation can potentially reduce carbon emission from fossil fuel power production. The MCFC can utilize CO2 in combustion flue gas at the cathode as oxidant and concentrate it at the anode through the cell reaction and thereby simplifying capture and storage. However, combustion flue gas often contains sulfur dioxide which, if entering the cathode, causes performance degradation by corrosion and by poisoning of the fuel cell. The effect of contaminating an MCFC with low concentrations of both SO2 at the cathode and H2S at the anode was studied. The poisoning mechanism of SO2 is believed to be that of sulfur transfer through the electrolyte and formation of H2S at the anode. By using a small button cell setup in which the anode and cathode behavior can be studied separately, the anodic poisoning from SO2 in oxidant gas can be directly compared to that of H2S in fuel gas. Measurements were performed with SO2 added to oxidant gas in concentrations up to 24 ppm, both for short-term (90 min) and for long-term (100 h) contaminant exposure. The poisoning effect of H2S was studied for gas compositions with high- and low concentration of H-2 in fuel gas. The H2S was added to the fuel gas stream in concentrations of 1, 2 and 4 ppm. Results show that the effect of SO2 in oxidant gas was significant after 100 h exposure with 8 ppm, and for short-term exposure above 12 ppm. The effect of SO2 was also seen on the anode side, supporting the theory of a sulfur transfer mechanism and H2S poisoning. The effect on anode polarization of H2S in fuel gas was equivalent to that of SO2 in oxidant gas.

  • 204.
    Rexed, Ivan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Performance degradation of Molten Carbonate Fuel Cells caused by SO2 in simulated flue gasManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The effect on MCFC performance degradation SO2 contaminant at the cathode, in combination with operating the fuel cell with CO2 lean oxidant gas, simulating combustion flue gas, was evaluated. Of special focus was the effect of electrolyte degradation.

     Measurements were performed to test the effect of SO2 in the oxidant gas stream, followed by regeneration with clean gas. A 3cm2 button cell MCFC allowing active electrolyte management by refilling was for 1500h to benchmark the performance degradation without contaminants. In order to study the poisoning effect of SO2 entering the fuel cell gas, the MCFC was operated for 250h with the addition of 18ppm SO2 in the oxidant gas. Electrolyte was added after 1500h of benchmark operation and after 250h of contaminant operation. The addition of 18ppm SO2 greatly accelerated the performance degradation of the fuel cell. Measurements showed that the internal resistance was the single factor which was most affected by the SO2 poisoning, and that the performance degradation after 250h was not reversed by regeneration with clean gas, but with the addition of fresh electrolyte. This led us to conclude that SO2 in oxidant gas leads to an accelerated loss of electrolyte and subsequent decrease in conductivity of the electrolyte, causing loss of performance and meeting end of life criteria after relatively short operational time. Other factors, such as poisoning of the anode and corrosion of cathode side current collectors, were also detected. 

  • 205. Ringuede, Armelle
    et al.
    Wijayasinghe, Athula
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Albin, Valerie
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cassir, Michel
    Bergman, Bill
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Solubility and electrochemical studies of LiFeO2-LiCoO2-NiO materials for the MCFC cathode application2006Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 160, nr 2, s. 789-795Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The dissolution of the state-of-the-art lithiated NiO is still considered as one of the main obstacles to the commercialisation of the molten carbonate fuel cell (MCFC). Development of alternative cathode materials has been considered as a main strategy for solving this problem. Ternary compositions of LiFeO2, LiCoO2 and NiO are expected to decrease the cathode solubility while ensuring a good electrical conductivity and electrochemical activity towards the oxygen reduction. In this work, new material compositions in the LiFeO2-LiCoO2-NiO ternary system were synthesised using Pechini method and investigating their electrical conductivity by the DC four probe method. Then the influence of the cobalt content in the composition was determined in terms of AC impedance analysis and solubility measurements after 200 h of immersion in Li2CO3-Na2CO3 at 650 degrees C. The DC electrical conductivity study reveals the ability of improving the electrical conductivity, adequate for MCFC cathode application, by controlling the Co content of the composition. A special attention was given to the evolution of the open circuit potential as a function of time and to the impedance spectroscopy characterization related to microstructure modifications. Taking into account solubility, electrical conductivity, as well as electrochemical performance in the fuel cell, this study reveals the possibility of using LiFeO2-LiCoO2-NiO ternary materials for MCFC cathode.

  • 206. Samarasingha, Pushpaka B.
    et al.
    Wijayasinghe, Athula
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Dissanayake, Lakshman
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Development of cathode materials for lithium ion rechargeable batteries based on the system Li(Ni1/3Mn1/3Co(1/3-x)Mx)O-2, (M = Mg, Fe, Al and x=0.00 to 0.33)2014Inngår i: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 268, s. 226-230Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study was based on developing Li(Ni1/3Mn1/3Co(1/3-x)Mx)O-2, (M = Mg, Fe, Al and x = 0 to 0.33) materials by substituting expensive Co content in this NMC system with cheaper Mg, Fe and Al additives for the cathode application in rechargeable lithium ion batteries (LIB). The Pechini method, which is a low-cost wet chemical technique, was used for powder synthesis in this study. The XRD phase analysis revealed the formation of solid solutions of appropriate layered Li(Ni1/3Mn1/3Co(1/3-x)Mx)O-2 phase.of R-3m structure in the prepared compositions over x = 0.11 substitution of Fe and Mg. Furthermore, these Fe and Mg substituted compositions showed considerably higher electrical conductivity than the base material Li(Ni1/3Mn1/3Co(1/3-x)Mx)O-2 (over 0.9 x 10(-5) S/cm at 25 degrees C). In the cell studies, the Fe and Mg substituted compositions with x = 0.11 showed a specific capacity of 122 and 125 mAhg(-1), respectively, which are comparable to the specific capacity of the state-of-the-art LiCoO2 cathode material of LIB. Altogether, this study shows the ability of preparing these NMC materials by Pechini method with appropriate structural and electrochemical properties suitable for the LIB cathode.

  • 207. Samarasingha, Pushpaka
    et al.
    Tran-Nguyen, Diem-Hang
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wijayasinghe, Athula
    LiNi1/3Mn1/3Co1/3O2 synthesized by the Pechini method for the positive electrode in Li-ion batteries: Material characteristics and electrochemical behaviour2008Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, nr 27, s. 7995-8000Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The feasibility of the Pechini method for the preparation of LiNi1/3Mn1/3Co1/3O2 with characteristics appropriate for Li-ion battery positive electrodes was investigated. The method involves formation of one single chemically homogenous precursor material and thus permits reduced calcination times and minimal lithium evaporation. The physical and electrochemical properties of the materials were investigated with variation in final calcination temperature. Chemical analysis showed that the materials could be prepared with high crystallinity and yet little or no loss of lithium. The material calcined at 1000 degrees C showed the highest specific capacity-180 mAh g(-1) when cycled between 4.5 and 3 V, and it maintained its capacity over 50 cycles. The advantage of this material over those prepared at 800 and 900 degrees C can probably be attributed to the fact that the degree of crystallinity, crystallite size and size of the primary particles increase with calcination temperature, and that the powder attains a more suitable morphology which promotes electronic connectivity to all of the oxide material. A temperature above 1000 degrees C should however not be used as indicated by an abrupt change in lattice parameters and decrease in electronic conductivity when going from 1000 to 1050 degrees C. The Pechini method presents an attractive option for the preparation of LiNi1/3Mn1/3Co1/3O2 positive electrode material.

  • 208.
    Sandin, Staffan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cheritat, Alicia
    Backström, Joakim
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Deposition efficiency in the preparation of ozone-producing nickel and antimony doped tin oxide anodes2017Inngår i: Journal of Electrochemical Science and Engineering, ISSN 1847-9286, Vol. 7, nr 1, s. 51-64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of precursor salts in the synthesis of nickel and antimony doped tin oxide (NATO) electrodes using thermal decomposition from dissolved chloride salts was investigated. The salts investigated were SnCl4 center dot 5H(2)O, SnCl2 center dot 2H(2)O, SbCl3 and NiCl2 center dot 6H(2)O. It was shown that the use of SnCl4 center dot 5H(2)0 in the preparation process leads to a tin loss of more than 85 %. The loss of Sb can be as high as 90 % while no indications of Ni loss was observed. As a consequence, the concentration of Ni in the NATO coating will be much higher than in the precursor solution. This high and uncontrolled loss of precursors during the preparation process will lead to an unpredictable composition in the NATO coating and will have negative economic and environmental effects. It was found that using SnCl2 center dot 2H(2)0 instead of SnCl4 center dot 5H(2)O can reduce the tin loss to less than 50 %. This tin loss occurs at higher temperatures than when using SnCl4 center dot 5H(2)O where the tin loss occurs from 56 - 147 degrees C causing the composition to change both during the drying (80 - 110 degrees C) and calcination (460 - 550 degrees C) steps of the preparation process. Electrodes coated with NATO based on the two different tin salts were investigated for morphology, composition, structure, and ozone electrocatalytic properties.

  • 209.
    Sandin, Staffan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Karlsson, Rasmus K. B.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Catalyzed and uncatalyzed decomposition of hypochlorite in dilute solutions2015Inngår i: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 54, nr 15, s. 3767-3774Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hypochlorite decomposition has been investigated by the combined measurement of aqueous concentrations of total hypochlorite, chlorate, and chloride, as well as that of evolved oxygen. In all experiments, the initial concentrations of NaOCl and NaCl were 80 mM, and the temperature was 80°C. The pH was kept constant in the range 5-10.5. The uncatalyzed decomposition of hypochlorite and the formation of chlorate and oxygen were all found to be third order of the form r<inf>i</inf> = k<inf>i</inf>[HOCl]2[OCl-], and k<inf>O</inf><inf>2</inf> was determined to be 0.046 M-2 s-1. A reaction mechanism in which oxygen and chlorate formation share an intermediate is proposed. Several compounds were tested for catalytic effects. The addition of chloride salts of cobalt and iridium showed catalytic effects on oxygen formation. The addition of iridium chloride also catalyzed the formation of chlorate with increasing selectivity for chlorate with increasing pH.

  • 210. Seidel, Yvonne E.
    et al.
    Jusys, Zenonas
    Lindström, Rakel
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Stenfeldt, Marie
    Kasemo, Bengt
    Krischer, Katharina
    Oscillatory behaviour in Galvanostatic Formaldehyde Oxidation on Nanostructured Pt/Glassy Carbon Model Electrodes2010Inngår i: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 11, nr 7, s. 1405-1415Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 211.
    Sevencan, Suat
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Economic Aspects of Fuel Cell-Based Stationary Energy Systems2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    It is evident that human activity has an important impact on climate. Constantly increasing energy demand is one of the biggest causes of climate change. The fifth assessment report of the Inter-governmental panel on climate change states that decarbonisation of electricity generation is a key component of climate change mitigation. Increased awareness of this fact and escalating concerns around energy security has brought public attention to the energy industry, especially sustainable power generation systems.

    Future energy systems may need to include hydrogen as an energy carrier in order to achieve necessary levels of CO2 emission reductions, and overcome the challenges renewable energy systems present. Fuel cells could be a corner stone of future hydrogen inclusive energy solutions.

    New solutions like fuel cells have to compete with existing technologies and overcome the shortcomings of emerging technology. Though these shortcomings are well-recognised, fuel cells also have many advantages which makes continued research and development in the field highly worthwhile and viable. Key to their adoption is the identification of a niche market to utilise their advantages while overcoming their shortcomings with continuous research and development.

    This thesis aims to evaluate some of the stationary fuel cell applications and determine whether one could become the niche market as an entry point for fuel cells. This is achieved by economic evaluations of real and hypothetical applications.

    Results of the studies here imply that to decrease the total life cycle impacts of fuel cells to more acceptable levels, resource use in the manufacturing phase and recycling in decommissioning should be shown more attention. Results also present a picture showing that none of the applications investigated are economically feasible, given the current state of technology and energy prices. However, fuel cell-based combined cooling, heating and power systems for data centres show the potential to become the niche market that fuel cells need to grow. A further conclusion is that a broad market, longer stack lifetime, the possibility of selling electricity back to the grid and governmental subsidies are essential components of an environment in which fuel cells can permeate through the niche market to the mainstream markets.

  • 212.
    Sevencan, Suat
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Altun Çiftçioǧlu, G.
    Kadirgan, N.
    A preliminary environmental assessment of power generation systems for a stand-alone mobile house with cradle to gate approach2011Inngår i: Gazi University Journal of Science, ISSN 1303-9709, Vol. 24, nr 3, s. 487-494Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Due to the sporadic characteristics of solar and wind power it has been a challenge to generate a highly reliable power with photovoltaic and or wind turbines alone. A fuel cell as a supplementary energy source is an alternative to overcome this challenge. PV/wind/fuel cell hybrid power system may be a feasible solution for stand-alone applications. In this study, which is a preliminary work of a comprehensive Life Cycle Assessment (LCA), comparison of the power generation alternatives in terms of environmental impacts by evaluating their environmental and energy efficiencies and impacts during the productions of the system components was given. Also, impacts during the production of wind turbines, PV panels, fuel cells and diesel generators were inspected. Eco-Indicator 99 impact assessment method was used as the impact assessment method. It was shown that the in human health and ecosystem quality damage categories the PV panels are less environmentally efficient when compared with other power generation technologies with similar capacities.

  • 213.
    Sevencan, Suat
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Altun-Ciftcioglu, Gokcen Alev
    Kadirgan, Mehmet Arif Neset
    A Preliminary Feasibility Study of a Fuel Cell Based Combined Cooling Heating and Power System2011Inngår i: Gazi University Journal of Polytechnic, ISSN 1302-0900, Vol. 14, nr 3, s. 199-202Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Combined cooling, heating and power (CCHP) systems, provide an alternative for the world to meet and solve energy – related problems, such as energy shortages, supply security, emissions, the economy, and conservation of energy, etc. CCHP systems do not just provide electricity and heating but also cooling for space air conditioning or processes. Recent studies points out that the overall efficiencies of CCHP systems that exploit an advanced thermally activated technology are superior to conventional systems. This study is a preliminary feasibility of a fuel cell based combined heat and power (CHP) system coupled with an open cycle desiccant cooling. The technology is based on the principle of outside air dehumidification by an adsorbent. The study shows that the payback time is around 13 years. With governmental and European Union incentives, possible increases in power prices and decreases in costs by mass production the payback time is expected to decrease in the future.

  • 214.
    Sevencan, Suat
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Ciftcioglu, Gokcen A.
    Life cycle assessment of power generation alternatives for a stand-alone mobile house2013Inngår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 38, nr 34, s. 14369-14379Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents comparative life cycle assessment of nine different hybrid power generation solutions that meet the energy demand of a prototypical mobile home. In these nine solutions, photovoltaic panels and a wind turbine are used as the main energy source. Fuel cell and diesel generator are utilized as backup systems. Batteries, compressed H-2, and H-2 in metal hydrides are employed as backup energy storage. The findings of the study shows that renewable energy sources, although they are carbon-free, are not as environmentally friendly as may generally be thought. The comparative findings of this study indicate that a hybrid system with a wind turbine as a main power source and a diesel engine as backup power system is the most environmentally sound solution among the alternatives.

  • 215.
    Sevencan, Suat
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Guan, Tingting
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Alvfors, Per
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Ridell, Bengt
    Fuel cell based cogeneration: Comparison of electricity production cost for Swedish conditions2013Inngår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 38, nr 10, s. 3858-3864Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A good portion of greenhouse gas emissions is caused by the energy used in the built environment. Emission reduction goals may be achieved by combining cogeneration with fuel cells (PC). This paper investigates electricity production costs for PC based cogeneration systems with recent data for Swedish conditions. The types of FCs that are investigated are proton exchange membrane PC and molten carbonate FC. Based solely on cost, PC based cogeneration systems cannot compete with conventional systems. However, our results show that Molten Carbonate PC based cogeneration systems will be profitable by 2020. To compete with conventional systems, the capital cost, lifetime and efficiency of FCs must be improved. Creation of a reasonably broad market is essential since it will greatly help to reduce capital costs and operation and maintenance (O&M) costs, the dominating parts of the overall costs according to the analysis.

  • 216.
    Sevencan, Suat
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Alvfors, Per
    An Economical Comparison of Power-to-Gas Alternatives in Bozcaada - TurkeyManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Although currently conventional electricity generation methods dominate the market, the share of renewable energy systems is constantly increasing. Intermittent nature of solar and wind cause several problems. Power-to-gas is a method that can help with these problems by generating and storing hydrogen gas during off-peak hours so it can be reconverted into electricity via fuel cells and/or H2 internal combustion engines coupled with electricity generators during peak hours. In this study an economical evaluation of power-to-gas systems for an existing photovoltaic-Wind hybrid power system was made. Results indicate that although the photovoltaic-Wind may reduce the energy bill considerably when it is possible to sell electricity to the grid, coupling it with a power-to-gas system makes it unprofitable over the lifetime of the system.

  • 217.
    Sevencan, Suat
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Alvfors, Per
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Economic feasibility study of a fuel cell-based combined cooling, heating and power system for a data centre2016Inngår i: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 111, s. 218-223Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The energy use of data centres is increasing as the data storage needs increase. One of the largest items in the energy use of these facilities is cooling. A fuel cell-based combined cooling, heating and power system can efficiently meet such a centre's need for cooling and in the meantime generate enough electricity for the centre and more. In this paper the economic feasibility of a fuel cell-based combined cooling, heating and power system that meets the energy demands of such a facility is investigated using operational data from an existing data centre in Stockholm, Sweden. The results show that although the system is not feasible with current energy prices and technology it may be feasible in the future with the projected changes in energy prices.

  • 218.
    Soares, Rudi
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Bessman, Alexander
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Svens, Pontus
    Design Aspects of an Experimental Setup for Investigating Current Ripple Effects in Lithium-ion Battery Cells2015Inngår i: Power Electronics and Applications (EPE'15 ECCE-Europe), 2015 17th European Conference on, IEEE conference proceedings, 2015, s. 1-8Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper describes an experimental setup for investigating the effects of current ripple on lithium-ion battery cells. The experimental setup is designed so that twelve li-ion cells can be simultaneously tested in a controlled environment. The experimental setup allows for a wide range of current ripple in terms of frequency and amplitude. Additionally, the quantification of the current ripple effects such as the aging of li-ion cells implies that a precise measurement system has to be designed which also are discussed in the paper.

  • 219.
    Soares, Rúdi
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Bessman, Alexander
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Li-ion battery and dc-link capacitor technologies – Electric drivetrain applications: A literature study2014Rapport (Annet vitenskapelig)
    Abstract [en]

    Modern electrical vehicle drivetrains use a DC-link capacitor to decouple the battery from the power electronics.This topology is thought to be necessary for a number of reasons, including among others preventing damage to the battery and reducing electromagnetic interference.However, the DC-link capacitor is a bulky component which makes the entire drivetrain less modular by its presence.For this reason, an interdisciplinary research project has been launched to investigate the possibility of improving electrical vehicle drivetrains by having PhD students from the fields of electrical engineering and applied electrochemisty working closely together.The initial goal of this project will be to attempt to remove the DC-link capacitor entirely, in order to determine whether this adversely affects the battery longevity.Depending on the results from this initial test, other potential problems with removing the DC-link capacitor will be identfied and addessed.

  • 220.
    Soares, Rúdi
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Bessman, Alexander
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elkraftteknik.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Svens, P.
    Measurements and analysis of battery harmonic currents in a commercial hybrid vehicle2017Inngår i: 2017 IEEE Transportation and Electrification Conference and Expo, ITEC 2017, Institute of Electrical and Electronics Engineers Inc. , 2017, s. 45-50Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, the harmonic content of the battery current in a commercial hybrid vehicle (bus) is measured and analyzed for a number of different driving situations. It is found that the most prominent harmonic reaches peak magnitudes that can be higher than 10% of the maximum dc-current level with a maximum frequency less than 150 Hz. Further, it is found that this harmonic can be approximated using a fitted, simple analytical expression with reasonable agreement for all driving situations considered.

  • 221.
    Svens, Pontus
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Development of a Novel Method for Lithium-Ion Battery Testing on Heavy-Duty Vehicles2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Increasing demands for lower environmental impact from vehicles, including heavy-duty vehicles, have driven several vehicle manufacturers to consider adding hybrid electrical vehicles (HEV’s) to the product portfolio. Present research on batteries for HEV’s is mainly focused on lithium-ion battery chemistries, since lithium-ion batteries has the most promising technical potential compared to other types of batteries. However, the uncertainty regarding battery lifetime combined with a high battery cost can have a negative impact on large scale commercialisation of heavy-duty hybrid vehicles in the near future.

    A large part of present lithium-ion battery research is focused on new materials, but there is also research focusing on ageing of already established lithium-ion battery chemistries. Cycle ageing of batteries often includes complete charging and discharging of batteries or the use of standardized test cycles. Battery cycling in real HEV applications is however quite different compared to this kind of laboratory testing, and real life testing on vehicles is a way of verifying the soundness of laboratory ageing.

    The aim of this study was to develop a test method suitable for real life testing of lithium-ion batteries for heavy-duty HEV-usage, with the purpose of investigating the correlation of battery ageing and usage in real life applications. This concept study includes both cell level battery cycling and performance testing on board vehicles. The performance tests consist of discharge capacity measurements and hybrid pulse power characterization (HPPC) tests. The main feature of this test equipment is that it is designed to be used on conventional vehicles, emulating an HEV environment for the tested battery. The functionality of the equipment was verified on a heavy-duty HEV with satisfying results. Results from real life testing of 8 batteries using the developed test equipment on four conventional heavy-duty trucks shows that the concept of comparing battery ageing with battery usage has a most promising potential to be used as a tool when optimizing battery usage vs. lifetime. Initial results from this real life study shows significant differences in state of charge (SOC) and power distributions between cycled batteries, but so far only small differences in ageing. Lithium-ion batteries of the type lithium manganese spinel/lithium titanate (LMO/LTO) were used in this study.

  • 222.
    Svens, Pontus
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Methods for Testing and Analyzing Lithium-Ion Battery Cells intended for Heavy-Duty Hybrid Electric Vehicles2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Lithium-ion batteries designed for use in heavy-duty hybrid vehicles are continuously improved in terms of performance and longevity, but they still have limitations that need to be considered when developing new hybrid vehicles.               

    The aim of this thesis has been to study and evaluate potential test and analysis methods suitable for being used in the design process when maximizing lifetime and utilization of batteries in heavy-duty hybrid vehicles.

    A concept for battery cell cycling on vehicles has been evaluated. The work included development of test equipment, verification of hardware and software as well as an extended period of validation on heavy-duty trucks. The work showed that the concept has great potential for evaluating strategies for battery usage in hybrid vehicles, but is less useful for accelerated aging of battery cells.                            

    Battery cells encapsulated in flexible packaging material have been investigated with respect to the durability of the encapsulation in a demanding heavy-duty hybrid truck environment. No effect on water intrusion was detected after vibration and temperature cycling of the battery cells.                   

    Aging of commercial battery cells of the type lithium manganese oxide - lithium cobalt oxide / lithium titanium oxide (LMO-LCO/LTO) was investigated with different electrochemical methods to gain a deeper understanding of the origin of performance deterioration, and to understand the consequences of aging from a vehicle manufacturer's perspective. The investigation revealed that both capacity loss and impedance rise were largely linked to the positive electrode for this type of battery chemistry.                          

    Postmortem analysis of material from cycle-aged and calendar-aged battery cells of the type LMO-LCO/LTO and LiFePO4/graphite was performed to reveal details about aging mechanisms for those cell chemistries. Analysis of cycle-aged LMO-LCO/LTO cells revealed traces of manganese in the negative electrode and that the positive electrode exhibited the most severe aging. Analysis of cycle-aged LFP/graphite cells revealed traces of iron in the negative electrode and that the negative electrode exhibited the most severe aging.

  • 223.
    Svens, Pontus
    et al.
    Scania CV AB, Sweden.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lithium-Ion Battery Cell Cycling and Usage Analysis in a Heavy-Duty Truck Field Study2015Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 8, nr 5, s. 4513-4528Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents results from a field test performed on commercial power-optimized lithium-ion battery cells cycled on three heavy-duty trucks. The goal with this study was to age battery cells in a hybrid electric vehicle (HEV) environment and find suitable methods for identifying cell ageing. The battery cells were cycled on in-house developed equipment intended for testing on conventional vehicles by emulating an HEV environment. A hybrid strategy that allows battery usage to vary within certain limits depending on driving patterns was used. This concept allows unobtrusive and low-cost testing of battery cells under realistic conditions. Each truck was equipped with one cell cycling equipment and two battery cells. One cell per vehicle was cycled during the test period while a reference cell on each vehicle experienced the same environmental conditions without being cycled. Differential voltage analysis and electrochemical impedance spectroscopy were used to identify ageing of the tested battery cells. Analysis of driving patterns and battery usage was performed from collected vehicle data and battery cell data.

  • 224.
    Svens, Pontus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Eriksson, Rickard
    Uppsala University.
    Hansson, Jörgen
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Gustafson, Torbjörn
    Uppsala University.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Analysis of ageing of commercial composite metal oxide: Li4Ti5O12 battery cellsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Commercial battery cells with Li4Ti5O12 negative electrode and composite metal oxidepositive electrode have been analyzed with respect to ageing mechanisms. Electrochemical impedancespectroscopy (EIS), differential capacity analysis (dQ/dV), differential voltage analysis (dV/dQ) andscanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) were used to identifydifferent ageing mechanisms such as lithium inventory loss, loss of active electrode material andsurface film growth. The active material of the positive electrode was also examined by X-raydiffraction (XRD). Ageing mechanisms were studied for both calendar-aged and cycle-aged cells. Datafrom half cells prepared from post mortem harvested electrode material, using lithium foil as negativeelectrode and pouch material as encapsulation, were used as reference to full cell data. Electrochemicalanalysis of full and half cells combined with material analysis showed to be a powerful method toidentify ageing mechanisms in this type of commercial cells. The calendar-aged cell showedinsignificant ageing while the cycle-aged cell showed noticeable loss of positive electrode activematerial and loss of cyclable lithium, but only minor loss of negative electrode active material. Theresults imply that Li4Ti5O12 negative electrode material is a good alternative to other materials if highenergy density is not the primary goal.

  • 225.
    Svens, Pontus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. Scania CV AB, Sweden .
    Eriksson, Rickard
    Hansson, Jörgen
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Gustafsson, Torbjörn
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Analysis of aging of commercial composite metal oxide - Li 4Ti5O12 battery cells2014Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 270, s. 131-141Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Commercial battery cells with Li4Ti5O12 negative electrode and composite metal oxide positive electrode have been analyzed with respect to aging mechanisms. Electrochemical impedance spectroscopy (EIS), differential capacity analysis (dQ/dV), differential voltage analysis (dV/dQ) and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) were used to identify different ageing mechanisms such as lithium inventory loss, loss of active electrode material and surface film growth. The active material of the positive electrode was also examined by X-ray diffraction (XRD). Aging mechanisms were studied for both calendar-aged and cycle-aged cells. Data from half cells prepared from post mortem harvested electrode material, using lithium foil as negative electrode and pouch material as encapsulation, were used as reference to full cell data. Electrochemical analysis of full and half cells combined with material analysis showed to be a powerful method to identify aging mechanisms in this type of commercial cells. The calendar-aged cell showed insignificant aging while the cycle-aged cell showed noticeable loss of positive electrode active material and loss of cyclable lithium, but only minor loss of negative electrode active material. The results imply that Li4Ti5O12 negative electrode material is a good alternative to other materials if high energy density is not the primary goal.

  • 226.
    Svens, Pontus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hellqvist Kjell, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Tengstedt, Carl
    Flodberg, Göran
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Li-Ion Pouch Cells for Vehicle Applications-Studies of Water Transmission and Packing Materials2013Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 6, nr 1, s. 400-410Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study includes analysis of encapsulation materials from lithium-ion pouch cells and water vapour transmission rate (WVTR) measurements. WVTR measurements are performed on both fresh and environmentally stressed lithium-ion pouch cells. Capacity measurements are performed on both the fresh and the environmentally stressed battery cells to identify possible influences on electrochemical performance. Preparation of the battery cells prior to WVTR measurements includes opening of battery cells and extraction of electrode material, followed by resealing the encapsulations and adhesively mounting of gas couplings. A model describing the water diffusion through the thermal welds of the encapsulation are set up based on material analysis of the encapsulation material. Two WVTR equipments with different type of detectors are evaluated in this study. The results from the WVTR measurements show how important it is to perform this type of studies in dry environment and apply a rigorous precondition sequence before testing. Results from modelling confirm that the WVTR method has potential to be used for measurements of water diffusion into lithium-ion pouch cells. Consequently, WVTR measurements should be possible to use as a complement or alternative method to for example Karl Fisher titration.

  • 227.
    Svens, Pontus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindström, Johan
    Scania CV AB, Södertälje, Sweden.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    HEV lithium-ion battery testing and driving cycle analysis in a heavy-duty truck field study2012Inngår i: ECS Transactions: Volume 41, Issue 32, 2012, 2012, s. 12-26Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents early results from an ongoing field test of HEV batteries on heavy-duty trucks. The presented results focus on the parameters that can affect ageing, such as SOC and power. The goal with this study is to correlate battery ageing to battery usage. Commercial LMO/LTO lithium-ion battery cells were tested onboard four Scania trucks. The test equipment was designed for this type of HEV battery testing on conventional vehicles by emulating an HEV environment. This concept allows unobtrusive and low cost testing of battery cells under realistic conditions. Each truck is equipped with test equipment containing one cycled battery cell and one calendar aged cell. The hybrid strategy used in this test allows battery power and SOC to vary depending on drive pattern within certain limits. Battery capacity and resistance is measured periodically and this makes it possible to receive information about battery ageing without bringing the cells to the lab.

  • 228.
    Svens, Pontus
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindström, Johan
    Scania CV AB, Södertälje, Sweden.
    Gelin, Olle
    Scania CV AB, Södertälje, Sweden.
    Behm, Mårten
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Novel Field Test Equipment for Lithium-Ion Batteries in Hybrid Electrical Vehicle Applications2011Inngår i: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 4, nr 5, s. 741-757Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Lifetime testing of batteries for hybrid-electrical vehicles (HEV) is usually performed in the lab, either at the cell, module or battery pack level. Complementary field tests of battery packs in vehicles are also often performed. There are, however, difficulties related to field testing of battery-packs. Some examples are cost issues and the complexity of continuously collecting battery performance data, such as capacity fade and impedance increase. In this paper, a novel field test equipment designed primarily for lithium-ion battery cell testing is presented. This equipment is intended to be used on conventional vehicles, not hybrid vehicles, as a cheaper and faster field testing method for batteries, compared to full scale HEV testing. The equipment emulates an HEV environment for the tested battery cell by using real time vehicle sensor information and the existing starter battery as load and source. In addition to the emulated battery cycling, periodical capacity and pulse testing capability are implemented as well. This paper begins with presenting some background information about hybrid electrical vehicles and describing the limitations with today's HEV battery testing. Furthermore, the functionality of the test equipment is described in detail and, finally, results from verification of the equipment are presented and discussed.

  • 229. Tondi, Gianluca
    et al.
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. SP Tecnical Research Institute of Sweden, Stockholm, Sweden .
    Leijonmarck, Simon
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Trey, Stacy
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. SP Tecnical Research Institute of Sweden, Stockholm, Sweden .
    Tannin based foams modified to be semi-conductive: Synthesis and characterization2015Inngår i: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 78, s. 488-493Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The objective of this study was to modify highly insulative and lightweight biorenewable foam thermosets to be semi-conductive for primarily building material applications. The foams were formed and then posttreated with in-situ polymerization of polyaniline, both doped and undoped, adsorbing and possibly absorbing (observed by SEM-EDX) to the foam structure at levels of 100-120 wt%. The modified tannin foams were shown to be semi-conductive in comparison to the highly insulative structure prior to polyaniline modification. While the 50% protonated polyaniline modified foams, or doped foams, had a higher conductivity than the undoped polyaniline modified foams, the acid used in fabrication of the foams provided some degree of conductivity to the undoped PANI modified foams. Moreover, the modified foams had an increased volume of 15% after modification, were more sensitive to moisture, and the polyaniline did not affect the degradation temperature of the foams.

  • 230. van Wuellen, Leo
    et al.
    Sofina, N.
    Hildebrandt, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Muehle, Claus
    Jansen, M.
    NMR studies of cation transport in the crystalline ion conductors MCF3SO3 (M = Li, Na) and Li7TaO62006Inngår i: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 177, nr 19-25, s. 1665-1672Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this contribution we present studies on the mechanism of ion transport in crystalline solid electrolytes employing a range of different solid state nuclear magnetic resonance (NMR) experiments. The first part is devoted to the elucidation of a possible correlation of cation transport and anion reorientation in the dynamically disordered rotor phases of alkali trifluoromethane sulfonates MCF3SO3 (M = Li, Na) employing Li-7, C-13, O-17 and Na-23 NMR line shape analysis, whereas the second part focuses on the tracking of cation diffusion pathways in the hexaoxometalate Li7TaO6 utilizing Li-6 1D and 2D exchange MAS NMR approaches.

  • 231. van Wullen, L.
    et al.
    Hildebrandt, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Jansen, M.
    Cation mobility and anion reorientation in lithium trifluoromethane sulfonate, LiCF3SO32005Inngår i: Solid State Ionics, ISSN 0167-2738, E-ISSN 1872-7689, Vol. 176, nr 15-16, s. 1449-1456Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a detailed study of the dynamic processes present in the lithium ionic conductor lithium trifluoromethane sulfonate, LiCF3SO3. Using Li-7-, O-17- and F-19 solid state NMR line shape analysis and T-1-NMR, the anionic (CF3- and SO3-reorientation) and cationic dynamics (Li motion) could be studied separately. Whereas the CF3- and SO3 reorientations are active at ambient temperatures and not correlated to the cation motion, the NMR data indicate a strong correlation between the Li motion and the reorientation of the complete triflate anion.

  • 232.
    Vernersson, Thomas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Mass transport in proton conducting membranes for the direct methanol fuel cell2005Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 233.
    Vernersson, Thomas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lafitte, B.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Jannasch, P.
    A sulfophenylated polysulfone as the DMFC electrolyte membrane - an evaluation of methanol permeability and cell performance2006Inngår i: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 6, nr 5, s. 340-346Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A sulfophenylated polysulfone (PSU-sph), carrying 0.8 sulfonic acid units per repeating unit of the polymer, is evaluated as a membrane electrolyte for DMFC applications. The liquid uptake, methanol transport characteristics, electrolyte conductivity, and fuel cell performance are investigated. The methanol transport and DMFC performance results are compared to those of Nafion(R) 117. The PSU-sph membrane investigated shows superior qualities with regard to methanol crossover, with a methanol permeability of approximately 25% compared to that of Nafion(R). The conductivity measured to be 15% compared to that of Nafion(R). However, this could not fully account for the internal resistance of the cell, implying that the contact resistance between the electrodes and electrolyte is higher when PSU-sph is used, probably because the electrodes are developed for use with Nafion(R) membranes. The stability of the PSU-sph membrane seems promising, with very low degradation observed over a period of 72 hours. It was concluded that although the mass transport properties of the PSU-sph membrane sample investigated were superior, it could not match the performance of Nafion(R) 117 in a DMFC application. However, a higher degree of sulfonation may have a significant positive effect on cell performance. The results also showed that a fully intergrated MEA is needed to fully assess new membrane materials.

  • 234.
    Vernersson, Thomas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    A model for mass transport in the electrolyte membrane of a DMFC2007Inngår i: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 37, nr 4, s. 429-438Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A steady state model for multicomponent mass transport was derived for the direct methanol fuel cell membrane. Data for development and validation of the model was taken both from experiments and literature. The experimental data was collected in a polarisation cell, where mass transport of methanol across the electrolyte membrane was measured through a potentiostatic method. The results from modelling and experiments showed good agreement. The model was capable of describing the non-linear response in mass transport to increased methanol feed concentration. The model also accurately described the change in membrane conductivity with methanol concentration. From the model transport equations, it was also possible to derive some characteristic transport parameters, namely the electro osmotic drag of both water and methanol, diffusive drag of water and methanol, and effective, concentration dependent, diffusion coefficients for methanol and water.

  • 235.
    von Kraemer, Sophie
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Membrane Electrode Assemblies Based on Hydrocarbon Ionomers and New Catalyst Supports for PEM Fuel Cells2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The proton exchange membrane fuel cell (PEMFC) is a potential electrochemicalpower device for vehicles, auxiliary power units and small-scale power plants. In themembrane electrode assembly (MEA), which is the core of the PEMFC single cell,oxygen in air and hydrogen electrochemically react on separate sides of a membraneand electrical energy is generated. The main challenges of the technology are associatedwith cost and lifetime. To meet these demands, firstly, the component expensesought to be reduced. Secondly, enabling system operation at elevated temperatures,i.e. up to 120 °C, would decrease the complexity of the system and subsequentlyresult in decreased system cost. These aspects and the demand for sufficientlifetime are the strong motives for development of new materials in the field.In this thesis, MEAs based on alternative materials are investigatedwith focus on hydrocarbon proton-conducting polymers, i.e. ionomers, and newcatalyst supports. The materials are evaluated by electrochemical methods, such ascyclic voltammetry, polarisation and impedance measurements; morphological studiesare also undertaken. The choice of ionomers, used in the porous electrodes andmembrane, is crucial in the development of high-performing stable MEAs for dynamicoperating conditions. The MEAs are optimised in terms of electrode compositionand preparation, as these parameters influence the electrode structure andthus the MEA performance. The successfully developed MEAs, based on the hydrocarbonionomer sulfonated polysulfone (sPSU), show promising fuel cell performancein a wide temperature range. Yet, these membranes induce mass-transportlimitations in the electrodes, resulting in deteriorated MEA performance. Further,the structure of the hydrated membranes is examined by nuclear magnetic resonancecryoporometry, revealing a relation between water domain size distributionand mechanical stability of the sPSU membranes. The sPSU electrodes possessproperties similar to those of the Nafion electrode, resulting in high fuel cell performancewhen combined with a high-performing membrane. Also, new catalystsupports are investigated; composite electrodes, in which deposition of platinum(Pt) onto titanium dioxide reduces the direct contact between Pt and carbon, showpromising performance and ex-situ stability. Use of graphitised carbon as catalystsupport improves the electrode stability as revealed by a fuel cell degradation study.The thesis reveals the importance of a precise MEA developmentstrategy, involving a broad methodology for investigating new materials both as integratedMEAs and as separate components. As the MEA components and processesinteract, a holistic approach is required to enable successful design of newMEAs and ultimately development of high-performing low-cost PEMFC systems.

  • 236.
    von Kraemer, Sophie
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lafitte, Benoit
    Polymer and Materials Chemistry, Department of Chemistry, Lund University.
    Puchner, Mario
    Polymer and Materials Chemistry, Department of Chemistry, Lund University.
    Jannasch, Patric
    Polymer and Materials Chemistry, Department of Chemistry, Lund University.
    Substitution of Nafion with Sulfonated Polysulfone in Membrane-Electrode Assembly Components for 60-120 °C PEMFC Operation2008Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 155, nr 10, s. B1001-B1007Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To investigate the influence of sulfonated polysulfone (sPSU) in membrane–electrode assemblies (MEAs), sPSU-based gas diffusion electrodes (GDEs) and sPSU membranes were studied both as complete MEAs and as separate components in assembled MEAs at 60–120°C. The complete sPSU MEAs showed mass-transport limitations, irrespective of ion exchange capacity, compared to Nafion MEAs. Cyclic voltammetry and low-current impedance analysis revealed comparable electrochemically active catalyst areas and kinetic properties in the sPSU and Nafion GDEs, while gas-crossover measurements showed a lower gas permeability in sPSU compared to Nafion. The sPSU and Nafion GDEs, deposited on Nafion membranes, possessed comparable fuel cell characteristics at 120°C and 100% relative humidity, demonstrating no considerable limitations when utilizing sPSU as an alternative to Nafion in the GDE, thus implying a sufficient gas permeability in the sPSU GDE at high humidity. Furthermore, the results clearly showed that the sPSU membrane induced mass-transport limitations in both sPSU and Nafion GDEs, revealing that the limiting factor of the sPSU MEAs was primarily the membrane-induced cathode flooding due to unoptimized water transport in the sPSU membrane. The work demonstrates the importance of electrochemical evaluation of ionomers as complete MEAs and as separate components when studying MEAs.

  • 237.
    von Kraemer, Sophie
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Puchner, Mario
    Division of Polymer and Materials Chemistry, Lund University.
    Jannasch, Patric
    Division of Polymer and Materials Chemistry, Lund University.
    Lundblad, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Erratum: Gas Diffusion Electrodes and Membrane Electrode Assemblies Based on a Sulfonated Polysulfone for High-Temperature PEMFC [J. Electrochem. Soc., 153, A2077 (2006)]2006Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 153, nr 12, s. L35-L35Artikkel i tidsskrift (Fagfellevurdert)
  • 238.
    von Kraemer, Sophie
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Puchner, Mario
    Division of Polymer and Materials Chemistry, Lund University.
    Jannasch, Patric
    Division of Polymer and Materials Chemistry, Lund University.
    Lundblad, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Gas Diffusion Electrodes and Membrane Electrode Assemblies Based on a Sulfonated Polysulfone for High-Temperature PEMFC2006Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 153, nr 11, s. A2077-A2084Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Membrane electrode assemblies MEAs with a sulfonated polysulfone sPSU as the proton-conducting phase were fuel cellevaluated at varying temperatures in over-humidified conditions. The sPSU was prepared by a direct polycondensation involvinga commercially available sulfonated naphthalene diol monomer. The gas diffusion electrodes GDEs and MEAs were successfullyfabricated and a thorough morphological study was subsequently carried out on GDEs with varying sPSU contents and inksolvents. The scanning electron microscopy and porosimetry studies revealed highly porous GDE morphologies at sPSU contentsbelow 20 wt %. Double-layer capacitance measurements showed an almost fully sPSU-wetted electronic phase when the sPSUcontent was 10 wt %. The MEAs were prepared by applying the GDEs directly onto sPSU membranes. MEAs with a total Ptloading of 0.2 mg/cm2 were successfully fuel cell operated at 120°C. The MEAs showed mass-transport limitations in the rangeof 600–800 mA/cm2, most probably caused by abundant water due to the overhumidified measuring conditions. The low resistanceof the MEAs indicated a well-integrated structure between the GDEs and the membrane.

  • 239.
    von Kraemer, Sophie
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Sagidullin, Alexandr I.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Furó, István
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Persson, E.
    Polymer and Materials Chemistry, Department of Chemistry, Lund University.
    Jannasch, P.
    Polymer and Materials Chemistry, Department of Chemistry, Lund University.
    Pore Size Distribution and Water Uptake in Hydrocarbon and Perfluorinated Proton-Exchange Membranes as Studied by NMR Cryoporometry2008Inngår i: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 8, nr 3-4, s. 262-269Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sulfonated polysulfone (sPSU) membranes were analysed by nuclear magnetic resonance (NMR) cryoporometry, conventional gravimetric water uptake measurements as well as by differential scanning calorimetry (DSC). NMR cryoporometry is based on the relation between the pore size and the melting point depression of the pore-filling liquid, i.e. water in fuel cell membranes; thus providing a relation between the amount of molten water and the temperature shift, i.e. the pore size, in hydrated membranes. An sPSU membrane with high ion-exchange capacity (IEC 1.45 mequiv. g –1) possessed a significant amount of large pores after hydrothermal pretreatment at 80

  • 240.
    von Kraemer, Sophie
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wikander, Kjell
    Applied Surface Chemistry, Department of Chemical and Biological Engineering, Chalmers University of Technology.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lundblad, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Palmqvist, Anders E. C.
    Applied Surface Chemistry, Department of Chemical and Biological Engineering, Chalmers University of Technology.
    Evaluation of TiO2 as catalyst support in Pt-TiO2/C composite cathodes for the proton exchange membrane fuel cell2008Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 180, nr 1, s. 185-190Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Anatase TiO2 is evaluated as catalyst support material in authentic Pt-TiO2/C composite gas diffusion electrodes (GDEs), as a different approach in the context of improving the proton exchange membrane fuel cell (PEMFC) cathode stability. A thermal stability study shows high carbon stability as Pt nanoparticles are supported on TiO2 instead of carbon in the Pt-TiO2/C composite material, presumably due to a reduced direct contact between Pt and C. The performance of Pt-TiO2/C cathodes is investigated electrochemically in assembled membrane-electrode assemblies (MEAs) considering the added carbon fraction and Pt concentration deposited on TiO2. The O-2 reduction current for the Pt-TiO2 alone is expectedly low due to the low electronic conductivity in bulk TiO2. However, the Pt-TiO2/C composite cathodes show enhanced fuel cell cathode performance with growing carbon fraction and increasing Pt concentration deposited on TiO2. The proposed reasons for these observations are improved macroscopic and local electronic conductivity, respectively. Electron micrographs of fuel cell tested Pt-TiO2/C composite cathodes illustrate only a minor Pt migration in the Pt-TiO2/C structure, in which anatase TiO2 is used as Pt support. On the whole, the study demonstrates a stable Pt-TiO2/C Composite material possessing a performance comparable to conventional Pt-C materials when incorporated in a PEMFC cathode.

  • 241.
    Wallmark, Cecilia
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Enback, Sofia
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Rissanen, Markku
    Alvfors, Per
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Integration of the components in a small-scale stationary research PEFC system2006Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 159, nr 1, s. 613-625Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    With the primary aim of studying the integration of the components in a polymer electrolyte fuel cell (PEFC) system, a test facility for research on small-scale stationary PEFC systems has been built at the Royal Institute of Technology in Stockholm. In this paper the PEFC system with control system and measurement equipment is described in detail together with the first experimental data. The research PEFC system has a flexible configuration and allows fuel cell systems from approximately 0.2 to 4 kW(el) to be tested. The main feed is natural gas, but the fuel cell stack can also be run on humidified hydrogen. The main limitation in the system integration is the power mismatch of the fuel cell stack and fuel processor. The paper begins with a literature review of research/test PEFC systems.

  • 242. Wesselmark, M.
    et al.
    Wickman, B.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    The impact of iridium on the stability of platinum on carbon thin-filmmodel electrodes2013Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 111, s. 152-159Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Increasing the stability and lifetime of the electrodes is one of the most important factors in order to realise a large scale use of polymer electrolyte membrane fuel cells (PEMFC). By using well-defined thin-film model electrodes, the stability of Pt and Pt on Ir were examined as cathode catalysts in a single cell PEMFC setup. The electrodes were fabricated by evaporating thin layers of Pt and Pt on Ir onto the microporous layer of a gas diffusion layer. The amount of Pt deposited was equivalent to 3 nm (about 6.3 mu g cm(-2)) and the amount of Ir was varied between 1.5 nm and 20 nm (between 3.4 mu g cm(-2) and 45.3 mu g cm(-2)). All samples with Ir showed an increased stability over samples with sole Pt during cyclic corrosion test between 0.6V and 1.2V vs. the reversible hydrogen electrode. For thin layers of Ir, the initial activity for the oxygen reduction reaction was equal to or superior to that of sole Pt but for thicker Ir films it was somewhat lower. Hydrogen underpotential deposition and CO stripping were used to estimate the electrochemical surface area during the experiments and physical characterisation using scanning electron microscopy and X-ray photoelectron spectroscopy were used to determine the structure of the samples. The results suggest that Ir can stabilise Pt in the cathode electrode.

  • 243.
    Wesselmark, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Electrochemical Reactions in Polymer Electrolyte Fuel Cells2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The polymer electrolyte fuel cell converts the chemical energy in a fuel, e.g. hydrogen or methanol, and oxygen into electrical energy. The high efficiency and the possibility to use fuel from renewable sources make them attractive as energy converters in future sustainable energy systems. Great progress has been made in the development of the PEFC during the last decade, but still improved lifetime as well as lowered cost is needed before a broad commercialization can be considered. The electrodes play an important role in this since the cost of platinum used as catalyst constitutes a large part of the total cost for the fuel cell. A large part of the degradation in performance can also be related to the degradation of the porous electrode and a decreased electrochemically active Pt surface.

    In this thesis, different fuel cell reactions, catalysts and support materials are investigated with the aim to investigate the possibility to improve the activity, stability and utilisation of platinum in the fuel cell electrodes.

    An exchange current density, i0, of 770 mA cm-2Pt was determined for the hydrogen oxidation reaction in the fuel cell with the model electrodes. This is higher than previously found in literature and implies that the kinetic losses on the anode are very small. The anode loading could therefore be reduced without imposing too high potential losses if good mass transport of hydrogen is ensured. It was also shown that the electrochemically active surface area, activity and stability of the electrode can be affected by the support material. An increased activity was observed at higher potentials for Pt deposited on tungsten oxide, which was related to the postponed oxide formation for Pt on WOx. An improved stability was seen for Pt deposited on tungsten oxide and on iridium oxide. A better Pt stability was also observed for Pt on a low surface non-graphitised support compared to a high surface graphitised support. Pt deposited on titanium and tungsten oxide, displayed an enhanced electrochemically active surface area in the cyclic voltammograms, which was explained by the good proton conductivity of the metal oxides. CO-stripping was shown to provide the most reliable measure of the electrochemically active surface area of the electrode in the fuel cell. It was also shown to be a useful tool in characterization of the degradation of the electrodes. In the study of oxidation of small organic compounds, the reaction was shown to be affected by the off transport of reactants and by the addition of chloride impurities. Pt and PtRu were affected differently, which enabled extraction of information about the reaction mechanisms and rate determining steps.

    The polymer electrolyte fuel cell converts the chemical energy in a fuel, e.g. hydrogen or methanol, and oxygen into electrical energy. The high efficiency and the possibility to use fuel from renewable sources make them attractive as energy converters in future sustainable energy systems. Great progress has been made in the development of the PEFC during the last decade, but still improved lifetime as well as lowered cost is needed before a broad commercialization can be considered. The electrodes play an important role in this since the cost of platinum used as catalyst constitutes a large part of the total cost for the fuel cell. A large part of the degradation in performance can also be related to the degradation of the porous electrode and a decreased electrochemically active Pt surface.

    In this thesis, different fuel cell reactions, catalysts and support materials are investigated with the aim to investigate the possibility to improve the activity, stability and utilisation of platinum in the fuel cell electrodes.

    An exchange current density, i0, of 770 mA cm-2Pt was determined for the hydrogen oxidation reaction in the fuel cell with the model electrodes. This is higher than previously found in literature and implies that the kinetic losses on the anode are very small. The anode loading could therefore be reduced without imposing too high potential losses if good mass transport of hydrogen is ensured. It was also shown that the electrochemically active surface area, activity and stability of the electrode can be affected by the support material. An increased activity was observed at higher potentials for Pt deposited on tungsten oxide, which was related to the postponed oxide formation for Pt on WOx. An improved stability was seen for Pt deposited on tungsten oxide and on iridium oxide. A better Pt stability was also observed for Pt on a low surface non-graphitised support compared to a high surface graphitised support. Pt deposited on titanium and tungsten oxide, displayed an enhanced electrochemically active surface area in the cyclic voltammograms, which was explained by the good proton conductivity of the metal oxides. CO-stripping was shown to provide the most reliable measure of the electrochemically active surface area of the electrode in the fuel cell. It was also shown to be a useful tool in characterization of the degradation of the electrodes. In the study of oxidation of small organic compounds, the reaction was shown to be affected by the off transport of reactants and by the addition of chloride impurities. Pt and PtRu were affected differently, which enabled extraction of information about the reaction mechanisms and rate determining steps.

  • 244.
    Wesselmark, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Methanol and formic acid oxidising anodes in zinc electrowinning2006Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Electrowinning is an energy demanding process, in which the electrolysis accounts for the major part of the energy consumption. The anodic reaction in the electrolysis of zinc from sulphate based electrolytes is oxygen evolution, which has a standard potential of 1.23 V at 25 ºC. The lead anodes used in zinc electrowinning today have a high overpotential for oxygen evolution and the operating anode potential is as high as 2 V vs NHE. Since the lead anodes are not stable some of the lead can dissolve and incorporate in the zinc metal on the cathode. The lead anodes are also undesired because of health concerns. By introducing formic acid or methanol oxidation as anode reaction, the anode potential could be lowered significantly. This would reduce the energy consumption and also enable the use of new types of electrodes.

    The general aim of this thesis was to investigate how depolarised anodes for methanol and formic acid oxidation can be used in electrowinning processes.

    Several electrodes were shown to be suitable as anodes in zinc electrowinning. A high activity was obtained with porous electrodes, whereas a platinum coated titanium was the most stable electrode. The choice of electrode will however always be a compromise between activity, stability and costs. All electrodes were deactivated with time and the best method for reactivation tested in this study, was periodic current reversal (PCR).

    An operating procedure was established for methanol and formic acid oxidation on high surface area electrodes, Pt-TySAR®. With the use of PCR at process current density, a potential lower than 0.7 V vs NHE could be maintained for 36 hour in synthetic electrolyte. The use of formic acid oxidation resulted in lower potentials than the use of methanol oxidation.

    The activities for methanol and formic acid oxidation in industrial electrolyte were very low and chloride impurities were shown to cause the major part of the activity reduction. Even small amounts of chloride (10-6-10-5 M) affected the activity of the electrodes. The chloride impurities are considered as the main problem to overcome in order to introduce the oxidation of formic acid or methanol in the zinc electrowinning process.

  • 245.
    Wesselmark, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Degradation studies of PEMFC cathodes based on different types of carbon2009Inngår i: ECS Transactions, 2009, Vol. 25, nr 1 PART 2, s. 1241-1250Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this study different accelerated degradation tests were used evaluating three different carbon supports as well as a thin model electrode. Cyclic ADTs, by 1000 cycles beween 0.6 and 1.2 V in nitrogen, did not degrade the porous electrodes to any larger extent in terms of oxygen reduction activity, whereas a significant loss of electrochemical surface area was seen, often more than 50%. Potentiostatic hold at 1.4 V during 3 h, did not permanently degrade the electrodes but instead an improved activity was obtained after rest during night. A correlation of increase in double layer capacitance and improved performance was seen and believed to be caused by the good proton conductivity of carbon surface oxides. CO-stripping peaks revealed that the humidity and wetting of Nafion™ may have caused the observed temporary changes during the potentiostatic hold. ©The Electrochemical Society.

  • 246.
    Wesselmark, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Methanol and formic acid oxidation in zinc electrowinning under process conditions2008Inngår i: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 38, nr 1, s. 17-24Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The possibility of using methanol or formic acid oxidation as the anode process in zinc electrowinning was examined. The activity for methanol and formic acid oxidation on Pt coated high surface area electrodes was investigated over 36 h, at a current density used in industry. The activity could be maintained at a constant potential level in a synthetic electrowinning electrolyte if the current was reversed for short periods. During the tests, the anode potential was, more than 1.2 V below the potential for the oxygen evolving lead anodes used in modern zinc electrowinning. The lowered anode potential would lead to a significant energy reduction. However, tests in industrial electrolyte resulted in a very low activity for both methanol and formic acid oxidation. The low activity was shown to be caused mainly by chloride impurities. A reduction of the chloride content below 10(-5) M is needed in order to obtain sufficient activity for methanol oxidation on Pt for use in zinc electrowinning. Pt and PtRu electrodes were compared regarding their activity for methanol oxidation and the latter was shown to be more affected by chloride impurities. However, at a potential of 0.7 V vs NHE, with a chloride content of 10(-4) M, formic acid oxidation on PtRu gives the highest current density.

  • 247.
    Wesselmark, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Methanol oxidation as anode reaction in zinc electrowinning2005Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 152, nr 11, s. D201-D207Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, different types of Pt- and PtRu-based electrodes were compared regarding their activity and stability for methanol oxidation in an acid zinc sulfate solution. The lead anodes used in zinc electrowinning today are not dimensionally stable and have a high overvoltage for oxygen evolution. By replacing the oxygen evolution in sulfate-based electrolytes with methanol oxidation, the anode potential could be significantly lowered. This would reduce the energy consumption and also enable the use of new and more stable types of electrodes. The activities of the electrodes studied were found sufficient for electrowinning. The highest activity was obtained with porous PtRu, while platinized titanium was the most stable electrode. All electrodes were deactivated with time, and the deactivation rate of PtRu was influenced by mass transport. The dominating reaction mechanism seemed to be different on Pt and on PtRu. Due to deactivation of the electrodes with time, a reactivation method was needed. The best method tested in this study was to periodically reverse the current. After assessing the electrodes with respect to important properties, the platinized titanium electrode was considered to be most suitable for use in electrowinning processes.

  • 248.
    Wesselmark, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wickman, B.
    Chalmers University of Technology.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Electrochemical performance and stability of thin film electrodes with metal oxides in polymer electrolyte fuel cells2010Inngår i: Electrochimica Acta, ISSN 0013-4686, Vol. 55, nr 26, s. 7590-7596Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thin film electrodes are prepared by thermal evaporation of nanometer thick layers of metal oxide and platinum on a gas diffusion layer (GDL), in order to evaluate different metal oxides' impact on the activity and stability of the platinum cathode catalyst in the polymer electrolyte fuel cell. Platinum deposited on tin, tantalum, titanium, tungsten and zirconium oxide is investigated and the morphology and chemistry of the catalysts are examined with scanning electron microscopy and X-ray photoelectron spectroscopy. Cyclic sweeps in oxygen and nitrogen are performed prior and after potential cycling degradation tests. Platinum seems to disperse better on the metal oxides than on the GDL and increased electrochemically active surface area (ECSA) of platinum is observed on tin, titanium and tungsten oxide. A thicker layer metal oxide results in a higher ECSA. Platinum deposited on tungsten performs better than sole platinum in the polarisation curves and displays higher Tafel slopes at higher current densities than all other samples. The stability does also seem to be improved by the addition of tungsten oxide, electrodes with 3 nm platinum on 3, 10 and 20 nm tungsten oxide, performs better than all other electrodes after the accelerated degradation tests.

  • 249.
    Wesselmark, Maria
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wickman, B.
    Chalmers University of Technology.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hydrogen oxidation reaction on thin platinum electrodes in the polymer electrolyte fuel cell2010Inngår i: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 12, nr 11, s. 1585-1588Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method for measuring the kinetics of the hydrogen oxidation reaction (HOR) in a fuel cell under enhanced mass transport conditions is presented. The measured limiting current density was roughly 1600 mA cmPt− 2, corresponding to a rate constant of the forward reaction in the Tafel step of 0.14 mol m− 2 s− 1 at 80 °C and 90% RH. The exchange current density for the HOR was determined using the slope at low overvoltages and was found to be 770 mA cmPt− 2. The high values for the limiting and exchange current densities suggest that the Pt loading in the anode catalyst can be reduced further without imposing measurable voltage loss.

  • 250.
    Wickman, Björn
    et al.
    Competence Centre for Catalysis, Department of Applied Physics, Chalmers.
    Wesselmark, Maria
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Tungsten oxide in polymer electrolyte fuel cell: A thin-film model electrode study2011Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 56, nr 25, s. 9496-9503Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thin films of WO(x) and Pt on WO(x) were evaporated onto the microporous layer of a gas diffusion layer (GDL) and served as model electrodes in the polymer electrolyte fuel cell (PEFC) as well as in liquid electrolyte measurements. In order to study the effects of introducing WO, in PEFC electrodes, precise amounts of WO(x) (films ranging from 0 to 40 nm) with or without a top layer of Pt (3 nm) were prepared. The structure of the thin-film model electrodes was characterized by scanning electron microscopy and X-ray photoelectron spectroscopy prior to the electrochemical investigations. The electrodes were analyzed by cyclic voltammetry and the electrocatalytic activity for hydrogen oxidation reaction (HOR) and CO oxidation was examined. The impact of Nafion in the electrode structure was examined by comparing samples with and without Nafion solution sprayed onto the electrode. Fuel cell measurements showed an increased amount of hydrogen tungsten bronzes formed for increasing WO(x) thicknesses and that Pt affected the intercalation/deintercalation process, but not the total amount of bronzes. The oxidation of pre-adsorbed CO was shifted to lower potentials for WO(x) containing electrodes, suggesting that Pt-WO(x) is a more CO-tolerant catalyst than Pt. For the HOR. Pt on thicker films of WO(x) showed an increased limiting current, most likely originating from the increased electrochemically active surface area due to proton conductivity and hydrogen permeability in the WO(x) film. From measurements in liquid electrolyte it was seen that the system behaved very differently compared to the fuel cell measurements. This exemplifies the large differences between the liquid electrolyte and fuel cell systems. The thin-film model electrodes are shown to be a very useful tool to study the effects of introducing new materials in the PEFC catalysts. The fact that a variety of different measurements can be performed with the same electrode structure is a particular strength.

23456 201 - 250 of 282
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