An electrochemical cell is a device that can either generate electrical energy from chemical reactions or use electrical energy to cause chemical reactions. Electrochemical cells can be divided into two types: voltaic or galvanic cells, which generate an electric current, and electrolytic cells, which generate chemical reactions via electrolysis. Both types of cells can be thought of as having two half-cells, consisting of separate oxidation and reduction reactions. When one or more electrochemical cells are connected in parallel or series, they make a battery. Electrochemical cells generally consist of a cathode and an anode, which are made from various conducting metals that are conducting or semiconducting. The cathode is the electrode at which electrons are accepted or consumed, while the anode is the electrode at which the electrons are released or liberated. The key features of the cathode and the anode are tabulated below:
| Cathode | Anode |
|---|---|
| Denoted by a positive sign since electrons are consumed here | Denoted by a negative sign since electrons are liberated here |
| A reduction reaction occurs in the cathode of an electrochemical cell | An oxidation reaction occurs here |
| Electrons move into the cathode | Electrons move out of the anode |
In a full electrochemical cell, species from one half-cell lose electrons (oxidation) to their electrode while species from the other half-cell gain electrons (reduction) from their electrode. The cell potential depends on the concentration and type of the reactants, and as the cell is discharged, the concentration of the reactants decreases and the cell potential also decreases.
