Graphite Intercalation Compound - Potassium Graphite

Potassium Graphite

The KC₈ form of potassium graphite is one of the strongest reducing agents known. It is prepared under inert atmosphere by melting potassium over graphite powder. The potassium is absorbed into the graphite and its color changes from black to bronze. The resulting solid is also quite pyrophoric, and explodes on contact with water. Structurally, composition can be explained by assuming that the potassium to potassium distance is twice the distance between hexagons in the carbon framework. The bond between graphite and potassium atoms is ionic and the compound is more electrically conductive than α-graphite. KC₈ is a superconductor with a very low critical temperature T_c = 0.14 K. It has also been used as a catalyst in polymerizations and as a coupling reagent for aryl halides to biphenyls. In one study, freshly prepared KC₈ was treated with 1-iodododecane delivering a modification (micrometre scale carbon platelets with long alkyl chains sticking out providing solubility) that is soluble in chloroform. Another potassium graphite compound, KC₂₄, has been used as a neutron monochromator. A new essential application for potassium graphite was introduced by the invention of the potassium-ion battery. Like the lithium-ion battery, the potassium-ion battery should use a carbon-based anode instead of a metallic anode. In this circumstance, the stable structure of potassium graphite is an important advantage.

Heating KC₈ leads to the formation of a series of decomposition products as the K atoms are eliminated, ultimately giving the blue compound KC₆₀:

KC₈ → KC₂₄ → KC₃₆ → KC₄₈ → KC₆₀