Electrochemical Cell

Electrochemical cells are devices based on the principle that when a chemical oxidation-reduction reaction takes place, electrons are being transferred from one chemical species to another. In one type of electrochemical cell called a voltaic or galvanic cell, these electrons are deliberately taken outside the cell and made to flow through an electric circuit to operate some kind of electrical device. A flashlight battery is an example of a voltaic electrochemical cell.

In the other type of electrochemical cell, called an electrolytic cell, the reverse process is taking place: electrons in the form of an electric current are deliberately being pumped through the chemicals in the cell in order to force an oxidation-reduction reaction to take place. An example of an electrolytic cell is the setup that is used to decompose water into hydrogen and oxygen by electrolysis.

Thus, a voltaic cell produces electricity from a chemical reaction, while an electrolytic cell produces a chemical reaction from electricity. Voltaic and electrolytic cells are considered separately below, following a general discussion of the relationship between chemistry and electricity.