An electrochemical cell (also known as a simple cell) is a device that generates electrical energy from chemical reactions. The earliest forms of electrochemical cells were invented by Luigi Galvani, Alessandro Volta and John Frederic Daniell, and hence the terms Galvanic cell, Voltaic cell and Daniell cell respectively.
The simplest electrochemical cell consists of two dissimilar metals (preferably far apart from each other on the metal reactivity series or electrochemical series) dipped in a conducting solution and connected by a wire. For example, the diagram above has Zn and Cu (electrodes) dipped in a H2SO4 solution (electrolyte), which consists of H+ and SO42– from sulphuric acid, and H+ and OH– from water.
Due to the different reactivity of the two metals making up the electrodes, and the ions in the electrolyte, chemical reactions occur. The electrode where oxidation reactions occur is called the anode, while the electrode where reduction reactions take place is known as the cathode.
