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  • 1.
    Abou-Hamad, Edy
    et al.
    Universite Montpellier II.
    Kim, Y
    University of Pennsylvania.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Physics.
    Goze-Bac, Christophe
    Universite Montpellier II.
    Luzzi, David
    University of Pennsylvania.
    Rubio, Angelo
    University of Basque Country.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Physics.
    Hydrogenation of C-60 in Peapods: Physical Chemistry in Nano Vessels2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 20, p. 8583-8587Article in journal (Refereed)
    Abstract [en]

    Hydrogenation of C-60 molecules inside SWNT was achieved by direct reaction with hydrogen gas at elevated pressure and temperature. Evidence for the C-60 hydrogenation in peapods is provided by isotopic engineering with specific enrichment of encapsulated species and high resolution C-13 and H-1 NMR spectroscopy with the observation of characteristic diamagnetic and paramagnetic shifts of the NMR lines and the appearance of sp(3) carbon resonances. We estimate that approximately 78% of the C-60 molecules inside SWNTs are hydrogenated to an average degree of 14 hydrogen atoms per C-60 molecule. As a consequence, the rotational dynamics of the encapsulated C60Hx molecules is clearly hindered. Our successful hydrogenation experiments open completely new roads to understand and control confined chemical reactions at the nano scale

  • 2. Ajuria, Jon
    et al.
    Arnaiz, Maria
    Botas, Cristina
    Carriazo, Daniel
    Mysyk, Roman
    Rojo, Teofilo
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Goikolea, Eider
    Graphene-based lithium ion capacitor with high gravimetric energy and power densities2017In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 363, p. 422-427Article in journal (Refereed)
    Abstract [en]

    Hybrid capacitor configurations are now of increasing interest to overcome the current energy limitations of supercapacitors. In this work, we report a lithium ion capacitor (LIC) entirely based on graphene. On the one hand, the negative-battery-type- electrode consists of a self-standing, binder-free 3D macroporous foam formed by reduced graphene oxide and decorated with tin oxide nanoparticles (SnO2-rGO). On the other hand, the positive-capacitor-type- electrode is based on a thermally expanded and physically activated reduced graphene oxide (a-TEGO). For comparison purposes, a symmetric electrical double layer capacitor (EDLC) using the same activated graphene in 1.5 M Et4NBE4/ACN electrolyte is also assembled. Built in 1 M LiPF6 EC:DMC, the graphene-based LIC shows an outstanding, 10-fold increase in energy density with respect to its EDLC counterpart at low discharge rates (up to 200 Wh kg(-1)). Furthermore, it is still capable to deliver double the energy in the high power region, within a discharge time of few seconds.

  • 3.
    Andersson, Ove
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Filinchuk, Yaroslav
    Dmitriev, Vladimir
    Quwar, Issam
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Phase coexistence and hysteresis effects in the pressure-temperature phase diagram of NH3BH32011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 2, p. 024115-Article in journal (Refereed)
    Abstract [en]

    The potential hydrogen storage compound NH3BH3 has three known structural phases in the temperature and pressure ranges 110–300 K and 0–1.5 GPa, respectively. We report here the boundaries between, and the ranges of stability of, these phases. The phase boundaries were located by in situ measurements of the thermal conductivity, while the actual structures in selected areas were identified by in situ Raman spectroscopy and x-ray diffraction. Below 0.6 GPa, reversible transitions involving only small hysteresis effects occur between the room-temperature tetragonal plastic crystal I4mm phase and the low-temperature orthorhombic Pmn21 phase. Transformations of the I4mm phase into the high-pressure orthorhombic Cmc21 phase, occurring above 0.8 GPa, are associated with very large hysteresis effects, such that the reverse transition may occur at up to 0.5 GPa lower pressures. Below 230 K, a fraction of the Cmc21 phase is metastable to atmospheric pressure, suggesting the possibility that dense structural phases of NH3BH3, stable at room temperature, could possibly be created and stabilized by alloying or by other methods. Mixed orthorhombic Pmn21/Cmc21 phases were observed in an intermediate pressure-temperature range, but a fourth structural phase predicted by Filinchuk et al. [ Phys. Rev. B 79 214111 (2009)] was not observed in the pressure-temperature ranges of this experiment. The thermal conductivity of the plastic crystal I4mm phase is about 0.6 W m−1 K−1 and only weakly dependent on temperature, while the ordered orthorhombic phases have higher thermal conductivities limited by phonon-phonon scattering.

  • 4. Anoshkin, Ilya
    et al.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nasibulin, Nasibulin
    Krasheninnikov, Arkady
    Jiang, Hua
    Nieminen, Risto
    Kauppinen, Esko
    Coronene Encapsulation in Single-Walled Carbon Nanotubes: Stacked Columns, Peapods, and Nanoribbons2014In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 15, no 8, p. 1660-1665Article in journal (Refereed)
    Abstract [en]

    Encapsulation of coronene inside single-walled carbon nanotubes (SWNTs) was studied under various conditions. Under high vacuum, two main types of molecular encapsulation were observed by using transmission electron microscopy: coronene dimers and molecular stacking columns perpendicular or tilted (45-608) with regard to the axis of the SWNTs. A relatively small number of short nanoribbons or polymerized coronene molecular chains were observed. However, experiments performed under an argon atmosphere (0.17 MPa) revealed reactions between the coronene molecules and the formation of hydrogen-terminated graphene nanoribbons. It was also observed that the morphology of the encapsulated products depend on the diameter of the SWNTs. The experimental results are explained by using density functional theory calculations through the energies of the coronene molecules inside the SWNTs, which depend on the orientation of the molecules and the diameter of the tubes.

  • 5. Araújo, C. Moysés
    et al.
    Ahuja, Rajeev
    Talyzin, Alexandr V
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Pressure-induced structural phase transition in NaBH42005In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, no 5, p. 054125-Article in journal (Refereed)
    Abstract [en]

    We present a combined experimental and theoretical study of the technologically important NaBH4 compound under high pressure. Using Raman spectroscopy at room temperature, we have found that NaBH4 undergoes a structural phase transformation starting at 10.0 GPa with the pure high-pressure phase being established above 15.0 GPa. In order to compare the Raman data recorded under high pressure with the low-temperature tetragonal phase of NaBH4, we have also performed a cooling experiment. The known order-disorder transition from the fcc to the tetragonal structure was then observed. However, the new high pressure phase does not correspond to this low-temperature structure. Using first-principle calculations based on the density functional theory, we show that the high-pressure phase corresponds to the alpha-LiAlH4–type structure. We have found a good agreement between the measured and calculated transition pressures. Additionally, we present the electronic structure of both the fcc and the high-pressure phases.

  • 6. Baburin, Igor A
    et al.
    Klechikov, Alexey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mercier, Guillaume
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Seifert, Gotthard
    Hydrogen adsorption by perforated graphene2015In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 40, no 20, p. 6594-6599Article in journal (Refereed)
    Abstract [en]

    We performed a combined theoretical and experimental study of hydrogen adsorption in graphene systems with defect-induced additional porosity. It is demonstrated that perforation of graphene sheets results in increase of theoretically possible surface areas beyond the limits of ideal defect-free graphene (∼2700 m2/g) with the values approaching ∼5000 m2/g. This in turn implies promising hydrogen storage capacities up to 6.5 wt% at 77 K, estimated from classical Grand canonical Monte Carlo simulations. Hydrogen sorption was studied for the samples of defected graphene with surface area of ∼2900 m2/g prepared using exfoliation of graphite oxide followed by KOH activation. The BET surface area of studied samples thus exceeded the value of single-layered graphene. Hydrogen uptake measured at 77 K and 296 K amounts to 5.5 wt% (30 bar) and to 0.89 wt% (120 bar), respectively. 

  • 7. Chernov, Alexander I
    et al.
    Fedotov, Pavel V
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Suarez Lopez, Inma
    Anoshkin, Ilya V
    Nasibulin, Albert G
    Kauppinen, Esko I
    Obraztsova, Elena D
    Optical properties of graphene nanoribbons encapsulated in single-walled carbon nanotubes2013In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 7, no 7, p. 6346-6353Article in journal (Refereed)
    Abstract [en]

    We report the photoluminescence (PL) from graphene nanoribbons (GNRs) encapsulated in single-walled carbon nanotubes (SWCNTs). New PL spectral features originating from GNRs have been detected in the visible spectral range. PL peaks from GNRs have resonant character, and their positions depend on the ribbon geometrical structure in accordance with the theoretical predictions. GNRs were synthesized using confined polymerization and fusion of coronene molecules. GNR@SWCNTs material demonstrates a bright photoluminescence both in infrared (IR) and visible regions. The photoluminescence excitation mapping in the near-IR spectral range has revealed the geometry-dependent shifts of the SWCNT peaks (up to 11 meV in excitation and emission) after the process of polymerization of coronene molecules inside the nanotubes. This behavior has been attributed to the strain of SWCNTs induced by insertion of the coronene molecules.

  • 8. Chumakova, Natalia A.
    et al.
    Rebrikova, Anastasya T.
    Talyzin, Aleksandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Paramonov, Nikita A.
    Vorobiev, Andrey Kh
    Korobov, Mikhail, V
    Properties of Graphite Oxide Powders and Membranes as Revealed by Electron Paramagnetic Resonance Spectroscopy2018In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 39, p. 22750-22759Article in journal (Refereed)
    Abstract [en]

    The spin probe technique was used to study graphite oxide (GO) powders swelled in polar liquids (CH3CN, CH3OH, and H2O) and liquid-free GO membranes (GOM). The nitroxide radicals TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl) and TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) readily penetrated into the interplane space of GO from the solution. Electron paramagnetic resonance (EPR) spectra of these radical probes were sensitive to molecular mobility and orientation ordering within the internal space of GO. The radicals embedded in swelled GO were in two states with different rotational mobilities. The small fraction of radicals located in the interplane space of GO and detected in the broad range of temperatures was in the state of fast rotation, similar to the same radicals dissolved in bulk liquids, thus providing experimental evidence of formation of a liquid-like media within the interplane space of GO. Such mobile media may be responsible for the unusual permeation properties of GOM, which is reported in the literature. Second, less-mobile fraction of radicals was found to be immobilized at the internal surface of GO and was sensitive to phase transformations in the swelled GO structures. The transformations were detected as anomalies at temperature dependences of rotational mobility of radicals. The detected dependence of EPR spectra of probe radicals on orientation of GOM, relative to the direction of magnetic field in the EPR spectrometer, was used for quantitative characterization of orientation alignment of GO planes within the membranes. Such an approach may serve as an elegant method to estimate the relative quality of membranes and other GO-layered structures.

  • 9. Dmitriev, Vladimir
    et al.
    Filinchuk, Yaroslav
    Chernyshov, Dmitry
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Dzwilewski, Andrzej
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kurnosov, Alexander
    Pressure-temperature phase diagram of LiBH4: Synchrotron x-ray diffraction experiments and theoretical analysis2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, no 17, article id 174112Article in journal (Refereed)
    Abstract [en]

    An in situ combined high-temperature high-pressure synchrotron radiation diffraction study has been carried out on LiBH4. The phase diagram of LiBH4 is mapped to 10 GPa and 500 K, and four phases are identified. The corresponding structural distortions are analyzed in terms of symmetry-breaking atomic position shifts and anion ordering. Group-theoretical and crystal-chemical considerations reveal a nontrivial layered structure of LiBH4. The layers and their deformations define the structural stability of the observed phases.

  • 10.
    Dzwilewski, Andrzej
    et al.
    Umeå University, Faculty of Science and Technology, Physics. Umeå University, Faculty of Science and Technology, Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Physics. Umeå University, Faculty of Science and Technology, Physics. Experimental Physics.
    Bromiley, G.
    Dub, S.
    Dubrovinsky, Leonid
    Characterization of phases synthesized close to the boundary of C60 collapse at high temperature high pressure conditions2007In: Diamond and related materials, ISSN 0925-9635, E-ISSN 1879-0062, Vol. 16, no 8, p. 1550-1556Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Two sets of samples were synthesized at high pressure high temperature conditions in the P-T region where C-60 molecules collapse into a nearly amorphous graphite-like hard carbon phase. For the first set, heating temperature was varied at fixed pressure and preparation time. For the second set, synthesis time was varied at fixed pressure and fixed temperature. Detailed structural characterization of samples was performed using Raman spectroscopy and powder XRD. Mechanical properties of the samples have been studied by nanoindentation method. It has been found that duration of heat treatment under high pressure is an important parameter which influences the temperature of fullerene cage collapse. Both tetragonal and rhombohedral polymeric phases transform into hard carbon phase over a rather narrow temperature interval, but the tetragonal phase shows somewhat increased stability against C-60 collapse. Viscoelastic mechanical behavior during nanoindentation was observed for fullerene polymers but not for graphite-like hard carbon phase. Possible mechanism for nucleation of the hard carbon phase in polymeric C-60 networks is discussed.

  • 11. Fedotov, Pavel V.
    et al.
    Chernov, Alexander I.
    Talyzin, Alexander V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Anoshkin, Ilya V.
    Nasibulin, Albert G.
    Kauppinen, Esko I.
    Obraztsova, Elena D.
    Optical Study of Nanotube and Coronene Composites2013In: Journal of Nanoelectronics and Optoelectronics, ISSN 1555-130X, E-ISSN 1555-1318, Vol. 8, no 1, p. 16-22Article, review/survey (Refereed)
    Abstract [en]

    A novel nanomaterial, graphene nanoribbons encapsulated inside single-walled carbon nanotubes (GNR@SWNT), was studied by combined optical methods. This nanomaterial was found to have a bright photoluminescence both in IR and UV-Vis spectral ranges. Its spectral features have a complicated resonant structure different from the features of initial components: coronene molecules and SWNTs. The encapsulation ability appears to correlate strongly with the geometry of SWNTs. A weak interaction between nanotube walls and encapsulated species has been discovered: no evidence of charge or energy transfer has been registered.

  • 12. Feicht, Patrick
    et al.
    Siegel, Renee
    Thurn, Herbert
    Neubauer, Jens W.
    Seuss, Maximilian
    Szabo, Tamas
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Halbig, Christian E.
    Eigler, Siegfried
    Kunz, Daniel A.
    Fery, Andreas
    Papastavrou, Georg
    Senker, Jurgen
    Breu, Josef
    Systematic evaluation of different types of graphene oxide in respect to variations in their in-plane modulus2017In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 114, p. 700-705Article in journal (Refereed)
    Abstract [en]

    Graphene oxide samples prepared in various laboratories following a diversity of synthesis protocols based on Brodie's (BGO) and Hummers/Offeman's (HGO) methods were compared in respect of their in plane moduli. A simple wrinkling method allowed for a spatial resolution <1.5 pm by converting the wrinkling frequency. Quite surprisingly, a drastic variation of the in-plane moduli was found spanning the range from 600 GPa for the best BGO types, which is in the region of chemically derived graphene, all the way down to less than 200 GPa for HGO types. This would suggest that there are no two equal GO samples and GO should not be regarded a compound but rather a class of materials with very variable physical properties. While large differences between Brodie's and Hummers/Offeman's types might have been expected, even within the group of Hummers/Offeman's types pronounced differences are observed that, based on C-13 solid-state NMR, were related to over-functionalization versus over-oxidation.

  • 13. Filinchuk, Yaroslav
    et al.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Physics. Umeå University, Faculty of Science and Technology, Physics.
    Chernyshov, D.
    Dmitriev, V.
    High-pressure phase of NaBH4: Crystal structure from synchrotron powder diffraction data2007In: PHYSICAL REVIEW B, ISSN 1098-0121, Vol. 76, no 9, p. 092104-Article in journal (Refereed)
  • 14. Filinchuk, Yaroslav
    et al.
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hagemann, Hans
    Dmitriev, Vladimir
    Chernyshov, Dmitry
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Cation Size and Anion Anisotropy in Structural Chemistry of Metal Borohydrides. The Peculiar Pressure Evolution of RbBH42010In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 49, no 11, p. 5285-5292Article in journal (Refereed)
    Abstract [en]

    The pressure evolution of RbBH4 has been characterized by synchrotron powder X-ray diffraction and Raman spectroscopy up to 23 GPa. Diffraction experiments at ambient temperature reveal three phase transitions, at 3.0, 10.4, and 18 GPa (at 2.6, 7.8, and 20 GPa from Raman data), at which the space group symmetry changes in the order Fm-3m(Z=4) → P4/nmm(2) → C222(2) → I-42m(4). Crystal structures and equations of state are reported for all four phases. The three high-pressure structure types are new in the crystal chemistry of borohydrides. RbBH4 polymorphs reveal high coordination numbers (CNs) for cation and anion sites, increasing with pressure from 6 to 8, via an intermediate 4 + 4 coordination. Different arrangements of the tetrahedral BH4 group in the Rb environment define the crystal symmetries of the RbBH4 polymorphs. The structural evolution in the MBH4 series is determined by the cation’s size, as it differs drastically for M = Li (CNs = 4, 6), Na (CN = 6), and Rb. The only structure common to the whole MBH4 family is the cubic one. Its bulk modulus linearly decreases as the ionic radius of M increases, indicating that the compressibility of the material is mainly determined by the repulsive BH4···BH4 interactions.

  • 15. Gorkina, Alexandra L
    et al.
    Tsapenko, Alexey P
    Gilshteyn, Evgenia P
    Koltsova, Tatiana S
    Larionova, Tatiana V
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Anisimov, Anton S
    Anoshkin, Ilya V
    Kauppinen, Esko I
    Tolochko, Oleg V
    Nasibulin, Albert G
    Transparent and conductive hybrid graphene/carbon nanotube films2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 100, p. 501-507Article in journal (Refereed)
    Abstract [en]

    Carbon nanomaterials (carbon nanotubes (CNTs) and graphene) are promising materials for optoelectronic applications, including flexible transparent and conductive films (TCFs) due to their extraordinary electrical, optical and mechanical properties. However, the performance of CNT- or graphene-only TCFs still needs to be improved. One way to enhance the optoelectrical properties of TCFs is to hybridize CNTs and graphene. This approach leads to creation of a novel material that exhibits better properties than its individual constituents. In this work, the novel hybrid CNT-graphene nanomaterial was fabricated by graphene oxide deposition on top of CNT films. The graphene oxide was then reduced by thermal annealing at ambient atmosphere or in H2 atmosphere. At the final step the CNT-graphene hybrids were chemically doped using gold(III) chloride. As a result, we show that the hybrids demonstrate excellent optoelectrical performance with the sheet resistance as low as 73 Ω/□ at 90% transmittance.

  • 16.
    Han, Kyoo-Hyun
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Physics.
    Dzwilewski, Andrzej
    Umeå University, Faculty of Science and Technology, Physics.
    Makarova, Tatiana
    Höhne, Roland
    Esquinazi, Pablo
    Spemann, D.
    Dubrovinsky, Leonid S.
    Magnetic properties of carbon phases synthesized using high-pressure high-temperature treatment.2005In: Physical Review B, Vol. 72, p. 224424-Article in journal (Refereed)
  • 17.
    Iakunkov, Artem
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Skrypnychuk, Vasyl
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nordenström, Andreas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shilayeva, Elizaveta A.
    Korobov, Mikhail
    Prodana, Mariana
    Enachescu, Marius
    Larsson, Sylvia H.
    Talyzin, Aleksandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Activated graphene as a material for supercapacitor electrodes: effects of surface area, pore size distribution and hydrophilicity2019In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 32, p. 17901-17912Article in journal (Refereed)
    Abstract [en]

    Activated reduced graphene oxide (a-rGO) is a material with a rigid 3D porous structure and high specific surface area (SSA). Using variation of activation parameters and post-synthesis mechanical treatment we prepared two sets of materials with a broad range of BET (N2) SSA ∼1000–3000 m2 g−1, and significant differences in pore size distribution and oxygen content. The performance of activated graphene as an electrode in a supercapacitor with KOH electrolyte was correlated with the structural parameters of the materials and water sorption properties. a-rGO is a hydrophobic material as evidenced by the negligibly small BET (H2O) SSA determined using analysis of water vapor sorption isotherms. However, the total pore volume determined using water vapor sorption and sorption of liquid water is almost the same as the one found by analysis of nitrogen sorption isotherms. Ball milling is found to provide an improved bulk density of activated graphene and collapse of all pores except the smallest ones (<2 nm). A decrease in the activation temperature from 850 °C to 550 °C is found to result in materials with a narrow micropore size distribution and increased oxygen content. Elimination of mesopores using ball milling or a lower activation temperature provided materials with better specific capacitance despite a significant decrease (by ∼30%) of the BET (N2) SSA. The best gravimetric and volumetric capacitances in KOH electrolyte were achieved not for samples with the highest value of the BET (N2) SSA but for materials with 80–90% of the total pore volume in micropores and an increased BET (H2O) SSA. Comparing the performance of electrodes prepared using rGO and a-rGO shows that a more hydrophilic surface is favorable for charge storage in supercapacitors with KOH electrolyte.

  • 18.
    Iakunkov, Artem
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sun, Jinhua
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rebrikova, Anastasia
    Korobov, Mikhail
    Klechikov, Alexey
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Physics and Astronomy, Uppsala University, Uppsala, 751 20, Sweden.
    Vorobiev, Alexei
    Boulanger, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Aleksandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Swelling of graphene oxide membranes in alcohols: effects of molecule size and air ageing.2019In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 7, p. 11331-11337Article in journal (Refereed)
    Abstract [en]

    Swelling of Hummers graphene oxide (HGO) membranes in a set of progressively longer liquid alcohols (methanol to 1-nonanol) was studied using synchrotron radiation XRD after air ageing over prolonged periods of time. Both precursor graphite oxides and freshly prepared HGO membranes were found to swell in the whole set of nine liquid alcohols with an increase of interlayer spacing from ∼7 Å (solvent free) up to ∼26 Å (in 1-nonanol). A pronounced effect of ageing on swelling in alcohols was found for HGO membranes stored in air. The HGO membranes aged for 0.5–1.5 years show progressively slower swelling kinetics, a non-monotonic decrease of saturated swelling in some alcohols and complete disappearance of swelling for alcohol molecules larger than hexanol. Moreover, the HGO membranes stored under ambient conditions for 5 years showed a nearly complete absence of swelling in all alcohols but preserved swelling in water. In contrast, precursor graphite oxide powder showed unmodified swelling in alcohols even after 4 years of ageing. Since the swelling defines the size of permeation channels, the ageing effect is one of the important parameters which could explain the strong variation in reported filtration/separation properties of GO membranes. The time and conditions of air storage require standardization for better reproducibility of results related to performance of GO membranes in various applications. The ageing of GO membranes can be considered not only as a hindrance/degradation for certain applications, but also as a method to tune the swelling properties of HGO membranes for better selectivity in sorption of solvents and for achieving better selective permeability.

  • 19. Kim, Y
    et al.
    Abou-Hamad, E
    Rubio, A
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Boesch, D
    Aloni, S
    Zettl, A
    Luzi, D E
    Goze-Bac, C
    Communications: nanomagnetic shielding: high-resolution NMR in carbon allotropes2010In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 132, no 2, p. 021102-Article in journal (Refereed)
    Abstract [en]

    The understanding and control of the magnetic properties of carbon-based materials is of fundamental relevance in applications in nano- and biosciences. Ring currents do play a basic role in those systems. In particular the inner cavities of nanotubes offer an ideal environment to investigate the magnetism of synthetic materials at the nanoscale. Here, by means of 13 C high resolution NMR of encapsulated molecules in peapod hybrid materials, we report the  largest diamagnetic shifts (down to -68.3 ppm) ever observed in carbon allotropes, which is connected to the enhancement of the aromaticity of the nanotube envelope upon doping. This diamagnetic shift can be externally controlled by in situ modifications such as doping or electrostatic charging. Moreover, defects such as C-vacancies, pentagons, and chemical functionalization of the outer nanotube quench this diamagnetic effect and restore NMR signatures to slightly paramagnetic shifts compared to nonencapsulated molecules. The magnetic interactions reported here are robust phenomena independent of temperature and proportional to the applied magnetic field. The magnitude, tunability, and stability of the magnetic effects make the peapod nanomaterials potentially valuable for nanomagnetic shielding in nanoelectronics and nanobiomedical engineering.

  • 20.
    Klechikov, Alexey G.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mercier, Guillaume
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Merino, Pilar
    Blanco, Santiago
    Merino, Cesar
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hydrogen storage in bulk graphene-related materials2015In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 210, p. 46-51Article in journal (Refereed)
    Abstract [en]

    Hydrogen sorption properties of graphene-related materials were studied by gravimetric and volumetric methods at 2931< and 77K. Rapid thermal exfoliation of different types of graphite oxide (GO) precursors yielded samples with maximal surface areas up to 850 m(2)/g, whereas surface areas up to 2300 m(2)/g were achieved by post-exfoliation activation treatments. Therefore, hydrogen storage parameters of graphene materials could be evaluated in a broad range of surface areas. The H-2 uptake vs surface area trend revealed in this study shows that hydrogen storage by graphene materials do not exceed 1 Wt% at 120 Bar H-2 at ambient temperatures. Linear increase of hydrogen adsorption vs surface area was observed at 77 K with maximal observed value of similar to 5 Wt% for 2300 m(2)/g sample. It can be concluded that bulk graphene samples obtained using graphite oxide exfoliation and activation follow standard for other nanostructured carbons hydrogen uptake trends and do not demonstrate superior hydrogen storage parameters reported in several earlier studies. Nevertheless, graphene remains to be one of the best materials for physisorption of hydrogen, especially at low temperatures.

  • 21.
    Klechikov, Alexey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mercier, Guillaume
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sharifi, Tiva
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Baburin, Igor A.
    Technische Universität Dresden, Theoretische Chemie, Bergstraße 66b, 01062 Dresden, Germany .
    Seifert, Gotthard
    Technische Universität Dresden, Theoretische Chemie, Bergstraße 66b, 01062 Dresden, Germany .
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hydrogen storage in high surface area graphene scaffolds2015In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 51, no 83, p. 15280-15283Article in journal (Refereed)
    Abstract [en]

    Using an optimized KOH activation procedure we prepared highly porous graphene scaffold materials with SSA values up to 3400 m2 g−1 and a pore volume up to 2.2 cm3 g−1, which are among the highest for carbon materials. Hydrogen uptake of activated graphene samples was evaluated in a broad temperature interval (77–296 K). After additional activation by hydrogen annealing the maximal excess H2 uptake of 7.5 wt% was obtained at 77 K. A hydrogen storage value as high as 4 wt% was observed already at 193 K (120 bar H2), a temperature of solid CO2, which can be easily maintained using common industrial refrigeration methods.

  • 22.
    Klechikov, Alexey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sun, Jinhua
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Baburin, Igor A.
    Seifert, Gotthard
    Rebrikova, Anastasiia T.
    Avramenko, Natalya V.
    Korobov, Mikhail V.
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Multilayered intercalation of 1-octanol into Brodie graphite oxide2017In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 9, no 20, p. 6929-6936Article in journal (Refereed)
    Abstract [en]

    Multilayered intercalation of 1-octanol into the structure of Brodie graphite oxide (B-GO) was studied as a function of temperature and pressure. Reversible phase transition with the addition/removal of one layer of 1-octanol was found at 265 K by means of X-ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC). The same transition was observed at ambient temperature upon a pressure increase above 0.6 GPa. This transition was interpreted as an incongruent melting of the low temperature/high pressure B-GO intercalated structure with five layers of 1-octanol parallel to GO sheets (L-solvate), resulting in the formation of a four-layered structure that is stable under ambient conditions (A-solvate). Vacuum heating allows the removal of 1-octanol from the A-solvate layer by layer, while distinct sets of (00 l) reflections are observed for three-, two-, and one-layered solvate phases. Step by step removal of the 1-octanol layers results in changes of distance between graphene oxide planes by similar to 4.5 angstrom. This experiment proved that both L- and A-solvates are structures with layers of 1-octanol parallel to GO planes. Unusual intercalation with up to five distinct layers of 1-octanol is remarkably different from the behaviour of small alcohol molecules (methanol and ethanol), which intercalate B-GO structure with only one layer under ambient conditions and a maximum of two layers at lower temperatures or higher pressures. The data presented in this study make it possible to rule out a change in the orientation of alcohol molecules from parallel to perpendicular to the GO planes, as suggested in the 1960s to explain larger expansion of the GO lattice due to swelling with larger alcohols.

  • 23.
    Klechikov, Alexey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sun, Jinhua
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hu, Guangzhi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zheng, Mingbo
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Graphene decorated with metal nanoparticles: Hydrogen sorption and related artefacts2017In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 250, p. 27-34Article in journal (Refereed)
    Abstract [en]

    Hydrogen sorption by reduced graphene oxides (r-GO) is not found to increase after decoration with Pd and Pt nanoparticles. Treatments of metal decorated samples using annealing under hydrogen or air were tested as a method to create additional pores by effects of r-GO etching around nanoparticles. Increase of Specific Surface Area (SSA) was observed for some air annealed r-GO samples. However, the same treatments applied to activated r-GO samples with microporous nature and higher surface area result in breakup of structure and dramatic decrease of SSA. Our experiments have not revealed effects which could be attributed to spillover in hydrogen sorption on Pd or Pt decorated graphene. However, we report irreversible chemisorption of hydrogen for some samples which can be mistakenly assigned to spillover if the experiments are incomplete.

  • 24.
    Klechikov, Alexey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Comment on "Nanohole-Structured and Palladium-Embedded 3D Porous Graphene for Ultrahigh Hydrogen Storage and CO Oxidation Multifunctionalities"2016In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 10, no 10, p. 9055-9056Article in journal (Refereed)
  • 25.
    Klechikov, Alexey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    You, Shujie
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lackner, Lukas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sun, Jinhua
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Iakunkov, Artem
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rebrikova, Anastasia
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Chemistry, Moscow State University, Moscow, Russia.
    Korobov, Mikhail
    Baburin, Igor
    Seifert, Gotthard
    Talyzin, Aleksandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Graphite oxide swelling in molten sugar alcohols and their aqueous solutions2018In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 140, p. 157-163Article in journal (Refereed)
    Abstract [en]

    Graphite oxides (GO) are intercalated rapidly by one to several layers of solvent when immersed in liquid but the GO solvates are typically unstable on air due to solvent evaporation. Here we study swelling of GO in solvents (sugar alcohols) with melting temperature point above ambient. Using in situ synchrotron radiation XRD experiments we demonstrated GO swelling in molten xylitol and sorbitol. The expanded GO structure intercalated with one layer of xylitol or sorbitol is preserved upon solidification of melt and cooling back to ambient conditions. The structure of solid solvates of GO with xylitol and sorbitol is based on non-covalent interaction and pristine GO can be recovered by washing in water. Intercalation of xylitol and sorbitol into GO structure in aqueous solutions yields similar but less ordered structure of GO/sugar alcohol solid solvates. Very similar inter-layer distance was observed for GO intercalated by sugar alcohols in melt and for GO immersed in sugar solutions. This result shows that sugar alcohols penetrate into GO inter-layer space without hydration shell forming 2D layers with orientation parallel to graphene oxide sheets. Therefore, hydration diameter of molecules should not be considered as decisive factor for permeation through graphene oxide inter-layers in multilayered membranes.

  • 26.
    Klechikov, Alexey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Yu, Junchun
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Thomas, Diana
    Sharifi, Tiva
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Structure of graphene oxide membranes in solvents and solutions2015In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 7, no 37, p. 15374-15384Article in journal (Refereed)
    Abstract [en]

    The change of distance between individual graphene oxide sheets due to swelling is the key parameter to explain and predict permeation of multilayered graphene oxide (GO) membranes by various solvents and solutions. In situ synchrotron X-ray diffraction study shows that swelling properties of GO membranes are distinctly different compared to precursor graphite oxide powder samples. Intercalation of liquid dioxolane, acetonitrile, acetone, and chloroform into the GO membrane structure occurs with maximum one monolayer insertion (Type I), in contrast with insertion of 2-3 layers of these solvents into the graphite oxide structure. However, the structure of GO membranes expands in liquid DMSO and DMF solvents similarly to precursor graphite oxide (Type II). It can be expected that Type II solvents will permeate GO membranes significantly faster compared to Type I solvents. The membranes are found to be stable in aqueous solutions of acidic and neutral salts, but dissolve slowly in some basic solutions of certain concentrations, e.g. in NaOH, NaHCO3 and LiF. Some larger organic molecules, alkylamines and alkylammonium cations are found to intercalate and expand the lattice of GO membranes significantly, e.g. up to similar to 35 angstrom in octadecylamine/methanol solution. Intercalation of solutes into the GO structure is one of the limiting factors for nano-filtration of certain molecules but it also allows modification of the inter-layer distance of GO membranes and tuning of their permeation properties. For example, GO membranes functionalized with alkylammonium cations are hydrophobized and they swell in non-polar solvents.

  • 27.
    Klechikov, Alexey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sun, Jinhua
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Vorobiev, Alexei
    Talyzin, Aleksandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Swelling of Thin Graphene Oxide Films Studied by in Situ Neutron Reflectivity2018In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 24, p. 13106-13116Article in journal (Refereed)
    Abstract [en]

    Permeation of multilayered graphene oxide (GO) membranes by polar solvents is known to correlate with their swelling properties and amount of sorbed solvent. However, quantitative estimation of sorption using standard (e.g., gravimetric) methods is technically challenging for few nanometers thick GO membranes/films exposed to solvent vapors. Neutron reflectivity (NR) was used here to evaluate the amount of solvents intercalated into the film which consists of only ∼31.5 layers of GO. Analysis of NR data recorded from the GO film exposed to vapors of polar solvents provides information about change of film thickness due to swelling, amount of intercalated solvent, and selectivity in sorption of solvents from binary mixtures. A quantitative study of GO film sorption was performed for D2O, d-methanol, ethanol, dimethyl sulfoxide (DMSO), acetonitrile, dimethylformamide (DMF), and acetone. Using isotopic contrast, we estimated selectivity in sorption of ethanol/d-methanol mixtures by the GO film. Estimation of sorption selectivity was also performed for D2O/DMF, D2O/DMSO, and D2O/acetonitrile binary mixtures. Sorption of polar solvents was compared for the thin GO film, micrometer thick free standing GO membranes, and graphite oxide powders.

  • 28. Korobov, Mikhail V.
    et al.
    Talyzin, Aleksandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rebrikova, Anastasiya T.
    Shilayeva, Elizaveta A.
    Avramenko, Natalya V.
    Gagarin, Alexander N.
    Ferapontov, Nikolay B.
    Sorption of polar organic solvents and water by graphite oxide: thermodynamic approach2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 102, p. 297-303Article in journal (Refereed)
    Abstract [en]

    Sorption of polar organic solvents CH3OH, C4H8O (THF), CH3CN, C3H7NO (DMF), C2H6OS (DMSO), C5H9NO (NMP) and water was quantitatively evaluated for Hummers (H-GO) and Brodie (B-GO) graphite oxides at T = 298K and at melting temperature (Tm) of the solvents. H-GO showed stronger sorption compared to B-GO for all studied solvents and the increase of sorption upon lowering temperature was observed for both H-GO and B-GO. Thermodynamic equations allowed to explain earlier reported "maximums" of swelling/sorption in the binary systems H-GO – solvent at Tm. The specific relation between the values of enthalpies of sorption and melting leads to the change of sign in enthalpies of sorption at Tm and causes maximal swelling/sorption. The same thermodynamic explanation was given for the "maximum" on the swelling vs. pressure dependence in B-GO and H-GO – H2O systems earlier reported at pressure of phase transition "liquid water-ice VI". Notably higher sorption of H2O was observed for H-GO compared to H-GO membrane (H-GOm) at high relative humidity (RH), RH > 0.75. Experimental sorption isotherm of H-GOm was used to simulate permeation rates of water through H-GOm and to estimate effective diffusion coefficient of water through the membrane.

  • 29. Kvashnina, K.O.
    et al.
    Guo, J.-H.
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Physics.
    Modin, A.
    Käämbre, T.
    Butorin, S.M.
    Nordgren, Joseph
    X-ray absorption and emission study of hydrogenated fullerenes2006In: AIP Conference Proceedings vol. 837: Proceedings of ISOCHEM2005, 2006, p. 230-237Conference paper (Refereed)
  • 30.
    Luzan, Serhiy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Cataldo, Franco
    INAF—Osservatorio Astrofisico di Catania, Catania, Italy.
    Tsybin, Yury
    Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Thermal decomposition of C60H182009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 30, p. 13133-13138Article in journal (Refereed)
    Abstract [en]

    Products of thermal dehydrogenation of C 60H18(which mainly occurs at 450-600°C) were studied by XRD, Raman, IR and mass spectrometry. IR spectra indicate that dehydrogenation resulted in partial recovery of pristine C 60. XRD data indicate that the cell parameter of the face-centered cubic structure, which is higher for C 60H18(14.55 Å) than for C60(14.17 Å), remained higher following heat treatment, and heating at>500° C caused further expansion (to 14.78 Å). The increase in the cell parameter correlates with the beginning of partial fullerene cage collapse (corroborated by IR, Raman and MS data) and is suggested to result from “self-doping”.

  • 31.
    Luzan, Serhiy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Jung, Heejin
    Department of Applied Chemistry, College of Science and Technology, Hanyang University, Republic of Korea.
    Chun, Hyungphil
    Department of Applied Chemistry, College of Science and Technology, Hanyang University, Republic of Korea.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hydrogen storage in Co-and Zn-based metal-organic frameworks at ambient temperature2009In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 34, no 24, p. 9754-9759Article in journal (Refereed)
    Abstract [en]

    Hydrogen adsorption properties of some Co-and Zn-based Metal-Organic Framework (MOF) materials were studied at near ambient temperatures. Maximal hydrogen storage capacity of 0.75 wt% was found for a Zn-based material at 175 Bar hydrogen pressure and T = -4 degrees C. Hydrogen adsorption correlated linearly with BET surface area and strongly depends on temperature. Relatively low structural stability of some MOF's results in framework collapse during degassing and hydrogen adsorption measurements.

  • 32.
    Luzan, Serhiy M
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr V
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Effect of catalysts on the reaction of C60 with hydrogen2012In: Fullerenes, nanotubes, and carbon nanostructures (Print), ISSN 1536-383X, E-ISSN 1536-4046, Vol. 20, no 4-7, p. 319-323Article in journal (Refereed)
    Abstract [en]

    The reaction of C-60/catalyst with hydrogen gas was studied at 400 degrees C and 50 bar of H-2 pressure. The addition of Pt- or Ni-catalysts significantly accelerated kinetics of the hydrogenation reaction and resulted in a dramatic change of the C60Hx crystal structure. Samples reacted without catalyst preserved the fcc structure typical for pristine C-60 but with expanded unit cells. Fulleranes C60Hx obtained using catalytic hydrogenation exhibited not only the fcc structure (at relatively low hydrogenation degree) but also the bcc structure of C60Hx (with x > 18). The bcc structure corresponds to highly hydrogenated material with an average volume per C-60 molecule of 817-849 angstrom(3).

  • 33.
    Luzan, Serhiy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Comment to the “Response to “Hydrogen adsorption in Pt catalyst/MOF-5 materials”” by Li et al. [1]2011In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 139, no 1-3, p. 216-218Article in journal (Other academic)
  • 34.
    Luzan, Serhiy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hydration of graphite oxide in electrolyte and non-electrolyte solutions2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 50, p. 24611-24614Article in journal (Refereed)
    Abstract [en]

    Pressure induced insertion of liquid media was studied for graphite oxide (GO) immersed in excess amounts of aqueous copper acetate and sucrose solutions and compared to previous experiments with GO immersed in solute-free water media. Compression of GO in copper acetate solution resulted in significant enhancement of high pressure anomaly compared to pure water: interlayer distance reached 17.4 Å at 2.3 GPa while for pure water the maximal observed layer separation was 13.08 Å. Compression of GO in sucrose solution was found to be very similar to compression in solute-free water. These results confirm that copper ions can be pressure-inserted into GO structure while the expansion of structure is attributed to osmotic swelling. Sucrose dissolves in water in molecular form (nonelectrolyte) which results in weaker absorption into the GO structure and the absence of osmotic swelling. Pressure induced insertion of various solutions into the GO structure could possibly be promising for synthesis of new graphite intercalation materials or graphene-related composites.

  • 35.
    Luzan, Serhiy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hydrogen adsorption in Pt catalyst/MOF-5 materials2010In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 135, no 1-3, p. 201-205Article in journal (Refereed)
    Abstract [en]

    Hydrogen adsorption properties of well-known MOF-5 were studied at near ambient temperature and hydrogen pressures up to 120 bar. Pristine material was doped with Pt catalysts supported on activated carbon (AC) using two previously described procedures: physical mixture of a catalyst with MOF-5 and “bridging” procedure (MOF-5 and catalyst particles connected via carbon bridges) MOF-5. The maximum hydrogen adsorption measured on doped MOF-5 was 0.43 wt.%. These values are on the same level or even less than for catalyst free MOF-5 material. Therefore, doping of MOF-5 material with Pt catalyst has not resulted in increase of hydrogen storage value. Hydrogen adsorption for the samples with added catalyst showed correlation with BET surface area, exhibited isotherms typical for physisorption and no features which could be assigned to spillover effect.

  • 36.
    Luzan, Serhiy
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tsybin, Yury O.
    Biomolecular Mass Spectrometry Laboratory, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Reaction of C60 with Hydrogen gas: In Situ monitoring and pathways2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 23, p. 11484-11492Article in journal (Refereed)
    Abstract [en]

    Kinetics and pathways of C60 reaction with hydrogen gas were studied in a broad temperature interval and over extended periods of time. Specifically, hydrogenation was monitored in situ at high temperature and high hydrogen pressure conditions using the gravimetric method. The shape of gravimetric curve was found to depend on hydrogenation temperature: at 350–400 °C saturation of the sample weight was achieved, whereas at 420–440 °C the sample weight reached the maximum and decreased upon prolonged hydrogenation. The weight decrease is due to fullerene cage fragmentation with formation of light hydrocarbons evaporating from the sample. Hydrogenation products were studied by X-ray diffraction, MALDI TOF and APPI FT-ICR mass spectrometry, liquid chromatography, and elemental analysis. Hydrogenation pathways (from C60H18 up to C60H56) and possible mechanisms of hydrogenation-induced fragmentation of fulleranes are discussed.

  • 37.
    Martin, Natalia M.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Luzan, Serhiy
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    High-temperature reactions of C60 with polycyclic aromatic hydrocarbons2010In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 368, no 1-2, p. 49-57Article in journal (Refereed)
    Abstract [en]

    Fullerenes are proposed as a precursor for preparation of nanocarbon materials using controlled collapse of cage structure by high temperature reaction with polycyclic aromatic hydrocarbons. The chemical modification of C60 by reaction with anthracene and coronene was studied over a broad temperature interval. The products of the reaction were characterized by X-ray diffraction, and Raman and IR spectroscopy. Mono- and multi-adducts of C60 with anthracene were obtained in the temperature interval 290–400 °C. Above 400 °C the C60 adducts are not stable and decompose back to C60 and anthracene. No chemical adducts of C60 with coronene were found below 500 °C. Above this temperature fullerite structure was found to expand reflecting interaction with coronene melt and vapor. The reactions of C60 with anthracene and C60 with coronene at temperatures above 650 °C resulted in fullerene cage collapse and formation of nanocarbons. These nanocarbons were found to store up to 0.45 wt% of hydrogen at ambient temperatures despite negligible surface area. 

  • 38.
    Mercier, Guillaume
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Klechikov, Alexey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hedenstrom, Mattias
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Johnels, Dan
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Baburin, Igor A.
    Seifert, Gotthard
    Mysyk, Roman
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Porous Graphene Oxide/Diboronic Acid Materials: Structure and Hydrogen Sorption2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 49, p. 27179-27191Article in journal (Refereed)
    Abstract [en]

    Solvothermal reaction of graphite oxide (GO) with benzene-1,4-diboronic acid (DBA) was reported previously to result in formation of graphene oxide framework (GOP) materials. The theoretical structure of GOFs consists of graphene layers separated by benzene-diboronic "pillars" with similar to 1 nm slit pores thus providing the opportunity to use it as a model material to verify the effect of a small pore size on hydrogen adsorption. A set of samples with specific surface area (SSA) in the range of similar to 50-1000 m(2)/g were prepared using variations of synthesis conditions and GO/DBA proportions. Hydrogen storage properties of GOF samples evaluated at 293 and 77 K were found to be similar to other nanocarbon trends in relation to SSA values. Structural characterization of GO/DBA samples showed all typical features reported as evidence for formation of a framework structure such as expanded interlayer distance, increased temperature of thermal exfoliation, typical features in FTIR spectra, etc. However, the samples also exhibited reversible swelling in polar solvents which is not compatible with the idealized GOF structure linked by benzenediboronic molecular pillars. Therefore, possible alternative nonframework models of structures with pillars parallel and perpendicular to GO planes are considered.

  • 39. Quesnel, Etienne
    et al.
    Roux, Frédéric
    Emieux, Fabrice
    Faucherand, Pascal
    Kymakis, Emmanuel
    Volonakis, George
    Giustino, Feliciano
    Martín-García, Beatriz
    Moreels, Iwan
    Alkan Gürsel, Selmiye
    Bayrakçeken Yurtcan, Ayşe
    Di Noto, Vito
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Baburin, Igor
    Tranca, Diana
    Seifert, Gotthard
    Crema, Luigi
    Speranza, Giorgio
    Tozzini, Valentina
    Bondavalli, Paolo
    Pognon, Grégory
    Botas, Cristina
    Carriazo, Daniel
    Singh, Gurpreet
    Rojo, Teófilo
    Kim, Gunwoo
    Yu, Wanjing
    Grey, Clare
    Pellegrini, Vittorio
    Graphene-based technologies for energy applications, challenges and perspectives2015In: 2D Materials, ISSN 2053-1583, Vol. 2, no 3, p. 1-16Article in journal (Refereed)
    Abstract [en]

    Here we report on technology developments implemented into the Graphene Flagship European project for the integration of graphene and graphene-related materials (GRMs) into energy application devices. Many of the technologies investigated so far aim at producing composite materials associating graphene or GRMs with either metal or semiconducting nanocrystals or other carbon nanostructures (e.g., CNT, graphite). These composites can be used favourably as hydrogen storage materials or solar cell absorbers. They can also provide better performing electrodes for fuel cells, batteries, or supercapacitors. For photovoltaic (PV) electrodes, where thin layers and interface engineering are required, surface technologies are preferred. We are using conventional vacuum processes to integrate graphene as well as radically new approaches based on laser irradiation strategies. For each application, the potential of implemented technologies is then presented on the basis of selected experimental and modelling results. It is shown in particular how some of these technologies can maximize the benefit taken from GRM integration. The technical challenges still to be addressed are highlighted and perspectives derived from the running works emphasized.

  • 40. Rezania, B.
    et al.
    Severin, Nikolai
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rabe, Juergen P.
    Hydration of bilayered graphene oxide2014In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 14, no 7, p. 3993-3998Article in journal (Refereed)
    Abstract [en]

    The hydration of graphene oxide (GO) membranes is the key to understand their remarkable selectivity in permeation of water molecules and humidity-dependent gas separation. We investigated the hydration of single GO layers as a function of humidity using scanning force microscopy, and we determined the single interlayer distance from the step height of a single GO layer on top of one or two GO layers. This interlayer distance grows gradually by approximately 1 A upon a relative humidity (RH) increase in the range of 2 to similar to 80% and the immersion into liquid water increases the interlayer distance further by another 3 A. The gradual expansion of the single interlayer distance is in good agreement with the averaged distance measured by X-ray diffraction on multilayered graphite oxides, which is commonly explained with an interstratification model. However, our experimental design excludes effects connected to interstratification. Instead we determine directly if insertion of water into GO occurs strictly by monolayers or the thickness of GO layers changes gradually. We find that hydration with up to 80% RH is a continuous process of incorporation of water molecules into single GO layers, while liquid water inserts as monolayers. The similarity of hydration for our bilayer and previously reported multilayered materials implies GO few and even bilayers to be suitable for selective water transport.

  • 41.
    Sun, Jinhua
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Klechikov, Alexey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Moise, Calin
    Prodana, Mariana
    Enachescu, Marius
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    A Molecular Pillar Approach To Grow Vertical Covalent Organic Framework Nanosheets on Graphene: Hybrid Materials for Energy Storage2018In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 57, no 4, p. 1034-1038Article in journal (Refereed)
    Abstract [en]

    Hybrid 2D–2D materials composed of perpendicularly oriented covalent organic frameworks (COFs) and graphene were prepared and tested for energy storage applications. Diboronic acid molecules covalently attached to graphene oxide (GO) were used as nucleation sites for directing vertical growth of COF-1 nanosheets (v-COF-GO). The hybrid material has a forest of COF-1 nanosheets with a thickness of 3 to 15 nm in edge-on orientation relative to GO. The reaction performed without molecular pillars resulted in uncontrollable growth of thick COF-1 platelets parallel to the surface of GO. The v-COF-GO was converted into a conductive carbon material preserving the nanostructure of precursor with ultrathin porous carbon nanosheets grafted to graphene in edge-on orientation. It was demonstrated as a high-performance electrode material for supercapacitors. The molecular pillar approach can be used for preparation of many other 2D-2D materials with control of their relative orientation.

  • 42.
    Sun, Jinhua
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Morales-Lara, Francisco
    Klechikov, Alexey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Baburin, Igor A.
    Seifert, Gotthard
    Cardano, Francesca
    Baldrighi, Michele
    Frasconi, Marco
    Giordani, Silvia
    Porous graphite oxide pillared with tetrapod-shaped molecules2017In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 120, p. 145-156Article in journal (Refereed)
    Abstract [en]

    Porous pillared graphene oxide (GO) materials were prepared using solvothermal reaction of Hummers GO with solution of Tetrakis(4-aminophenyl)methane (TKAm) in methanol. The intercalation of TKAm molecules between individual GO sheets, performed under swelling condition, results in expansion of inter-layer distance of GO from ∼7.5 Å to 13-14 Å. Pillaring GO with bulky, rigid 3D shaped TKAm molecules could be an advantage for the preparation of stable pillared structures compared to e.g. aliphatic or aromatic diamines. Insertion of TKAm molecules into inter-layer space of GO results in formation of interconnected network of sub-nanometer slit pores. The expanded GO structure prepared with optimized GO/TKAm composition shows Specific Surface Area (SSA) up to 660 m2/g which is among the highest reported for GO materials pillared using organic spacers. Modelling of GO structures pillared with TKAm molecules shows that maximal SSA of about 2300 m2/g is theoretically possible for realistic concentration of pillaring molecules in GO interlayers. Hydrogen sorption by pillared GO/TKAm is found to follow standard correlation with SSA both at ambient and liquid nitrogen temperatures with highest uptakes of 1.66 wt% achieved at 77 K and 0.25 wt% at 295 K. Our theoretical simulations show that pillared GO structures do not provide improvement of hydrogen storage beyond well-established physisorption trends even for idealized materials with subnanometer pores and SSA of 2300–3700 m2/g.

  • 43.
    Sundqvist, Bertil
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Quwar, Issam
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Talyzin, Alexandr V.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Low temperature phase diagram of NH3BH32011In: Materials Research Society Symposium Proceedings: Proceedings of Symposium EE: Solid-State Chemistry of Inorganic Materials VIII / [ed] P.S. Halasyamani, D.G. Mandrus, K.-S. Choi and S.J. Clarke, Cambridge: Cambridge University Press , 2011, p. mrsf10-1309-ee06-25-Conference paper (Refereed)
    Abstract [en]

    The pressure-temperature (p-T) phase diagram of NH3BH3 has been investigated by thermal conductivity measurements up to 1.5 GPa at temperatures between 100 and 300 K, and the phase boundaries between the three known structural phases have been identified. The transformation between the room temperature tetragonal I4mm phase and the low temperature orthorhombic Pmn21 phase (Tc = 218 K at p = 0) shows only a small hysteresis. The transformation into the high pressure orthorhombic Cmc21 phase (at 1.0 GPa near 292 K) has a very strong hysteresis, up to Δp = 0.5 GPa, and below 230 K a fraction of this phase is metastable even at atmospheric pressure.

  • 44.
    Sundqvist, Bertil
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Physics.
    Phase transitions in hydrogen storage compounds under pressure2007In: Journal of Physics Condensed Matter, vol. 19, issue 42: Proceedings of the 3rd Asian Conference on High Pressure, Lijiang City 2006, Bristol: Intitute of Physics , 2007, p. 425201-Conference paper (Refereed)
    Abstract [en]

    Solid, hydrogen-rich compounds, such as alkali metal hydrides, MAH4, where

    M is an alkali metal and A is boron or aluminium, may be used for hydrogen

    storage. We briefly review recent high-pressure work in this field aimed at

    exploring the phase behaviour, and especially the possibility to find highly

    dense new structures. In particular we present experimental data on the

    structure, lattice dynamics, phase diagrams, and thermal properties obtained by

    us and others by Raman scattering, x-ray diffraction, and thermal conductivity

    measurements under pressure between 100 and 400 K. From these data and the

    results of theoretical calculations we map observed structural phases and phase

    transitions in the pressure–temperature plane for the materials that have so far

    been investigated under pressure.

  • 45.
    Sundqvist, Bertil
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Physics.
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Physics.
    Complex hydrides studied by Raman spectroscopy and thermal conductivity measurements under high pressure2006In: Hydrogen Storage Technologies: Proceedings of Symposium Z at the 2006 MRS Fall Meeting, Boston, MA, USA; Materials Research Society Symposium Proceedings vol. 971E, Warrendale: Materials Research Society , 2006, p. 7-12Conference paper (Refereed)
    Abstract [en]

    The pressure-temperature phase diagrams of alkali metal alanates and borohydrides are of large current interest, and we have recently studied phase transformations under pressure in several of these materials. We here report Raman studies of KBH4 under pressure at room temperature, showing a phase transition near 6 GPa. Although no structural information is yet available, the similarity between KBH4 and NaBH4 suggests the new structure is orthorhombic. We also report studies on LiBH4 showing that the high pressure phase of this material is metastable to zero pressure below 200 K.

  • 46. Szabó, Tamás
    et al.
    Péter, Zsolt
    Illés, Erzsébet
    Janovák, László
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stability and dye inclusion of graphene oxide/polyelectrolyte layer-by-layer self-assembled films in saline, acidic and basic aqueous solutions2017In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 111, p. 350-357Article in journal (Refereed)
    Abstract [en]

    We demonstrate that a simple spectrophotometric method can be efficiently applied for the characterization of structural and chemical stability and adsorption properties of composite graphene oxide (GO) films in various solutions. The immersion stability of GO layer-by-layer (LbL) self-assembled with a polycation into ultrathin multilayered films was studied in water and in concentrated salty, acidic and basic solutions by UV-visible spectroscopy. These films were found to retain both their chemical stability and physical integrity in water, salt and HCl solutions with a slight rearrangement of the nanoscale structure as shown by the change in their visible spectrum. However, immersion into NaOH solutions above molar concentration led to the deconstruction of the multilayer structure by base-induced deoxygenation of GO. The adsorption of methylene blue on polymer/GO LbL films of various thicknesses revealed that the multilayers are largely impermeable towards this cationic dye.

  • 47.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Comment on "Laser controlled magnetism in hydrogenated fullerene films": [J. Appl. Phys. 109, 083941 (2011)]2013In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 3, p. 036101-Article in journal (Other academic)
    Abstract [en]

    Hydrogenation of C-60 films with formation of single hydrogen adduct reported by Makarova et al. [J. Appl. Phys. 109, 083941 (2011); Phys. Status Solidi B 246, 2778 (2009)] was supported only by several features found in Raman spectra of treated samples. However, no spectra were shown for untreated samples. Data shown in this comment prove that all Raman peaks assigned by Makarova et al. [J. Appl. Phys. 109, 083941 (2011); Phys. Status Solidi B 246, 2778 (2009)] to effects of hydrogenation can be found in spectra of pristine untreated commercial C-60 powder. These peaks represent some second order vibrations of C-60 as well as some possible solvent impurities. Therefore, all magnetic effects reported in this study should be assigned to unknown effects but not necessarily to hydrogenation. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4775821]

  • 48.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Feasibility of H2–THF–H2O clathrate hydrates for hydrogen storage applications2008In: International Journal of Hydrogen Energy, Vol. 33, no 1, p. 111-115Article in journal (Refereed)
    Abstract [sv]

    Hydrogen storage capacity of hydrogen clathrate hydrates H2–THF–H2O was directly measured using gravimetric method. The amount of hydrogen stored in a bulk piece of ice was below even after prolonged exposure to hydrogen at . It is confirmed that fine dispersion of material is required to improve kinetics of hydrogen uptake. To achieve a fine dispersion of ice grains, it is proposed to use rather common light framework materials with size of pore sizes of about as a support media. The samples dispersed in foamed polyurethane showed measurable hydrogen uptake at pressure and release. However, the amount of stored hydrogen was found maximum on the level of .

  • 49.
    Talyzin, Alexandr
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fulleranes by direct reaction with hydrogen gas at elevated conditions2010In: Fulleranes: the hydrogenated fullerenes / [ed] Franco Cataldo, Susana Iglesias-Groth, Dordrecht: Springer Netherlands, 2010, p. 85-103Chapter in book (Other academic)
    Abstract [en]

    Reaction of solid fullerenes with hydrogen gas occurs with or without catalysts at elevated conditions. Composition of hydrofullerene mixture obtained in this reaction depends strongly on temperature (350–450°C), hydrogen pressure (typically 10–120 bar) and duration of treatment. Saturation of hydrogenation occurs after tens of hours, depending on temperature of reaction. In case of extra strong hydrogenation prolonged reaction leads to formation of fulleranes with composition C60Hx approaching number of hydrogen atoms X = 60. These fulleranes are highly unstable and decompose first with formation of fragmented hydrofullerenes with progressively smaller number of carbon atoms C59, C58, C57 etc., followed by collapse of cage structure. Since the collapse occurs at the conditions of high temperature and high hydrogen pressure, all breaking C–C bonds are saturated immediately with hydrogen and new C–H bonds are formed. Therefore, large fragments of fullerane molecules are able to survive and large polycyclic aromatic hydrocarbons (PAH’s) formed as a result of cage structure collapse.

  • 50.
    Talyzin, Alexandr
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Andersson, Ove
    Umeå University, Faculty of Science and Technology, Physics.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Kurnosov, Alexander
    Dubrovinsky, Leonid
    High pressure phase transition in LiBH42007In: Journal of Solid State Chemistry, ISSN 0022-4596, Vol. 180, no 2, p. 510-7Article in journal (Refereed)
    Abstract [en]

    The high-pressure phase transition from ambient pressure alpha-LiBH4 to high-pressure beta-LiBH4 was observed by Raman spectroscopy and X-ray diffraction between 0.8 and 1.1 GPa. The phase boundary between these two phases was mapped over a large range of temperatures using thermal conductivity studies and differential thermal analysis. The structure of the high-pressure phase could not be identified due to small number of experimentally observed reflections, but it was shown that it is different from previously reported theoretical predictions.

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