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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.

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.

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.

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 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.

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.

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.

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.

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 ...

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.

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.

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.

The low‐doped Li x C60 compounds (x≤6) were investigated using laboratory X‐ray and synchrotron radiation diffraction, 13C NMR and Raman spectroscopy. Li4C60 shows an unusual 2D polymerisation in which the C60 units are connected both by [2+2] cycloaddition and by single carbon–carbon bonds, a unique feature among the known polymerised fullerene compounds. This picture is fully supported also by static NMR and Raman measurements. The charge transfer to C60 in the polymeric phase was evaluated from the shift of the Ag(2) mode. The depolymerisation process was investigated as well; despite the presence of two different bonds, the polymer‐to‐monomer transition induced by thermal treatments is a single‐step phenomenon.

Magnetic properties of graphene nanostructures functionalized with aromatic radicals were investigated by electron spin resonance (ESR) and superconducting quantum interference device (SQUID) techniques. Three types of functionalized graphene samples were investigated (functionalization was performed by 4-bromoaniline, 4-nitroaniline, or 4-chloroaniline). According to SQUID measurements, in case of functionalization by nitroaniline, sharp change in temperature dependence of magnetic susceptibility was observed near 120 K. Such behavior was explained as antiferromagnetic ordering. The same but more extended effect was observed in ESR measurements below 160 K. In the ESR measurements, only one resonance line with g-factor equal to 2.003 was observed. Based on the temperature dependencies of spin concentration and resonance position and intensity, the effect was explained as antiferromagnetic ordering along the extended defects on the basal planes of the graphene.

NMR and high-resolution x-ray diffraction of several lithium-doped fullerides ${\mathrm{Li}}_{x}{\mathrm{C}}_{60}$ show that the stoichiometry $x=12$ represents a stable Li doping for a high symmetry ${\mathrm{C}}_{60}$-like phase, which might extend to much larger x. ${\mathrm{Li}}_{12}{\mathrm{C}}_{60}$ is fcc at high temperature, and it distorts to tetragonal upon cooling. We have evidence from ${}^{13}\mathrm{C}$ NMR that the ${\mathrm{C}}_{60}$ units are static in the tetragonal phase at least up to $T=373 \mathrm{K}.$ Rietvelt refinement of the fcc phase favors a hybrid cluster intercalated structure with shortening of selected Li-C distances.

The discovery in 1991 of high temperature superconductivity (SC) in A3C60 compounds, where A is an alkali ion, has been initially ascribed to a BCS mechanism, with a weak incidence of electron correlations. However various experimental evidences taken for compounds with distinct alkali content established the interplay of strong correlations and Jahn Teller distortions of the C60 ball. The importance of electronic correlations even in A3C60 has been highlighted by the recent discovery of two expanded fulleride Cs3C60 isomeric phases that are Mott insulators at ambient pressure. Both phases undergo a pressure induced first order Mott transition to SC with a (p, T) phase diagram displaying a dome shaped SC, a common situation encountered nowadays in correlated electron systems. NMR experiments allowed us to establish that the bipartite A15 phase displays N\'eel order at 47K, while magnetic freezing only occurs at lower temperature in the fcc phase. NMR data do permit us to conclude that well above the critical pressure, the singlet superconductivity found for light alkalis is recovered. However deviations from BCS expectations linked with electronic correlations are found near the Mott transition. So, although SC involves an electron-phonon mechanism, correlations have a significant incidence on the electronic properties, as had been anticipated from DMFT calculations., Comment: 9 pages, 6 figures, invited at M2SHTSC Conference Washington (2012)

${\mathrm{Li}}_{4}{\mathrm{C}}_{60}$, one of the best representatives of lithium intercalated fullerides, features an unusual type of two-dimensional polymerization. Extensive investigations, including laboratory x-ray and synchrotron radiation diffraction, $^{13}\mathrm{C}$ NMR, magic angle spinning, and Raman spectroscopy, show a monoclinic $I2∕m$ structure, characterized by chains of $[2+2]$-cycloaddicted fullerenes, sideways connected by single $\mathrm{C}--\mathrm{C}$ bonds. This leads to the formation of polymeric layers, whose insulating nature, deduced from the NMR and Raman spectra, denotes the complete localization of the electrons involved in the covalent bonds.

Inelastic neutron scattering experiments and ab-initio calculations have been used to investigate the vibrational modes, in a wide energy region between 0 and 200 meV, of hydrogenated graphene produced by chemical method. The results show the presence of atomic hydrogen chemisorbed at the graphene surface. At 10 K, the measured high energy density of states is remarkably similar to that of hydrogenated ball-milled graphite, in which hydrogen is most likely bonded to C atoms at the edges. In fact, in both hydrogenated graphene and hydrogenated ball-milled graphite, the high frequency modes (100-200 meV) show strong similarities with the C-H bending modes of the coronene molecule, in which hydrogen is bonded at the edges. This hypothesis has been supported by ab-initio calculations.

A representative rare earth doped fulleride, Eu 6 C 60 , has been studied using several spectroscopic and magnetometry techniques. We find that europium ions are present both in their magnetic bivalent state and nonmagnetic trivalent state. The Eu 2+ /Eu 3+ ratio seems to critically depend on sample preparation conditions. Muon relaxation rates show a large magnetic field distribution near the ordered phase, whereas 13 C NMR lineshapes at room temperature are consistent with dipolar field broadening (∼100 G) from neighbouring Eu 2+ magnetic moments.

Using muon-spin spectroscopy, we study the exceptional dynamical properties of rotating molecular struts engineered within a Zn-based metal–organic framework at cryogenic temperatures, where the internal motions of almost any other organic substance are quenched. Muon-spin spectroscopy is particularly suited for this aim, as the experimental evidence suggests several implantation sites for the muons, among which at least one directly onto the rotating moiety. The dynamics of the molecular rotors are characterized by the exceptionally low activation energy EA ∼ 30 cal mol–1. At the same time, we evidence a highly unusual temperature dependence of the dipolar interaction of muons with nuclear magnetic moments on the rotors, suggesting a complex influence of the rotations on the muon implantation and diffusion.

Modification of graphene has been undertaken in many research contexts in order to improve its properties. In this study, we examine Ni-nanoparticles decoration on graphene and its effect on sodium-ion battery performance. A definite trend is observed on the relationship between Ni-nanoparticles concentration (and hence size) and battery performance. Comparable capacities on the order of 420 mAhg −1 after 20 cycles at 100 mAg −1 is observed for the 3 relatively high Ni-concentration samples NiC 10 , NiC 40 , and NiC 80 . As the Ni:C ratio decreases, a decreasing trend is observed in the measured capacity, with NiC 200 , NiC 500 , and NiC 1000 producing capacities of 350 mAhg −1 , 380 mAhg −1 , and 300 mAhg −1 respectively after 20 cycles at the same rate. Ex situ energy dispersive X-ray spectroscopy, scanning, and transmission electron microscopy shows the morphology of the Ni-nanoparticles decorated graphene and assists in quantifing their sodium content, emphasizing the increasing sodium content with increasing Ni-nanoparticles concentration. This systematic study details how Ni-nanoparticles concentration on graphene surfaces can be manipulated to enhance electrochemical performance, and that higher concentrations up to NiC 10 favour better performance. For a compromise between performance and cost (Ni cost), the best composition is NiC 500 which favors best performance with the least Ni decoration.

We herein report on the ability of fullerene C60 and hydrogenated fullerene C60Hx (x∼39) to operate as negative electrodes in novel Na-ion batteries. Building upon the known solubility of C60 in common organic electrolytes used in batteries, we developed a suitably optimized solid-state Na-(polyethylene oxide) electrolyte for this application. Electrochemical and structural properties of the fullerene electrodes were investigated through cyclic voltammetry, fixed-current charge/discharge of the electrodes, impedance spectroscopy and powder X-ray diffraction. Both C60 and hydrogenated C60 have been electrochemically intercalated with sodium. Specific capacities after the first cycle are 250 mAh g−1 and 230 mAh g−1 for C60 and C60Hx respectively. However, C60 electrode shows a strong irreversible character after the first discharge, probably due to the formation of stable polymeric NaxC60 phases, where Na+ ions diffusion is hindered. On the contrary, C60Hx displays better reversibility, suggesting that hydrogenation of the buckyball could be effective to preserve sufficiently large interstitial pathways for Na+ diffusion upon intercalation.