Electrochemical preparation of hydrogen free carbyne-like materials Original Research Article

Natural carbyne-like structures (linear end-capped polyynes) occur in space and in certain biological objects. The synthetically demonstrated species contain up to 30–300 carbon atoms; even longer chains should be accessible by electrochemical defluorination of PTFE. Cathodic carbonization of perfluorinated hydrocarbons with alkali metal (MLi, Na, K) amalgams gives a solid composite of n-doped elemental carbon and the equivalent amount of MF. Raman spectra of CMF show an unusually strong band at 2000–2100 cm−1 which was assigned to the CC stretching mode of polyyne (“carbyne”). The optimum synthesis of carbyne-like materials represents the electrochemical reduction of stretch-oriented PTFE films with K or Na amalgams. Electrochemical polyyne is partly stabilized against interchain crosslinking towards graphene by interspersed MF. A polyyne-to-graphene conversion occurs by aging in a long time scale (years). It can be monitored by well-defined changes of electronic and optical properties of CMF. The electrochemical amalgam carbonization of highly-oriented (frictiondeposited) PTFE films is superior to the carbonization with alkali metal vapor. The product showed larger conjugation length than that from ordinary unoriented precursor.