Hydrogen storage mechanism and lithium dynamics in Li12C60 investigated by μSR

Abstract

Please cite this article as: Gaboardi, M., Cavallari, C., Magnani, G., Pontiroli, D., Rols, S., Riccò, M., Hydrogen storage mechanism and lithium dynamics in Li 12 C 60 investigated by μSR, Carbon (2015), doi: http://dx.Abstract: 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.

Synthesis and characterization of mixed sodium and lithium fullerides for hydrogen storage

“…5(d)]. An average value of ν d =30.3(4) kHz and ν Q =38.1(6) kHz was obtained for x =1-3, very close to what found for Li 12 C 60 [35(2) kHz and 41(3) kHz respectively] 21 . Such values correspond to an average Mu-Li distance of about 1.7Å, close to a covalent bond 24 .…”

“…However, their identification is complicated by the very low fraction (below 10% of the missing asymmetry). For x =1-3 the ZF data were fitted according to the function previously reported for Li 12 C 60 21 , which consists of the sum of a slow-oscillating component and a Gaussian:…”

In Situ Neutron Powder Diffraction of Li6C60 for Hydrogen Storage

“…Na or Li), [3][4][5]13 it is possible to maintain the fcc structure by forming small alkali-metal clusters centered in the octahedral or tetrahedral voids of the structure, as happens for Na 6 C 60 , Na 10 C 60 , and Li 12 C 60 . [3][4][5]8 Li 6 C 60 is isostructural to C 60 , exhibiting an fcc structure at room temperature. Different from the other systems, it contains a minor fraction of polymeric Li 4 C 60 (below 5%), 14 irrespective of the synthesis procedure.…”

Investigation of Li and H dynamics in Li6C60 and Li6C60H

“…In particular, due to the known ability of solid C 60 to intercalate high amount of Li atoms per molecule avoiding segregation, [9] it would be interesting to investigate Li ion properties in Li x C 60 also at the higher stiochiometries of Li, where fullerene polymerisation is prevented and Li form clusters in the C 60 lattice interstices. [10,11] On the other hand, Li fullerides appeared suitable also for solid-state hydrogen storage applications.…”