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  • 51.
    Farnum, Byron H.
    et al.
    Johns Hopkins University.
    Gardner, James M.
    Johns Hopkins University.
    Meyer, Gerald J.
    Johns Hopkins University.
    Flash-Quench Technique Employed To Study the One-Electron Reduction of Triiodide in Acetonitrile: Evidence for a Diiodide Reaction Product2010Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 49, nr 22, s. 10223-10225Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The one-electron reduction of triiodide (I3?) by a reduced ruthenium polypyridyl compound was studied in an acetonitrile solution with the flash-quench technique. Reductive quenching of the metal-to-ligand charge-transfer excited state of [RuII(deeb)3]2+ by iodide generated the reduced ruthenium compound [RuII(deeb?)(deeb)2]+ and diiodide (I2??). The subsequent reaction of [RuII(deeb?)(deeb)2]+ with I3? indicated that I2?? was a product that appeared with a second-order rate constant of (5.1 ± 0.2) ? 109 M?1 s?1. After correction for diffusion and some assumptions, Marcus theory predicted a formal potential of ?0.58 V (vs SCE) for the one-electron reduction of I3?. The relevance of this reaction to solar energy conversion is discussed.

  • 52.
    Fonoll Almansa, Xavier
    KTH, Skolan för kemivetenskap (CHE). KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Innovative biomass fuelled SOFC's for polygeneration2011Independent thesis Advanced level (degree of Master (One Year)), 30 poäng / 45 hpOppgave
    Abstract [en]

    The  supply  of  energy  and  the  protection  of  the  environment  have  been  two  of  the most  important problems  to have affected mankind  in  recent decades.The waste management  is become a very  crucial environmental problem in the world, due to the ever increasing amount of waste material, domiciliary and industrial, generated. The main strategies for the waste management are the protection of the environment and used to produce energy. 

    Lignin, the second most abundant component besides cellulose in biomass. In this study,  lignosulfonate, is used as fuel in the solid oxide fuel cell to produce a power and heat, which is a byproducts from the wood pulp using sulfite pulping. To enhance the performance and conductivity of the biomass based fuel cell, the lignin was treated with hydroxides (Li/K) and chlorides (Fe2Cl3) at different temperature 200 -500 °C.  The maximum obtained power density was about 20 mW/cm2. And the calculated electrical efficiency of the cell was about 30%.   Also,  this kind of biomass fuel was used  in single component fuel cell and  results were compared with three components fuel cell.  The phase analysis, microstructure and conductivity of lignin was analysed by XRD, SEM and AC impedance technique.  It has been concluded that a sulfonated  lignin from waste of the paper industry can be used  as a energy

    sources with fuel cell operation.

  • 53. Forsberg, J.
    et al.
    Hedberg, Jonas
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Nordgren, J.
    Duda, L. C.
    The Initial Stages of Atmospheric Corrosion of Iron in a Saline Environment Studied with Time-Resolved In Situ X-Ray Transmission Microscopy2010Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, nr 3, s. C110-C115Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated atmospheric corrosion of a 50 nm layer of iron covered with a thin layer of NaCl by in situ X-ray transmission spectromicroscopy. We find that upon its deliquescence, a small part of the NaCl layer is rapidly transformed into a sodium oxide (NaOH) species. A large part of the sodium and chlorine ions forms a concentrated solution on the iron surface and becomes segregated, whereby the sodium ions appear stationary and passive during further corrosion progression. In contrast, the chlorine ions appear highly mobile and become concentrated at and travel with the corrosion front, apparently acting as a corrosion catalyst. The corrosion front progression is partly of filiform and partly of radial type. The early iron corrosion products (chloride-containing oxyhydroxides) are short-lived (for some hours) and undergo a transformation as the corrosion front sweeps by from a chlorinated species to a less chlorinated species.

  • 54.
    Freys, Jonathan C.
    et al.
    Uppsala University.
    Gardner, James M.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    D'Amario, Luca
    Uppsala University.
    Brown, Allison M.
    Uppsala University.
    Hammarström, Leif
    Uppsala University.
    Ru-based donor-acceptor photosensitizer that retards charge recombination in a p-type dye-sensitized solar cell2012Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, nr 42, s. 13105-13111Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the synthesis and characterization of a donor-acceptor ruthenium polypyridyl complex as a photosensitizer for p-type dye-sensitized solar cells (DSSCs). The electrochemical, photophysical, and photovoltaic performance of two ruthenium-based photosensitizers were tested in NiO-based DSSCs; bis-(2,2'-bipyridine-4,4'-dicarboxylic acid)(2)N-(1,10-phenanthroline)-4-nitronaphthalene-1,8-dicarboximide ruthenium(ii), ([Ru(dcb)(2)(NMI-phen)](PF(6))(2)) and tris-(2,2'-bipyridine-4,4'-dicarboxylic acid)(3) ruthenium(ii), [(Ru(dcb)(3))Cl(2)]. The presence of an electron-accepting group, 4-nitronaphthalene-1,8-dicarboximide (NMI), attached to the phenanthroline of [Ru(dcb)(2)(NMI-phen)](2+) resulted in long-lived charge separation between reduced [Ru(dcb)(2)(NMI-phen)](2+) and NiO valence band holes; 10-50 μs. In the reduced state for [Ru(dcb)(2)(NMI-phen)](2+), the electron localized on the distal NMI group. In tests with I(3)(-)/I(-) and Co(4,4'-di-tert-butyl-bipyridine)(3)(2+/3+) electrolytes, [Ru(dcb)(2)(NMI-phen)](2+) outperformed [Ru(dcb)(3)](2+) in solar cell efficiency in devices. A record APCE (25%) was achieved for a ruthenium photosensitizer in a p-type DSSC. Insights on photosensitizer regeneration kinetics are included.

  • 55.
    Gamstedt, Helene
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Hagfeldt, Anders
    Physical Chemistry, Uppsala University.
    Kloo, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Photoelectrochemical studies of ionic liquid-containing solar cells sensitized with different polypyridyl-ruthenium complexes2009Inngår i: Polyhedron, ISSN 0277-5387, E-ISSN 1873-3719, Vol. 28, nr 4, s. 757-762Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The efficiency of dye-sensitized nanocrystalline solar cells containing ionic liquids, composed of organic sulfonium or imidazolium iodides, or a standard organic-liquid-based electrolyte was studied, while using sensitizers based on different polypyridyl-ruthenium complexes. The dyes N-719, [cis-Ru(II)(H(2)dcbpy)(2)(NCS)(2)(TBA)(2)] and Z-907, [cis-Ru(II)(H(2)dcbpy)(dnbpy)(NCS)(2), Z-907 having a more hydrophobic character. as well as a bidentate beta-diketonato complex, [(dcbpy)(2)Ru(acetylacetonate)]Cl-, was studied. Solar cells sensitized with the dye N-719 were more efficient than the Z-907 cells, for all electrolytes studied. Adding a co-adsorbent, the amphiphilic hexadecylmalonic acid (HDMA), to Z-907 solar cells containing an organic-liquid electrolyte resulted in increased overall light-to-electricity conversion efficiencies, from 3.7% to 4.0%, (100 W m(-2), AM 1.5). Possibly, this is caused by an insulating hydrophobic barrier formed to suppress unwanted electron losses. By applying TiO2 (P25) nanoparticles, assumed to support electron transfer reactions, to the organic-liquid electrolyte, the conversion efficiency was increased from 4.1% to 4.6% (100 W m(-2), AM 1.5). In 1000 W m(-2) illumination, the highest overall short-circuit current density, 9.3 mA cm(-2), was achieved with the N-719 sensitized cells, with the TiO2 nanocomposite-containing organic-liquid-based electrolyte. For solar cells sensitized with N-719, Z-907 or the beta-diketonato complex, and containing imidazolium or sulfonium iodide ionic liquids, no improvements of the overall conversion efficiency could be noticed at addition of HDMA to the dye or nanoparticles to the electrolyte.

  • 56.
    Gamstedt, Heléne
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Ionic Liquid Electrolytes for Photoelectrochemical Solar Cells2005Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Potential electrolytes for dye-sensitized photoelectrochemical solar cells have been synthesized and their applicability has been investigated. Different experimental techniques were used in order to characterize the synthesized electrolytes, such as elemental analysis, electrospray ionisation/mass spectrometry, cyclic voltammetry, dynamic viscosity measurements, as well as impedance, Raman and NMR spectroscopy. Some crystal structures were characterized by using single crystal X-ray diffraction.

    In order to verify the eligibility of the ionic compounds as electrolytes for photoelectrochemical solar cells, photocurrent density/photovoltage and incident photon-to-current conversion efficiency measurements were performed, using different kinds of light sources as solar simulators. In electron kinetic studies, the electron transport times in the solar cells were investigated by using intensitymodulated photocurrent and photovoltage spectroscopy. The accumulated charge present in the semiconductor was studied in photocurrent transient measurements.

    The ionic liquids were successfully used as solar cell electrolytes, especially those originating from the diethyl and dibutyl-alkylsulphonium iodides. The highest overall conversion efficiency of almost 4 % was achieved by a dye-sensitized, nanocrystalline solar cell using (Bu2MeS)I:I2 (100:1) as electrolyte (Air Mass 1.5 spectrum at 100 W m-2), quite compatible with the standard efficiencies provided by organic solvent-containing cells. Several solar cells with iodine-doped metal-iodidebased electrolytes reached stable efficiencies over 2 %. The (Bu2MeS)I:I2-containing cells showed better long-term stabilities than the organic solvent-based cells, and provided the fastest electron transports as well as the highest charge accumulation.

    Several polypyridyl-ruthenium complexes were tested as solar cell sensitizers. No general improvements could be observed according to the addition of amphiphilic co-adsorbents to the dyes or nanopartices of titanium dioxide to the electrolytes. For ionic liquid-containing solar cells, a saturation phenomena in the short-circuit current densities emerged at increased light intensities, probably due to inherent material transport limitation within the systems.

    Some iodoargentates and -cuprates were structurally characterized, consisting of monomeric or polymeric entities with anionic networks or layers. A system of metal iodide crownether complexes were employed and tested as electrolytes in photoelectrochemical solar cells, though with poorer results. Also, the crystal structure of a copper-iodide-(12-crown-4) complex has been characterized

  • 57.
    Garcia Garcia, Sandra
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    The impact of groundwater chemistry on the stability of bentonite colloids2007Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [sv]

    I det svenska djupförvaret för kärnbränsle ska kompakterad bentonit användas som barriär mellan kopparkapslar med utbränt kärnbränsle och berget. I kontakt med vattenförande sprickor kan bentonitbarriären under vissa omständigheter avge montmorillonitkolloider. Förutom att barriärens egenskaper urholkas pga förlusten av material kan kolloiderna, om de är stabila, underlätta transporten av sorberade radionuklider ut mot biosfären.

    Den här studien fokuserar på att undersöka vilka effekter grundvattenkemin har på montmorillonitkolloiders stabilitet. Grundvattnets sammansättning, pH och jonstyrka, kommer sannolikt att förändras under djupförvarets livslängd, delvis pga inträngandet av glactialt smältvatten. Initialt kommer omgivande berg att värmas upp pga värmealstring från det radioaktiva sönderfallet i det utbrända kärnbränslet. Effekterna av pH, jonstyrka och temperatur på montmorillonitkolloiders stabilitet har analyserats genom att följa hur kolloiderna aggregerar med tiden. Minskningen av partikelkoncentration med tiden mättes med Photon Correlation Spectroscopy (PCS).

    Aggregationsexperimenten visar att, vid ett givet pH och en given temperatur, ökar hastighetskonstanten för aggregation med ökande jonstyrka. Kritiska koaguleringskoncentrationen (CCC) för NaCl och CaCl2 för Na-montmorillonit och Ca-montmorillonit beräknas utifrån ett samband mellan hastighetskonstanterna och jonstyrkan.

    Hastighetskonstanten för aggregation minskar med ökande pH eftersom ytpotentialen ökar. Effekten blir tydligare vid högre jonstyrkor och högre temperaturer, men kan däremot inte observeras vid låga temperaturer.

    Temperatureffekten på bentonitkolloidernas stabilitet är pH-beroende. Vid pH≤4 ökar hastighetskonstanten för kolloidaggregation med ökande temperatur, oavsett jonstyrka.Vid pH≥10 minskar hastighetskonstanten med ökande temperatur. I mellanliggande pH-område minskar hastighetskonstanten för aggregation med ökande temperatur, förutom vid den högsta jonstyrkan, där den ökade. Beräkningar baserade på DLVO-teori matchar de experimentella resultaten.

  • 58.
    García García, Sandra
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Generation, stability and migration of montmorillonite colloids in aqueous systems2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In Sweden the encapsulated nuclear waste will be surrounded by compacted bentonite in the granitic host rock. In contact with water-bearing fractures the bentonite barrier may release montmorillonite colloids that may be further transported in groundwater. If large amounts of material are eroded from the barrier, the buffer functionality can be compromised. Furthermore, in the scenario of a leaking canister, strongly sorbing radionuclides, can be transported by montmorillonite colloids towards the biosphere. This thesis addresses the effects of groundwater chemistry on the generation, stability, sorption and transport of montmorillonite colloids in water bearing rock fractures.

    To be able to predict quantities of montmorillonite colloids released from the bentonite barrier in contact with groundwater of varying salinity, generation and sedimentation test were performed. The aim is first to gain understanding on the processes involved in colloid generation from the bentonite barrier. Secondly it is to test if concentration gradients of montmorillonite colloids outside the barrier determined by simple sedimentation experiments are comparable to generation tests. Identical final concentrations and colloid size distributions were achieved in both types of tests.

    Colloid stability is strongly correlated to the groundwater chemistry. The impact of pH, ionic strength and temperature was studied. Aggregation kinetics experiments revealed that for colloid aggregation rate increased with increasing ionic strength. The aggregation rate decreased with increasing pH. The temperature effect on montmorillonite colloid stability is pH-dependent. At pH≤4, the rate constant for colloid aggregation increased with increasing temperature, regardless of ionic strength. At pH≥10, the aggregation rate constant decreased with increasing temperature. In the intermediate pH interval, the aggregation rate constant decreased with increasing temperature except at the highest ionic strength, where it increased. The relationship between the rate constant and the ionic strength allowed the critical coagulation concentration (CCC) for Na- and Ca-montmorillonite to be determined.

    In order to distinguish the contribution of physical filtration and sorption to colloid retention in transport, the different retention mechanisms were quantified. Sorption on different representative minerals in granite fractures was measured for latex colloids (50, 100, 200 nm) and montmorillonite colloids as a function of ionic strength and pH. Despite of the negative charge in mineral surfaces and colloids, sorption was detected. The sorption is correlated to the mineral point of zero charge and the zeta potential of the colloids, and increases with increasing ionic strength and decreasing pH. In transport experiments with latex colloids in columns packed with fracture filling material, the retention by sorption could clearly be seen. In particular at low flow rates, when the contact time for colloids with the mineral surfaces were the longest, sorption contributed to retention of the transport significantly. The retention of latex colloids appeared to be irreversible in contrary to the reversible montmorillonite colloid retention.

    Generation, stability and sorption of the montmorillonite colloids are controlled by electrostatic forces; hence, the results were in qualitative agreement with DLVO.

  • 59.
    Gavrilov, Nemanja
    et al.
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia..
    Momcilovic, Milan
    Univ Belgrade, Inst Nucl Sci Vinca, POB 522, Belgrade 11000, Serbia..
    Dobrota, Ana S.
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia..
    Stankovic, Dalibor M.
    Univ Belgrade, Inst Nucl Sci Vinca, POB 522, Belgrade 11000, Serbia.;Univ Belgrade, Innovat Ctr, Fac Chem, Studentski Trg 12, Belgrade 11158, Serbia..
    Jokic, Bojan
    Univ Belgrade, Fac Technol & Met, Karnegijeva 4, Belgrade 11000, Serbia.;Univ Arts Belgrade, Fac Appl Arts, Kralja Petra 4, Belgrade 11000, Serbia..
    Babic, Biljana
    Univ Belgrade, Inst Phys, Pregrev 118, Belgrade 11080, Serbia..
    Skorodumova, Natalia
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Uppsala Univ, Dept Phys & Astron, Box 516, S-75120 Uppsala, Sweden..
    Mentus, Slavko V.
    Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia.;Serbian Acad Arts & Sci, Knez Mihajlova 35, Belgrade 11000, Serbia..
    Pašti, Igor
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia..
    A study of ordered mesoporous carbon doped with Co and Ni as a catalyst of oxygen reduction reaction in both alkaline and acidic media2018Inngår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 349, s. 511-521Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The incorporation of trace amounts (< 0.2%) of Co and Ni noticeably enhanced the catalytic activity of nitrogen free ordered mesoporous carbon (OMC) towards oxygen reduction reaction (ORR). (Co,Ni)-doped OMCs were characterized by N-2-adsorption measurements, X-ray powder diffraction, field emission scanning electron microscopy and Raman spectroscopy methods, and their ORR activity was estimated by voltammetry on rotating disk electrode in acidic and alkaline media. (Co,Ni)-doped OMCs show modest activities in acidic media, while the catalytic activity in alkaline media is rather high. The measured activities are compared to the Pt-based and Pt-free ORR catalysts reported in the literature. The number of electrons consumed per O-2 in metal-doped OMCs was found to vary between 2 and 4, which is advantageous in comparison to metal-free OMC. Also, the mass activities of metal-doped OMCs were found to be up to 2.5 times higher compared to that of metal-free OMC. We suggest that the ORR activity is governed by a balance between (i) textural properties, which determine the electrochemically accessible surface of the catalyst and which are influenced by the addition of a metal precursor, and (ii) novel active sites formed upon the introduction of metals into the carbon structure. In particular, our Density Functional Theory calculations suggest that Co and Ni atoms embedded into the single vacancies of graphene can activate the O-2 molecule and contribute to the decomposition of peroxide.

  • 60.
    Geilhufe, Matthias
    et al.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Borysov, Stanislav
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Bouhon, A.
    Balatsky, Alexander V.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Data Mining for Three-Dimensional Organic Dirac Materials: Focus on Space Group2017Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, nr 1, artikkel-id 7298Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We combined the group theory and data mining approach within the Organic Materials Database that leads to the prediction of stable Dirac-point nodes within the electronic band structure of three-dimensional organic crystals. We find a particular space group P212121 (#19) that is conducive to the Dirac nodes formation. We prove that nodes are a consequence of the orthorhombic crystal structure. Within the electronic band structure, two different kinds of nodes can be distinguished: 8-fold degenerate Dirac nodes protected by the crystalline symmetry and 4-fold degenerate Dirac nodes protected by band topology. Mining the Organic Materials Database, we present band structure calculations and symmetry analysis for 6 previously synthesized organic materials. In all these materials, the Dirac nodes are well separated within the energy and located near the Fermi surface, which opens up a possibility for their direct experimental observation.

  • 61.
    Gorlov, Mikhail
    et al.
    KTH, Tidigare Institutioner, Kemi.
    Fischer, Andreas
    KTH, Tidigare Institutioner, Kemi.
    Kloo, Lars A.
    KTH, Tidigare Institutioner, Kemi.
    Synthesis and crystal structures of new palladium(II) - Gallium(III) complexes with bridging halogenide ligands2004Inngår i: Zeitschrift für Anorganische und Allgemeines Chemie, ISSN 0044-2313, E-ISSN 1521-3749, Vol. 630, nr 2, s. 324-326Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The reaction of palladium(H) bromide or palladium(II) iodide with the respective gallium(III) halogenide in the presence of aromatic solvents leads to the formation of palladium(II) tetrabromo- and tetraiodogallate. The compounds are isostructural {monoclinic, C2/m, Pd[GaBr4](2): a=1267(2), b=808(1), c=722(1) pm, beta=94.5(1)degrees; Pd[GaI4](2): a=1363(1), b=849.9(4), c=756.6(7) pm, beta=95.38(3)degrees}. The structures contain mononuclear complexes Pd[GaX4](2), where X- = Br- (1), I- (2). The crystal structures of 1 and 2 were determined by single-crystal X-ray diffraction. Crystals of both compounds turned out to be similarly twinned.

  • 62.
    Gustafsson, Jon Petter
    et al.
    KTH.
    Van Schaik, J. W. J.
    Kleja, Dan Berggren
    KTH.
    Persson, I.
    Mechanisms of iron(III) binding to organic matter and its competitive effect on trace metals2007Inngår i: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 71, nr 15, s. A364-A364Artikkel i tidsskrift (Annet vitenskapelig)
  • 63.
    Gustavsson, John
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Nylen, Linda
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Rare earth metal salts as potential alternatives to Cr(VI) in the chlorate process2010Inngår i: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 40, nr 8, s. 1529-1536Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chromate is today added to industrial chlorate electrolyte, where it forms a thin cathode film of chromium hydroxide that hinders unwanted reduction of hypochlorite and chlorate. The aim of this study was to investigate rare earth metal (REM) ions as an environmentally friendly alternative to the toxic chromate addition. Potential sweeps and iR-corrected polarisation curves were recorded using rotating disc electrodes of iron and gold. Addition of Y(III), La(III) or Sm(III) to 5 M NaCl at 70 A degrees C suppressed hypochlorite reduction. Activation of hydrogen evolution by REM ion addition to 0.5 M NaCl was more significant at 25 A degrees C than at 50 and 70 A degrees C. Increasing the chloride concentration to 5 M had a detrimental effect on this activation. The major problem in replacing chromate with REM salts is the poor solubility of REM ions at normal chlorate process conditions, and therefore REM salts are not a realistic alternative to chromate addition.

  • 64.
    Gustavsson, Marie
    et al.
    Chalmers tekniska högskola, Göteborg.
    Ekström, Henrik
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hanarp, Per
    Chalmers tekniska högskola, Göteborg.
    Eurenius, Lisa
    Chalmers tekniska högskola, Göteborg.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Olsson, Eva
    Chalmers tekniska högskola, Göteborg.
    Kasemo, Bengt
    Chalmers tekniska högskola, Göteborg.
    Thin film Pt/TiO2 catalysts for the polymer electrolyte fuel cell2007Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 163, nr 2, s. 671-678Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Thin film Pt/TiO2 catalysts are evaluated in a polymer electrolyte electrochemical cell. Individual thin films of Pt and TiO2, and bilayers of them, were deposited directly on Nafion membranes by thermal evaporation with varying deposition order and thickness (Pt loadings of 3-6 mu g cm(-2)). Structural and chemical characterization was performed by transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Oxygen reduction reaction (ORR) polarization plots show that the presence of a thin TiO2 layer between the platinum and the Nation increases the performance compared to a Pt film deposited directly on Nation. Based on the TEM analysis, we attribute this improvement to a better dispersion of Pt on TiO2 compared to on Nalion and in addition, substantial proton conduction through the thin Ti02 layer. It is also shown that deposition order and the film thickness affects the performance.

  • 65. Habib, K.
    et al.
    Mohammad, W.
    Karim, F.
    Dutta, Joydeep
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Resistance values of aluminum oxide film in situ during anodization of aluminum by fabry-pérot interferometry2017Inngår i: ECS Transactions, Electrochemical Society Inc. , 2017, nr 10, s. 1221-1229Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A combination of Fabry-Pérot interferometry and the DC electrochemical method have been used for the first time, in situ, to measure the resistance of aluminum oxide films in 2% sulfuric acid solution. Values of the corresponding resistance of the obtained Al2O3 film thickness were determined during anodization of aluminum (Al) in 2% H2SO4. The obtained resistance values were verified by electrochemical impedance spectroscopy (EIS) and holographic interferometry. The corresponding resistance (2.4 x109 Ohms) to the final thickness of the aluminum oxide film was found in an agreement with the resistance value that was measured by holographic interferometry, 2.54x109 Ohms, in 2% H2SO4. On the contrary, the corresponding resistance (2.4 x109 Ohms) to the final thickness of the aluminum oxide film was found twice the value of the resistance that was measured by the electrochemical impedance spectroscopy (EIS), 1.25x109 Ohms, in 2% H2SO4.

  • 66.
    Hedberg, Jonas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Baldelli, Steven
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Molecular Structural Information of the Atmospheric Corrosion of Zinc Studied by Vibrational Spectroscopy Techniques II. Two and Three-Dimensional Growth of Reaction Products Induced by Formic and Acetic Acid2010Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, nr 10, s. C363-C373Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In an effort to obtain a more molecular view of atmospheric corrosion, we present experimental data from three complementary acting vibrational spectroscopy techniques that have been used in parallel exposures to follow the initial atmospheric corrosion of zinc during exposure in dry or humid air to which formic acid or acetic acid was added, with the primary aim to simulate indoor exposure conditions. The techniques used were vibrational sum frequency spectroscopy (interface sensitive), IR reflection absorption spectroscopy (near-surface sensitive), and confocal Raman microspectroscopy (bulk sensitive with submicrometer surface lateral resolution). The growth of two-dimensional interface species of zinc formate or zinc acetate could be monitored in situ and distinguished from three-dimensional growth of ZnO and zinc hydroxy formate or acetate. These interface species are believed to act as precursors of the dissolution of aqueous zinc carboxylate species that subsequently deposit at the surface and result in local growth of crystalline or amorphous ZnO and local zinc hydroxy carboxylate. Differences in the growth of corrosion products induced by acetic or formic acid were mainly attributed to differences in pH of the aqueous adlayer and in different deposition velocities of the acids into the aqueous adlayer. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3479255] All rights reserved.

  • 67.
    Hedberg, Jonas
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Baldelli, Steven
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Tyrode, Eric
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Molecular Structural Information of the Atmospheric Corrosion of Zinc Studied by Vibrational Spectroscopy Techniques I. Experimental Approach2010Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 157, nr 10, s. C357-C362Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As the nature of the interactions taking place on a metal surface during atmospheric corrosion is inherently complex, it imposes demands on the analytical studies that are needed to understand the fundamentals on a molecular level. Corrosion products may spread on the metal surface forming two-and three-dimensional structures. Thus, it is imperative to use different techniques to resolve the different types of growth. In this first part of a series of two papers, a systematic investigation is made to obtain detailed information on the mechanisms of the onset of atmospheric corrosion of zinc exposed to 115 ppb acetic acid in either dry or humidified air. The vibrational spectroscopy techniques used were vibrational sum frequency spectroscopy (VSFS, interface sensitive), infrared reflection absorption spectroscopy (IRAS, near-surface sensitive), and confocal Raman microspectroscopy (CRM, bulk sensitive). The VSFS selectively targeted the two-dimensional structures, IRAS followed the growth of three-dimensional corrosion products, and CRM could provide a laterally resolved chemical map on localized aggregates of zinc hydroxy acetate and ZnO with bulk character. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3479207] All rights reserved.

  • 68.
    Hellberg, Jonas
    et al.
    KTH, Tidigare Institutioner, Kemi.
    Dahlstedt, Emma
    KTH, Tidigare Institutioner, Kemi.
    Woldegiorgis, Andreas
    KTH, Tidigare Institutioner, Kemi.
    Umpolung of the 5-alkyl-2-dimethylamino-1,3-dithiolium-4-thiolate mesoion and its application in the synthesis of some new tetrathiafulvalenes2004Inngår i: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, nr 7, s. 1455-1463Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The 5-alkyl-2-dimethylamino-1,3-dithiolium-4-thiolate mesoion could be umpoled with sulfuryl chloride to yield a dicationic electrophile 3 that reacted with various electron-rich aromatic substrates to yield arylthio-substituted 1,3-dithiolium salts 13-25. Two of these compounds have been transformed to the corresponding symmetrical tetrathiafulvalenes 43 and 44, and their cyclovoltammetric behaviour recorded.

  • 69.
    Henderson, Pamela
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Hjörnhede, Anders
    Vattenfall Power Consultant AB.
    Combating corrosion in biomass and waste-fired plant2010Inngår i: 9th Liege conference on Materials for Advanced Power engineering 2010 / [ed] J. Lecomte-Beckers et al, Forschungszentrum Jülich GmbH , 2010, s. 986-999Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Many biomass- or waste-fired plants have problems with high temperature corrosion especially if the steam temperature is greater than500°C.  An increase in the combustion of waste fuels means that an increasing number of boilers have had problems. Therefore, there is great interest in reducing the costs associated with high temperature corrosion and at the same time there exists a desire to improve the electrical efficiency of a plant by the use of higher steam temperatures.  Assuming that the fuel is well-mixed and that there is good combustion control, there are in addition a number of other measures which can be used to reduce superheater corrosion in biomass and waste fired plants, and these are described in this paper.  These include the use of fuel additives, specifically sulphur-containing ones; design aspects like placing superheaters in less corrosive positions in a boiler, using tube shielding, a wider pitch between the tubes; operational considerations such as more controlled soot-blowing and the use of better materials.

  • 70.
    Holmboe, Michael
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    The Bentonite Barrier: Microstructural properties and the influence of γ-radiation2011Doktoravhandling, med artikler (Annet vitenskapelig)
  • 71.
    Hossain, Mohammad Moshin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Ekeroth, Ella
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Effects of HCO3- on the kinetics of UO2 oxidation by H2O22006Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 358, nr 2-3, s. 202-208Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of HCO3- on the kinetics of UO2 oxidation by H2O2 in aqueous solution has been studied using powder suspensions where the concentration of H2O2 was monitored as a function of time. By varying the UO2 surface to solution volume ratio second order rate constants were obtained for HCO3- concentrations ranging from 0 to 100 mM. The second order rate constant increases linearly with HCO3- concentration from 0 to approximately 1 mM. Above 1 mM HCO3- the rate constant is 4.4 × 10-6 m min-1 independent of [HCO3-]. This indicates that the kinetics of the reaction depends on both oxidation and dissolution below 1 mM HCO3- while at higher concentrations it is solely governed by oxidation. Hence, the rate constant obtained at HCO3- concentrations above 1 mM is the true rate constant for oxidation of UO2 by H2O2. The results also imply that the reaction between HCO3- and oxidized UO2 on the UO2 surface (i.e. HCO3- facilitated dissolution) is limited by diffusion (ca 10-3 m min-1 in the present system). Furthermore, the experimental results were used to estimate the oxidation site density of the powder used (126 sites nm-1) and the rate constant for dissolution of UO22 + from the UO2 surface (7 × 10-8 mol m-2 s-1).

  • 72. Hu, Ronggang
    et al.
    Ornberg, Andreas
    Pan, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Korrosionslära.
    Investigation of Influence of Small Particles in MP35N on the Corrosion Resistance in Synthetic Biological Environment2009Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 156, nr 10, s. C341-C344Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A cobalt-based alloy, MP35N, is currently used as a conductor material for thin wires in pacemaker leads. In this study, electrochemical impedance spectroscopy and cyclic polarization measurements of the alloy in a phosphate-buffered saline solution with 100 mM H2O2 indicated a high corrosion resistance and no passivity breakdown. Scanning electron microscopy and energy-dispersive spectroscopy analyses showed the existence of micrometer-sized TiN particles in the microstructure. Volta potential mapping by scanning Kelvin probe force microscopy revealed that the Volta potential of the TiN particles wits several tens of millivolts higher than that of the alloy matrix. By in situ atomic force microscopy measurements in the solution, small pitlike holes were observed in the vicinity of TiN particles and in other areas after 2 weeks of exposure. However, deposition of corrosion products within the pits was observed in the following days, and the pitlike holes were sealed upon further exposure. The results indicated a negligible risk for localized corrosion of this alloy despite the TiN particles present in the microstructure.

  • 73.
    Hussami, Linda
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Synthesis, Characterization and Application of Multiscale Porous Materials2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis work brings fresh insights and improved understanding of nanoscale materials through introducing new hybrid composites, 2D hexagonal in MCM-41 and 3D random interconnected structures of different materials, and application relevance for developing fields of science, such as fuel cells and solar cells.New types of porous materials and organometallic crystals have been prepared and characterized in detail. The porous materials have been used in several studies: as hosts to encapsulate metal-organic complexes; as catalyst supports and electrode materials in devices for alternative energy production. The utility of the new porous materials arises from their unique structural and surface chemical characteristics as demonstrated here using various experimental and theoretical approaches.New single crystal structures and arene-ligand exchange properties of f-block elements coordinated to ligand arene and halogallates are described in Paper I. These compounds have been incorporated into ordered 2D-hexagonal MCM-41 and polyhedral silica nanofoam (PNF-SiO2) matrices without significant change to the original porous architectures as described in Paper II and III. The resulting inorganic/organic hybrids exhibited enhanced luminescence activity relative to the pure crystalline complexes.A series of novel polyhedral carbon nanofoams (PNF-C´s) and inverse foams were prepared by nanocasting from PNF-SiO2’s. These are discussed in Paper IV. The synthesis conditions of PNF-C’s were systematically varied as a function of the filling ratio of carbon precursor and their structures compared using various characterization methods. The carbonaceous porous materials were further tested in Paper V and VI as possible catalysts and catalyst supports in counter- and working electrodes for solar- and fuel cell applications.

  • 74.
    Hussami, Linda
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Barnettb, Aleyandro O.
    Corkeryc, Robert W.
    Institute for Surface Chemistry.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Polyhedral Carbon Nanofoams as Working Electrodes in PEM Fuel CellsManuskript (preprint) (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Polyhedral carbon nanofoams (PNF-C´s) of various pore sizes were prepared and tested as working electrode support materials with relatively low Pt loading in Polymer Electrolyte Membrane Fuell Cell (PEMFs). The electrochemically active surface area (ECSA), carbon double layer capacitance (DLC), as well as fuel performance were evaluated by Cyclic Voltammetry (CV), Polarization Curves (PC) and Electrochemica lImpedance Spectroscopy (EIS) and compared to that of commercial working electrode material. The 3D interconnected, highly porous open structure, good electrical conductivity and unique surface characteristics of PNF-C´s offer increased mass transport and access to catalytic sites in fuel cells. One of the PNF-C supported Pt catalysts studied here out performed the standard commercial Pt/Vulcan catalyst due to its lower ionomer resistance and increased mass transport character.

  • 75.
    Hussami, Linda
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Corkery, Robert W.
    Institution of Surface Chemistry.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Polyhedral carbon nanofoams with minimum surface area partitions produced using silica nanofoams as templates2010Inngår i: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 48, nr 11, s. 3121-3130Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polyhedral silica nanofoam (PNF-SiO2) analogues of dry soap froths with minimal surface area were used as templates for making polyhedral carbon nanofoams (PNF-C). Furfuryl alcohol or triblock copolymers were used as carbon sources. The volume of carbon precursor relative to the internal pore volume of PNF-SiO2's was systematically varied between 50% and 100% in order to investigate the effect of filling fraction on internal structure of the corresponding PNF-C's. Transmission electron microscopy, small-angle X-ray scattering and nitrogen physisorption were used to characterize the samples. To aid the interpretation of the experimental data, a model for X-ray scattering from spherical shells was used to approximate scattering from the polyhedral foam cells. PNF-C's cast from the PNF-SiO2's, displayed the characteristic Plateau borders of minimal surface area foams defining interconnected, slit-like pore systems at all filling fractions. At relatively high filling fractions, inverse foam structures were obtained with the slit-like pores systems interpenetrating aggregated, close-packed, relatively low density polyhedral carbon nanoparticles co-joined by carbon struts. At relatively low filling fractions, polyhedral carbon nanofoams with relatively thin, fused double-wall structures and interconnected polyhedral pore systems were obtained.

  • 76.
    Hussami, Linda
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Incorporating mononuclear lanthanide organometallic species into mesoporous MCM-41 host materialManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Mesoporous inorganic/organometallic hybrid materials incorporating rare earth metal complexes with mesoporous silica MCM-41 as a host material have been investigated. Lanthanide halides, Ce(III), Dy(III) and Yb(III) halides, in the presence of Ga(III) halides and aromatic solvents, such as toluene, p-xylene and 1,2,4-trichlorobenzene give complexes with the general formula of [Ln(η6-arene)(GaX4)3]. The incorporation of these species into MCM-41 has been performed via wet impregnation (WI) at room temperature and the resulting mixed systems have been investigated by powder X-ray diffraction (XRD), fluorescence spectroscopy and been further characterized by nitrogen physisorption and elemental analysis. The great diversity of possible coordination patterns through bond formation via the accessible hydroxyl groups of the silica surface can be described by Σ{Si(OH)n-x(O)x[Ln(η6-arene)(GaX4)3]}.

  • 77.
    Hutchinson, Daniel J.
    et al.
    Department of Chemistry, University of Otago.
    Cameron, S. A.
    Department of Chemistry, University of Otago.
    Hanton, Lyall R.
    Department of Chemistry, University of Otago.
    Moratti, S. C.
    Department of Chemistry, University of Otago.
    Sensitivity of silver(I) complexes of a pyrimidine-hydrazone ligand to solvent, counteranion, and metal-to-ligand ratio changes2012Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 51, nr 9, s. 5070-81Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Metal complexation studies were performed with AgSO(3)CF(3) and AgBF(4) and the ditopic pyrimidine-hydrazone ligand 6-(hydroxymethyl)pyridine-2-carboxaldehyde (2-methylpyrimidine-4,6-diyl)bis(1-methylhydrazone) (1) in both CH(3)CN and CH(3)NO(2) in a variety of metal-to-ligand ratios. The resulting complexes were studied in solution by NMR spectroscopy and in the solid state by X-ray crystallography. Reacting either AgSO(3)CF(3) or AgBF(4) with 1 in either CH(3)CN or CH(3)NO(2) in a 1:1 metal-to-ligand ratio produced a double helicate in solution. This double helicate could be converted into a linear complex by increasing the metal-to-ligand ratio; however, the degree of conversion depended on the solvent and counteranion used. Attempts to crystallize the linear AgSO(3)CF(3) complex resulted in crystals with the dimeric structure [Ag(2)1(CH(3)CN)(2)](2)(SO(3)CF(3))(4) (2), while attempts to crystallize the AgSO(3)CF(3) double helicate from CH(3)CN resulted in crystals of another dimeric complex, [Ag(2)1(SO(3)CF(3))(CH(3)CN)(2)](2)(SO(3)CF(3))(2).H(2)O (3). The AgSO(3)CF(3) double helicate was successfully crystallized from a mixture of CH(3)CN and CH(3)NO(2) and had the structure [Ag(2)1(2)](SO(3)CF(3))(2).3CH(3)NO(2) (4). The linear AgBF(4) complex could not be isolated from the double helicate in solution; however, crystals grown from a solution containing both the AgBF(4) double helicate and linear complexes in CH(3)CN had the structure [Ag(2)1(CH(3)CN)(2)](BF(4))(2) (5). The AgBF(4) double helicate could only be crystallized from CH(3)NO(2) and had the structure [Ag(2)1(2)](BF(4))(2).2CH(3)NO(2) (6).

  • 78.
    Hutchinson, Daniel J.
    et al.
    Institut für Anorganische Chemie, Universität Leipzig.
    Clauss, R.
    Institut für Anorganische Chemie, Universität Leipzig.
    Sarosi, M. B.
    Institut für Anorganische Chemie, Universität Leipzig.
    Hey-Hawkins, Evamarie
    Institut für Anorganische Chemie, Universität Leipzig.
    Supramolecular self-assembly of heterobimetallic complexes: a new N,P-based, selective heteroditopic ligand2018Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 47, nr 4, s. 1053-1061Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pyrimidine-hydrazone and phosphole architectures have been combined to create a new heteroditopic ligand capable of forming heterobimetallic Zn(II)/Pd(II), Pb(II)/Pd(II) and Cu(II)/Pd(II) complexes in high yielding stepwise or one pot reactions. The catalytic activity of these complexes in Heck coupling and Miyaura borylation reactions was investigated.

  • 79.
    Hutchinson, Daniel J.
    et al.
    Department of Chemistry, University of Otago.
    Hanton, Lyall R.
    Department of Chemistry, University of Otago.
    Moratti, S. C.
    Department of Chemistry, University of Otago.
    2-Methyl-4,6-bis-(1-methyl-hydrazino)pyrimidine2009Inngår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 65, nr Pt 7, s. o1546-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the title compound, C(7)H(14)N(6), the amine groups of the two methyl-hydrazino substituents are orientated in the opposite direction to the methyl substituent at the 2-position of the pyrimidine ring. The mol-ecule is almost planar with only the two amine N atoms lying substanti-ally out of the mean plane of the pyrimidine ring [by 0.1430 (2) and 0.3092 (2) A]. The H atoms on these amine groups point inwards towards the aromatic ring, such that the lone pair of electrons points outwards from the mol-ecule. Each mol-ecule is linked to two others through N-Hcdots, three dots, centeredN hydrogen bonds between the two amino groups, forming a one-dimensional chain in the [010] direction. Offset face-to-face pi-pi stacking inter-actions between the pyrimidine rings organize these chains into a two-dimensional array [centroid-centroid distance = 3.789 (2) A].

  • 80.
    Hutchinson, Daniel J.
    et al.
    Department of Chemistry, University of Otago.
    Hanton, Lyall R.
    Department of Chemistry, University of Otago.
    Moratti, S. C.
    Department of Chemistry, University of Otago.
    Control of self-assembly through the influence of terminal hydroxymethyl groups on the metal coordination of pyrimidine-hydrazone Cu(II) complexes2010Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 49, nr 13, s. 5923-34Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The synthesis and characterization of 6-hydroxymethylpyridine-2-carboxaldehyde (2-methyl-pyrimidine-4,6-diyl)bis(1-methylhydrazone) (1) is reported. Ligand 1 was designed as a ditopic pyrimidine-hydrazone molecular strand with hydroxymethyl groups attached to the terminal pyridine rings. Coordination of 1 with Cu(ClO(4))(2) x 6 H(2)O or Cu(SO(3)CF(3))(2) x 4 H(2)O in a 1:2 molar ratio resulted in the dinuclear Cu(II) complexes [Cu(2)1(CH(3)CN)(4)](ClO(4))(4) x CH(3)CN (4) and [Cu(2)1(SO(3)CF(3))(2)(CH(3)CN)(2)](SO(3)CF(3))(2) x CH(3)CN (5). X-ray crystallography and (1)H NMR NOESY experiments showed that 1 adopted a horseshoe shape with both pyrimidine-hydrazone (pym-hyz) bonds in a transoid conformation, while 4 and 5 were linear in shape, with both pym-hyz bonds in a cisoid conformation. Coordination of 1 with Cu(ClO(4))(2) x 6 H(2)O or Cu(SO(3)CF(3))(2) x 4 H(2)O in a 1:1 molar ratio resulted in three different bent complexes, [Cu(1H)(ClO(4))(2)](ClO(4)) (6), [Cu(1H)(CH(3)CN)](ClO(4))(3) x 0.5 H(2)O (7), and [Cu1(SO(3)CF(3))](2)(SO(3)CF(3))(2) x CH(3)CN (8), where the pym-hyz bond of the occupied coordination site adopted a cisoid conformation, while the pym-hyz bond of the unoccupied site retained a transoid conformation. Both 6 and 7 showed protonation of the pyridine nitrogen donor in the empty coordination site; complex 8, however, was not protonated. A variety of Cu(II) coordination geometries were seen in structures 4 to 8, including distorted octahedral, trigonal bipyramidal, and square pyramidal geometries. Coordination of the hydroxymethyl arm in the mononuclear Cu(II) complexes 6, 7, and 8 appeared to inhibit the formation of a [2 x 2] grid by blocking further access to the Cu(II) coordination sphere. In addition, the terminal hydroxymethyl groups contributed to the supramolecular structures of the complexes through coordination to the Cu(II) ions and hydrogen bonding.

  • 81.
    Hutchinson, Daniel J.
    et al.
    Department of Chemistry, University of Otago.
    Hanton, Lyall R.
    Department of Chemistry, University of Otago.
    Moratti, S. C.
    Department of Chemistry, University of Otago.
    Influence of terminal acryloyl arms on the coordination chemistry of a ditopic pyrimidine-hydrazone ligand: comparison of Pb(II), Zn(II), Cu(II), and Ag(I) complexes2013Inngår i: Inorg Chem, Vol. 52, nr 5, s. 2716-28Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new ditopic pyrimidine-hydrazone ligand, 6-hydroxymethylacryloyl-2-pyridinecarboxaldehyde, 2,2'-[2,2'-(2-methyl-4,6-pyrimidinediyl)bis(1-methylhydrazone)] (L2), was synthesized with terminal acryloyl functional groups to allow incorporation into copolymer gel actuators. NMR spectroscopy was used to show that L2 adopted a horseshoe shape with transoid-transoid pym-hyz-py linkages. Metal complexation studies were performed with L2 and salts of Pb(II), Zn(II), Cu(II), and Ag(I) ions in CH3CN in a variety of metal to ligand ratios. Reacting L2 with an excess amount of any of the metal ions resulted in linear complexes where the pym-hyz-py linkages were rotated to a cisoid-cisoid conformation. NMR spectroscopy showed that the acryloyl arms of L2 did not interact with the bound metal ions in solution. Seven of the linear complexes (1-7) were crystallized and analyzed by X-ray diffraction. Most of these complexes (4-7) also showed no coordination between the acryloyl arms and the metal ions; however, complexes 1-3 showed some interactions. Both of the acryloyl arms were coordinated to Pb(II) ions in [Pb2L2(SO3CF3)4] (1), one through the carbonyl oxygen donor and the other through the alkoxy oxygen donor. One of the acryloyl arms of [Cu2L2(CH3CN)3](SO3CF3)4 (2) was coordinated to one of the Cu(II) ions through the carbonyl oxygen donor. There appeared to be a weak association between the alkoxy donors of the acryloyl arms and the Pb(II) ions of [Pb2L2(ClO4)4].CH3CN (3). Reaction of excess AgSO3CF3 with L2 was repeated in CD3NO2, resulting in crystals of {[Ag7(L2)2(SO3CF3)6(H2O)2] SO3CF3}infinity (8), the polymeric structure of which resulted from coordination between the carbonyl donors of the acryloyl arms and the Ag(I) ions. In all cases the coordination and steric effects of the acryloyl arms did not inhibit isomerization of the pym-hyz bonds of L2 or the core shape of the linear complexes.

  • 82.
    Hutchinson, Daniel J.
    et al.
    Department of Chemistry, University of Otago.
    Hanton, Lyall R.
    Department of Chemistry, University of Otago.
    Moratti, S. C.
    Department of Chemistry, University of Otago.
    Metal ion-controlled self-assembly using pyrimidine hydrazone molecular strands with terminal hydroxymethyl groups: a comparison of Pb(II) and Zn(II) complexes2011Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 50, nr 16, s. 7637-49Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Metal complexation studies were performed with the ditopic pyrimidine-hydrazone (pym-hyz) strand 6-hydroxymethylpyridine-2-carboxaldehyde (2-methyl-pyrimidine-4,6-diyl)bis(1-methylhydrazone) (1) and Pb(ClO(4))(2).3H(2)O, Pb(SO(3)CF(3))(2).H(2)O, Zn(SO(3)CF(3))(2), and Zn(BF(4))(2) to examine the ability of 1 to form various supramolecular architectures. X-ray crystallographic and NMR studies showed that coordination of the Pb(II) salts with 1 on a 2:1 metal/ligand ratio in CH(3)CN and CH(3)NO(2) resulted in the linear complexes [Pb(2)1(ClO(4))(4)] (2), [Pb(2)1(ClO(4))(3)(H(2)O)]ClO(4) (3), and [Pb(2)1(SO(3)CF(3))(3)(H(2)O)]SO(3)CF(3) (4). Two unusually distorted [2 x 2] grid complexes, [Pb1(ClO(4))](4)(ClO(4))(4) (5) and [Pb1(ClO(4))](4)(ClO(4))(4).4CH(3)NO(2) (6), were formed by reacting Pb(ClO(4))(2).6H(2)O and 1 on a 1:1 metal/ligand ratio in CH(3)CN and CH(3)NO(2). These grids formed despite coordination of the hydroxymethyl arms due to the large, flexible coordination sphere of the Pb(II) ions. A [2 x 2] grid complex was formed in solution by reacting Pb(SO(3)CF(3))(2).H(2)O and 1 on a 1:1 metal/ligand ratio in CH(3)CN as shown by (1)H NMR, microanalysis, and ESMS. Reacting the Zn(II) salts with 1 on a 2:1 metal/ligand ratio gave the linear complexes [Zn(2)1(H(2)O)(4)](SO(3)CF(3))(4).C(2)H(5)O (7) and [Zn(2)1(BF(4))(H(2)O)(2)(CH(3)CN)](BF(4))(3).H(2)O (8). (1)H NMR studies showed the Zn(II) and Pb(II) ions in these linear complexes were labile undergoing metal ion exchange. All of the complexes exhibited pym-hyz linkages in their cisoid conformation and binding between the hydroxymethyl arms and the metal ions. No complexes were isolated from reacting either of the Zn(II) salts with 1 on a 1:1 metal/ligand ratio, due to the smaller size of the Zn(II) coordination sphere as compared to the much larger Pb(II) ions.

  • 83.
    Hutchinson, Daniel J.
    et al.
    Department of Chemistry, University of Otago.
    Hanton, Lyall R.
    Department of Chemistry, University of Otago.
    Moratti, S. C.
    Tetratopic pyrimidine-hydrazone ligands modified with terminal hydroxymethyl and acryloyl arms and their Pb(II), Zn(II), Cu(II) and Ag(I) complexes2014Inngår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 43, nr 22, s. 8205-18Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The first tetratopic pyrimidine-hydrazone (pym-hyz) molecular strands containing terminal hydroxymethyl (L1) and acryloyl (L2) functional groups have been synthesised. L1 was produced by step-wise imine condensation reactions, starting with 6-hydroxymethyl-2-pyridinecarboxaldehyde. L2 was then synthesised through the treatment of L1 with acryloyl chloride. NMR spectroscopy and X-ray crystallography showed that the ligands adopted a helical shape, comprised of 1 and 1/3 helical turns. Both L1 and L2 uncoiled upon reaction with an excess amount of Pb(II), Zn(II) and Cu(II) ions, resulting in linear M4LA8 complexes (where M = Pb(II), Zn(II), or Cu(II); L = L1 or L2; and A = ClO4(-), SO3CF3(-) or BF4(-)). Horse-shoe shaped Pb2LA4 complexes were also formed by reacting Pb(II) ions with either L1 or L2 in a 2 : 1 metal to ligand ratio. The addition of Ag(I) ions to either L1 or L2 resulted in Ag2L2A2 double helicates, which were stable in the presence of excess Ag(I). The Pb(II), Zn(II) and Ag(I) complexes were characterised by NMR spectroscopy, while UV-Vis spectroscopy was used to probe the Cu(II) complexes. In addition, X-ray crystallography was used to analyse the linear Pb4L1A8, horse-shoe shaped Pb2L1(ClO4)4, twisted Cu3L2(SO3CF3)6, and double helicate Ag2L12(SO3CF3)2 complexes yielding the structures [Pb4L1(ClO4)7(H2O)]ClO4.4CH3NO2 (1), [Pb4L1(SO3CF3)8]2.6CH3CN.H2O (2), [Pb2L1(ClO4)2(CH3CN)(H2O)](ClO4)2.2CH3CN.C4H10O.H2O (3), [Cu3L2(SO3CF3)3(CH3CN)2(H2O)](SO3CF3)3.2CH3CN.H2O (4) and [Ag2L12](SO3CF3)2.CH3CN.H2O (5), respectively.

  • 84.
    Hutchinson, Daniel J.
    et al.
    Department of Chemistry, University of Otago.
    Hanton, Lyall R.
    Department of Chemistry, University of Otago.
    Moratti, Stephen C.
    Department of Chemistry, University of Otago.
    The one pot synthesis of heterobimetallic complexes from a homoditopic pyrimidine–hydrazone ligand2014Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, nr 28, s. 14550-14556Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The symmetrical, homoditopic, pyrimidine-hydrazone (pym-hyz) ligand L1 was used to synthesise three new heterobimetallic complexes, CuPbL1(ClO4)4, CuAgL1(SO3CF3)3, and CuZnL1(SO3CF3)4. Each of the complexes was produced in a one-pot reaction in CH3CN, and was isolated in high yield and purity simply by precipitation through the addition of diethyl ether. Analysis was carried out by IR, UV-Vis and ESMS spectroscopy, as well as microanalysis. Crystals were also grown for the purposes of X-ray diffraction studies, which yielded the structures [CuPbL1(ClO4)(CH3CN)2(H2O)](ClO4)3(1),[CuAgL1(SO3CF3)(CH3CN)2](SO3CF3)2$CH3CN (2), and CuZnL1(SO3CF3)2(CH3CN)(H2O)](SO3CF3)2$CH3CN (3), all of which were linear complexes containing a Cu(II) ion in one of the pym-hyz-py coordination sites, and either a Pb(II), Ag(I), or Zn(II) ion in the other.

  • 85.
    Hutchinson, Daniel J.
    et al.
    Institut für Anorganische Chemie, Universität Leipzig.
    Hey-Hawkins, Evamarie
    Institut für Anorganische Chemie, Universität Leipzig.
    The Self-Assembly of AgI -Containing Heterobimetallic Complexes with a Discriminatory N,P-Based Heteroditopic Ligand2018Inngår i: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, Vol. 2018, nr 44, s. 4790-4796Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pyrimidine-hydrazone and phosphole architectures have been combined to create a new heteroditopic ligand capable of forming heterobimetallic ZnII/PdII,PbII/PdII and CuII/PdII complexes in high yielding stepwise or one pot reactions. The catalytic activity of these complexes in Heck coupling and Miyaura borylation reactions was investigated.

  • 86.
    Hutchinson, Daniel J.
    et al.
    Department of Chemistry, University of Otago.
    James, M. P.
    Department of Chemistry, University of Otago.
    Hanton, Lyall R.
    Department of Chemistry, University of Otago.
    Moratti, S. C.
    Department of Chemistry, University of Otago.
    Metal-induced isomerization of a molecular strand containing contradictory dynamic coordination sites2014Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 53, nr 4, s. 2122-32Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new hydroxymethyl terminated pyrimidine-hydrazone (pym-hyz) ligand (L1) was synthesized with a central hyz-pyridine-hyz (hyz-py-hyz) motif replacing the usual hyz-pym-hyz unit, to create a molecular strand that underwent metal-induced isomerization with a minimal net change in ligand length. NMR spectroscopy showed that L1 had a horseshoe shape due to the hyz-py-hyz and pym-hyz bonds adopting transoid conformations. The ligand was successfully reacted with Pb(II), Zn(II), and Ag(I) salts in either CH3CN or CH3NO2 resulting in horseshoe-shaped M(n+)3L1A3n (where A = ClO4(-) or SO3CF3(-)) complexes in the solution phase. Crystals were grown from these solutions, the structures of which were highly dependent on the metal ion and solvent used, and were distinctly different from those seen in solution. The crystals grown from mixtures of Pb(ClO4)2.3H2O and L1 in either CH3CN or CH3NO2 resulted in the horseshoe-shaped [Pb3L1(ClO4)4(H2O)2](ClO4)2.CH3CN (1) complex or the {[Pb3L1(ClO4)4(H2O)](ClO4)2}infinity.CH3NO2 (2) helical coordination polymer, respectively. The horseshoe-shaped [Pb3L1(SO3CF3)6].CH3CN (3) complex was crystallized from a solution of Pb(SO3CF3)2.H2O and L1 in CH3CN, while the crystals grown from the solution of Zn(SO3CF3)2 and L1 in CH3CN consisted of the zigzag-shaped [Zn3L1(H2O)7](SO3CF3)6 (4) complex. The [Ag3(L1)2](SO3CF3)3 (5) double-helicate and the macrocycle-like [Ag6(L1)2](SO3CF3)6 (6) complex were crystallized from solutions of AgSO3CF3 and L1 in either CH3CN or CH3NO2, respectively.

  • 87.
    Höglund, Martin
    KTH, Skolan för kemivetenskap (CHE).
    Synthesis of Zinc (dithiolene) Coordination Nanosheet and Transmetalation using Metal Salts2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Metal-ligand coordination nanosheets have shown both good and novel electrical properties and have sparked research in to organic metals. A dithiolene complex based nanosheet can be produced using benzene hexathiol (BHT) as ligand and have, for example, shown high conductance when using copper as a metal centre. (1)  Zinc coordinates relatively weakly to BHT and in a square planar composition, making it a prime candidate for synthesizing a nanosheet which can be transmetalated. This can be used to generate novel electrical materials within a single lattice framework. In this study, a robust bottom up method is set up for producing large domain zinc(dithiolene) coordination nanosheets (ZnDT). Nickel, copper, and cobalt metal salts are then used to transmetalate the nanosheets. Showing the possibility of using ZnDT as a template to produce a single lattice framework dithiolene nanosheets consisting of different metal centres.

  • 88. Innocenti, M.E.
    et al.
    Goldman, M.
    Newman, D.
    Markidis, Stefano
    KTH, Skolan för datavetenskap och kommunikation (CSC), High Performance Computing and Visualization (HPCViz).
    Lapenta, G.
    Evidence of magnetic field switch-off in collisionless magnetic reconnection2015Inngår i: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 810, nr 2Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The long-term evolution of large domain particle-in-cell simulations of collisionless magnetic reconnection is investigated following observations that show two possible outcomes for collisionless reconnection: toward a Petschek-like configuration or toward multiple X points. In the present simulation, a mixed scenario develops. At earlier time, plasmoids are emitted, disrupting the formation of Petschek-like structures. Later, an almost stationary monster plasmoid forms, preventing the emission of other plasmoids. A situation reminiscent of Petschek’s switch-off then ensues. Switch-off is obtained through a slow shock/rotational discontinuity compound structure. Two external slow shocks (SS) located at the separatrices reduce the in-plane tangential component of the magnetic field, but not to zero. Two transitions reminiscent of rotational discontinuities (RD) in the internal part of the exhaust then perform the final switch-off. Both the SS and the RD are characterized through analysis of their Rankine-Hugoniot jump conditions. A moderate guide field is used to suppress the development of the firehose instability in the exhaust.

  • 89. Jacks, G.
    et al.
    Harikumar, P. S.
    CWRDM, Kozhikode 673571, Kerala, India..
    Bhattacharya, Prosun
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik.
    Fluoride mobilisation in India2009Inngår i: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 73, nr 13, s. A578-A578Artikkel i tidsskrift (Annet vitenskapelig)
  • 90.
    JAKOBSSON, NICOLINE
    KTH, Skolan för kemivetenskap (CHE).
    Speciering av zink i dagvatten från motorvägstunnlar2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Environmental risks are being investigated more and more in Sweden in relation to large infrastructural projects such as the Stockholm Bypass, a 21km long motorway tunnel where 18km is underground. This project specifically evaluates the metal zinc’s effect on the nearby environment by determining the speciation that the metal is found in. The process included analyzing the stormwater from another tunnel in Stockholm called Södra Länken where samples at five independent locations were taken. A rain sample was taken as a background sample to compare with the natural conditions. The practical lab work was complemented with theoretical modeling by the software Medusa and MinTeq. The total accessible metal concentration was evaluated by decreasing the pH value successively. Results shows that the concentration accessible zinc is below the limit value set for Sweden at neutral to high pH values and the concentration increases with decreasing pH value. If humic substances are present, MinTeq modelling shows that low concentrations of free zinc ion are found accordingly. The conclusion of this study is that the planned construction of the Stockholm Bypass has a well-adapted stormwater treatment strategy that will function well. Future studies should complete this project with a study of the natural zinc concentrations fluctuations, which could contribute to a more detailed analysis of the stick samples taken.

  • 91.
    Jaouen, Frédéric
    et al.
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Lindbergh, Göran
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Wiezell, Katarina
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Transient techniques for investigating mass-transport limitations in gas diffusion electrodes: II. Experimental characterization of the PEFC cathode2003Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 150, nr 12, s. A1711-A1717Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The current-interrupt technique and electrochemical impedance spectroscopy were employed in order to study the behavior of a polymer electrolyte fuel cell (PEFC) cathode containing 30 wt % Nafion and 70 wt % Pt/C. The steady-state polarization curves were also recorded. The experimental results were analyzed with help of the mathematical models developed in Part I of this paper. The effect of a varying oxygen pressure and humidity on the dynamic response of the cathode was investigated. The double-layer capacitance, Tafel slope, oxygen solubility, a group containing the effective O-2 diffusion coefficient and agglomerate size, and finally, the effective proton conductivity in the cathode were obtained. The parameter values were reasonable and attest the robustness of the agglomerate model for describing the PEFC cathode. At low humidity, a second, low-frequency loop was observed that was attributed to the membrane behavior.

  • 92. Jena, Naresh K.
    et al.
    Araujo, Rafael B.
    Shukla, Vivekanand
    Ahuja, Rajeev
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. Uppsala University, Sweden.
    Borophane as a Benchmate of Graphene: A Potential 2D Material for Anode of Li and Na-Ion Batteries2017Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, nr 19, s. 16148-16158Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Borophene, single atomic-layer sheet of boron (Science 2015, 350, 1513), is a rather new entrant into the burgeoning class of 2D materials. Borophene exhibits anisotropic metallic properties whereas its hydrogenated counterpart borophane is reported to be a gapless Dirac material lying on the same bench with the celebrated graphene. Interestingly, this transition of borophane also rendered stability to it considering the fact that borophene was synthesized under ultrahigh vacuum conditions on a metallic (Ag) substrate. On the basis of first-principles density functional theory computations, we have investigated the possibilities of borophane as a potential Li/Na-ion battery anode material. We obtained a binding energy of -2.58 (-1.08 eV) eV for Li (Na)-adatom on borophane and Bader charge analysis revealed that Li(Na) atom exists in Li+(Na+) state. Further, on binding with Li/Na, borophane exhibited metallic properties as evidenced by the electronic band structure. We found that diffusion pathways for Li/Na on the borophane surface are anisotropic with x direction being the favorable one with a barrier of 0.27 and 0.09 eV, respectively. While assessing the Li-ion anode performance, we estimated that the maximum Li content is Li0.445B2H2, which gives rises to a material with a maximum theoretical specific capacity of 504 mAh/g together with an average voltage of 0.43 V versus Li/Li+. Likewise, for Na-ion the maximum theoretical capacity and average voltage were estimated to be 504 mAh/g and 0.03 V versus Na/Na+, respectively. These findings unambiguously suggest that borophane can be a potential addition to the map of Li and Na-ion anode materials and can rival some of the recently reported 2D materials including graphene.

  • 93. Jiang, Huijun
    et al.
    Hou, Zhonghuai
    Luo, Yi
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Unraveling the Mechanism for the Sharp-Tip Enhanced Electrocatalytic Carbon Dioxide Reduction: The Kinetics Decide2017Inngår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 56, nr 49, s. 15617-15621Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electrocatalytic reduction reaction of carbon dioxide can be significantly enhanced by the use of a sharp-tip electrode. However, the experimentally observed rate enhancement is many orders of magnitudes smaller than what would be expected from an energetic point of view. The kinetics of this tip-enhanced reaction are shown to play a decisive role, and a novel reaction-diffusion kinetic model is proposed. The experimentally observed sharp-tip enhanced reaction and the maximal producing rate of carbon monoxide under different electrode potentials are well-reproduced. Moreover, the optimal performance shows a strong dependence on the interaction between CO2 and the local electric field, on the adsorption rate of CO2, but not on the reaction barrier. Two new strategies to further enhance the reaction rate have also been proposed. The findings highlight the importance of kinetics in modeling electrocatalytic reactions.

  • 94.
    Jonsson, Mats
    et al.
    KTH, Tidigare Institutioner, Kemi.
    Ekeroth, Ella
    KTH, Tidigare Institutioner, Kemi.
    Roth, Olivia
    KTH, Tidigare Institutioner, Kemi.
    Dissolution of UO2 by one- and two-electron oxidants2004Inngår i: Materials Research Society Symposium Proceedings, ISSN 0272-9172, E-ISSN 1946-4274, Vol. 807, s. 77-82Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, the efficiency of one- and two-electron oxidants in oxidative dissolution Of UO2 has been investigated. This was accomplished by measuring the U(VI)-concentration in solution after exposing UO2-powder to controlled amounts of oxidants in aqueous solution. The oxidants used in this study are H2O2, IrCl62-, CO3.- and OH..H2O2 acts as a two-electron oxidant while the remaining three oxidants are one-electron oxidants. CO3.- and OH. were generated using gamma-radiolysis. The results clearly show that the dissolution yields for one-electron oxidants (per electron pair) are lower than the yields for two-electron oxidants. Furthermore, the yields for one-electron oxidants increase with increasing amount of oxidant (especially at low amounts of oxidant). The rationale for this is that U(VI) is the main soluble species which is formed directly upon two-electron oxidation. For one-electron oxidants the primary oxidation product is U(V) which can form U(VI) upon reaction with a second oxidant. The probability for a second oxidation is however low at low concentrations of oxidant.

  • 95.
    Jonsson, Mats
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Nielsen, Fredrik
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Roth, Olivia
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Ekeroth, Ella
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Nilsson, Sara
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Hossain, Mohammad Mohsin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Radiation induced spent nuclear fuel dissolution under deep repository conditions2007Inngår i: Environmental Science and Technology, ISSN 0013-936X, Vol. 41, nr 20, s. 7087-7093Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The dynamics of spent nuclear fuel dissolution in groundwater is an important part of the safety assessment of a deep geological repository for high level nuclear waste. In this paper we discuss the most important elementary processes and parameters involved in radiation induced oxidative dissolution of spent nuclear fuel. Based on these processes, we also present a new approach for simulation of spent nuclear fuel dissolution under deep repository conditions. This approach accounts for the effects of fuel age, burn up, noble metal nanoparticle contents, aqueous H-2 and HCO3- concentration, water chemistry, and combinations thereof. The results clearly indicate that solutes consuming H2O2 and combined effects of noble metal nanoparticles and H-2 have significant impact on the rate of spent nuclear fuel dissolution. Using data from the two possible repository sites in Sweden, we have employed the new approach to estimate the maximum rate of spent nuclear fuel dissolution. This estimate indicates that H-2 produced from radiolysis of groundwater alone will be sufficient to inhibit the dissolution, completely for spent nuclear fuel older than 100 years.

  • 96.
    Judith Cruz, M.
    et al.
    Univ Antofagasta, Dept Chem Engn & Mineral Proc, Antofagasta, Chile.;Univ Antofagasta, Ctr Adv Study Lithium & Ind Minerals CELiMIN, Antofagasta, Chile..
    Makarova, Irina V.
    Belarusian State Technol Univ, Dept Chem Technol Electrochem Prod & Elect Engn M, Minsk, BELARUS.;Lappeenranta Univ Technol, Sch Engn Sci, Dept Separat & Purificat, Skinnarilankatu 34, FI-53850 Lappeenranta, Finland..
    Kharitonov, Dmitry S.
    Belarusian State Technol Univ, Dept Chem Technol Electrochem Prod & Elect Engn M, Minsk, BELARUS.;Polish Acad Sci, Jerzy Haber Inst Catalysis & Surface Chem, Krakow, Poland..
    Dobryden, Illia
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Chernik, Alexander A.
    Belarusian State Technol Univ, Dept Chem Technol Electrochem Prod & Elect Engn M, Minsk, BELARUS..
    Grageda, Mario
    Univ Antofagasta, Dept Chem Engn & Mineral Proc, Antofagasta, Chile.;Univ Antofagasta, Ctr Adv Study Lithium & Ind Minerals CELiMIN, Antofagasta, Chile..
    Ushak, Svetlana
    Univ Antofagasta, Dept Chem Engn & Mineral Proc, Antofagasta, Chile.;Univ Antofagasta, Ctr Adv Study Lithium & Ind Minerals CELiMIN, Antofagasta, Chile..
    Corrosion properties of nickel coatings obtained from aqueous and nonaqueous electrolytes2019Inngår i: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 51, nr 9, s. 943-953Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nickel was deposited on a copper substrate from aqueous and nonaqueous ethanol electrolytes. X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy and chronovoltametry, scanning electron microscopy, and atomic force microscopy were used to study the effect of the solvent on the surface and corrosion properties of the Ni coatings formed. Unifom and relatively smooth Ni films were obtained as measured with microscopy techniques. The formation of a passive film in acidic, alkaline, and neutral chloride-containing media was confirmed with X-ray photoelectron spectroscopy. The water-based nickel-plating electrolyte makes it possible to deposit coatings with higher corrosion resistance as compared with coatings deposited from ethanol electrolyte in NaOH and NaCl media. The proposed mechanism of corrosion in a 0.5 M H2SO4 solution involves cycles of active-passive surface behavior due to its passivation by corrosion products.

  • 97. Kadas, K.
    et al.
    Iusan, D.
    Hellsvik, Johan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Cedervall, J.
    Berastegui, P.
    Sahlberg, M.
    Jansson, U.
    Eriksson, O.
    AlM2B2 (M = Cr, Mn, Fe, Co, Ni): a group of nanolaminated materials2017Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 29, nr 15, artikkel-id 155402Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Combining theory with experiments, we study the phase stability, elastic properties, electronic structure and hardness of layered ternary borides AlCr2B2, AlMn2B2, AlFe2B2, AlCo2B2, and AlNi2B2. We find that the first three borides of this series are stable phases, while AlCo2B2 and AlNi2B2 are metastable. We show that the elasticity increases in the boride series, and predict that AlCr2B2, AlMn2B2, and AlFe2B2 are more brittle, while AlCo2B2 and AlNi2B2 are more ductile. We propose that the elasticity of AlFe2B2 can be improved by alloying it with cobalt or nickel, or a combination of them. We present evidence that these ternary borides represent nanolaminated systems. Based on SEM measurements, we demonstrate that they exhibit the delamination phenomena, which leads to a reduced hardness compared to transition metal mono-and diborides. We discuss the background of delamination by analyzing chemical bonding and theoretical work of separation in these borides.

  • 98.
    Kaestner, Bernd
    et al.
    PTB, Abbestr 2-12, D-10587 Berlin, Germany..
    Johnson, C. Magnus
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Hermann, Peter
    PTB, Abbestr 2-12, D-10587 Berlin, Germany.;Deutschland GmbH & Co KG, West Pharmaceut Serv, Stolberger Str 21-41, D-52249 Eschweiler, Germany..
    Kruskopf, Mattias
    PTB, Bundesallee 100, D-38116 Braunschweig, Germany.;NIST, 100 Bur Dr, Gaithersburg, MD 20899 USA..
    Pierz, Klaus
    PTB, Bundesallee 100, D-38116 Braunschweig, Germany..
    Hoehl, Arne
    PTB, Abbestr 2-12, D-10587 Berlin, Germany..
    Hornemann, Andrea
    PTB, Abbestr 2-12, D-10587 Berlin, Germany..
    Ulrich, Georg
    PTB, Abbestr 2-12, D-10587 Berlin, Germany..
    Fehmel, Jakob
    PTB, Abbestr 2-12, D-10587 Berlin, Germany..
    Patoka, Piotr
    Free Univ Berlin, Inst Chem & Biochem, Phys Chem, Takustr 3, D-14195 Berlin, Germany..
    Ruehl, Eckart
    Free Univ Berlin, Inst Chem & Biochem, Phys Chem, Takustr 3, D-14195 Berlin, Germany..
    Ulm, Gerhard
    PTB, Abbestr 2-12, D-10587 Berlin, Germany..
    Infrared Nanospectroscopy of Phospholipid and Surfactin Monolayer Domains2018Inngår i: ACS OMEGA, ISSN 2470-1343, Vol. 3, nr 4, s. 4141-4147Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A main challenge in understanding the structure of a cell membrane and its interactions with drugs is the ability to chemically study the different molecular species on the nanoscale. We have achieved this for a model system consisting of mixed monolayers (MLs) of the biologically relevant phospholipid 1,2-distearoyl-sn-glycero-phosphatidylcholine and the antibiotic surfactin. By employing nano-infrared (IR) microscopy and spectroscopy in combination with atomic force microscopy imaging, it was possible to identify and chemically detect domain formation of the two constituents as well as to obtain IR spectra of these species with a spatial resolution on the nanoscale. A novel method to enhance the near-field imaging contrast of organic MLs by plasmon interferometry is proposed and demonstrated. In this technique, the organic layer is deposited on gold and ML graphene substrates, the latter of which supports propagating surface plasmons. Plasmon reflections arising from changes in the dielectric environment provided by the organic layer lead to an additional contrast mechanism. Using this approach, the interfacial region between surfactin and the phospholipid has been mapped and a transition region is identified.

  • 99.
    Karlsson, Rasmus
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Theoretical and Experimental Studies of Electrode and Electrolyte Processes in Industrial Electrosynthesis2015Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Heterogeneous electrocatalysis is the usage of solid materials to decrease the amount of energy needed to produce chemicals using electricity. It is of core importance for modern life, as it enables production of chemicals, such as chlorine gas and sodium chlorate, needed for e.g. materials and pharmaceuticals production. Furthermore, as the need to make a transition to usage of renewable energy sources is growing, the importance for electrocatalysis used for electrolytic production of clean fuels, such as hydrogen, is rising. In this thesis, work aimed at understanding and improving electrocatalysts used for these purposes is presented.

    A main part of the work has been focused on the selectivity between chlorine gas, or sodium chlorate formation, and parasitic oxygen evolution. An activation of anode surface Ti cations by nearby Ru cations is suggested as a reason for the high chlorine selectivity of the “dimensionally stable anode” (DSA), the standard anode used in industrial chlorine and sodium chlorate production. Furthermore, theoretical methods have been used to screen for dopants that can be used to improve the activity and selectivity of DSA, and several promising candidates have been found. Moreover, the connection between the rate of chlorate formation and the rate of parasitic oxygen evolution, as well as the possible catalytic effects of electrolyte contaminants on parasitic oxygen evolution in the chlorate process, have been studied experimentally.

    Additionally, the properties of a Co-doped DSA have been studied, and it is found that the doping makes the electrode more active for hydrogen evolution. Finally, the hydrogen evolution reaction on both RuO2 and the noble-metal-free electrocatalyst material MoS2 has been studied using a combination of experimental and theoretically calculated X-ray photoelectron chemical shifts. In this way, insight into structural changes accompanying hydrogen evolution on these materials is obtained.

  • 100. Kienzier, B.
    et al.
    Vejmelka, P.
    Romer, J.
    Schild, D.
    Jansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Experiences with underground laboratory experiments2006Inngår i: Proceedings of the 11th International High Level Radioactive Waste Management Conference, IHLRWM, 2006, Vol. 2006, s. 271-277Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Within the scope of a bilateral cooperation a series of Actiniae Migration Experiments were performed by FZK-INE at the Äspo Hard Rock Laboratory in Sweden. Several in-situ experiments investigating the migration of the actinides 241Am, 237Np, 242/244Pu, as well as of 233U and 99Tc were performed in single fractured granite drill cores. These migration experiments were complemented by laboratory investigations. In all experiments, breakthrough of elements having relatively slow retention kinetics such as Np, Tc and U followed the tendency of the inert HTO tracer resulting in an initial breakthrough. Am and Pu was not found in the eluted water. The breakthrough behaviors could not be explained by a simple sorption mechanism. The redox sensitive actinides and Tc are reduced onto the surfaces of the natural fractures. In contrast, U(VI) remains stable and shows little sorption. Natural uranium present in the minerals of the granite was mobilized. The results of the in-situ experiments performed under conditions as close to nature as possible are summarized and some conclusions are drawn relevant for performance assessment.

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