Question

(a) Explain the difference between charging current and faradaic current.

(b) What is the purpose of waitingafter a voltage pulse before measuring current in sampled current voltammetry?

(c) Why is square wave voltammetry more sensitive than sampled

current voltammetry?

Short answer

a. The charging current and faradic current and its differences are explained

b. The advantage of gap of one second before measuring current in voltammetry.

c. The sensitivity of square wave voltammetry.

Step-by-step solution

Define the charging current and faradic current and its differences.

Faradic current:

- In working electrode, reduction or oxidation of analyte leads to faradic current.

- In Faradic current, due to higher reaction rate the analyte does not diffuse fast to electrode which leads to decay of faradic current.

Charging current:

- In charging current, cations move towards the electrode in solution and anions move away from the electrode in solution.

- The movement of electrons and ions are known as charging current.

- Charging current also known as condenser current or capacitor current.At any point

a) To explain: The charging current and faradic current and its differences.

Faradic current:

- In working electrode, reduction or oxidation of analyte leads to faradic current.

- In Faradic current, due to higher reaction rate the analyte does not diffuse fast to electrode which leads to decay of faradic current.

Charging current:

- In charging current, cations move towards the electrode in solution and anions move away from the electrode in solution.

- The movement of electrons and ions are known as charging current.

- Charging current also known as condenser current or capacitor current.

b) The advantage of gap of one second before measuring current in voltammetry.

Decay of charging current is faster than faradic current. The time interval of one second after potential leads to decay of charging current to zero but still there is considerably faradic current. Now the ratio of faradic current to charging current is greater than earlier. But if the time gap is more, both current signals become very less to measure.

c) The sensitivity of square wave voltammetry.

- Cathodic pulse is followed by anodic pulse and the difference between them is the signal in square wave voltammetry.

- Each cathodic pulse is oxidized by anodic pulse which reloads the surface of electrode by electro active species.

- Thus, at electrode surface the analyte concentration is more in square wave voltammetry.