Arrangement and Dynamics of Diamine, Etheric, and Tetraalkylammonium Intercalates within Graphene or Graphite Oxide Galleries by ²H NMR

Abstract

Ternary graphite intercalation compounds (GICs), which consist of graphite, alkali metal (Li, Na, K) cations, and organic cointercalates such as ethylenediamine (en) or tetrahydrofuran (thf), are useful precursors to graphene-based materials and tetraalkylammonium GICs. This study investigates the gallery arrangements and intercalate dynamics of the deuterated en(d4), thf(d8), piperazine(d10), or 1,4-diazabicyclo[2.2.2]octane(dabco)(d12) in ternary GICs containing Na+ or K+ cations using XRD and solid state 23Na and 2H NMR line-shape analyses. An en(d4)-graphite oxide (GO) intercalation compound and the trihexylmethyl(d3)-ammonium (thma) GIC were also prepared and evaluated by XRD and NMR. The 2H NMR spectra exhibit a narrow peak ascribed to intercalates undergoing isotropic rotation and a broad powder pattern ascribed to intercalates in a rigid state or undergoing uniaxial rotations. The thma intercalates in thma(d3)-GIC and the en(d4) intercalates in en(d4)-GO are relatively mobile and can diffuse; this may arise because there are no alkali metal cations in the galleries. The molecular dynamics as well as the synthetic challenges presented by some GICs are explained in terms of different affinities of alkali metal cations to the cointercalates.