Alkali metal intercalated graphite

Graphite intercalation compoimds of the heavier alkali metals, C24M (M == K, Rb, Cs) are able to absorb dihydrogen into the metal layers to form compoimds C24M(H2)2. The molecules are centred in the plane of 

---

Doping of alkali-metals into CNTs has been examined [11]. The X-ray powder diffraction (XRD) patterns of the K- or Rb-doped CNTs show that alkali-metals are intercalated between the CNT layers. The hexagonal unit cell is essentially the same as that of the stage-1 alkali-metal intercalated graphite ACg (A=K, Rb). For a sample doped with Rb, the observed lattice parameter of the perpendicular... 

In alkali metal intercalation compounds, the guest is ionised in the host, donating its outer s electron to the host s electronic energy levels. Thus there are two aspects to consider, the sites where the ion resides, and the energy levels or bands that the electron occupies. Guests such as water that remain neutral will only be discussed in the section on cointercalation. In some hosts, notably graphite, some guests accept electrons from the... 

Many samples are unstable in air. Examples of air-sensitive compounds are alkali metal intercalated C60, carbon nanotubes, and graphite, which are... 

This situation, clear in the case of more ionic structures, is less stringent in graphite intercalates where, presumably, there is electron transfer to (in the case of alkali-metal intercalates) or from (in the case of metal halide intercalates) the half-filled conduction bands of the graphite layers (produced by overlap of the 7t orbitals). Similarly, the periodicity requirements are less stringent for the alternating composite layers of layer silicates with complex intralayer and interlayer charge balance. 

Table 3 Graphite-alkali metal intercalation compounds...

The catalytic properties of the intercalates depends on the material asso-cated with the graphite. Alkali-metal intercalates favour base-catalysed reactions of hydrocarbons and these were reviewed by Pines and Schaap in 1960. In all cases, the catalytic activity of the graphite intercalate is different from that expected on the basis of the components alone. 

Herold has made a further substantial contribution to the chemistry of alkali-metal intercalates. Lithium intercalates of the first, second, third, and fourth stages have been prepared by (i) heating graphite and lithium at 400 °C in a copper or stainless steel tube, and (ii) compressing lithium powder with crushed graphite in an argon atmosphere. The unit cells of first-stage CeLi(5) and... 

Intercalation of Quaternary Compounds with Hydrogen and Two Alkali Metals into Graphite. 

Matsuzaki, S., M. Taniguchi, M Semo,Polymerization of benzene occluded in graphite-alkali metal intercalation compounds. Synthetic metals, 1986,16(3), 343-348. 

Graphite reacts with alkali metals, for example potassium, to form compounds which are non-stoichiometric but which all have limiting compositions (for example K C) in these, the alkaU metal atoms are intercalated between the layers of carbon atoms. In the preparation of fluorine by electrolysis of a molten fluoride with graphite electrodes the solid compound (CF) polycarbon fluoride is formed, with fluorine on each carbon atom, causing puckering of the rings. 

Cj(K prepared — the first alkali metal-graphite intercalation compound. 

Figure 8.16 Layer-plane sequence along the c-axis for graphite in various stage I -5 of alkali-metal graphite intercalation compounds. Comparison with Fig. 8.15 shows that the horizontal planes are being viewed diagonally across the figure. /,. is the interlayer repeat distance along the c-axis.

Whereas the electrochemical decomposition of propylene carbonate (PC) on graphite electrodes at potentials between 1 and 0.8 V vs. Li/Li was already reported in 1970 [140], it took about four years to find out that this reaction is accompanied by a partially reversible electrochemical intercalation of solvated lithium ions, Li (solv)y, into the graphite host [64], In general, the intercalation of Li (and other alkali-metal) ions from electrolytes with organic donor solvents into fairly crystalline graphitic carbons quite often yields solvated (ternary) lithiated graphites, Li r(solv)yC 1 (Fig. 8) [7,24,26,65,66,141-146],... 

First reported by Fredenhagen in 1926 F3, F4), the graphite-alkali-metal compounds possess a relative simplicity with respect to other intercalation compounds. To the physicist, their uncomplicated structure and well defined stoichiometry permit reasonable band-structure calculations to be made S2,12) to the chemist, their identity as solid, "infinite radical-anions frequently allows their useful chemical substitution for such homogeneous, molecular-basis reductants as alkali metal-amines and aromatic radical anions N2, B5). 

Intercalation of some guest species, such as alkali metals, can simply be performed via a chemical reaction of a gaseous reactant with graphite. 

---