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The molecular Pt nanocluster [Pt27(CO)31]4- (14-) was obtained by thermal decomposition of [Pt15(CO)30]2- in tetrahydrofuran under a H2 atmosphere. The reaction of 14- with increasing amounts of HBF4·Et2O afforded the previously reported [Pt26(CO)32]2- (32-) and [Pt26(CO)32]- (3-). The new nanocluster 14- was characterized by IR and UV-visible spectroscopy, single-crystal X-ray diffraction, direct-current superconducting quantum interference device magnetometry, cyclic voltammetry, IR spectroelectrochemistry (IR SEC), and electrochemical impedance spectroscopy. The cluster displays a cubic-close-packed Pt27 framework generated by the overlapping of four ABCA layers, composed of 3, 7, 11, and 6 atoms, respectively, that encapsulates a fully interstitial Pt4 tetrahedron. One Pt atom is missing within layer 3, and this defect (vacancy) generates local deformations within layers 2 and 3. These local deformations tend to repair the defect (missing atom) and increase the number of Pt-Pt bonding contacts, minimizing the total energy. The cluster 14- is perfectly diamagnetic and displays a rich electrochemical behavior. Indeed, six different oxidation states have been characterized by IR SEC, unraveling the series of 1n- (n = 3-8) isostructural nanoclusters. Computational studies have been carried out to further support the interpretation of the experimental data.

Medium-temperature fluoroalkylation of microporous activated carbons (ACs) with 1,1,1,2-tetrafluoroethane is presented. Supercapacitor (SC) electrodes based on the fluoroalkylated ACs showed enhanced specific capacitance and high specific energy in electrolytes, either aqueous potassium hydroxide solution or tetraethylammonium tetrafluoroborate-acetonitrile solution. We found the largest increase in the specific capacitance, up to 89 F g–1, and in the specific energy, up to 7.5 Wh kg–1, at the voltage of 1.5 V. The specific capacitance of the SC electrode based on the sample prepared at 350 °C increases by a factor of ~ 2–3 × for certain scan rates in the organic electrolyte. The fluoroalkylated ACs have good electrochemical stability in the tested model systems. We associate the registered enhanced SC parameters with an increase in the total fluorine content and high specific surface areas of the carbon electrode materials. The surface “isolated fluorine” formed during fluoroalkylation at 300–400 °C ensures the production of improved electrode materials for SC applications. Fluoroalkylation is a simple and cost-effective method of improving the specific capacitance of carbon-based SC electrodes.

Thermal exfoliation of graphite oxide is a scalable way to produce macroscopic amount of defective graphene-based compounds with high specific surface area, ideal as electrode materials in high-performance electrochemical supercapacitors. In order to increase the stored energy, defective graphene has been decorated with Ni nanoparticles without exposing the system to air. During the first charge cycle in an aqueous electrolyte (KOH 3.5M), Ni anchored to graphene proved to easily convert to Ni(OH)2 at the nanoscale and hence to reversibly assume Ni2+ and Ni3+ valence during cyclic voltammetry, through its conversion to NiOOH. Such reversible faradaic mechanism led to a one order of magnitude increase of the specific capacitance of electrodes, reaching up to 1900 F/g at 2 mV/s in KOH 3.5M. An asymmetric supercapacitor was obtained by coupling a pure graphene negative electrode with a Ni decorated graphene positive one. The supercapacitor, operating with aqueous electrolyte, was successfully cycled in the 0-1.5 V voltage range, reaching a maximum specific energy of 37 Wh/kg and a maximum specific power of 5 kW/kg. The devices displayed good reversibility and retained 72 % of the specific energy over 10 thousand of cycles. Such promising results disclose to possible industrial implementation of graphene-based supercapacitors, for a wide range of energetic application.

Typically, the solid state is not well suited to sustaining fast molecular motion - however, in recent years a variety of molecular machines, switches and rotors have been successfully engineered within porous crystals and on surfaces. Here, we report on a combined 1H-NMR [1] and SR [2] study of fast-rotating molecular rotors within the bicyclopentane-dicarboxylate struts of a zinc-based metal-organic framework. Here, the carboxylate groups anchored to the metal clusters act as an axle while the bicyclic units are free to rotate. The three-fold bipyramidal symmetry of the rotator conflicts with the four-fold symmetry of the struts, frustrating the formation of stable conformations and favouring the continuous, unidirectional, ultrafast rotation of the bicyclic units down to cryogenic temperatures. As a remarkable consequence, the fast-motions regime for the 1H-NMR spin-lattice relaxation rate is maintained down to at least 2 K, as confirmed by its dependence on temperature and magnetic field. These results are confirmed by zero-field and longitudinal-field SR experiments and, in particular, by the dependence of the longitudinal relaxation rate on temperature. At the same time, the experimental evidences suggest several implantation sites for the muons, among which one directly onto the rotating moiety. Muons thermalized in this latter site generate clear oscillations in the depolarization (shown in the picture) resulting from the dipolar interaction with the 1H nuclear moments on the rotors. We evidence a highly unusual dependence of these oscillations on temperature, suggesting a complex influence of the rotations on the muon implantation and diffusion. [1] J. Perego et al., Nature Chemistry 12 845 (2020). [2] G. Prando et al., Nano Letters 20 7613 (2020).

Surface decoration of graphene-based nanostructures with metals has been predicted to be an efficient way towards the development of resistant catalysts and novel materials for energy applications, such as hydrogen production and storage. We report on an extensive neutron scattering study of a defective graphene-based material decorated with nickel nanoparticles, obtained via the chemical decoration of thermally exfoliated graphite oxide. The combination of neutron diffraction and inelastic neutron scattering measurements has been used to characterize the low-dimensional carbon backbone and the presence of the nickel nanoparticles, organized at the nanometer scale on the graphene plane. The structural features of this system, along with the nickel capability of dissociating the hydrogen molecule upon hydrogen treatment, are herein discussed.

Physisorption of hydrogen in nanoporous materials offers an efficient and competitive alternative for hydrogen storage. At low temperatures (e.g. 77 K) and moderate pressures (below 100 bar) molecular H2 adsorbs reversibly, with very fast kinetics, at high density on the inner surfaces of materials such as zeolites, activated carbons and metal–organic frameworks (MOFs). This review, by experts of Task 40 ‘Energy Storage and Conversion based on Hydrogen’ of the Hydrogen Technology Collaboration Programme of the International Energy Agency, covers the fundamentals of H2 adsorption in nanoporous materials and assessment of their storage performance. The discussion includes recent work on H2 adsorption at both low temperature and high pressure, new findings on the assessment of the hydrogen storage performance of materials, the correlation of volumetric and gravimetric H2 storage capacities, usable capacity, and optimum operating temperature. The application of neutron scattering as an ideal tool for characterising H2 adsorption is summarised and state-of-the-art computational methods, such as machine learning, are considered for the discovery of new MOFs for H2 storage applications, as well as the modelling of flexible porous networks for optimised H2 delivery. The discussion focuses moreover on additional important issues, such as sustainable materials synthesis and improved reproducibility of experimental H2 adsorption isotherm data by interlaboratory exercises and reference materials.

Graphene-based miniaturized supercapacitors, obtained via laser conversion of suitable precursors, have been attracting recent attention for the production of energy storage small-scale devices. In this work, a one-pot synthesis of TiO2 nanoparticles embedded in porous graphene-based electrodes has been obtained with the LightScribe® technology, by converting the precursor materials through the absorption of a DVD burner infrared laser light. Enhanced electrochemical performance of devices has been achieved thanks to the combination of faradic surface reactions, arising from metal oxide nanoparticles, with the conventional electrochemical double layer capacitance, arising from porous graphene. Micro-supercapacitors, consisting of TiO2-graphene electrodes, have been tested by investigating two hydrogel polymer electrolytes, based on polyvinyl alcohol/H3PO4 and polyvinyl alcohol/H2SO4, respectively. Specific areal capacitance up to 9.9 mF/cm2 are obtained in TiO2-graphene devices, corresponding to a volumetric capacitance of 13 F/cm3 and doubling the pristine graphene-based device results. The micro-supercapacitors achieved specific areal energy and specific areal power of 0.22 μWh/cm2 and 39 μW/cm2, along with a cyclability greater than 3000 cycles. These high-performance results suggest laser-scribed TiO2-graphene nanostructures as remarkable candidates in micro-supercapacitors for environment-friendly, large-scale and low-cost applications.

High power mid-infrared light pulses of tunable pulse length were generated to stabilize light-induced superconductivity in K3C60 for nanoseconds. This metastable state showed a vanishing electrical resistance at five times the material’s equilibrium critical temperature.

Oxidation of activated carbon (AC) with nitric acid was carried out, and the resulting AC/HNO 3 showed high capacity when used as supercapacitor electrode material operated in the KOH electrolyte. Oxidation caused different structural changes in the AC, reducing the specific surface area and the total pore volume. After oxidation, the content of all types of oxygen-containing groups and, especially, carboxyl groups showed a significant increase. Despite the significant reduction of the specific surface area, the specific capacitance of the oxidized AC in symmetric supercapacitor electrodes is 1.4 times larger than that for the pristine AC.

Optical excitation at terahertz frequencies has emerged as an effective means to manipulate complex solids dynamically. In the molecular solid K3C60, coherent excitation of intramolecular vibrations was shown to transform the high temperature metal into a non-equilibrium state with the optical conductivity of a superconductor. Here we tune this effect with hydrostatic pressure, and we find it to disappear around 0.3 GPa. Reduction with pressure underscores the similarity with the equilibrium superconducting phase of K3C60, in which a larger electronic bandwidth is detrimental for pairing. Crucially, our observation excludes alternative interpretations based on a high-mobility metallic phase. The pressure dependence also suggests that transient, incipient superconductivity occurs far above the 150 K hypothesised previously, and rather extends all the way to room temperature., 33 pages, 17 figures, 2 tables

We report on the C-60, Na, and Li dynamics in NaxLi6xC60 fullerides (x = 0, 1, 5, and 6) in the temperature range 80-550 K by using C-13, Na-23, and Li-7 solid state NMR. The results show that the C-60 reorientation dynamics is hindered at room temperature for the Li-enriched fullerides, but it is active for the Na rich ones with a rate of the order of few kilohertz. Na-23 and Li-7 NMR measurements show the presence of two dominant thermally activated dynamics that can be associated with Li/Na ionic motions within the octahedral sites (intrasite motion) and between the octahedral and tetrahedral sites (intersite motion). The substitution of one Na or one Li ion in the end members Li6C60 and Na6C60, respectively, yields to an increase of the hopping rate of the intersite motion, which is necessary for the ionic diffusion in possible fulleride-based ionic conductors.

Having single atoms or small clusters docked onto a single layer graphene represents a charming feature for energy-storage and catalysis. Unfortunately, the large cohesion energy of transition metals often prevents the isolation of nanoscopic clusters, which invariably tend to aggregate. The decoration of defective graphene layers with single Pt atoms and sub-nanometric clusters is herein achieved by exploiting metal carbonyl clusters, as precursor, and investigated by means of transmission electron microscopy and X-ray photoemission spectroscopy. Unexpectedly, the process of aggregation of Pt into larger clusters is inhibited onto the surface of defective graphene, where the Pt-clusters are found to fragment even into single metal atoms.

The addition of transition metals to alkali intercalated fullerides proved to enhance their already good hydrogen absorption properties. Herein we present a study based on two different synthetic strategies, allowing the addition of nickel as aggregates with different size to the lithium fulleride Li6C60: the former is based on the metathesis of nickel chloride, while the latter on the thermal decomposition of nickel carbonyl clusters. The hydrogen-storage properties of the obtained materials have been investigated with manometric and calorimetric measurements, which indicated a clear enhancement of the final absorption value and kinetics with respect to pristine Li6C60, as a consequence of nickel surface catalytic activity towards hydrogen molecules dissociation. We found up to 10 % increase of the total H2 weight % absorbed (5.5 wt% H2) in presence of Ni aggregates. Furthermore, the control of the transition metal particles size distribution allowed reducing the hydrogen desorption enthalpy of the systems.

The applicability of Cu/C catalysts is limited by sintering of Cu leading to deactivation in catalytic reactions. We show that the problem of sintering could be resolved by N-doping of the carbon support. Cu nanocatalysts with 1 at% of metal were synthesized by Cu acetate decomposition on N-free and N-doped (5.7 at% N) mesoporous carbon supports as well as on thermally expanded graphite oxide. Catalytic properties of these samples were compared in hydrogen production from formic acid decomposition. The N-doping leads to a strong interaction of the Cu species with the support providing stabilization of Cu in the form of clusters of less than 5 nm in size and single Cu atoms, which were observed in a significant ratio by atomic resolution HAADF/STEM even after testing the catalyst under harsh conditions of the reaction at 600 K. The mean size of the obtained Cu clusters was by a factor of 7 smaller than that of the particles in the N-free catalyst. The N-doped Cu catalyst possessed good stability in the formic acid decomposition at 478 K for at least 7 h on-stream and a significantly higher catalytic activity than the N-free Cu catalysts. The nature of the strongly interacting Cu species was studied by XPS, XRD and other methods as well as by DFT calculations. The presence of single Cu atoms in the N-doped catalysts should be attributed to their strong coordination by pyridinic nitrogen atoms at the edge of the graphene sheets of the support. We believe that the N-doping of the carbon support will allow expanding the use of Cu/C materials for different applications avoiding sintering and deactivation.

Melanophlogite (type I clathrate) has a microporous framework of corner sharing SiO4 tetrahedra, which can host guest gases. Here, a multi–analytical approach has been employed to understand the phase transitions with temperature and the degassing behaviour of a melanophlogite sample, which contains CO2 together with minor CH4 amount as enclathrated molecules.Synchrotron powder diffraction data collected between 110 and 380 K (ESRF, ID22 beamline) show a clear splitting of the major peaks up to about 360 K. Le Bail analysis shows that the low temperature phase is monoclinic, changing to cubic at ∼370 K. Landau theory analysis indicates that the transition is second order, with Tc = 369(1) K. Moreover, significant volume strain related to the phase transitions accounts for the lower thermal expansion at higher temperature. Differential scanning calorimetry shows evidence of a further phase transition between 220 and 250 K. The transition is confirmed by powder diffraction, with a change in slope in the b unit cell parameter and in volume expansion in the same temperature range. High temperature X-Ray powder diffraction between 313 and 673 K shows that thermal expansion decreases with temperature, possibly in relation with a structural rearrangement within the cubic structure during degassing. Thermogravimetric analysis shows that degassing of the guest gases begins at 450 K, and occurs at a higher rate above 750 K, but it is not completed even at T = 1273 K. Melanophlogite confirms to be a good host carrier for the gases, with gas loss only at higher temperature. Moreover, as degassing occurs with almost no thermal expansion, it could open promising application for its mechanical stability during degassing.

We report on the preparation of a novel hierarchically-porous super-activated carbon originating from organic waste with specific surface area exceeding 3000 m2/g, obtained starting from biochar derived by the pyrolysis of poultry litter. The chemical activation process proved to be efficient to remove the majority of impurities other than carbon, stabilizing a highly porous hierarchical structure with local graphene-like morphology. The presence of P and S with concentration below 0.1 wt% distinguishes this activated carbon from the usual ones obtained from vegetal sources. Thanks to these features, the obtained porous compound demonstrated to behave as an excellent electrode material for high-performance symmetric supercapacitors, reaching high specific capacitance up to 229 (13) F/g. Remarkably, the devices also supply high current density of 10 A/g without using any conducting additives and display high power density and reliability. Moreover, these optimal performances have been obtained operating by using simple eco-friendly electrolytes, like KOH and Na2SO4 aqueous solutions. The availability, the biocompatibility and the inexpensiveness of the starting materials, together with the low environmental impact of the electrolyte, suggest possible large-scale applications for such devices, for example in the field of transportation or in renewable energy-grids, but also in the field of bio-medicine.

The new bimetallic [HCo15Pd9C3(CO)(38)](2-) tri-carbide carbonyl cluster has been obtained from the reaction of [H2Co20Pd16C4(CO)(48)](4-) with an excess of acid in CH2Cl2 solution. The mono-hydride di-anion can be reversibly protonated and deprotonated by means of acid-base reactions leading to closely related [H3-nCo15Pd9C3(CO)(38)](n-) (n = 0-3) clusters. The crystal structures of the three anionic and the neutral clusters have been determined as their H3Co15Pd9C3(CO)(38)center dot 2thf, [NEt4][H2Co15Pd9C3(CO)(38)]center dot 0.5C(6)H(14), [NMe3(CH2Ph)](2)[HCo15Pd9C3(CO)(38)]center dot C6H14 and [NEt4](3)[Co15Pd9C3(CO)(38)]center dot thf salts. They are composed of a Pd-9(mu(3)-CO)(2) core stabilised by three Co5C(CO)(12) organometallic fragments. The poly-hydride nature of these clusters has been indirectly inferred via chemical, electrochemical and magnetic measurements. Besides, cyclic voltammetry shows that the [H3-nCo15Pd9C3(CO)(38)](n-) (n = 1-3) anions are multivalent, since they undergo two or three reversible oxidations. SQUID measurements of [HCo15Pd9C3(CO)(38)](2-) indicate that this even electron cluster is paramagnetic with two unpaired electrons, giving further support to its hydride nature. Finally, structural studies show that the Pd-9 core of [H3-nCo15Pd9C3(CO)(38)](n-) (n = 0,1) is a tri-capped octahedron, which becomes a tri-capped trigonal prism in the more charged [H3-nCo15Pd9C3(CO)(38)](n-) (n = 2,3) anions. Such a significant structural rearrangement of the metal core of a large carbonyl cluster upon protonation-deprotonation reactions is unprecedented in cluster chemistry, and suggests that interstitial hydrides may have relevant stereochemical effects even in large carbonyl clusters.

Li6C60 is so far the best performing fullerene-based hydrogen-storage material. The mechanism of its reversible hydrogen absorption is not, however, totally known. Here, we report the thermal evolution of Li6C60 upon deuterium absorption up to 330 °C and under 60 bar deuterium gas pressure using in situ high-intensity neutron powder diffraction. The temporal resolution of the collected data allowed the hydrogenation of Li6C60 and the segregation of lithium hydride (here LiD) processes to be distinguished from a mechanistic point of view. During absorption, Li6C60 undergoes several phase transitions, involving the partial segregation of Li in the form of hydride and the expansion of the face-centered cubic (fcc) lattice, followed by a body-centered cubic (bcc) rearrangement of the deuterated fullerenes. The amount of absorbed deuterium was determined by the analysis of the variation in the scattered neutron intensity and confirmed by an ex situ desorption measurement. This analysis clarifies the complex ph...

The lithium cluster intercalated fulleride Li 12 C 60 was investigated by means of Muon Spin Relaxation (μSR) spectroscopy with the intent of unveil its hydrogen storage mechanism. Thanks to the well-known propensity of positive muons to form Muonium, a light isotope of the hydrogen atom, the final stages of the absorption process can be probed. The appearance of a slow oscillating signal in the time evolution of the muon polarization indicates the presence of Li–Mu covalent pair, never observed before in lower doped Li fullerides, which mimics the formation of LiH at the first stage of hydrogen chemisorption in the material. In addition, the μSR signal shows a clear transition above 150 K, compatible with a thermally activated Li cluster rearrangement. The combined Inelastic Neutron Scattering analysis suggests that tetrahedral Li clusters may undergo a progressive melting upon heating, which could favour room temperature ionic diffusion.

The performance of graphene, and a few selected derivatives, was investigated as a negative electrode material in sodium- and lithium-ion batteries. Hydrogenated graphene shows significant improvement in battery performance compared with as-prepared graphene, with reversible capacities of 488 mA h g−1 for lithium-ion batteries after 50 cycles and 491 mA h g−1 for sodium-ion batteries after 20 cycles. Notably, high rates of 1 A g−1 for graphene and 5 A g−1 for hydrogenated graphene indicate higher capacities in sodium-ion batteries than in lithium-ion batteries. Alternatively, nickel-nanoparticle-decorated graphene performed relatively poorly in lithium-ion batteries. However, in sodium-ion batteries they showed the highest reversible capacities of all studied batteries and graphene derivatives, with 826 mA h g−1 after 25 cycles with ≈97 % coulombic efficiency. Overall, minor modifications to graphene can dramatically improve electrochemical performance in both lithium-ion and sodium-ion batteries.

We herein report on the synthesis of mixed alkali cluster intercalated fullerides NaxLiy−xC60 (y = 12; x = 1–6) by a two-steps mechanochemical reaction of fullerene with sodium and lithium. These compounds crystallize in the cubic lattice of C60 displaying a contracted lattice parameter with respect to the Na6C60 parent structure. The analysis of the hydrogen sorption behaviour shows a slight decrease in the dehydrogenation enthalpy for y = 12 with respect to the sodium free member. Raman spectroscopy highlighted a partial electron transfer from alkali metals to C60, suggesting the presence of charged sodium/lithium clusters. Finally, we applied muon spectroscopy to understand the different hydrogenation mechanisms in NaxLi6−xC60 and NaxLi12−xC60 and explain their different performance.

For different hydrogenated metal intercalated fullerides (Na10C60-H, Li12C60-H, and Li28C60-H) the activation energies for hydrogen desorption were determined by DSC. The Vyazovkin advanced method (VA) was used for the calculation of the reaction model free activation energy as a function of the extent of conversion a. Activation energies are highest for low a and decrease for increasing alpha, between around 200-145 and 245-175 kJ/mol for the Na and Li compounds, respectively. The decrease of activation energy as a function of the extent of conversion can be explained by an increasing charge transfer to the C60H36+y cage during desorption. Na intercalation leads to a significant thermodynamic destabilization for hydrogen desorption. Dehydrogenation enthalpies of 52 (Na10C60-H), 66 (Li12C60-H), and 69 kJ/mol H-2 (Li28C60-H) were determined. These values are lower compared to literature values for desorption of pure C60H36 (74 kJ/mol H-2). The onsets of hydrogen desorption are 185 degrees C (Na10C60-H), 260 degrees C (Li12C60-H), and 250 degrees C (Li28C60-H) compared to >400 degrees C for pure C60H36.

Li6C60 has been chosen as the most representative system to study the hydrogenation mechanism in alkali-cluster intercalated fullerides. We present here a muon spin relaxation (mu SR) experiment that hints the chance to achieve a higher storage capacity on fullerene with respect to the values suggested in literature. Moreover, a linear relationship between the muonium adduct radical hyperfine frequency and the level of C-60 hydrogenation was found and it can be exploited to probe the C-60 hydrogenation level, giving more credit to this technique in the field of hydrogen storage materials. (C) 2017 Elsevier Ltd. All rights reserved.

Two few-layer graphene materials, strongly distinguished in structure, were compared as electrode materials for supercapacitor. The stacks of flat sheets with basal size of a few microns have been obtained as the result of ultrasonication of bromine intercalated graphite dispersion. The highly crumpled large-size layers have been produced by rapid heating of bromine intercalated graphite fluoride. The average number of layers and in-plane crystalline size in the materials were evaluated from Raman spectroscopy. The functional composition was studied using X-ray photoelectron and Infrared spectroscopy. Electrochemical testing of the graphene materials detected re-stacking of thin crumpled layers during the electrode preparation. Furthermore, graphene material produced from the fluorinated graphite showed poor wettability. The mild oxidation of the material in a mixture of sulfuric and nitric acids allowed increasing the capacitance in several times.

We report the structural analysis of the highly-doped lithium fulleride Li12C60, performed using low-temperature neutron powder diffraction. Although the main reflections could be initially indexed with a fcc cell, Monte Carlo Simulated Annealing suggests an unusual monoclinic arrangement for the fullerene molecules. In this structure, C60 units with the same orientation are alternatively stacked to form layers, thus maximising their sterical crowding. Rietveld refinement allowed to localise Li ions, which are organised in clusters belonging to the pseudo-tetrahedral voids with a non-complete charge transfer as confirmed by Raman spectroscopy.

Within the reinvestigation of Ni–Sb carbonyl cluster chemistry, we report here the synthesis and characterization of the new [Ni19Sb4(CO)26]4– cluster and the synthesis, structure, magnetic characterization and electrical resistivity of the viologen salts of the previously known [Ni13Sb2(CO)24]n– (n = 2, 3) anionic species. The crystal structures of [NEt4]4[Ni19Sb4(CO)26], [EtV]8[Ni13Sb2(CO)24]3·4DMF·2C6H14 and [EtV]3[Ni13Sb2(CO)24]·1.5THF (EtV = 1,1′-diethyl-4,4′-bipyridilium cation, DMF = N,N-dimethylformamide, THF = tetrahydrofuran) are described. Notably, the unit cell of [EtV]8[Ni13Sb2(CO)24]3·4DMF·2C6H14 involves a mixture of two [Ni13Sb2(CO)24]3– trianions and one [Ni13Sb2(CO)24]2– dianion, as it also contains eight [EtV]+· radical monocations, which are assembled in infinite stacks. In contrast, the unit cell of the [EtV]3[Ni13Sb2(CO)24]·1.5THF salt contains four [Ni13Sb2(CO)24]3– trianions along with twelve [EtV]+· radical monocations, four of which are arranged into two pairs of isolated dimers, whereas the other two sets of four form two infinite stacks that extend over the whole crystal. The charges of the miscellaneous ions have been assigned on the basis of electroneutrality and spectroscopic evidence. More specifically, the infrared spectra of [EtV]8[Ni13Sb2(CO)24]3·4DMF·2C6H14, both in the solid state and in solution, clearly indicate the presence of a 2:1 mixture of [Ni13Sb2(CO)24]3– and [Ni13Sb2(CO)24]2– anions. Resistivity measurements performed on pellets of powdered samples indicate that the [EtV]8[Ni13Sb2(CO)24]3·4DMF·2C6H14 salt substantially behaves as an insulator. A study of the magnetic behaviour of [EtV]8[Ni13Sb2(CO)24]3·4DMF·2C6H14 evidences pairing among the electrons of the EtV+· molecules, in agreement with DFT calculations, and the odd-electron clusters behave as paramagnetic centres of spin S = 1.

After the successful electrochemical intercalation of C 60 with sodium, we report here the preparation of novel negative electrodes for Na-ion batteries composed by commercial C 60 :C 70 mixture, this being significantly less expensive than pure fullerenes. An optimized solid-state Na-poly(ethylene oxide) electrolyte was used for the battery assembly. While pure C 60 electrodes show a strong irreversible behavior after the first discharge, the peculiar disordered crystalline arrangement of C 60 and C 70 in the mixture, increased by a high-energy ball milling treatment, allows to improve the specific capacity at the first discharge up to 320 mAh/g, as well as the overall reversibility.

Graphene obtained from thermal exfoliation of graphite oxide was chemically functionalized with nickel nanoparticles (NPs) without exposing the system to oxidizing agents. Its structural, physical and chemical properties have been studied by means of TEM, X-ray photoelectron and Raman spectroscopies, and SQuID magnetometry. The formation of 17 nm super-paramagnetic (SPM) monodispersed Ni NPs was observed. Nitrogen sorption experiments at 77 K yield a Brunauer-Emmet-Teller specific surface area (BET-SSA) of 505 m2 g-1 and helium adsorption at room temperature gives a skeletal density of 2.1 g cm-3. The interaction with atomic hydrogen was investigated by means of Muon Spin Relaxation (µSR) showing a considerable fraction of captured muonium (~38%), indicative of strong hydrogen-graphene interactions. Hydrogen adsorption has been measured via pressure concentration isotherms demonstrating a maximum of 1.1 mass% of adsorbed hydrogen at 77 K and thus a 51% increased hydrogen adsorption compared to other common carbon based materials.

The lithium-intercalated fulleride Li12C60 was investigated in view of a lightweight hydrogen storage material due to the low molecular weight of its constituents. Deuterium (D2) absorption in Li12C60 shows an uptake of up to 9.5 mass % D2 (equivalent to ∼5 mass % H2 for the same stoichiometry). Under a pressure of 190 bar the onset of absorption was observed at a temperature below 100 C, which is 200 C lower than that for pure C60. Deuterium desorption was investigated by in-situ neutron powder diffraction, and at a pressure of 1 bar desorption was observed above 300 C. The ab/desorption is accompanied by a partial de/reintercalation of lithium, observed by the appearance and disappearance of LiD reflections after absorption and during desorption, respectively. A minor part of deuterium is present in ionic form in LiD, and the major part is covalently bound in a Li-depleted compound Li 12-xC60D36+y. © 2013 American Chemical Society.

Single-walled carbon nanotubes (SWCNTs) possessing a confined inner space protected by chemically resistant shells are promising for delivery, storage, and desorption of various compounds, as well as carrying out specific reactions. Here, we show that SWCNTs interact with molten mercury dichloride (HgCl2) and guide its transformation into dimercury dichloride (Hg2Cl2) in the cavity. The chemical state of host SWCNTs remains almost unchanged except for a small p-doping from the guest Hg2Cl2 nanocrystals. The density functional theory calculations reveal that the encapsulated HgCl2 molecules become negatively charged and start interacting via chlorine bridges when local concentration increases. This reduces the bonding strength in HgCl2, which facilitates removal of chlorine, finally leading to formation of Hg2Cl2 species. The present work demonstrates that SWCNTs not only serve as a template for growing nanocrystals but also behave as an electron-transfer catalyst in the spatially confined redox reaction by donation of electron density for temporary use by the guests.

Lithium and hydrogen dynamics in Li12C60 and Li12C60Hy are investigated by means of 7Li and 1H solid state Nuclear Magnetic Resonance (NMR) in the temperature range 80–550 K. Differential scanning calorimetry characterization on the hydrogen sorption and X-rays structural analysis are also reported. In the pure phase, the 7Li results show a thermally activated dynamics that can be associated to Li motions within the crystal interstices. Upon hydrogenation, Li ionic motion is considerably hindered by the presence of hydrofullerene molecules. The 1H measurements show that C–H bonds are stable on the local scale up to 400–450 K. The NMR results at higher temperatures are compatible with a H diffusion mechanism which anticipates the H desorption process.

Through the substitution of Li with Na in Li6C60, we synthesized a series of mixed alkali cluster intercalated fullerides, NaxLi6−xC60. These compounds share lattices of Na6C60 and Li6C60 with a cubic parameter linearly dependent on x. H2 absorption and desorption were studied by means of charge/discharge kinetic measurements and coupled calorimetric–manometric evaluation. By varying the stoichiometry, we found the best compromise among the absorption rate, temperature and amount of hydrogen for x = 0.5 and 1. Small concentrations of Na substituted to Li significantly lower the absorption temperature of Li6C60, improving the hydrogenation capacity, the kinetics, and the dehydrogenation enthalpy, the latter being 43.8 kJ mol−1 H2 for x = 1. This study moves further toward the utilization of intercalated fullerides for hydrogen storage applications.

Two chemically synthesized defective graphene materials with distinctly contrasting extended structures and surface chemistry are used to prepare sodium-ion battery electrodes. The difference in electrode performance between the chemically prepared graphene materials is qualified based on correlations with intrinsic structural and chemical dissimilarities. The overall effects of the materials’ physical and chemical discrepancies are quantified by measuring the electrode capacities after repeated charge/discharge cycles. Solvothermal synthesized graphene (STSG) electrodes produce capacities of 92 mAh/g in sodium-ion batteries after 50 cycles at 10 mA/g, while thermally exfoliated graphite oxide (TEGO) electrodes produce capacities of 248 mAh/g after 50 cycles at 100 mA/g. Solid-state 23Na nuclear magnetic resonance spectroscopy is employed to locally probe distinct sodium environments on and between the surface of the graphene layers after charge/discharge cycles that are responsible for the variations in ...

The hydrogen absorption of sodium intercalated fullerenes (Na xC60) was determined and compared to pure fullerenes (C60). Up to 3.5 mass% hydrogen can reversibly be absorbed in Na xC60 at 200 °C and a hydrogen pressure of 200 bar. The absorbed amount of hydrogen is significantly higher than for the case when only the sodium would be hydrogenated (∼1 mass% for x = 10). At 200 bar the onset of hydrogen absorption is observed at 150 °C. At a pressure of 1 bar hydrogen the major desorption starts at 250 °C and is completed at 300 °C (heating rate 1 °C min-1). This absorption and desorption temperatures are significantly reduced compared to pure C60, either due to a catalytic reaction of hydrogen on sodium or due to the negatively charged C60. The hydrogen ab/desorption is accompanied by a partial de/reintercalation of sodium. A minor part of the hydrogen is ionically bonded in NaH and the major part is covalently bonded in C60Hx. The sample can be fully dehydrogenated and no NaH is left after desorption. In contrast to C60, where the fullerene cages for high hydrogen loadings are destroyed during the sorption process, the NaxC60 sample stays intact. The samples were investigated by X-ray, in-situ neutron powder diffraction and infrared spectroscopy. NaxC60 was synthesized by reacting sodium azide (NaN3) with C60 (molar ratio of Na:C60 is 10:1). © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Here, we present the first muon spectroscopy investigation of graphene, focused on chemically produced, gram-scale samples, appropriate to the large muon penetration depth. We have observed an evident muon spin precession, usually the fingerprint of magnetic order, but here demonstrated to originate from muon-hydrogen nuclear dipolar interactions. This is attributed to the formation of CHMu (analogous to CH(2)) groups, stable up to 1250 K where the signal still persists. The relatively large signal amplitude demonstrates an extraordinary hydrogen capture cross section of CH units. These results also rule out the formation of ferromagnetic or antiferromagnetic order in chemically synthesized graphene samples.

The reaction of Ni(NO3)2·6H2O with Na2SeO3 in the presence of tetramethylethylenediamine (TMEDA) in a water/ethanol mixture yielded the heteroleptic complex [{Ni(TMEDA)SeO3}2] (1). Single-crystal X-ray diffraction analysis showed that complex 1 consists of a dinuclear species in which the two nickel atoms are held together by two bridging selenito anions. The crystal packing of 1 is determined by networks of hydrogen bonds, involving cocrystalized water molecules and the oxygen atoms of the bridging SeO32– groups. The two nickel ions in 1 exhibit antiferromagnetic coupling with J = –25.7 ± 0.1 cm–1, in good agreement with DFT calculations. In addition, when a less sterically hindered ancillary ligand, such as ethylenediamine (en), was used, the homoleptic complex [Ni(en)3](SeO3) (2) was obtained.

We report here on the preparation and characterization of a fullerenium salt in the solid state, where the fullerene is in the 2+ oxidized state. To succeed in this long-standing challenge, we exploit the oxidizing power of one of the strongest Lewis acids, AsF(5). The weak nucleophilic character of its conjugate base is essential in stabilizing the fullerene dication in a crystal lattice. High-resolution structural analysis of this compound, with the formula C(60)(AsF(6))(2), indicates that the highly reactive C(60)(2+) units are arranged according to a novel 1D "zigzag" polymer structure. The molecules are connected by an alternating sequence of four-membered carbon rings ([2 + 2] cycloaddition) and single C-C bonds. The long awaited high-T(c) superconductivity and magnetism, expected in a hole-doped C(60) compound, are replaced instead by a semiconducting behavior, quite probably originating from the reduced crystal and molecular symmetry upon polymerization. The small value of the energy gap (approximately 70 meV) suggests, nevertheless, the proximity of a metallic phase.

The structural relaxation of nanographite ball-milled in argon atmosphere and stored in evacuated ampoules, has been studied by monitoring the evolution of the Raman spectra. Reduction of some Raman bands associated with "in-plane" structural defects, such as vacancies, dislocations or grain boundaries, and those associated with "out-of-plane" defects, such as stacking faults, is accompanied by the rise of new bands around 1180 and 2000 cm -1 . The development of these bands is suppressed in nanographite samples exposed to a flux of pure anhydrous hydrogen.

Bulk defective graphene produced by thermal exfoliation of graphite oxide was treated under H-2 and investigated with X-ray photoemission spectroscopy, neutron spectroscopy, and solid state nuclear magnetic resonance. Graphene defects appear effective in dissociating H2 molecule and in promoting H covalent absorption on the carbon backbone. Measured generalized phonon density of states shows the presence of localized peaks ascribed to C H bending modes already in pristine graphene, whose intensities enhance when samples are treated under H2 at 1273 K. However, H-1 NMR evidences a thermally activated dynamics with a correlation time of a few microseconds assigned to a part of H atoms bound onto the graphene plane. These findings point toward a diffusive dynamics of the hydrogen chemically e, bound to graphene sheets, already active at room temperature.

Within the reinvestigation of Ni–Sb carbonyl cluster chemistry, we report here the synthesis and characterization of the new [Ni19Sb4(CO)26]4– cluster and the synthesis, structure, magnetic characterization and electrical resistivity of the viologen salts of the previously known [Ni13Sb2(CO)24]n– (n = 2, 3) anionic species. The crystal structures of [NEt4]4[Ni19Sb4(CO)26], [EtV]8[Ni13Sb2(CO)24]3·4DMF·2C6H14 and [EtV]3[Ni13Sb2(CO)24]·1.5THF (EtV = 1,1-diethyl-4,4-bipyridilium cation, DMF = N,N-dimethylformamide, THF = tetrahydrofuran) are described. Notably, the unit cell of [EtV]8[Ni13Sb2(CO)24]3·4DMF·2C6H14 involves a mixture of two [Ni13Sb2(CO)24]3– trianions and one [Ni13Sb2(CO)24]2– dianion, as it also contains eight [EtV]+· radical monocations, which are assembled in infinite stacks. In contrast, the unit cell of the [EtV]3[Ni13Sb2(CO)24]·1.5THF salt contains four [Ni13Sb2(CO)24]3– trianions along with twelve [EtV]+· radical monocations, four of which are arranged into two pairs of isolated dimers, whereas the other two sets of four form two infinite stacks that extend over the whole crystal. The charges of the miscellaneous ions have been assigned on the basis of electroneutrality and spectroscopic evidence. More specifically, the infrared spectra of [EtV]8[Ni13Sb2(CO)24]3·4DMF·2C6H14, both in the solid state and in solution, clearly indicate the presence of a 2:1 mixture of [Ni13Sb2(CO)24]3– and [Ni13Sb2(CO)24]2– anions. Resistivity measurements performed on pellets of powdered samples indicate that the [EtV]8[Ni13Sb2(CO)24]3·4DMF·2C6H14 salt substantially behaves as an insulator. A study of the magnetic behaviour of [EtV]8[Ni13Sb2(CO)24]3·4DMF·2C6H14 evidences pairing among the electrons of the EtV+· molecules, in Agreement with DFT calculations, and the odd-electron clusters behave as paramagnetic centres of spin S = 1.

We report the extensive investigation of Li and H dynamics in Li6C60 and Li6C60Hy, by combining 7Li and 1H solid state NMR measurements with DC/AC conductivity, in order to evaluate the potential application of these systems for energy-storage purposes. 7Li NMR results show a local motion of Li ions above 200 K in both pristine and hydrogenated compounds, with activation energies of 90–150 meV and correlation times of about 30 ps. Evidences of Li interdiffusive dynamics are given by conductivity measurements in Li6C60 already above 120 K, with activation energies of 240 meV, suggesting that ionic conductivity is of the order of 10−5 S cm−1 at room temperature, with correlation times of about 150 ps. On the other hand, the Li6C60Hy behaves like a semiconductor with a high energy gap (ca. 2.5 eV), suggesting that diffusion of intercalated Li ions is prevented. 1H NMR measurements indicate the absence of H motions for the whole temperature range investigated (up to 360 K), neither on macroscopic or local scale. Li6C60 good properties for H2-storage are confirmed in terms of absorption capacity (5 wt% H2), moreover we found that around 35% of lithium segregates in LiH form, leaving Li4C60H40 as the final hydrogenation product.

Mixed ionic-electronic conductors (MIEC) are of growing interest for fuel cells, batteries and sensors. Here, by exploiting the unique properties of Li 4 C 60 2D fulleride and poly(ethylene oxide) (PEO), we demonstrate the feasibility of a MIEC where the nature of transport can be tuned from ionic, to mixed, to almost entirely electronic, simply by changing the weight ratio of the two basic components. By coupling 7 Li MAS-NMR, electrochemical impedance spectroscopy and open circuit voltage (OCV) measurements of a Li/composite/LiFePO 4 cell we demonstrate that: i) a fraction of Li + ions is extracted by Li 4 C 60 and confined into PEO amorphous strands similarly to what happens in PEO-salt systems; ii) a transition between prevalently ionic and electronic conductivity takes place at 33 wt% Li 4 C 60 . This new class of MIEC is very promising for the design of both chemically and electrochemically stable semi-cells and interfaces which can be employed in batteries and supercapacitors.

The possibility of producing magnetic graphene nanostructures by functionalization with aromatic radicals has been investigated. Functionalization of graphene basal plane was performed with three types of anilines: 4-bromoaniline, 4-nitroaniline and 4-chloroaniline. The samples were examined by composition analysis with energy-dispersive X-ray spectroscopy and magnetic measurements by SQUID magnetometry and electron paramagnetic resonance. Initial graphene was produced by thermal exfoliation. Both pristine and functionalized samples demonstrate strong paramagnetic contribution at low temperatures, which originates from intrinsic defects. Attachment of an organic molecule with the formation of a covalent bond with carbon atom on the basal plane generates a delocalized spin in the graphene pi - electron system. Nitroaniline proved to be the most suitable and sufficiently reactive to attach to the basal plane carbon atoms in large amounts. Functionalization of graphene with nitroaniline resulted in appearance both ferromagnetic and antiferromagnetic features with a clear antiferromagnetic transition near 120 K. (C) 2015 Elsevier B.V. All rights reserved.