Ternary graphite intercalation compounds of type M(NH3)xCy with M = Be, Mg, Al, Sc, Y, La. electrochemical synthesis, stability and NMR studies

Abstract

Abstract Ternary graphite intercalation compounds with the formula M(NH 3 ) x C y , where M represents one of the elements Be, Mg, Al, Sc, Y, La were synthesized by reaction of graphite with a liquid ammonia solution of the metal. These solutions were obtained by anodic dissolution of the metals. The layer sequence in each compound was determined using (00 l ) X-ray diffraction. Solid state 1 H NMR studies were performed on the Mg, Al, Y and La compounds to elucidate the structure and motions of the metal-ammonia units. The room temperature NMR spectrum of magnesium-ammonia graphite consists of a central line and two satellites which is in agreement with the following structural model: (i) NH 3 is coordinated to Mg 2+ ; (ii) the C 3 molecular axes of the coordinated NH 3 are perpendicular to the c -axis of the graphite lattice; (iii) the protons of NH 3 rotate rapidly about the C 3 -axis being parallel to the graphene sheets; (iv) the Mg-NH 3 complex rotates around an axis parallel to the graphite c -axis. The decomposition of Mg-NH 3 graphite was followed by NMR measurements. The NMR spectra of M-NH 3 graphite compounds with M = Al , Y or La show one central line which is split. The low frequency line is due to metal amide formed by electron transfer to NH 3 molecules. The other line indicates the presence of noncoordinated NH 3 molecules in the graphite galleries.