Browsing by Author "Pontiroli, D"

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    Graphene and selected derivatives as negative electrodes in sodium- and lithium-ion batteries
    (John Wiley & Sons, Inc, 2015-05-02) Pramudita, JC; Pontiroli, D; Magnani, G; Gaboardi, M; Riccò, M; Milanese, C; Brand, HEA; Sharma, N
    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. © 2015 Wiley-VCH Verlag GmbH & Co.
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    Muons probe strong hydrogen interactions with defective graphene
    (American Chemical Society, 2011-11-01) Riccò, M; Pontiroli, D; Mazzani, M; Choucair, M; Stride, JA; Yazyev, OV
    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. © 2011, American Chemical Society