# Electrodes

Device that moves electrons into or out of a solution by conduction.

The positive electrode is called the anode and the negative electrode is called the cathode.

Electrodes are found in: Batteries, Electrolysis, Vacuum Tubes.

### Active Material

The material in the electrodes that takes part in the electrochemical reactions which store-deliver the electrical energy.

### Activation Overpotential

The overpotential which results from the restrictions imposed by the kinetics of charge transfer at an electrode.

### Geometric Electrode Area

The surface area of an electrode calculated from its geometrical dimensions.

### Irreversible Electrode

An electrode with an irreversible electrode reaction.

### Standard Electrode Potential

The reversible potential of an electrode with all the active materials in their standard states.

### True Electrode Area

The surface area of an electrode taking into consideration the surface roughness. For a perfectly smooth electrode, it is equal to the geometric electrode area, but it is larger than that for most electrodes. The ratio of the two defines the roughness factor.

**See also: **Anode, Calomel Electrode, Cathode, Charge Density, Charge Transfer Resistance, Combination Electrode, Counter Electrode, Electrolysis, Negative Electrode, Reference Electrode, Standard Electrode Potential, Standard Rate Constant of Electrode Reaction, Working Electrode.