CYCLIC VOLTAMMETRY

VOLTAMMETRY :- 

It is a current versus potential technique where the potential of the W.E. is varied between two set values and the resulting current flow is recorded as a function of applied potential. The recording is termed as VOLTAMMOGRAM.

Differences from Other Electrochemical Methods ? 

1. Potentiometry: measure potential of sample or system at or near zero current. voltammetry – measure current as a change in potential
2. Coulometry: use up all of analyte in process of measurement at fixed current or potential.voltammetry – use only small amount of analyte while varying potential. 

 

Voltage-Time Signals in Voltammetry :- 

1. A variable potential excitationexcitation signal is applied toto the working electrode
2. Different voltammetric techniques use Different Waveforms 
3. Many other waveforms are available (even FT techniques are in use)

Effect of Scan Rate :- 

In a slow voltage scan rate the diffusion layer will grow much farther from the electrode in comparison to a Fast scan.

Flux to the electrode is smaller at slow scan rates vs. faster rates.

The current is proportional to flux towards the electrode.

CV of Irreversible systems :- 

1. In case of irreversible electrode reaction, the rate of electron transfer is insufficient to maintain the Nernstian equilibrium.
2. Shape of CV in that case is different from that for reversible system
3. At low sweep rate system behaves reversibly because rate of ET is higher than MT and reversible CV is obtained.
4. As sweep rate increased rate of MT  ET and peakseparation becomes noticable.