Question

Ferrocene is an organometallic complex that contains iron sandwiched between two five-membered cyclopentadiene rings (C5H5). Ferrocene methanol, a derivative, is another convenient reference redox couple used in electrochemistry. Sketch and interpret the cyclic voltammogram for the ferrocene methanol couple (Fc+/Fc) measured with respect to SHE; the standard redox potential is 0.64 V.

Short answer

The cyclic voltammogram for the ferrocene methanol couple${\text{(Fc}}^{\text{+}}\text{/Fc)}$was measured concerning SHE.

Step-by-step solution

Cyclic voltammetry

Cyclic voltammetry is a widely used technique for determining reaction mechanisms. This technique measures the current as a function of the electrode potential. The potential is changed cyclically. In cyclic voltammetry, the potential is first scanned towards more negative potential, and the current obtained is due to the reduction of the species.

The graph obtained from cyclic voltammetry is called a cyclic voltammogram.

A cyclic voltammogram for Fc+/Fc

he cyclic voltammogram for the ferrocene methanol couple ${\text{(Fc}}^{\text{+}}\text{/Fc)}$is shown below,

In the above voltammogram, the potential (E or V) is plotted on the x-axis. The current (I) is plotted on the y-axis.

explanation.

The curve shows that at point ‘A,’ no current is observed on increasing the potential in the forward direction. At point ‘A,’ some current is observed at a potential of around 0.78 V.

This current keeps on increasing till it reaches point ‘B.’ Here, the current is maximum at a potential of around 0.55 V. This current peak is due to the reduction of ferrocene methanol cation at the cathode.

After reaching the maximum, the current decreases as the potential is scanned in a more forward direction. After attaining saturation in the current, the potential is reversed and scanned in the backward direction.

At point ‘C,’ the current shows a decline at a potential of around 0.40 V. this reverse current keeps decreasing and peaks at a potential 0.74 V. This reverse current curve is obtained due to the re-oxidation of ferrocene methanol to ferrocene methanol cation.

After point ‘D,’ the current again starts increasing till it reaches point ‘E,’ at a potential of 0.77 V. Then show saturation on further scanning the potential in the backward direction.

Hence, the ferrocene methanol couple shows a reversed cyclic voltammogram, in which ferrocene methanol cation is reduced to ferrocene methanol, in the forward scan of potential and ferrocene methanol re-oxidized to ferrocene methanol cation, in the backward scan of potential