Electrochemical Synthesis of Carbyne-Like Materials and Other Nanocarbons - Polyynes: Synthesis, Properties, and Applications - page 60

is doping. This process was explored in detail for cathodic carbonizations
(Eq. 4.11b), and it turned out that the n-doping (superstoichiometric
over-reduction) generally accompanies reaction 4.11b (see Sections 4.2.1

and 4.2.2 ) .

4.2.1 C ARBYNE -L IKE M ATERIALS M ADE BY ''W ET ''
E LECTROCHEMISTRY

4.2.1.1 Low-Molecular Weight Precursors

There is only one example of the polyyne formation by an anodic reaction.
Ohmura et al. [34] oxidized acetylene in dimethylformamide electrolyte
solution containing CuCl catalyst:

−2 n (e − +H + )

(4.14) ( C C )

C C H

n H

n

Cu

This reaction is an alternative of the Hay oxidative coupling, and it produces
a carbonaceous material with some proportion of IR active sp-bonded
carbon chains [34].
The cathodic production of carbyne was explored more extensively.
Nishihara et al. [35-38] have carbonized hexachlorobuta-1,3-diene on Pt or
glass-like carbon electrode in acetonitrile medium. Kijima et al. [39-41] have
found that the product contained also considerable proportion of sp-bonded
carbon atoms in addition to sp 2 carbon:

Cl Cl

e −

C C Cl

(C) n ( C C)

(4.15) C C

m

Cl C C

−Cl −

Cl Cl

The product of reaction 4.14 was, actually, over-reduced (n-doped) to a
formal composition:

1 : 5

ð C C Þ 10 ð C

j ¼Þ 6

(The n-doping of carbon during cathodic dehalogenation is a common side-

reaction (see Tables 4.1 , 4.2 and the text below). Kijima et al. [39,42,43]

reduced diiodoacetylene to carbon at a platinum electrode in dimethyl-
formamide media:

e − , Ni cat.

(4.16)

( C

n C C C)

I I

n

−I −