The galvanic cell is an electrochemical cell that obtains an electrical current from chemical energy. This device consists of two different metals connected by means of a salt bridge or a porous disk located between each half cell. It receives its name in honor of Luigi Galvani.
The galvanic cell or voltaic pile (named after Alessandro Volta) is similar to the galvanic cell. The discoveries of Luigi Galvani and Alessandro Volta paved the way for electric batteries.
The voltaic cell, the first electrical cell that can provide an electrical potential in a circuit, obtains electrical energy from a chemical reaction.
How Does a Galvanic Cell Work?
A galvanic cell consists of two electrodes immersed in a tank containing an electrolyte. In general, the electrolyte consists of two electrolyte solutions that can exchange ions through a salt bridge or a porous septum.
The metal in a galvanic cell dissolves in the electrolyte at two different speeds. The metals become positive ions in dissolving and the electrons remain in the undissolved part.
As a result, the metal immersed in the electrolyte solution acquires a net negative charge as the electrolyte becomes positively charged. If there is an electrical connection, the electrons flow generating an electrical current.
What Is Anode and Cathode?
The anode is the most active metal, for example metallic zinc. The cathode is the most inactive metal, for example metallic copper.
At the same time, an equal electric current but with positive ions appears in the electrolyte. The anode ions are transferred to the electrolyte. Dissolved ions are also transferred to the cathode, which is the least active metal.
In this way the anode is consumed or corroded. When the anode material has been totally consumed the electric current stops.
Metal can be considered as the fuel that provides the energy to the device.
A similar process is to use electrolysis. The electric current in the electrolyte is equal to the current in the external circuit. That is to say, the complete electrical circuit is formed by both the external path of the electrons and the part of the electrolyte, which the positive ions travel through.
There is a flow of electrons from the anode, the oxidized ions, to the cathode, the reduced atoms (which take up electrons). This flow produced by an oxidation-reduction (redox) reaction is what constitutes the electrical current produced by the galvanic cell.
Galvanic Cell Types
Of types of galvanic cells we distinguish three:
A concentration cell is a primary cell (not rechargeable) that uses two galvanic half cells with the same chemical species but with different concentrations.
For example, such a cell can be made up of two copper electrodes immersed in two solutions containing copper sulfate (CuSO 4 ). The two solutions have different concentrations and the electrodes are separated by a porous septum or by a salt bridge.
The battery will discharge when the electrolyte concentration in the two half cells is the same.
An electrolytic cell consists of two electrodes immersed in a tank containing an electrolyte. Generally, the electrolyte consists of two electrolyte solutions that can exchange ions through a salt bridge or a porous septum.
An oxidation reaction occurs at the anode. On the other hand, a reduction reaction occurs at the cathode. The result is that a redox reaction occurs in the cell that takes advantage of external electrical energy to produce it.
The signs of the poles are reversed with respect to a galvanic cell. In an electrolytic cell the anode is the positive pole, while the cathode is the negative pole.
Electrochemical cells are made up of two half-elements, also called half cells.
These semi-elements are kept separated by a semi-permeable membrane or are contained in separate containers connected by a salt bridge. By connecting the half elements, a half element releases electrons through the oxidation reaction. In turn, these electrons are transferred to the other to trigger the reduction reaction.