Cathode

In an electrochemical system, Electrochemical System the cathode is the electrode Electrode at which reduction Reduction  is occurring.

 

The terms cathode and anode Anode are most frequently used in two-electrode systems, Two-Electrode System such as fuel cells Fuel Cell and batteries. Battery They are less commonly used in typical three-electrode systems. Three-Electrode System

 

In the context of fuel cells and batteries, the cathode is also sometimes called the positive electrode, and may be denoted with a plus sign.  In the context of secondary (rechargeable) batteries where both the cathode and anode may alternatively undergo both oxidation Oxidation and reduction (depending on whether the battery is being charged or discharged), the cathode is defined as the electrode experiencing reduction during discharge.