Ändra sökning
Avgränsa sökresultatet
12 1 - 50 av 70
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 1.
    Abbasi, M.
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Backstrom, J.
    Mid Sweden Univ, FSCN Mat Phys, Dept Nat Sci, SE-85170 Sundsvall, Sweden..
    Cornell, Ann M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Fabrication of Spin-Coated Ti/TiHx/Ni-Sb-SnO2 Electrode: Stability and Electrocatalytic Activity2018Ingår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 165, nr 9, s. H568-H574Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel three-layer anode having the composition Ti/TiHx/Ni-Sb-SnO2 (Ti/TiHx/NATO) was successfully prepared by a spin-coating and pyrolysis process aiming at a long service lifetime and good electrocatalytic properties for ozone formation. The TiHx as an interlayer was produced by electrochemical cathodic reduction of a coated layer of the TiOx on the titanium substrate. Spin coating and thermal decomposition were used to deposit the Sn-Sb-Ni precursor on the surface of the prepared Ti/TiHx electrode. Cyclic and linear scanning voltammetry, Raman spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to reveal the electrode performance and morphology. Results show that the onset potential for the oxygen evolution reaction (OER) of Ti/TiHx /NATO is higher than for Ti/NATO. They also indicate that the service lifetime of the Ti/TiHx/NATO is twice as long as the Ti/NATO at a current density of 50 mA.cm(-2) at room temperature. Electrochemical ozone generation and degradation of the methylene blue were investigated to confirm selectivity and activity of the electrodes. After 5 min electrolysis, a current efficiency for ozone generation of 56% was obtained the electrode with TiHx while 38% was obtained on Ti/NATO under same conditions. The results also confirm that the Ti/TiH x /NATO has a higher kinetic rate constant and decolorization efficiency for removal of the methylene blue compare to the Ti/NATO. The rate constant for the pseudo-first ordered reaction of methylene blue degradation showed high values of 350 x 10(-3) min(-1) for Ti/NATO and 440 x 10(-3) min(-1) for Ti/TiHx/NATO. 

  • 2.
    Alexiadis, Alessio
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Dudukovic, M. P.
    Comparison between CFD calculations of the flow in a rotating disk cell and the Cochran/Levich equations2012Ingår i: Journal of Electroanalytical Chemistry, ISSN 1572-6657, Vol. 669, s. 55-66Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Three CFD (Computational Fluid Dynamics) models (single-phase. VOF and Euler-Euler) are employed to simulate the flow in a finite, rotating electrode cell under different operative conditions. The main dimensionless groups are derived and their effect on the flow is investigated. Except very close to the rotating electrode (i.e. in the hydrodynamic layer), the results show a flow pattern considerably different from Cochran's approximate analytical solution often used in electrochemistry. Historically, the Cochran equation was used to derive the Levich equation, which permits the calculation of the limiting current density on a rotating electrode. Despite the general inadequacy of Cochran's analytical solution, however, we show that the Levich equation often retains its validity because, in many practical situations, the concentration boundary layer is considerably smaller than the hydrodynamic boundary layer. When bubbles are generated on the electrode and a certain critical void fraction is exceeded, however, the Levich equation also becomes inaccurate. We propose, therefore, an amended version of this equation, which provides results closer to the CFD calculations.

  • 3.
    Alexiadis, Alessio
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Dudukovic, M. P.
    Ramachandran, P.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    On the stability of the flow in multi-channel electrochemical systems2012Ingår i: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 42, nr 9, s. 679-687Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The importance of the fluid dynamics in the modelling of electrochemical systems is often underestimated. The knowledge of the flow velocity pattern in an electrochemical cell, in fact, can allow us to associate certain electrochemical reactions with specific fluid patterns to maximize the yield of some reaction and, conversely, to minimize unwanted or side reactions. The correct evaluation of the convective term in the Nernst-Planck equation, however, requires the solution of the so-called Navier-Stokes equations, and computational fluid dynamics (CFD) is today the established method to numerically solve these equations. In this work, a CFD model is employed to show that the gas-liquid flow pattern can be remarkably different in a single channel or in a multi-channel gas-evolving electrochemical system. In the single channel, in fact, under certain conditions, vortices and recirculation regions can appear in the flow, which does not appear in the multi-channel case. The reason of this difference is found in the uneven distribution of the small bubbles in the two cases. Additionally, a second, simplified, model of the flow is discussed to show how a higher concentration of small bubbles in the single channel system can destabilize the flow.

  • 4.
    Alexiadis, Alessio
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Dudukovic, M. P.
    Ramachandran, P.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wanngard, J.
    Bokkers, A.
    Liquid-gas flow patterns in a narrow electrochemical channel2011Ingår i: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 66, nr 10, s. 2252-2260Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The flow in a narrow (3 mm wide) vertical gap of an electrochemical cell with gas evolution at one electrode is modeled by means of the two-phase Euler-Euler model. The results indicate that at certain conditions an unsteady type of flow with vortices and recirculation regions can occur. Such flow pattern has been observed experimentally, but not reported in previous modeling studies. Further analysis establishes that the presence of a sufficient amount of small (similar to 10 mu m) bubbles is the main factor causing this type of flow at high current densities.

  • 5.
    Alexiadis, Alessio
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Dudukovic, M P
    Ramachandran, P
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wanngard, J
    Bokkers, A
    On the electrode boundary conditions in the simulation of two phase flow in electrochemical cells2011Ingår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 36, nr 14, s. 8557-8559Artikel i tidskrift (Refereegranskat)
  • 6.
    Alexiadis, Alessio
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Dudukovic, M. P.
    Ramachandran, P.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wanngård, J.
    Bokkers, A.
    The flow pattern in single and multiple submerged channels with gas evolution at the electrodes2012Ingår i: International Journal of Chemical Engineering, ISSN 1687-806X, E-ISSN 1687-8078, Vol. 2012, s. 392613-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We show that the gas-liquid flow pattern in a single gas-evolving electrochemical channel can be remarkably different from the flow pattern in multiple submerged gas-evolving electrochemical channels. This is due to the fact that in a single channel there is a higher accumulation of small bubbles and these can considerably affect the liquid velocity pattern which in turn may affect the performance of a cell. Since experimental work is often carried out in single channels, while industrial applications almost always involve multiple channels, this study provides insight into the factors that affect the flow pattern in each situation and establishes the basis for relating the behavior of single-and multiple-channel devices.

  • 7.
    Alexiadis, Alessio
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Dudukovic, M. P.
    Ramachandran, P.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Wanngård, J.
    Bokkers, A.
    Transition to pseudo-turbulence in a narrow gas-evolving channel2012Ingår i: Theoretical and Computational Fluid Dynamics, ISSN 0935-4964, E-ISSN 1432-2250, Vol. 26, nr 6, s. 551-564Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Different flow regimes have been observed, both experimentally and in CFD simulations, in narrow channels with gas evolution. In this manuscript, we examine, using the Euler-Euler model, the flow in a narrow channel, where gas is evolved from a vertical wall. We find some pseudo-turbulent features at conditions described in this manuscript. The transition to this pseudo-turbulent regime is associated with the value of a specific dimensionless group.

  • 8. Bebelis, S.
    et al.
    Bouzek, K.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Ferreira, M. G. S.
    Kelsall, G. H.
    Lapicque, F.
    Ponce de León, C.
    Rodrigo, M. A.
    Walsh, F. C.
    Highlights during the development of electrochemical engineering2013Ingår i: Chemical engineering research & design, ISSN 0263-8762, E-ISSN 1744-3563, Vol. 91, nr 10, s. 1998-2020Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Over the last century, electrochemical engineering has contributed significantly to societal progress by enabling development of industrial processes for manufacturing chemicals, such as chlorine and the Nylon precursor adiponitrile, as well as a wide range of metals including aluminium and zinc. In 2011, ca. 17 M tonne Cu p.a. was electro-refined to 99.99%+ purity required by electrical and electronic engineering applications, such as for electrodepositing with exquisite resolution multi-layer inter-connections in microprocessors. Surface engineering is widely practised industrially e.g. to protect steels against corrosion e.g. by electroplating nickel or using more recent novel self-healing coatings. Complex shapes of hard alloys that are difficult to machine can be fabricated by selective dissolution in electrochemical machining processes. Electric fields can be used to drive desalination of brackish water for urban supplies and irrigation by electrodialysis with ion-permeable membranes; such fields can also be used in electrokinetic soil remediation processes. Rising concerns about the consequences of CO2 emissions has led to the rapidly increasing development and deployment of renewable energy systems, the intermittency of which can be mitigated by energy storage in e.g. redox flow batteries for stationary storage and novel lithium batteries with increased specific energies for powering electric vehicles, or when economically viable, in electrolyser-fuel cells. The interface between electrochemical technology and biotechnology is also developing rapidly, with applications such as microbial fuel cells.Some of these applications are reviewed, the challenges assessed and current trends elucidated in the very active area of Chemical Engineering bordering with material science and electrochemistry.

  • 9. Bouzek, K.
    et al.
    Cornell, Ann M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Rodrigo, M. A.
    Preface on the special issue 2nd workshop on electrochemical engineering: new bridges for a new knowledge on electrochemical engineering2018Ingår i: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 48, nr 12, s. 1305-1306Artikel i tidskrift (Refereegranskat)
  • 10.
    Cornell, Ann
    KTH, Tidigare Institutioner, Kemiteknik.
    Activated Cathodes for the Hydrogen Evolution Reaction in Chlorate Manufacture1993Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 11.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Chlorate cathodes and electrode design2014Ingår i: Encyclopedia of applied electrochemistry / [ed] R.F. Savinell,K. Ota,G. Kreysa, Springer, 2014, s. 175-181Kapitel i bok, del av antologi (Refereegranskat)
  • 12.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Chlorate synthesis cells and technology2014Ingår i: Encyclopedia of applied electrochemistry / [ed] R.F. Savinell, K. Ota, G. Kreysa, Springer, 2014, s. 181-187Kapitel i bok, del av antologi (Refereegranskat)
  • 13.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE).
    Electrochemical Reactor Engineering2009Ingår i: Electrochemical Engineering: Industrial, Energy and Environmental Applications: Book of Lectures of the ESSEE5 / [ed] Pablo Canizares Canizares, Castilla La Mancha: Department of Chemical Engineering UCLM , 2009, 1, s. 159-188Kapitel i bok, del av antologi (Övrig (populärvetenskap, debatt, mm))
  • 14.
    Cornell, Ann
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Electrode reactions in the chlorate process2002Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 15.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Industrial Electrolysis: Electrochemical Synthesis of Organic and Inorganic Products and Intermediates2012Ingår i: 6th European Summer School on Electrochemical Engineering: Lectures and Book of Abstracts / [ed] Zoran Mandic, Aleksandar Dekanski, Zagreb: Faculty of Chemical Engineering and Technology , 2012, 1, s. 225-256Konferensbidrag (Övrig (populärvetenskap, debatt, mm))
  • 16.
    Cornell, Ann
    et al.
    KTH, Skolan för kemivetenskap (CHE).
    Herlitz, Fredrik
    Permascand AB.
    Ruthenium Based DSA® in Chlorate Electrolysis2004Ingår i: 4th KURT SCHWABE CORROSION SYMPOSIUM, Mechanisms of Corrosion and Corrosion Prevention Proceedings, Helsingfors, Finland: Helsinki University of Technology , 2004, 1, s. 326-332Konferensbidrag (Refereegranskat)
  • 17.
    Cornell, Ann
    et al.
    KTH, Tidigare Institutioner, Kemiteknik.
    Håkansson, Bo
    Lindbergh, Göran
    KTH, Tidigare Institutioner, Kemiteknik.
    Ruthenium based DSA in chlorate electrolysis–critical anode potential and reaction kinetics2003Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 48, nr 5, s. 473-481Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ruthenium based DSA®s have been investigated in chlorate electrolyte using rotating discs made from commercial electrodes. Measurements of the voltammetric charge, q*, and of iR-corrected polarisation curves up to current densities of 40 kA/m2 were recorded on new anodes and on aged anodes from 3 years of production in a chlorate plant. Anodic polarisation curves in chloride containing electrolytes bend towards a higher slope at approximately 1.2 V versus Ag/AgCl, likely due to oxidation of ruthenium. The potential and current density at which the curves bend have been defined as the critical potential, Ecr, and the critical current density, icr. New anodes that operate at a relatively high potential, >Ecr, obtain an increase in real surface area and thereby a decrease in anode potential and in the selectivity for oxygen formation during the first months of operation. Experiments at constant ionic strength under chlorate process conditions showed that Ecr decreased with increasing chloride concentration with a factor of −0.09 V/log Cl, whereas icr increased with increasing chloride concentration. The chlorine evolution reaction was of the first order with respect to chloride concentration. A possible reaction mechanism for chlorine formation is suggested.

  • 18.
    Cornell, Ann
    et al.
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Håkansson, Bo
    Lindbergh, Göran
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Ruthenium-based dimensionally stable anode in chlorate electrolysis - Effects of electrolyte composition on the anode potential2003Ingår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 150, nr 1, s. D6-D12Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work the anodic reactions taking place on a dimensionally stable anode (DSA) in chlorate electrolyte have been investigated. Rotating disk electrodes were made from commercial RuO2-catalyzed DSAs and studied in steady-state polarization measurements, mainly IR-corrected polarization curves. Effects of varying pH and electrolyte concentrations of chloride, chlorate, chromium(VI), hypochlorite (ClO- + ClOH) as well as mass transport were studied. The kinetics for the chlorine evolution reaction, with a Tafel slope of 40 mV/decade of current, was not dependent on pH in the region 2-8, at potentials lower than 1.2 V vs. Ag/AgCl. The slope of the polarization curves increased at about 1.2 V vs. Ag/AgCl, a pH-dependent bend not due to mass-transport limitations in the electrolyte. At a pH of 6.5, typical for the chlorate process, oxygen evolution is an important side reaction favored by the dichromate buffer and by increased mass transport, both keeping down the pH at the anode. In the chlorine evolution region the potentials increased when adding Cr(VI) to the electrolyte, whereas no major effect was seen from additions of NaClO. (C) 2002 The Electrochemical Society.

  • 19.
    Cornell, Ann
    et al.
    KTH, Skolan för kemivetenskap (CHE).
    Håkansson, Bo
    Eka Chemicals AB.
    Simonsson, Daniel
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Anodic Reactions in the Chlorate Process2001Ingår i: Energy and Electrochemical Processes for a Cleaner Environment: Proceedings of the International Symposium / [ed] C. Comninellis, M. Doyle and J. Winnick, Pennington, New Jersey, USA: The Electrochemical Scoiety, Inc. , 2001, 1, s. 117-128Kapitel i bok, del av antologi (Refereegranskat)
  • 20.
    Cornell, Ann
    et al.
    KTH, Tidigare Institutioner, Kemiteknik.
    Lindbergh, Göran
    KTH, Tidigare Institutioner, Kemiteknik.
    Simonsson, Daniel
    KTH, Tidigare Institutioner, Kemiteknik.
    The effect of addition of chromate on the hydrogen evolution reaction and on iron oxidation in hydroxide and chlorate solutions1992Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 37, nr 10, s. 1873-1881Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The addition of chromate to the electrolyte has been shown in previous papers to hinder almost completely the electroreduction of hypochlorite, while the hydrogen evolution reaction can still proceed on the cathode surface. The effect of chromate on the latter reaction has been studied with cyclic voltammetry and by measuring polarization curves for iron electrodes in both chlorate and hydroxide electrolyte. For the sake of comparison, the investigations have also included the effects on the gold electrode in hydroxide solution. The results showed that the kinetics is changed in a way that decreases the differences in electrocatalytic activity between different electrode materials. Also, the innermost layer of the chromium hydroxide film seems to be the most active part in the HER. The chromate also affects the oxidation of the iron surface. A practical result of this is that the activity for the HER on corroded iron in chlorate electrolyte depends on whether the electrolyte contained chromate during the period of corrosion. The activation becomes much smaller if chromate is present.

  • 21.
    Cornell, Ann
    et al.
    KTH, Skolan för kemivetenskap (CHE).
    Simonsson, Daniel
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Ruthenium Dioxide as Cathode Material for Hydrogen Evolution in Hydroxide and Chlorate Solutions1993Ingår i: Chlor-Alkali and Chlorate Production/New Mathematical and Computational Methods in Electrochemical Engineering / [ed] T. Jeffrey, K. Ota, J. Fenton och H. Kawamoto, Pennington, New Jersey, USA: The Electrochemical Society , 1993, s. 191-Kapitel i bok, del av antologi (Refereegranskat)
  • 22.
    Cornell, Ann
    et al.
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Simonsson, Daniel
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Ruthenium Dioxide as Cathode Material for Hydrogen Evolution in Hydroxide and Chlorate Solutions1993Ingår i: Journal of The Electrochemical Society, Vol. 140, nr 11, s. 3123-3129Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ruthenium dioxide as electrocatalyst on an activated cathode for chlorate production was investigated with respect toits activity towards hydrogen evolution, hypochlorite reduction, and chlorate reduction, respectively. Investigations weremade in the presence, as well as in the absence, of a chromium hydroxide film in 1M NaOH and in typical chlorateelectrolyte. Low overvoltages for hydrogen evolution were found and, at technical current densities, an effect of catalystcoating thickness. Commercial DSA® electrodes with RuO2 as the active compound were tested as cathodes and were lessactive but more stable than the coatings produced by us. Hypochlorite and chlorate were reduced in the absence ofchromate, chlorate reduction being fast on ruthenium dioxide compared to the other electrode materials and by far thedominating cathodic reaction in chlorate electrolyte without chromate and hypochlorite at 70°C, 3 kA/m2

  • 23.
    Endrodi, Balazs
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. University of Szeged, Hungary.
    Simic, Nina
    Wildlock, Mats
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    A review of chromium(VI) use in chlorate electrolysis: Functions, challenges and suggested alternatives2017Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 234, s. 108-122Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Sodium chlorate is industrially produced by electrolysis of an aqueous salt solution, in which chromium ( VI) constitutes an important excipient component. It is added to a concentration of a few grams Na2Cr2O7/ liter to the electrolyte and has several functions in the process, the most important being to increase the Faradaic efficiency for hydrogen evolution in the undivided electrochemical cells. A thin film of Cr(OH)(3) x nH(2)O formed by reductive deposition on the cathodes decreases the rate of unwanted side reactions, while still enabling hydrogen evolution to occur. In addition chromium(VI) buffers the electrolyte at the optimum pH for operation and promotes the desired homogeneous reactions in the electrolyte bulk. Chromium species also affect the rates of hydrogen and oxygen evolution at the electrodes and are said to protect the steel cathodes from corrosion. Although chromium(VI) stays in a closed loop during chlorate production, chromate is a highly toxic compound and new REACH legislation therefore intends to phase out its use in Europe from 2017. A production without chromium(VI), with no other process modifications is not possible, and today there are no commercially available alternatives to its addition. Thus, there is an urgent need for European chlorate producers to find solutions to this problem. It is expected that chromium-free production will be a requirement also in other parts of the world, following the European example. As the chromium(VI) addition affects the chlorate process in many ways its replacement might require a combination of solutions targeting each function separately. The aim of this paper is to explain the role and importance of chromium(VI) in the chlorate manufacturing process. Previous achievements in its replacement are summarized and critically evaluated to expose the current state of the field, and to highlight the most promising avenues to be followed. An attempt is also made to reveal connections with other research fields (e.g. photochemical water splitting, corrosion science) facing similar problems. Allied effort of these different communities is expected to open up research avenues to the mutual benefit of these fields.

  • 24.
    Endrodi, Balazs
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Smulders, Vera
    Univ Twente, Fac Sci & Technol, MESA Inst Nanotechnol, PhotoCatalyt Synth Grp, Meander 229,POB 217, NL-7500 AE Enschede, Netherlands..
    Simic, Nina
    Nouryon, SE-44580 Bohus, Sweden..
    Wildlock, Mats
    Nouryon, SE-44580 Bohus, Sweden..
    Mul, Guido
    Univ Twente, Fac Sci & Technol, MESA Inst Nanotechnol, PhotoCatalyt Synth Grp, Meander 229,POB 217, NL-7500 AE Enschede, Netherlands..
    Mei, Bastian
    Univ Twente, Fac Sci & Technol, MESA Inst Nanotechnol, PhotoCatalyt Synth Grp, Meander 229,POB 217, NL-7500 AE Enschede, Netherlands..
    Cornell, Ann M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    In situ formed vanadium-oxide cathode coatings for selective hydrogen production2019Ingår i: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 244, s. 233-239Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electrode selectivity towards hydrogen production is essential in various conversion technologies for renewable energy, as well as in different industrial processes, such as the electrochemical production of sodium chlorate. In this study we present sodium metavanadate as a solution additive, inducing selective cathodic formation of hydrogen in the presence of various other reducible species such as hypochlorite, chlorate, oxygen, nitrate, hydrogen-peroxide and ferricyanide. During electrolysis a vanadium-oxide coating forms from the reduction of sodium metavanadate, explaining the observed enhanced selectivity. The hydrogen evolution reaction proceeds without significantly altered kinetics on such in situ modified electrode surfaces. This suggests that the reaction takes place at the interface between the electrode surface and the protective film, which acts as a diffusion barrier preventing the unwanted species to reach the electrode surface.

  • 25.
    Endrodi, Balazs
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi. Sch Engn Sci Chem Univ Szeged, Dept Phys Chem & Mat Sci, Rerrich Bela Sq 1, H-6720 Szeged, Hungary..
    Stojanovic, Aleksandra
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Cuartero, Maria
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Simic, Nina
    Nouryon Pulp & Performance Chem AB, Farjevagen 1, SE-44580 Bohus, Sweden..
    Wildlock, Mats
    Nouryon Pulp & Performance Chem AB, Farjevagen 1, SE-44580 Bohus, Sweden..
    de Marco, Roland
    Univ Sunshine Coast, Fac Sci Hlth Educ & Engn, Sippy Downs Dr 90, Sippy Downs, Qld 4556, Australia.;Univ Queensland, Sch Chem & Mol Biosci, Cooper Rd 68, Brisbane, Qld 4072, Australia..
    Crespo, Gaston A.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Tillämpad fysikalisk kemi.
    Cornell, Ann M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Selective Hydrogen Evolution on Manganese Oxide Coated Electrodes: New Cathodes for Sodium Chlorate Production2019Ingår i: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 7, nr 14, s. 12170-12178Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The safety and feasibility of industrial electrochemical production of sodium chlorate, an important chemical in the pulp and paper industry, depend on the selectivity of the electrode processes. The cathodic reduction of anodic products is sufficiently suppressed in the current technology by the addition of chromium(VI) to the electrolyte, but due to the high toxicity of these compounds, alternative pathways are required to maintain high process efficiency. In this paper, we evaluate the electrochemical hydrogen evolution reaction kinetics and selectivity on thermally formed manganese oxide-coated titanium electrodes in hypochlorite and chlorate solutions. The morphology and phase composition of manganese oxide layers were varied via alteration of the annealing temperature during synthesis, as confirmed by scanning electron microscopy, X-ray diffraction, synchrotron radiation X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy measurements. As shown in mass spectroscopy coupled electrochemical measurements, the hydrogen evolution selectivity in hypochlorite and chlorate solutions is dictated by the phase composition of the coating. Importantly, a hydrogen evolution efficiency of above 95% was achieved with electrodes of optimized composition (annealing temperature, thickness) in hypochlorite solutions. Further, these electrode coatings are nontoxic and Earth-abundant, offering the possibility of a more sustainable chlorate production.

  • 26.
    Endrodi, Balázs
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi. Department of Physical Chemistry and Materials Science, University of Szeged, Szeged, Hungary.
    Sandin, Staffan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Wildlock, Mats
    Simic, Nina
    Cornell, Ann M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Suppressed oxygen evolution during chlorateformation from hypochlorite in the presenceof chromium(VI)2019Ingår i: Journal of chemical technology and biotechnology (1986), ISSN 0268-2575, E-ISSN 1097-4660, Vol. 94, nr 5, s. 1520-1527Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    BACKGROUND: Chromium(VI) is a crucial electrolyte component in industrial chlorate production. Due to its toxicity, iturgently needs to be abandoned and its functions fulfilled by new solutions. In the industrial production of sodium chlorate,homogeneous decomposition of the hypochlorite intermediate to chlorate is a key step. As a competing loss reaction,hypochlorite can decompose to oxygen. How chromium(VI) affects these reactions is not well understood.

    RESULTS: This work shows, for the first time, that chromium(VI) selectively accelerates the chlorate formation from hypochloriteboth in dilute and concentrated, industrially relevant solutions. The effect of the ionic strength and the specific contributionof different electrolyte components were systematically studied. By simultaneously measuring the concentration decayof hypochlorite (UV–vis spectroscopy) and the oxygen formation (mass spectrometry), both the rate and the selectivity of thereactions were evaluated.

    CONCLUSION: In the presence of chromium(VI) the hypochlorite decomposition is described by the sum of an uncatalyzedand a parallel catalyzed reaction, where oxygen only forms in the uncatalyzed reaction. When removing chromium(VI),the homogeneous oxygen formation increases, causing economic and safety concerns. The need for a catalyst selectivefor chlorate formation is emphasized.

  • 27.
    Gustavsson, John
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Hummelgård, Christine
    Institutionen för naturvetenskap, teknik och matematik, Mid Sweden University, Sundsvall, Sweden.
    Bäckström, Joakim
    Institutionen för naturvetenskap, teknik och matematik, Mid Sweden University, Sundsvall, Sweden.
    Odnevall Wallinder, Inger
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Rahman, Seikh Mohammad Habibur
    Chalmers, Dept Chem & Biol Engn, Gothenburg, Sweden.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Eriksson, Sten
    Chalmers, Dept Chem & Biol Engn, Gothenburg, Sweden.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    In-situ activated hydrogen evolution by molybdate addition to neutral and alkaline electrolytes2012Ingår i: Journal of Electrochemical Science and Engineering, ISSN 1847-9286, Vol. 2, nr 3, s. 105-120Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Activation of the hydrogen evolution reaction (HER) by in-situ addition of Mo(VI) to the electrolyte has been studied in alkaline and pH neutral electrolytes, the latter with the chlorate process in focus. Catalytic molybdenum containing films formed on the cathodes during polarization were investigated using scanning electron microscopy (SEM), energy-dispersive X ray analysis (EDS), X-ray photoelectron spectroscopy (XPS), and X ray fluorescence (XRF). In-situ addition of Mo(VI) activates the HER on titanium in both alkaline and neutral electrolytes and makes the reaction kinetics independent of the substrate material. Films formed in neutral electrolyte consisted of molybdenum oxides and contained more molybdenum than those formed in alkaline solution. Films formed in neutral electrolyte in the presence of phosphate buffer activated the HER, but were too thin to be detected by EDS. Since molybdenum oxides are generally not stable in strongly alkaline electrolyte, films formed in alkaline electrolyte were thinner and probably co-deposited with iron. A cast iron molybdenum alloy was also investigated with respect to activity for HER. When polished in the same way as iron, the alloy displayed a similar activity for HER as pure iron.

  • 28.
    Gustavsson, John
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hummelgård, Christine
    Department of Natural Sciences, Engineering and Mathematics, Mid Sweden University, SE 851 70 Sundsvall, Sweden.
    Bäckström, Joakim
    Department of Natural Sciences, Engineering and Mathematics, Mid Sweden University, SE 851 70 Sundsvall, Sweden.
    Odnevall Wallinder, Inger
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Rahman, Seikh Mohammed Habibur
    Department of Chemical and Biological Engineering, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Eriksson, Sten
    Department of Chemical and Biological Engineering, Chalmers University of Technology, SE 412 96 Gothenburg, Sweden.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    In-situ Activated Hydrogen Evolution by Molybdate Addition to Neutral and Alkaline ElectrolytesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Activation of the hydrogen evolution reaction (HER) by in-situ addition of Mo(VI) to the electrolyte has been studied in alkaline and pH neutral electrolytes, the latter with the chlorate process in focus. Catalytic molybdenum containing films formed on the cathodes during polarization were investigated using scanning electron microscopy (SEM), energy-dispersive X‑ray analysis (EDS), X-ray photoelectron spectroscopy (XPS), and X‑ray fluorescence (XRF). In-situ addition of Mo(VI) activates the HER on titanium in both alkaline and neutral electrolytes and makes the reaction kinetics independent of the substrate material. Films formed in neutral electrolyte consisted of molybdenum oxides and contained more molybdenum than those formed in alkaline solution. Films formed in neutral electrolyte in the presence of phosphate buffer activated the HER, but were too thin to be detected by EDS. Since molybdenum oxides are generally not stable in strongly alkaline electrolyte, films formed in alkaline electrolyte were thinner and probably co-deposited with iron. A cast iron‑molybdenum alloy was also investigated with respect to activity for HER. When polished in the same way as iron, the alloy displayed a similar activity for HER as pure iron.

  • 29.
    Gustavsson, John
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik.
    Li, Gongzhuo
    Hummelgård, Christine
    Bäckström, Joakim
    Permascand AB.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    On the suppression of cathodic hypochlorite reduction by electrolyte additions of molybdate and chromate ions2012Ingår i: Journal of Electrochemical Science and Engineering, ISSN 1847-9286, Vol. 2, nr 4, s. 155-169Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The goal of this study was to gain a better understanding of the feasibility of replacing Cr(VI) in the chlorate process by Mo(VI), focusing on the cathode reaction selectivity for hydrogen evolution on steel and titanium in a hypochlorite containing electrolyte. To evaluate the ability of Cr(VI) and Mo(VI) additions to hinder hypochlorite reduction, potential sweep experiments on rotating disc electrodes and cathodic current efficiency (CE) measurements on stationary electrodes were performed. Formed electrode films were investigated with scanning electron microscopy and energy-dispersive X-ray spectroscopy. Cathodic hypochlorite reduction is hindered by the Mo-containing films formed on the cathode surface after Mo(VI) addition to the electrolyte, but much less efficient compared to Cr(VI) addition. Very low levels of Cr(VI), in the mM range, can efficiently suppress hypochlorite reduction on polished titanium and steel. Phosphate does not negatively influence the CE in the presence of Cr(VI) or Mo(VI) but the Mo-containing cathode films become thinner if the electrolyte during the film build-up also contains phosphate. For a RuO2-TiO2 anode polarized in electrolyte with 40 mM Mo(VI), the anode potential increased and increased molybdenum levels were detected on the electrode surface.

  • 30.
    Gustavsson, John
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Li, Gongzhuo
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hummelgård, Christine
    Department of Natural Sciences, Engineering and Mathematics, Mid Sweden University, SE‐851 70 Sundsvall, Sweden.
    Bäckström, Joakim
    Department of Natural Sciences, Engineering and Mathematics, Mid Sweden University, SE‐851 70 Sundsvall, Sweden.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    On the Suppression of Cathodic Hypochlorite Reduction by ElectrolyteAdditions of Molybdate and Chromate IonsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The goal of this study was to gain a better understanding of the feasibility of replacing Cr(VI) in the chlorate process by Mo(VI), focusing on the cathode reaction selectivity for hydrogen evolution on steel and titanium in a hypochlorite containing electrolyte.

    To evaluate the ability of Cr(VI) and Mo(VI) additions to hinder hypochlorite reduction, potential sweep experiments on rotating disc electrodes and cathodic current efficiency (CE) measurements on stationary electrodes were performed. Formed electrode films were investigated with scanning electron microscopy and energy-dispersive X-ray spectroscopy. Cathodic hypochlorite reduction is hindered by the Mo-containing films formed on the cathode surface after Mo(VI) addition to the electrolyte, but much less efficient compared to Cr(VI) addition. Very low levels of Cr(VI), in the mM range, can efficiently suppress hypochlorite reduction on polished titanium and steel. Phosphate does not negatively influence the CE in the presence of Cr(VI) or Mo(VI) and the Mo-containing cathode films become thinner if the electrolyte during the film build-up also contains phosphate. For a RuO2-TiO2 anode polarized in electrolyte with 40 mM Mo(VI), the anode potential increased and on the electrode surface, increased molybdenum levels were detected. In an earlier study 40 mM Mo(VI) gave increased by-product oxygen.

  • 31.
    Gustavsson, John
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    In-situ activation of hydrogen evolution in pH-neutral electrolytes by additions of multivalent cations2012Ingår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 37, nr 12, s. 9496-9503Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Activation of the hydrogen evolution reaction (HER) in close to pH-neutral electrolytes can be achieved by addition of trivalent cations. This activation has been investigated using steady state polarization, electrochemical impedance spectroscopy (EIS) and chemical analysis of cathode films for yttrium. Several multivalent cations were included in this study, such as Al(III), Mg(II), Y(III), Sm(III), La(III) and Sc(III). In general the more acidic the metal ions the larger is the activation. Metal hydroxide films formed in the alkaline diffusion layer at the cathode surface can have a negative impact on the magnitude of this activation, and therefore complicate the interpretation of the results. The activation corresponds to a transport of metal ion complexes to the electrode surface and the reduction of bound ligand water to form hydrogen.

  • 32.
    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 process2010Ingår i: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 40, nr 8, s. 1529-1536Artikel i tidskrift (Refereegranskat)
    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.

  • 33. Hummelgard, Christine
    et al.
    Gustavsson, John
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Olin, Hakan
    Backstrom, Joakim
    Spin coated titanium-ruthenium oxide thin films2013Ingår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 536, s. 74-80Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Substrates of different roughness spin coated with Ti0.7Ru0.3O2 films have been evaluated as model system for fundamental studies of the industrially and scientifically interesting (Ti, Ru)O-2 based electrodes. The approach allowed for much more accurate control over the material synthesis than the traditionally used brush-, dip-, or spray-coating, on titanium-metal substrates. It moreover yielded well-defined samples suitable for basic studies of the surface properties that are of fundamental importance for understanding the electrochemical functionality of the electrode. We have compared the films on silicon substrates to films prepared by spin coating the same material on titanium-metal substrates. Samples have been characterized using atomic force microscopy (AFM), X-ray diffraction, scanning electronmicroscopy (SEM), and cyclic voltammetry. The samples displayed a uniformity of the films appropriate for AFM characterization. The smoother the substrate the less cracks in the coating. Using easily broken silicon wafers as substrate, a straightforward sample preparation technique was demonstrated for cross-section SEM. In addition, using high spinning velocities we have deposited the oxide films directly on silicon-nitride grids, thin enough to allow for studies with transmission electron microscopy without further sample preparation.

  • 34. Hummelgård, Christine
    et al.
    Karlsson, Rasmus K. S.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Bäckström, Joakim
    Rahman, Seikh M. H.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Eriksson, Sten
    Olin, Håkan
    Physical and electrochemical properties of cobalt doped (Ti,Ru)O-2 electrode coatings2013Ingår i: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 178, nr 20, s. 1515-1522Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The physical and electrochemical properties of ternary oxides Ti0.7Ru0.3-xCoxO2 (x = 0.093 and x = 0) have been investigated and compared. Samples of three different thicknesses were prepared by spin-coating onto polished titanium to achieve uniform and well-defined coatings. The resulting electrodes were characterized with a variety of methods, including both physical and electrochemical methods. Doping with cobalt led to a larger number of micrometer-sized cracks in the coating, and coating grains half the size compared to the undoped samples (10 instead of 20 nm across). This is in agreement with a voltammetric charge twice as high, as estimated from cyclic voltammetry. There is no evidence of a Co3O4 spinel phase, suggesting that the cobalt is mainly incorporated in the overall rutile structure of the (Ti,Ru)O-2. The doped electrodes exhibited a higher activity for cathodic hydrogen evolution compared to the undoped electrodes, despite the fact that one third of the active ruthenium was substituted with cobalt. For anodic chlorine evolution, the activity was similar for both electrode types.

  • 35. Ipek, N.
    et al.
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Vynnycky, M.
    A mathematical model for the electrochemical pickling of steel2007Ingår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 154, nr 10, s. P108-P119Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In industrial electrolytic pickling, a steel strip with oxidized surfaces is passed through an aqueous electrolyte between a configuration of electrodes, across which a potential difference is applied. The strip is thereby indirectly polarized, and electrochemical reactions at the strip surface result in the dissolution of the oxide layer and the evolution of hydrogen and oxygen. To obtain a better understanding of this process, we derive in this paper a mathematical model for predicting the potential, current density and ionic species distributions in a vertical pickling cell, as well as the oxide dissolution rate at the steel strip. The model is two dimensional, steady state and isothermal, and is based on the conservation equations for ionic species in dilute solution, involving convection, diffusion, migration and reaction. Kinetic Tafel expressions for the electrochemical gas evolving reactions at the lead anode, stainless steel cathode and at the bipolar steel strip surface are introduced. The derived model comprises six ionic species; numerical solutions for a full version and two reduced versions of this model are then obtained. Finally, the implications of the results for the actual pickling process are discussed.

  • 36. Ipek, N.
    et al.
    Vynnycky, M.
    Cornell, Ann M.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    A coupled electrochemical and hydrodynamical two-phase model for the electrolytic pickling of steel2008Ingår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 155, nr 4, s. P33-P43Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In industrial electrolytic pickling, a steel strip with oxidized surfaces is passed through an aqueous electrolyte between a configuration of electrodes, across which a potential difference is applied. The strip is thereby indirectly polarized, and electrochemical reactions at the strip surface result in the dissolution of the oxide layer and the evolution of hydrogen and oxygen bubbles. In this paper, we extend an earlier mathematical model for the electrochemical aspects of the process, which took account only of the liquid phase, to include the effect of the gas phase. The model is two-dimensional, steady-state and isothermal, and comprises five ionic species, the mixture velocity, pressure, and the gas fraction; numerical solutions of this model are then obtained. The results of the single and two-phase models are compared, and their implications for the actual pickling process are discussed.

  • 37.
    Ipek, Nulifer
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Centra, FaxénLaboratoriet. KTH, Tidigare Institutioner                               , Mekanik.
    Cornell, Ann
    KTH, Tidigare Institutioner                               , Kemiteknik.
    Vynnycky, Michael
    KTH, Skolan för teknikvetenskap (SCI), Centra, FaxénLaboratoriet. KTH, Tidigare Institutioner                               , Mekanik.
    Single- and two-phase modelling of the electrochemical pickling of steelManuskript (preprint) (Övrigt vetenskapligt)
  • 38.
    Karlsson, Rasmus K. B.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Selectivity between Oxygen and Chlorine Evolution in the Chlor-Alkali and Chlorate Processes2016Ingår i: Chemical Reviews, ISSN 0009-2665, E-ISSN 1520-6890, Vol. 116, nr 5, s. 2982-3028Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Chlorine gas and sodium chlorate are two base chemicals produced through electrolysis of sodium chloride brine which find uses, in many areas of industrial chemistry. Although the industrial production of these chemicals started over 100 years ago, there are still factors that limit the energy efficiencies of the processes. This review focuses on the unwanted production of oxygen gas, which decreases the charge yield by up to 5%. Understanding the factors that control the rate of oxygen production requires understanding of both chemical reactions occurring in the electrolyte, as well as surface reactions occurring on the anodes. The dominant anode material used in chlorate and chlor-alkali production is the dimensionally stable anode (DSA), Ti coated by a mixed oxide of RuO2 and TiO2. Although the selectivity for chlorine evolution on DSA is high, the fundamental reasons for this high selectivity are just now becoming elucidated. This review summarizes the research, since the early 1900s until today, concerning the selectivity between chlorine and oxygen evolution in chlorate and chlor-alkali production. It covers experimental as well as theoretical studies and highlights the relationships between process conditions, electrolyte composition, the material properties of the anode, and the selectivity for oxygen formation.

  • 39.
    Karlsson, Rasmus K. B.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Selectivity between oxygen and chlorine evolution in the chlor-alkali and chlorate processes: a comprehensive reviewManuskript (preprint) (Övrigt vetenskapligt)
  • 40.
    Karlsson, Rasmus K. B.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Catlow, Richard A.
    Sokol, Alexey A.
    Woodley, Scott M.
    Pettersson, Lars G. M.
    An improved force field for structures of mixed RuO2-TiO2 oxidesManuskript (preprint) (Övrigt vetenskapligt)
  • 41.
    Karlsson, Rasmus K. B.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Pettersson, L. G. M.
    Structural Changes in RuO2 during Electrochemical Hydrogen Evolution2016Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 13, s. 7094-7102Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A comprehensive theoretical study of the X-ray photoelectron shifts for RuO2 during hydrogen evolution has been performed. The shifts have been calculated using first-principles density functional theory and are compared with previous theoretical and experimental results to reconsider the proposed structural changes occurring during hydrogen evolution on RuO2. We find that during hydrogen evolution hydrogen enters the rutile RuO2 lattice and converts oxygen groups into hydroxyl groups and that this process explains the experimentally observed increase in unit cell dimensions as well as observed chemical shifts. Furthermore, carbon contamination is the most likely explanation for a set of peaks previously identified as caused by a new RuO(OH)2 phase. We find that formation of metallic Ru is just one possible explanation for another peak in the X-ray photoelectron spectrum and that explanations including conversion of RuO2 into Ru(OH)3, or removal of oxygen from Ru active surface sites, also can explain the observed shifts. (Figure Presented)

  • 42.
    Karlsson, Rasmus K. B.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Pettersson, Lars G. M.
    Structural changes in RuO2 during electrochemical hydrogen evolutionManuskript (preprint) (Övrigt vetenskapligt)
  • 43.
    Karlsson, Rasmus K. B.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Pettersson, Lars G. M.
    The electrocatalytic properties of doped TiO22015Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 180, s. 514-527Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To rationally control the catalytic properties of heterogeneous catalysts is the goal in heterogeneous (electro)catalysis research. Recent developments of theoretical methods based on density functional theory have enabled computational screening of catalysts, to achieve fundamental understanding of which catalyst is optimal for a certain reaction. In the present work, such screening is employed to elucidate the electrocatalytic properties of doped rutile TiO2. Electrodes based on this material are widely used in industrial production of, e.g., chlorine and sodium chlorate. The screening covers 38 different dopants, including all fourth, fifth and sixth row transition metals. Several dopants are predicted to activate TiO2, resulting in a material optimal either for the oxygen evolution reaction, or for selective chlorine evolution. The results can serve as a map for the rational design of electrocatalysts based on TiO2.

  • 44.
    Karlsson, Rasmus K. B.
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Hansen, Heine A.
    Bligaard, Thomas
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Pettersson, Lars G. M.
    Ti atoms in Ru0.3Ti0.7O2 mixed oxides form active and selective sites for electrochemical chlorine evolution2014Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 146, s. 733-740Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electrocatalytic properties of the (1 1 0) surface of Ru-doped TiO2, Ti-doped RuO2 and the industrially important Dimensionally Stable Anode (DSA) composition Ru0.3Ti0.7O2 have been examined using density functional theory. It is found that the oxygen adsorption energy on a Ti site is strongly affected by the presence of small amounts of Ru dopant, whereas oxygen adsorption is relatively unaffected by Ti dopants in RuO2. The calculations also indicate that coordinatively unsaturated Ti sites on Ru-doped TiO2 and on Ru0.3Ti0.7O2 could form active and selective sites for Cl-2 evolution. These results suggest a reason for why DSA shows a higher chlorine selectivity than RuO2 and propose an experimental test of the hypothesis.

  • 45.
    Kim, Hyeyun
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Guccini, Valentina
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden.
    Lu, Huiran
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi. Northvolt AB, Gamla Brogatan 26, SE-11120 Stockholm, Sweden.
    Salazar-Alvarez, German
    Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden..
    Lindbergh, Göran
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Cornell, Ann M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Lithium Ion Battery Separators Based On Carboxylated Cellulose Nanofibers From Wood2019Ingår i: ACS APPLIED ENERGY MATERIALS, ISSN 2574-0962, Vol. 2, nr 2, s. 1241-1250Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Carboxylated cellulose nanofibers, prepared by TEMPO-mediated oxidation (TOCN), were processed into asymmetric mesoporous membranes using a facile paper-making approach and investigated as lithium ion battery separators. Membranes made of TOCN with sodium carboxylate groups (TOCN-COO-Na+) showed capacity fading after a few cycles of charging and discharging. On the other hand, its protonated counterpart (TOCN-COOH) showed highly improved electrochemical and cycling stability, displaying 94.5% of discharge capacity maintained after 100 cycles at 1 C rate of charging and discharging. The asymmetric surface porosity of the membranes must be considered when assembling a battery cell as it influences the rate capabilities of the battery. The wood-based TOCN-membranes have a good potential as an ecofriendly alternative to conventional fossil fuel-derived separators without adverse side effects.

  • 46.
    Leijonmarck, Simon
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Danielsson, Carl-Ola
    Stora Enso, Karlstad Research Centre.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Electrochemical characterization of electrically induced adhesive debonding2011Ingår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 158, nr 10, s. P109-P114Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study concerns with controlled debonding of adhesive generated with electricity. This is a concept which could potentially be used in a wide range of applications, such as light-weight automotives, which can be easily recyclable at the touch of a button. The studied material is produced as a laminate with an epoxy adhesive bonded between aluminium foils. An electrochemical investigation of these debonding adhesives was performed. A three-electrode system with a circular quasi-reference electrode was validated and used together with electrical impedance spectroscopy and scanning electron microscope. It was found that the resistance at the debonding anodic interface of the laminate increased during polarization. This increase in resistance was shown to be reversible at open circuit. During the polarization, aluminium compounds were produced at the anode. These compounds grew to penetrate the adhesive. A debonding mechanism based on increasing mechanical stresses at the anodic interface is proposed.

  • 47.
    Leijonmarck, Simon
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Danielsson, Carl-Ola
    Åkermark, Torbjörn
    Brandner, Birgit D.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Electrolytically assisted debonding of adhesives: An experimental investigation2012Ingår i: International Journal of Adhesion and Adhesives, ISSN 0143-7496, E-ISSN 1879-0127, Vol. 32, s. 39-45Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The technology of electrically assisted delamination has potential applications in many fields, such as easy-to-open consumer packaging and recycling of lightweight materials. A better understanding about the mechanisms leading to debonding is important for further development of the technique, and is a goal of this study. A functional epoxy-based adhesive, applied between two aluminum foils, has been investigated using electrochemical and surface analytical techniques. Delamination occurred at the anodic adhesive boundary, which became acidic during polarization. The reactions during polarization of the laminates consisted of two steps, with aluminum oxide/hydroxide formation as the first and the build-up of a sulfur rich organic film as the second. Several possible debonding processes are discussed.

  • 48.
    Leijonmarck, Simon
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Flexible nano-paper-based positive electrodes for Li-ion batteries- Preparation process and properties2013Ingår i: Nano Energy, ISSN 2211-2855, Vol. 2, nr 5, s. 794-800Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Flexible battery solutions is an emerging field due to a demand for bendable electronic devices. In this study, a route to make flexible positive electrodes for Li-ion batteries by utilizing nanofibrillated cellulose (NFC) as binder material has been examined. These LiFePO4-based electrodes are made by filtration of a water dispersion of NFC, LiFePO4 and Super-P carbon particles, resembling a paper-making process. The resulting electrodes show good mechanical properties both dry as well as when soaked with battery electrolyte with a stress at break of typically at 5.2 and 2.2 MPa, respectively. The cycling performance was 151 mAh/g at C/10 and 132 mAh/g at 1C for samples dried at 170 degrees C. The drying temperature, after the filtration step, was found to be important and to affect both the mechanical properties, rendering the electrodes more ductile at lower temperatures, as well as the electrochemical properties, causing a higher coulombic efficiency at higher temperatures.

  • 49.
    Leijonmarck, Simon
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Cornell, Ann
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lindbergh, Göran
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Single-paper flexible Li-ion battery cells through a paper-making process based on nano-fibrillated cellulose2013Ingår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 1, nr 15, s. 4671-4677Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recently, a need for mechanically flexible and strong batteries has arisen to power technical solutions such as active RFID tags and bendable reading devices. In this work, a method for making flexible and strong battery cells, integrated into a single flexible paper structure, is presented. Nano-fibrillated cellulose (NFC) is used both as electrode binder material and as separator material. The battery papers are made through a paper-making type process by sequential filtration of water dispersions containing the battery components. The resulting paper structure is thin, 250 mm, and strong with a strength at break of up to 5.6 MPa when soaked in battery electrolyte. The cycling performances are good with reversible capacities of 146 mA h g(-1) LiFePO4 at C/10 and 101 mA h g(-1) LiFePO4 at 1 C. This corresponds to an energy density of 188 mW h g(-1) of full paper battery at C/10.

  • 50.
    Lindberg, Jonas
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Endrodi, Balazs
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi. Univ Szeged, Dept Phys Chem & Mat Sci, H-6720 Szeged, Hungary..
    Avall, Gustav
    Chalmers Univ Technol, Dept Phys, SE-41296 Gothenburg, Sweden..
    Johansson, Patrik
    Chalmers Univ Technol, Dept Phys, SE-41296 Gothenburg, Sweden..
    Cornell, Ann M.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Lindbergh, Göran
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Tillämpad elektrokemi.
    Li Salt Anion Effect on O-2 Solubility in an Li-O-2 Battery2018Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, nr 4, s. 1913-1920Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For the promising Li-O-2 battery to be commercialized, further understanding of its constituents is needed. This study deals with the role of O-2 in Li-O-2 batteries, both its influence on electrochemical performance and its solubility in lithium-salt-containing dimethyl sulfoxide (DMSO) electrolytes. Experimentally, the electrochemical performance was evaluated using cylindrical ultramicroelectrodes. Two independent techniques, using a mass spectrometer and an optical sensor, were used to evaluate the O-2 solubility, expressed as Henry's constant. Furthermore, the ionic conductivity, dynamic viscosity, and density were also measured. Density functional theory calculations were made of the interaction energy between O-2 and the different species in the electrolytes. When varying O-2 partial pressure, the current was larger at high pressures confirming that the O-2 concentration is of key importance when studying the kinetics of this system. Compared with neat DMSO, the O-2 solubility increased with addition of LiTFSI and decreased with addition of LiClO4, indicating that the salt influences the solubility. This solubility trend is best explained in terms of apparent molar volume and interaction energy between O-2 and the salt anion. In conclusion, this study shows the importance of O-2 concentration, not just its partial pressure, and that the choice of Li salt can make this concentration increase or decrease.

12 1 - 50 av 70
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf