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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.

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.

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.

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.

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, AsF5. 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 C60(AsF6)2, indicates that the highly reactive C602+ 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-Tc superconductivity and magnetism, expected in a hole-doped C60 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) su...

Avoided level crossing muon spin resonance effects are observed with polycrystalline norbornene in its plastic phase and analysed in terms of axial hyperfine anisotropy. The results agree with those of previous single crystal measurements. It is shown that the technique is sensitive to the detection of small anisotropies, and that it is ideally suited for the study of reorientational dynamics in polycrystalline or amorphous environments.