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The galvanic cell owes its name to its inventor, the Italian physicist Luigi Galvani. In 1780, Galvani showed that when two dissimilar metals are connected to each other at one end, while the other ends are connected by the legs of a frog, the frog’s legs contract, indicating the existence of a flow of electricity. At first he called his apparatus an “animal circuit.” With the idea of correcting Galvani’s idea that the presence of living matter was necessary for the circuit to function, Alessandro Volta developed the same cell without any biological component. It was an unprecedented achievement up to that point, which is why the terms “galvanic” and “voltaic” are used interchangeably today .
A galvanic or voltaic cell is an electrochemical space that converts chemical energy into electrical energy . This conversion is achieved by taking advantage of the energy produced by the redox reactions that take place inside the cell.
redox reactions
A galvanic cell is an electrochemical cell that is allowed to run spontaneously. In a galvanic cell, the two electrodes must be externally linked to complete the electrical circuit with an external charge and thus avoid short circuiting. In this way, the current can be harnessed and used to supply electrical energy in batteries or fuel cells. Thus, the energetically favorable conversion of chemical substances gives rise to electrical energy through redox reactions.
The chemical term “redox” is short for reduction-oxidation , and represents two chemical reactions that occur simultaneously to exchange electrons. From a chemical point of view, the reactant that loses its electrons is oxidized, while the reactant that gains those same electrons is reduced.
Galvanic cell configuration
There are two main configurations for a galvanic cell. In both cases, the oxidation and reduction half-reactions are separate and connected via a wire, forcing electrons to flow through it. In one of the configurations, the half-reactions are connected by a porous disk, in the other, the half-reactions are connected by a salt bridge.
The purpose of both the porous disk and the salt bridge is to allow ions to flow between half-reactions without much mixing of the solutions, thus allowing the solutions to be kept charge neutral.
The transfer of electrons from the oxidation half cell to the reduction half cell leads to an accumulation of positive charge in the first and negative charge in the second. On the other hand, if there were no way for ions to flow between the solution, this buildup of charge would oppose and halve the flow of electrons between the anode and cathode .
Sources
- Galvanic cells. (2019). Libretexts.
- Image: Wikimedia commons.
- Electrochemical portal: Voltaic cells. University of Wisconsin
