Galvanic (Voltaic) and Electrolytic Cells

Galvanic cells, also known as voltaic cells, are devices in which spontaneous oxidation-reduction reactions occur to produce electrical energy.
These cells consist of two different metal electrodes in contact with an electrolyte, which is often an acid or ionic solution.
The electrode at which oxidation takes place is called the anode, and it is the site of electron loss. It is connected to the negative terminal of the voltaic cell.
The electrode at which reduction takes place is termed the cathode, and it is the site of electron gain. It is connected to the positive terminal of the cell.
The electron flow in an external circuit from anode to cathode constitutes the electric current generated by the cell.
A salt bridge or porous disc is often employed in a galvanic cell to maintain electrical neutrality within the internal circuit, preventing the cell from quickly reaching equilibrium.

In contrast to galvanic cells, electrolytic cells utilise electrical energy to drive a non-spontaneous redox reaction.
These cells consist of an electrolyte (a solution or a molten salt) and two electrodes which are connected to an external source of direct current.
The electrode connected to the positive terminal of the battery is the anode, and oxidation occurs here.
The electrode connected to the negative terminal of the battery is the cathode, where reduction takes place.
Common examples of use for electrolytic cells include electroplating (the process of depositing a layer of metal onto a surface) and electrorefining (the process of purifying a metal).
An important application is the electrolysis of water, in which water is split into its constituent elements (hydrogen and oxygen) by electric current.

While galvanic cells convert chemical energy into electrical energy, electrolytic cells do the opposite – they use electrical energy to cause a chemical change.
In galvanic cells, the reactions occur spontaneously, while in electrolytic cells, the reactions are non-spontaneous and require energy to proceed.
The anode is negatively charged in galvanic cells but positively charged in electrolytic cells, while the cathode is positively charged in galvanic cells and negatively charged in electrolytic cells. This reveals that the direction of electron flow is opposite in the two types of cells.
Both types of cells are integral to modern life and find extensive applications in many areas, including batteries, metal plating and purification, and the production of chemicals.