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  • 1. Biendicho, Jordi Jacas
    et al.
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Offer, Colin
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Smith, Ronald I.
    Hull, Stephen
    New Opportunities for Air Cathode Batteries; in-Situ Neutron Diffraction Measurements2018In: Frontiers in energy research, ISSN 2296-598X, Vol. 6, article id UNSP 69Article in journal (Refereed)
    Abstract [en]

    Batteries with air electrodes are gaining interest as Energy Storage Systems (ESSs) for Electrical Vehicles (EVs) because of their high specific energy density. The electrochemical performance of these batteries is limited by the metallic electrode, which suffers structural transformations and corrosion during cycling that reduces the cycle life of the battery. In this context, relevant information on the discharge products may be obtained by in-situ neutron diffraction, a suitable technique to study electrodes that contain light elements or near neighbor elements in the periodic table. Case studies of MH-air and Fe-air batteries are highlighted.

  • 2.
    Biendicho, Jordi Jacas
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). STFC Rutherford Appleton Laboratory, England.
    Roberts, Matthew
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lagerqvist, Ulrika
    Smith, Ronald I.
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Norberg, Stefan T.
    Eriksson, Sten G.
    Hull, Stephen
    In situ investigation of commercial Ni(OH)(2) and LaNi5-based electrodes by neutron powder diffraction2015In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 30, no 3, p. 407-416Article in journal (Refereed)
    Abstract [en]

    Electrochemical reactions at both positive and negative electrodes in a nickel metal hydride (Ni-MH) battery during charge have been investigated by in situ neutron powder diffraction. Commercially available beta-Ni(OH)(2) and LaNi5-based powders were used in this experiment as positive and negative electrodes, respectively. Exchange of hydrogen by deuterium for the beta-Ni(OH)(2) electrode was achieved by ex situ cycling of the cell prior to in situ measurements. Neutron diffraction data collected in situ show that the largest amount of deuterium contained at the positive electrode is de-intercalated from the electrode with no phase transformation involved up to similar to 100 mA h/g and, in addition, the 110 peak width for the positive electrode increases on charge. The negative electrode of composition MmNi(3.6)Al(0.4)Mn(0.3)Co(0.7), where Mm = Mischmetal, exhibits a phase transformation to an intermediate hydride gamma phase first and then to the beta phase on charge. Unit cell dimensions and phase fractions have been investigated by Rietveld refinement of the crystal structure.

  • 3.
    Biendicho, Jordi Jacas
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). STFC Rutherford Appleton Laboratory, England.
    Roberts, Matthew
    Offer, Colin
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Widenkvist, Erika
    Smith, Ronald I.
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Edström, Kristina
    Norberg, Stefan T.
    Eriksson, Sten G.
    Hull, Stephen
    New in-situ neutron diffraction cell for electrode materials2014In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 248, p. 900-904Article in journal (Refereed)
    Abstract [en]

    A novel neutron diffraction cell has been constructed to allow in-situ studies of the structural changes in materials of relevance to battery applications during charge/discharge cycling. The new design is based on the coin cell geometry, but has larger dimensions compared to typical commercial batteries in order to maximize the amount of electrode material and thus, collect diffraction data of good statistical quality within the shortest possible time. An important aspect of the design is its modular nature, allowing flexibility in both the materials studied and the battery configuration. This paper reports electrochemical tests using a Nickel-metal-hydride battery (Ni-MH), which show that the cell is able to deliver 90% of its theoretical capacity when using deuterated components. Neutron diffraction studies performed on the Polaris diffractometer using nickel metal and a hydrogen-absorbing alloy (MH) clearly show observable changes in the neutron diffraction patterns as a function of the discharge state. Due to the high quality of the diffraction patterns collected in-situ (i.e. good peak-to-background ratio), phase analysis and peak indexing can be performed successfully using data collected in around 30 min. In addition to this, structural parameters for the beta-phase (charged) MH electrode obtained by Rietveld refinement are presented.

  • 4.
    Björling, T
    et al.
    Stockholm University.
    Noréus, D
    Stockholm University.
    Haussermann, U
    Polyanionic hydrides from polar intermetallica AeE(2) (Ae = Ca, Sr, Ba; E = Al, Ga, In)2006In: Journal of the American Chemical Society, Vol. 128, p. 817-824Article in journal (Refereed)
  • 5.
    Chamoun, Mylad
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Brant, William R.
    Tai, Cheuk-Wai
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Karlsson, Gunder
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Rechargeability of aqueous sulfate Zn/MnO2 batteries enhanced by accessible Mn2+ ions2018In: Energy storage materials, ISSN 2405-8289, Vol. 15, p. 351-360Article in journal (Refereed)
    Abstract [en]

    The Zn/MnO2 battery is safe, low cost and comes with a high energy density comparable to Li-ion batteries. However, irreversible spinel phases formed at the MnO2 electrode limits its cyclability. A viable solution to overcome this inactive phase is to use an aqueous ZnSO4-based electrolyte, where pH is mildly acidic leading to a different reaction mechanism. Most importantly, the addition of MnSO4 achieves excellent cyclability. How accessible Mn2+ ions in the electrolyte enhances the reversibility is presented. With added Mn2+, the capacity retention is significantly improved over 100 cycles. Zn2+ insertion plays an important role on the reversibility and a hydrated layered Zn-buserite structure formed during charge is reported. Furthermore, Zn4SO4(OH)(6) center dot 5H(2)O precipitates during discharge but is not involved in the electrochemical reaction. This precipitate both buffers the pH and partly insulates the surface. Described in operando study show how the phase transformations and the failure mechanisms depend on the presence of Mn2+-ions in the electrolyte. These results give insight necessary to improve this battery further to make it a worthy contender to the Li-ion battery in large scale energy storage solutions.

  • 6.
    Chamoun, Mylad
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Paulraj, Alagar Raj
    Kiros, Yohannes
    Svengren, Henrik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Göthelid, Mats
    Skårman, Björn
    Vidarsson, Hilmar
    Johansson, Malin
    Electrochemical Performance and in Operando Charge Efficiency Measurements of Cu/Sn-Doped Nano Iron ElectrodesManuscript (preprint) (Other academic)
    Abstract [en]

    Fe-air or Ni-Fe cells can offer low-cost and large-scale sustainable energy storage. At present, they are limited by low coulombic efficiency, low active material use, and poor rate capability. To overcome these challenges, two types of nanostructured doped iron materials were investigated: (1) copper and tin doped iron (CuSn); and (2) tin doped iron (Sn). Single-wall carbon nanotube (SWCNT) was added to the electrode and LiOH to the electrolyte. In the 2 wt. % Cu + 2 wt. % Sn sample, the addition of SWCNT increased the discharge capacity from 430 to 475 mAh g−1, and charge efficiency increased from 83% to 93.5%. With the addition of both SWCNT and LiOH, the charge efficiency and discharge capacity improved to 91% and 603 mAh g−1, respectively. Meanwhile, the 4 wt. % Sn substituted sample performance is not on par with the 2 wt. % Cu + 2 wt. % Sn sample. The dopant elements (Cu and Sn) and additives (SWCNT and LiOH) have a major impact on the electrode performance. To understand the relation between hydrogen evolution and charge current density, we have used in operando charging measurements combined with mass spectrometry to quantify the evolved hydrogen. The electrodes that were subjected to prolonged overcharge upon hydrogen evolution failed rapidly. This insight could help in the development of better charging schemes for the iron electrodes.

  • 7.
    Chamoun, Mylad
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Paulraj, Alagar Raj
    Skårman, Björn
    Vidarsson, Hilmar
    Kiros, Yohannes
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bifunctional Performance of Flow Assisted Rechargeable Iron-Air Alkaline BatteriesManuscript (preprint) (Other academic)
    Abstract [en]

    Low cost rechargeable iron-air alkaline batteries have all essential attributes to adapt for large scale energy storage applications. To actualize this implementation needs to overcome the challenges including poor efficiency and short cycle lifetime. Herein, suitable synthesized catalysts for the air electrode were investigated prior to iron-air cell testing. NiCo2O4 as sole catalyst proved exceptional bifunctional OER/ORR activity and stability over 440 h operation in air. This catalyst fitted into an electrolyte and oxygen flow assisted rechargeable iron-air prototype and performed stable over 588 h and had an energy density of 377 Wh kg-1 Fe. Inadequate coulombic efficiencies of 75 – 85% and energy efficiencies around 50% hurt the performance of the cell though and needed further development. Nevertheless, the findings in this work reports the opportunities and obstacles of the rechargeable iron-air battery.

  • 8.
    Chamoun, Mylad
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Skarman, Bjorn
    Vidarsson, Hilmar
    Smith, Ronald I.
    Hull, Stephen
    Lelis, Martynas
    Milcius, Darius
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Stannate Increases Hydrogen Evolution Overpotential on Rechargeable Alkaline Iron Electrodes2017In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 6, p. A1251-A1257Article in journal (Refereed)
    Abstract [en]

    Alkaline iron electrodes present some challenges for use in secondary batteries that are associated with low coulombic efficiency and discharge utilization. Low coulombic efficiency is correlated to the hydrogen evolution reaction that takes place during charge. In this work, we demonstrate rechargeable alkaline iron electrodes with significant capacity retention over 150 cycles with high efficiency by suppressing the hydrogen evolution with stannate. Adding stannate to the alkaline electrolyte when cycling the iron electrode drastically changes the electrochemistry. The additive brings on two advantageous attributes for the iron electrode: increased hydrogen evolution overpotential, and a flat and prolonged discharge curve at typical battery operation. These attributes were provided by a novel intermediate phase that was detected from in situ neutron diffraction measurements. This phase was only detected in situ while it decomposed ex situ, and indicated a solid solution constituted by some of the elements present in the electrode.

  • 9.
    Dong, Hanwu
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kiros, Yohannes
    Noreus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    An air-metal hydride battery using MmNi(3.6)Mn(0.4)Al(0.3)Co(0.7) in the anode and a perovskite in the cathode2010In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 35, no 9, p. 4336-4341Article in journal (Refereed)
    Abstract [en]

    Hydrogen storage alloy MmNi(3.6)Mn(0.4)Al(0.3)Co(0.7) (MH) was tested as anode material in a metal hydride-air cell. The cathode was a non-noble metal air electrode based on a mixture of perovskite and pyrolyzed macrocycles on carbon. Polarization and discharge capacities of the electrodes were measured and compared at 22 degrees C and 40 degrees C using air or oxygen at the cathode. Discharge capacity reaching 330 mAh/g MH with pure oxygen at 40 degrees C and 305 mAh/g MH with air at 22 degrees C were obtained. Power densities and/or energy densities were found to significantly depend on the increase of the electrode kinetics on both the ORR (oxygen reduction reaction) and HOR (hydrogen oxidation reaction). However, for air electrode, an increase of oxygen concentration by using pure oxygen gas plays a more important role than an 18 degrees C temperature increase. (C) 2010 Professor T. Nejat Veziroglu.

  • 10.
    Fahlquist, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Kadir, Abdulkarim
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Structural characterization of Sr4Mg4H4[CoH5]3 shows the importance of support from polarizingcounter ions to 3d transition metal hydrido complexesIn: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669Article in journal (Refereed)
    Abstract [en]

    The structure of the title compound was refined from neutronpowder diffraction data in the cubic space group P-43m (215). The unitcell contains one formula unit with 3 structurally equivalent [Co(I)H5]4-complexes as well as 4 interstitial hydride (H-) ions. The presence ofthe larger and less polarizing Sr2+ ions weakens the bond in thecomplexes and probably also the stability of the structure. Attempts tosynthesize the corresponding Ba analogue failed in contrast to usingsmaller and more polarizing Ca2+ and Yb2+ counterions.

  • 11.
    Fahlquist, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kadir, Karim
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Structural characterization of Sr4Mg4H4[CoH5](3) shows the importance of support from polarizing counter ions to 3d transition metal hydrido complexes2013In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 579, p. 31-33Article in journal (Refereed)
    Abstract [en]

    The structure of the title compound was refined from neutron powder diffraction data in the cubic space group P-43m (215). The unit cell contains one formula unit with 3 structurally equivalent [Co(I)H-5](4)-complexes as well as 4 interstitial hydride (H-) ions. The presence of the larger and less polarizing Sr2+ ions weakens the bond in the complexes and probably also the stability of the structure. Attempts to synthesize the corresponding Ba analogue failed in contrast to using smaller and more polarizing Ca2+ and Yb2+ counterions.

  • 12.
    Fahlquist, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Moser, David
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Noreus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Refson, Keith
    Parker, Stewart F.
    Stabilization of 3d Transition Metal Hydrido Complexes in SrH2Mg2[Co(I)H-5], BaH2Mg5[Co(-I)H-4](2), and RbH2Mg5[Co(-I)H4Ni(0)H-4] via Easily Polarizable Hydride Ligands2016In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 55, no 7, p. 3576-3582Article in journal (Refereed)
    Abstract [en]

    A combined study using neutron diffraction, inelastic neutron scattering, and first-principles calculations describe cobalt with a very low formal oxidation state of (-I) in a slightly distorted tetrahedral Co(-I)H-4-complex in BaH2Mg5[Co(-I)H-4](2) and in the structurally related RbH2Mg5[Co(-I)H4Ni(0)H-4]. This indicates that the electron back donating effect via the polarizable hydride ions to the counterions in the solid state hydrides, can be compared to more conventional back bonding able to reduce the oxidation state down to -I. The hydrides were synthesized by hot sintering of transition metal powders with corresponding binary alkali- and alkaline earth hydrides. In the similarly synthesized SrH2Mg2[Co(I)H-5], cobalt is formally + I-valent, showing a high sensitivity to differences in the counterion framework, which can also influence electrical properties.

  • 13.
    Fahlquist, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Moser, David
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Refson, Keith
    STFC Rutherford Appleton Laboratory.
    Parker, Stewart F.
    STFC Rutherford Appleton Laboratory.
    SrH2Mg2[Co(I)H5], BaH2Mg5[Co(-I)H4]2 and RbH2Mg5[Co(-I)H4 Ni(0)H4] illustrate how small variations in counter ions are important for the solid state stabilization of 3d-transition metal hydrido complexes as well as influencing electrical and magnetic propertiesManuscript (preprint) (Other academic)
    Abstract [en]

    Variations in the counter ion support to low valent 3d transition metal hydrido complexes in solids state hydrides influence formal oxidation states as well as their electrical properties. In a combined study using neutron scattering and first principle calculations a very low formal oxidation state of (-I) can be described for cobalt in a slightly distorted tetrahedral Co(-I)H4-complex in BaH2Mg5[Co(-I)H4]2 and in the structurally closely related RbH2Mg5[Co(-I)H4 Ni(0)H4]. This indicates that the electron “back donating” effect via the polarisable hydride ions to the counter ions in the solid state hydrides, can be compared to more conventional “back bonding” and reduce the oxidation state down to -I. The hydrides were synthesised by hot sintering of transition metal powders with the corresponding binary alkali- and alkaline earth hydrides. In the similarly synthesized SrH2Mg2[Co(I)H5] cobalt is formally +I-valent,  showing a high sensitivity to subtle differences in the counter ion framework.

  • 14.
    Fahlquist, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Noreus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Callear, Samantha
    David, William I. F.
    Haubackg, Bjorn C.
    Two New Cluster Ions, Ga[GaH(3)](4)(5-) with a Neopentane Structure in Rb(8)Ga(5)H(15) and [GaH(2)](n)(n-) with a Polyethylene Structure in Rb(n)(GaH(2))(n), Represent a New Class of Compounds with Direct Ga-Ga Bonds Mimicking Common Hydrocarbons2011In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 133, no 37, p. 14574-14577Article in journal (Refereed)
    Abstract [en]

    The first examples of a new class of gallium hydride clusters with direct Ga-Ga bonds and common hydrocarbon structures are reported. Neutron powder diffraction was used to find a Ga[GaH(3)](4)(5-) cluster ion with a neopentane structure in a novel cubic structure type of Rb(8)Ga(5)H(15). Another cluster ion with a polyethylene structure, [GaH(2)](n)(n-), was found in a second novel (RbGaH(2))(n) hydride. These hydrocarbon-like clusters in gallium hydride materials have significant implications for the discovery of hydrides for hydrogen storage as well as for interesting electronic properties.

  • 15.
    Fahlquist, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Cs10H[Ga3H8]3: A Hydrogenous Zintl Phase Containing Propane-Like Polyanions [Ga3H8]3- and Interstitial Hydrogen2013In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 52, no 12, p. 7125-7129Article in journal (Refereed)
    Abstract [en]

    The hydrogenous Zintl-phase Cs10H[Ga3H8](3) containing propane-like polyanions [Ga3H(D)(8)](3-) was successfully synthesized by direct hydrogenation of a 1:1 Cs/Ga metal mixture and characterized by powder X-ray and neutron diffraction. The charge of the polyanions is balanced by two different species of cations, hydrogen-centered octahedra [H(D)Cs-6](5+) and isolated Cs+. The structure crystallizes in the hexagonal space group P6(3)/mcm (193) with the cell parameters a = 11.1108(3) angstrom, c = 18.2149(5) angstrom, Z = 2.

  • 16.
    Fahlquist, Henrik
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sörby, Magnus H.
    Varying the Alkali-Metal Radii in (KxRb1−x)n[GaH2]n (0 ≤ x ≤ 1)Reorients a Stable Polyethylene-Structured [GaH2]nn− Anionic Chain2013In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 52, no 9, p. 4771-4773Article in journal (Refereed)
    Abstract [en]

    The stability of a negatively chargedpolyethylene-structured [GaH2]nn−cluster ion was inves-tigated by varying the K+/Rb+ratio in (KxRb1−x)n[GaH2]n(0≤x≤1). Neutron, X-ray, and IR spectroscopies wereused to characterize the new phases. Between the limitingcompositions Kn[GaH2]nand Rbn[GaH2]n, the [GaH2]nn−chains remained almost identical, indicating a stable specie.For rubidium-rich samples up to a potassium contentcorresponding to (K0.5Rb0.5)n[GaH2]n, two phases coexistin the samples, RbGaH2and (K0.5Rb0.5)n[GaH2]n, with aratio mirroring the relative alkali-ion content. The twophases have a different alignment of the [GaH2]nn−chains.For potassium-rich samples beyond (K0.5Rb0.5)n[GaH2]n,the samples were single-phased. The unit cell volume ofthe new (K0.5Rb0.5)n[GaH2]nstructure type shrinksaccording to Vegard’s law as smaller K+ions substitutefor larger Rb+ions. The [GaH2]nn−chains remained,however, almost identical. IR spectra from the differentphases were very similar, exhibited stretching, scissoring,and rocking modes similar to those in ordinary poly-ethylene, but shifted to lower frequencies, reflectingweaker Ga−H bonds. The existence of stable Kn[GaH2]nand Rbn[GaH2]n, would help to dehydrogenate KGaH4and RbGaH4upon heating. If this could be transferred tolighter alanates and borohydrides, it could be possible todevelop more functional hydrogen-storage systems.

  • 17.
    Hu, Wei-Kang
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Noreus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lab-size rechargeable metal hydride-air cells2010In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 195, no 17, p. 5810-5813Article in journal (Refereed)
    Abstract [en]

    Lab-size rechargeable metal hydride-air (MH-air) cells with a gas management device were designed in order to minimize the loss of electrolyte. An AB(5)-type hydrogen storage alloy was used as anode materials of the MH-air. The thickness of the metal hydride electrodes was in the range of 3.0-3.4 mm. Porous carbon-based air electrodes with Ag2O catalysts were used as bi-functional electrodes for oxygen reduction and generation. The electrodes were first examined in half-cells to evaluate their performance and then assembled into one MH-air cell. The results showed the good cycling stability of the rechargeable MH-air cell with a capacity of 1990 mAh. The discharge voltage was 0.69 V at 0.05-0.1 C. The charge efficiency was about 90%. The specific and volumetric energy densities were about 95 Wh kg(-1) and 140 Wh L-1, respectively.

  • 18.
    Hu, Wei-kang
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Noreus, Dag
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Metal hydrides as bi-functional catalysts for hydrogen generation and oxidation in reversible MH-air fuel cells.2009In: Electrochemistry Communications, Vol. 11, no 11, p. 2212-Article in journal (Refereed)
    Abstract [en]

    Two kinds of metal hydride alloys as the bi-functional catalyst concept for hydrogen generation and oxidation in hydrogen-diffusion electrodes were investigated. The AB5-type hydride electrode shows much higher catalytic activities than the Zr-based AB2-type hydride electrode. However, the activity of Zr-based hydride electrodes can be improved only after removal of zirconium oxides on surface by a 1.0 M HF solution. The experiments demonstrated that the both metal-hydride hydrogen-diffusion electrodes for cycles of hydrogen generation (12 h) and oxidation (12 h) had good stability under the current densities of 100 and 50 mA/cm2, respectively. The results also showed that small amounts of oxygen below 500 ppm and moisture up to 145,000 ppm in the hydrogen gas have little effect on the activity. It indicated that the hydride alloys as the non-noble-metal bi-functional catalysts in a reversible MH-air fuel cell have potential applications.

  • 19. Hu, WK
    et al.
    Gao, XP
    Noréus, D
    Stockholm University.
    Burchardt, T
    Nakstad, NK
    Evaluation of nano-crystal sized alpha-nickel hydroxide as an electrode material for alkaline rechargeable cells2006In: Journal of Power Sources, Vol. 160, p. 704-710Article in journal (Refereed)
  • 20. Hu, WK
    et al.
    Geng, MM
    Gao, XP
    Burchardt, T
    Gong, ZX
    Noréus, D
    Stockholm University.
    Nakstad, NK
    Effect of long-term overcharge and operated temperature on perfomance of rechargeable NiMH cells2006In: Journal of Power Sources, Vol. 159, p. 1478-1483Article in journal (Refereed)
  • 21.
    Kadir, Abdulkarim
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Moser, D.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Munzel, M.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Noreus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Investigation of Counterion Influence on an Octahedral IrH(6)-Complex in the Solid State Hydrides AAeIrH(6) (A = Na, K and Ae = Ca, Sr, Ba, and Eu) with a New Structure Type2011In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 50, no 23, p. 11890-11895Article in journal (Refereed)
    Abstract [en]

    A number of new quaternary iridium based hydrides and deuterides AAeIrH/D(6) (where A = Na and K; Ae = Ca, Ba, Sr, and Eu) have been synthesized by direct combination of the alkali, alkaline earth or europium binary hydrides/deuterides and iridium powder. The crystal structures were determined by Guinier-Hagg X-ray and neutron powder diffraction and a new cubic structure type was found. The structure is described in space group F (4) over bar 3m, but related to the K(2)PtCl(6) type structure. The new structure can be described as consisting of cubes of A(+) and Ae(2+) ions, where the A(+) and Ae(2+) ions alternates so that they occupy opposite corners in the cube. Every second cube contains a regular octahedral [Ir(III)H(6)](-3)-complex and the adjacent is empty. Solid-state IR spectroscopy was used to determine the Ir-allowed stretching and bending frequencies for the [Ir(III)H(6)](-3) complex with different counterions. These were also compared with the corresponding stretching frequencies for Fe(II)H(6), Ru(II)H(6), Os(II)H(6), and Ir(II)H(5) complexes in similar solid state hydrides, which increased when going from Fe through Ru, Os to Ir. The frequencies scaled almost linearly with the inverse of size of the cube surrounding the complexes but showed no significant dependence of the formal oxidation state or the experimentally obtained Ir-D distances. However, this was mainly because of difficulties in obtaining enough accurate atomic positions. The ab initio DFT calculations could reproduce the stretching frequencies within a few 10 cm(-1), indicating that experimental vibrational frequencies offer a sensitive test of DFT results.

  • 22.
    Kadir, Abdulkarim
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Noreus, Dag
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Structural determination of NaAl2Ga2 intermetallic compound having the ThCr2Si2 type structure.2009In: Journal of Alloys and Compounds, Vol. 477, no 1-2, p. 149-151Article in journal (Refereed)
    Abstract [en]

    NaAl2Ga2 intermetallic compound has been synthesized by direct combination of the elements in the atomic ratio Na:Ga:Al = 1:2:2. Guinier–Hägg X-ray and neutron powder diffraction determined a ThCr2Si2 type structure for the new compound with tetragonal unit cell axis a = 4.1817(5) and c = 11.388(2) Å.

  • 23. Kadir, K
    et al.
    Ahmed, TM
    Noréus, D
    Stockholm University.
    Eriksson, L
    Stockholm University.
    Octaammonium diaquahexa-mu 2- oxalato-dioxalatotetracopper(II) tetrahydrate2006In: Acta Crystallographica Section E-Structure Reports Online, Vol. 62, p. M1139-Article in journal (Refereed)
  • 24. Lee, Myeong H.
    et al.
    Björling, T.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Hauback, B. C.
    Utsumi, T.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Moser, D.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Bull, D.
    Noreus, Dag
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Sankey, Otto F.
    Haeussermann, Ulrich
    Crystal structure, electronic structure, and vibrational properties of MAlSiH (M=Ca,Sr,Ba): Hydrogenation-induced semiconductors from the AlB2-type alloys MAlSi2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 19, p. 195209-Article in journal (Refereed)
    Abstract [en]

    Superconducting AlB2-type silicides CaAlSi, SrAlSi, and BaAlSi (MAlSi) absorb hydrogen and form semiconducting monohydrides where hydrogen is exclusively attached to Al. This induces a metal-nonmetal transition which is accompanied with only a minor rearrangement of the metal atoms. We report the synthesis and structure determination of CaAlSiH and BaAlSiH as well as a first-principles study of the electronic structure and vibrational property changes associated with the metal-nonmetal transition. We find that incorporation of H in MAlSi removes the partly occupied antibonding pi(*) band responsible for metallic behavior and turns it into an energetically low-lying Al-H bonding band. The fully occupied bonding pi band in MAlSi changes to a weakly dispersed band with Si p(z) (lone-pair) character in the hydrides, which becomes located below the Fermi level. The soft phonon mode in MAlSi pivotal for the superconducting properties stiffens considerably in the hydride. This mode is associated with the out-of-plane Al-Si vibration and is most affected by the formation of the Al-H bond. The mode of the Al-Si in-plane vibration, however, is unaffected, indicating that the Al-Si bond is equally strong in the metallic precursor and the semiconducting hydride. Al-H modes for MAlSiH are weakly dispersed. The frequencies of the stretching mode are around 1200 cm(-1) and virtually invariant to the M environment, indicating a covalent but weak Al-H interaction, which is interpreted as a dative bond from hydridic hydrogen to Al [Al <- H1-].

  • 25. Lelis, Martynas
    et al.
    Milcius, Darius
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Substrate effects on formation and hydrogenation of Mg-Ni films2012In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 263, p. 202-209Article in journal (Refereed)
    Abstract [en]

    Usually metallic films for metal hydrides research applications are deposited on hard and flat substrates such as silicon, magnesium oxide, fused silica or quartz glass. With the film thickness increases all films during hydrogenation deals with typical problems such as film brittleness and cracking. In this paper we demonstrate that metal Mg-Ni films for hydrogen storage can be successfully deposited on to the flexible low surface energy expanded PTFE substrates. The received results for soft substrates (expanded PTFE) are compared to films being deposited on crystalline silicon substrate with and without plasma pretreatment. It is observed that different interface zone between substrate and film has great affect on both film crystallinity and its reaction with hydrogen. It is also demonstrated that modifying surface of the substrate might have affect on film microstructure before and after hydrogenation.

  • 26. Ma, Honglei
    et al.
    Zhang, Xuemei
    Liu, Bingbing
    Li, Quanjun
    Zeng, Qifeng
    Yu, Shidan
    Zou, Bo
    Cui, Tian
    Zou, Guangtian
    Liu, Zhenxian
    Wagberg, T.
    Sundqvist, B.
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Synchrotron X-ray Diffraction and Infrared Spectroscopy Studies of C60H18 under High Pressure2010In: The journal of physical chemistry letters, ISSN 1948-7185, Vol. 1, no 4, p. 714-719Article in journal (Refereed)
    Abstract [en]

    In situ high-pressure angle-dispersive synchrotron X-ray diffraction and high-pressure mid-infrared (IR) spectrum measurements of C-60-H-18 were carried out up,to 32 and 10.2 GPa, respectively. Our diffraction data indicated that the fcc structure of C60H18 was stable up to 32 GPa. The bulk modulus B-0 was determined to be 21 +/- 1.16 GPa, about 40% higher than that of C-60. The C-H vibrations still existed up to 10.2 GPa, and the vibrational frequencies decreased with increasing pressure. IR-active vibrational frequencies and their corresponding eigenvectors of C60H18 were simulated by DMOL3. The effects of the hydrogen atoms attached to the fullerene molecular cage on the stability of the structure under high pressure are discussed.

  • 27. Moser, D.
    et al.
    Baldissin, G.
    Bull, D. J.
    Riley, D. J.
    Morrison, I.
    Ross, D. K.
    Oates, W. A.
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    The pressure-temperature phase diagram of MgH(2) and isotopic substitution2011In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 23, no 30, p. 305403-Article in journal (Refereed)
    Abstract [en]

    Computational thermodynamics using density functional theory ab initio codes is a powerful tool for calculating phase diagrams. The method is usually applied at the standard pressure of p = 1 bar and where the Gibbs energy is assumed to be equal to the Helmholtz energy. In this work, we have calculated the Gibbs energy in order to study the release temperature and phase modifications of MgH(2) at high pressures up to 10 GPa (100 kbar). The isotopic substitution of hydrogen with deuterium (or tritium) does not bring about any strong effects on the phase diagram. These considerations are of extreme importance for (i) the synthesis of novel substitutional magnesium based materials at high pressure and (ii) the determination of the correct reference states for the calculation of phase diagrams at high pressure. The calculated results are compared with experimental data obtained with an in situ neutron diffraction measurement.

  • 28. Moser, D.
    et al.
    Bull, D. J.
    Cowpe, J. S.
    Roach, D. L.
    Ross, D. K.
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Tucker, M. G.
    An in situ neutron diffraction measurement of the pressure-temperature evolution of a MgD2:TiD2 mixture2010In: High Pressure Research, ISSN 0895-7959, E-ISSN 1477-2299, Vol. 30, no 4, p. 643-652Article in journal (Refereed)
    Abstract [en]

    The hydrogen storage capacity of Mg-Ti-H films is approximately five times that of conventional metal hydride electrodes in NiMH-batteries. Mg and Ti are considered to be immiscible in the bulk and the ambient pressure phase diagram of Mg and Ti indicates that no binary stable bulk compounds are formed. However, in the presence of hydrogen, an Mg-Ti-H phase has been obtained by Kyoi et al. using a high pressure synthesis - where magnesium hydride is compacted with different TM-hydrides in an anvil cell at pressures of the order several GPa (4-8GPa) and at a temperature of 873K. In this work, we have proved the feasibility of in situ powder diffraction using the Paris-Edinburgh high pressure cell for the observation of structural changes on this system and we propose modifications to improve the output of the experiment.

  • 29. Moser, D
    et al.
    Bull, DJ
    Sato, T
    Noreus, D
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Kyoi, D
    Sakai, T
    Kitamura, N
    Yusa, H
    Taniguchi, T
    Kalisvaart, WP
    Notten, P
    Structure and stability of high pressure synthesized Mg-TM hydrides (TM = Ti, Zr, Hf, V, Nb and Ta) as possible new hydrogen rich hydrides for hydrogen storage.2009In: Journal of Materials Chemistry, Vol. 19, no 43, p. 8150-Article in journal (Refereed)
    Abstract [en]

    A series of hydrogen rich Mg6–7TMH14–16 (TM = Ti, Zr, Hf, V, Nb and Ta) hydrides have been synthesized at 600 °C in a high pressure anvil cell above 4 GPa. All have structures based on a fluorite type metal atom subcell lattice with a ≈ 4.8 Å. The TM atom arrangements are, however, more ordered and can best be described by a superstructure where the 4.8 Å FCC unit cell axis is doubled. The full metal atom structure corresponds to the Ca7Ge type structure. This superstructure was also observed from electron diffraction patterns. The hydrogen atoms were found from powder X-ray diffraction using synchrotron radiation to be located in the two possible tetrahedral sites. One coordinates three Mg atoms and one TM atom and another coordinates four Mg atoms. These types of new hydrogen rich hydrides based on immiscible metals were initially considered as metastable but have been observed to be reversible if not fully dehydrogenated. In this work, DFT calculations suggest a mechanism whereby this can be explained: with H more strongly bonded to the TM, it is in principle possible to stepwise dehydrogenate the hydride. The remaining hydrogen in the tetrahedral site coordinating the TM would then act to prevent the metals from separating, thus making the system partially reversible

  • 30.
    Moser, D.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Haussermann, U.
    Utsumi, T.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Björling, T.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Noréus, D.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    A series of BaAl2-xSixH2-x (0.4 < x < 1.6) hydrides with compositions and structures in between BaSi2 and BaAl2H22010In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 505, no 1, p. 1-5Article in journal (Refereed)
    Abstract [en]

    By substituting Si- with (Al-H)(-) in trigonal BaSi2, a series of hydrides has been synthesized with compositions BaAl2-xSixH2-x (0.4 < x < 1.6). OFF calculations show that the end compositions BaSi2 and BaAl2H2 are conductors whereas the intermediate BaAlSiH is a semiconductor. The cell parameters for the trigonal cell vary linearly as a function of the Si-/(Al-H)(-) substitution in this MgB2 related structure type, opening up the possibility of continuously tunable electric properties.

  • 31. Parker, Stewart F.
    et al.
    Amieiro-Fonseca, Alvaro
    Gregory, Duncan
    Noreus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Yvon, Klaus
    Preface2011In: Faraday discussions (Online), ISSN 1359-6640, E-ISSN 1364-5498, Vol. 151, p. 9-9Article in journal (Refereed)
  • 32. Paulraj, Alagar Raj
    et al.
    Kiros, Yohannes
    Chamoun, Mylad
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Svengren, Henrik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Goethelid, Mats
    Skarman, Bjoern
    Vidarsson, Hilmar
    Johansson, Malin B.
    Electrochemical Performance and in Operando Charge Efficiency Measurements of Cu/Sn-Doped Nano Iron Electrodes2018In: Batteries, ISSN 2313-0105, Vol. 5, no 1, article id 1Article in journal (Refereed)
    Abstract [en]

    Fe-air or Ni-Fe cells can offer low-cost and large-scale sustainable energy storage. At present, they are limited by low coulombic efficiency, low active material use, and poor rate capability. To overcome these challenges, two types of nanostructured doped iron materials were investigated: (1) copper and tin doped iron (CuSn); and (2) tin doped iron (Sn). Single-wall carbon nanotube (SWCNT) was added to the electrode and LiOH to the electrolyte. In the 2 wt. % Cu + 2 wt. % Sn sample, the addition of SWCNT increased the discharge capacity from 430 to 475 mAh g(-1), and charge efficiency increased from 83% to 93.5%. With the addition of both SWCNT and LiOH, the charge efficiency and discharge capacity improved to 91% and 603 mAh g(-1), respectively. Meanwhile, the 4 wt. % Sn substituted sample performance is not on par with the 2 wt. % Cu + 2 wt. % Sn sample. The dopant elements (Cu and Sn) and additives (SWCNT and LiOH) have a major impact on the electrode performance. To understand the relation between hydrogen evolution and charge current density, we have used in operando charging measurements combined with mass spectrometry to quantify the evolved hydrogen. The electrodes that were subjected to prolonged overcharge upon hydrogen evolution failed rapidly. This insight could help in the development of better charging schemes for the iron electrodes.

  • 33.
    Sato, Toyoto
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Kyoi, D.
    Rönnebro, E.
    Kitamura, N.
    Sakai, T.
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Structural investigations of two new ternary magnesium–niobium hydrides, Mg6.5NbH~14 and MgNb2H~42006In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 417, no 1-2, p. 230-234Article in journal (Refereed)
    Abstract [en]

    Two new magnesium–niobium hydrides, Mg6.5NbH14 with a face centred cubic unit cell a = 9.548(1) Å (space group (No. 225), Z = 4, V = 870.49 Å3) and MgNb2H4 with a C-centred monoclinic unit cell a = 5.685 (4) Å, b = 3.2914(6) Å, c = 7.924(2) Å and β = 103.82(3)° (space group C2/m (No. 12), Z = 2, V = 143.98 Å3), were synthesized by reacting MgH2 and Nb in a high-pressure anvil cell at 8 GPa and 600 °C. The structures of the new hydrides were refined from synchrotron radiation data. Mg6.5NbH14 has a structure related to Mg7TiH16 (a = 9.532(2) Å space group (No. 225)) (D. Kyoi, T. Sato, E. Rönnebro, N. Kitamura, A. Ueda, M. Ito, S. Katsuyama, S. Hara, D. Noréus, T. Sakai, J. Alloys Compd. 372 (2004) 213). Where the metal atom structure is of the Ca7Ge type. Mg6.5NbH14, however, has some vacancies on one of the magnesium sites similar to the recently discovered Mg6VH14 (D. Kyoi, T. Sato, E. Rönnebro, Y. Tsuji, N. Kitamura, A. Ueda, M. Ito, S. Katsuyama, S. Hara, D. Noréus, T. Sakai, J. Alloys Compd. 375 (2004) 253). The metal atoms in MgNb2H4 have the AuTe2 type structure.

  • 34.
    Shen, Yang
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Starborg, Stina
    Increasing NiMH battery cycle life with oxygen2018In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 43, no 40, p. 18626-18631Article in journal (Refereed)
    Abstract [en]

    Nickel-Metal Hydride batteries (NiMH) have long cycle life. But in the end corrosion of the metal hydride is detrimental for life expectancy. Corrosion reduces the metal hydride capacity, but more severely it consumes water in the electrolyte resulting in increased internal resistance, which is the main cause for cell failure.

    The corrosion, further, evolves hydrogen, causing an unbalance between anode and cathode, leading to premature internal pressure increase when the cells are approaching end of charge. This accelerates the drying out, if the cells vent through the safety valve.

    In this study, a controlled addition of oxygen was used to rebalance the electrodes and replenish the electrolyte – as the added oxygen reacts with hydrogen that was formed during the corrosion process. Thus, the two most detrimental factors in cell ageing can be mitigated. To fully restore the electrolyte content as well as electrode balance, both oxygen and hydrogen are needed to compensate for the loss to hydroxide ions OH formed in the corrosion process. A proper optimization of the gas additions combined with a cell design including an excess amount of MH-alloy to compensate for the corrosion can substantially increase the cycle life of NiMH batteries.

  • 35.
    Shen, Yang
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Peng, Fei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kontos, Sofia
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Improved NiMH performance by a surface treatment that creates magnetic Ni-clusters2016In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 41, no 23, p. 9933-9938Article in journal (Refereed)
    Abstract [en]

    A surface treatment method has been developed to activate the surface of an AB(5) type (La-20 Ce-7 Pr-1 Nd-4 Al-2 Mn-5 Co-6 Ni-55) alloy. In the process the surface is covered with a porous surface layer containing needle shaped rare earth hydroxides after etching by a potassium hydroxide solution. TEM studies show in addition the presence of a denser surface oxide layer with embedded Ni containing clusters covering the bulk alloy. The magnetic properties of the alloy powders change with the surface treatment. In addition to a paramagnetic component of the bulk alloy, surface treated alloy also displays superparamagnetic and ferromagnetic properties. In electrochemical half-cell tests, the alloy shows better high-rate dischargeability with increasing presence of magnetic clusters in the metal hydride particles surface.

  • 36. Talyzin, Alexandr V.
    et al.
    Luzan, Serhiy
    Anoshkin, Ilya V.
    Nasibulin, Albert G.
    Jiang, Hue
    Kauppinen, Esko I.
    Mikoushkin, Valery M.
    Shnitov, Vladimir V.
    Marchenko, Dmitry E.
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hydrogenation, Purification, and Unzipping of Carbon Nanotubes by Reaction with Molecular Hydrogen: Road to Graphane Nanoribbons2011In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 5, no 6, p. 5132-5140Article in journal (Refereed)
    Abstract [en]

    Reaction of single-walled carbon nanotubes (SWNTs) with hydrogen gas was studied in a temperature interval of 400-550 degrees C and at hydrogen pressure of 50 bar. Hydrogenation of nanotubes was observed for samples treated at 400-450 degrees C with about 1/3 of carbon atoms forming covalent C-H bonds, whereas hydrogen treatment at higher temperatures (550 degrees C) occurs as an etching. Unzipping of some SWNTs Into graphene nanoribbons is observed as a result of hydrogenation at 400-550 degrees C Annealing in hydrogen gas at elevated conditions for prolonged periods of time (72 h) is demonstrated to result also in nanotube opening, purification of nanotubes from amorphous carbon, and removal of carbon coatings from Fe catalyst particles, which allows their complete elimination by acid treatment.

  • 37. Talyzin, AV
    et al.
    Tsybin, YO
    Purcell, JM
    Schaub, TM
    Shulga, YM
    Noréus, D
    Stockholm University.
    Sato, T
    Stockholm University.
    Dzwilewski, A
    Sundqvist, B
    Marshall, AG
    Reaction of hydrogen gas with C-60 at elevated pressure and temperature: Hydrogenation and cage fragmentation2006In: Journal of Physical Chemistry A, Vol. 110, p. 8528-8534Article in journal (Refereed)
  • 38. Tan, Semra
    et al.
    Shen, Yang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sahin, Ezgi Onur
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ozturk, Tayfur
    Activation behavior of an AB(2) type metal hydride alloy for NiMH batteries2016In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 41, no 23, p. 9948-9953Article in journal (Refereed)
    Abstract [en]

    Activation behavior of an AB(2), namely (Ti0.36Zr0.64) (V0.15Ni0.58Mn0.20Cr0.07)(2) Laves phase alloy, was investigated with regards to; particle size, ball milling and hot alkaline treatments. Galvanostatic cycling in open cells showed that an untreated alloy initially had almost no capacity, but reached a value of 220 mAh/g after 14 cycles. Experiments with different particle sizes showed that coarse particles activate faster yielding an improved capacity. In terms of activation more pronounced effect was obtained with boiling the alloy powder in a hot KOH solution. A capacity in excess of 300 mAh/g is reached in the first cycle after a 20 min treatment. The capacity was highest after 80 min, yielding a value of 390 mAh/g well above that expected from the gas-phase storage in the alloy. This was attributed to the formation of rough surface in the powder, which may stabilize hydrogen bubbles allowing pressures above 1 atm to be reached locally in the surface.

  • 39. Yartys, V.
    et al.
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Latroche, M.
    Metal hydrides as negative electrode materials for Ni-MH batteries2016In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 122, no 1Article in journal (Refereed)
    Abstract [en]

    Structural, thermodynamical and electrochemical properties of metallic hydrides belonging to the pseudo-binary family A-Mg-Ni (A: rare earths) are reviewed and compared. Technology aspects of bipolar cells are also discussed.

  • 40. Ye, Zhou
    et al.
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Metal hydride electrodes: The importance of surface area2016In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 664, p. 59-64Article in journal (Refereed)
    Abstract [en]

    A large active specific surface area is a very efficient way to improve charge/discharge rate capabilities of metal hydride electrodes. This can be promoted by washing oxidized, pre-hydrided AB(5) alloy particles in a hot KOH solution. This leads to magnetization of the alloy powder, making it possible to lift the powder with a simple permanent magnet, indicating that nickel liberated in the surface layer is essential for the improved kinetics. The overpotential of each step in the discharge process is analysed in detail using both half cells and sealed cells. The electrode polarisation depends inversely on the current density per active area. Untreated and treated alloy powders have similar current densities per active area, but treated powder exhibits superior kinetics due to its larger surface area. A NiMH cell with a surface-treated alloy has very good rate capability, only limited by the kinetics of the Ni electrode. At low overpotential, the electrochemical reaction gives the main contribution to the electrode polarisation. If the discharge current is increased to give an overpotential of more than 0.1 V, concentration polarisation will become important and a limiting factor at high current densities.

  • 41. Ye, Zhou
    et al.
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Oxygen and hydrogen gas recombination in NiMH cells2012In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 208, p. 232-236Article in journal (Refereed)
    Abstract [en]

    The kinetics of oxygen and hydrogen gas recombination on the metal hydride electrode in a NiMH cell is investigate as function of gas pressure, temperature, cycling and a hydrophobic additive. Both oxygen and hydrogen gas recombination rates in the NiMH cells are found to be linearly proportional to the gas pressure, indicating that surface processes with a constant number of reaction sites could be the rate limiting step. The rate of oxygen gas recombination is, however, more than 10 times faster than that of hydrogen at the same pressure. As the temperature increases, both reaction rates increase very rapidly, even though the solubilities of the gases in the KOH electrolyte decrease with temperature. The activation energies for oxygen and hydrogen gas recombination are 32.6 kJ mol(-1) and 27.0 kJ mol(-1), respectively. The reactions rates also increase as the cells are cycled. This indicates, that the number of active sites increases, as the surface area increases, due to the continuously decrepitating of the alloy particles. The hydrogen gas absorption rate increases dramatically after a large number of cycles due the drying of the MH electrode. A hydrophobic FTFE additive in the MH electrode can significantly improve hydrogen absorption efficiency in NiMH cells.

  • 42. Ye, Zhou
    et al.
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Howlett, John Richard, III
    Metal hydrides for high-power batteries2013In: MRS bulletin, ISSN 0883-7694, E-ISSN 1938-1425, Vol. 38, no 6, p. 504-508Article in journal (Refereed)
    Abstract [en]

    Rechargeable batteries are essentially unstable systems with respect to charging/discharging. The main electrode reactions of all battery chemistries are well known but are valid and reversible only at small currents. When batteries are used with nonzero current, gradients in voltage, current, and temperature will arise and initiate a number of less understood parasitic reactions. If all these rather complicated and interconnected reactions are not reversible upon charging/discharging, the battery will derail after a number of charging/discharging cycles. This article describes two ways to improve performance. One is to choose applications where the battery is not deeply discharged, such as in hybrid electric vehicles. In battery electric vehicle applications, this would correspond to working with a significantly oversized battery. The second way is to improve uniformity and quality of design and materials of metal hydride electrodes; however, this will also drastically increase cost, and for a battery application, the total throughput of available energy over the lifetime cost of the battery must be maximized. Uniform metal hydride particles with a large and uniform reaction surface are examples of how to increase battery performance by making the electrodes work under more ideal conditions, which slows down the deteriorating influence from the parasitic reactions.

  • 43. Ying, TK
    et al.
    Gao, XP
    Hu, WK
    Wu, F
    Noréus, D
    Stockholm University.
    Studies on rechargeable NiMH batteries2006In: International Journal of Hydrogen Energy, Vol. 31, p. 525-530Article in journal (Refereed)
1 - 43 of 43
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Output format
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  • asciidoc
  • rtf