The magnesium-air cell is a galvanic cell. It is composed of a half-cell with a magnesium electrode in a sodium-chloride-solution and a half-cell containing a membrane, which enables the use of atmospheric oxygen for the redox reaction. Since atmospheric oxygen can continuously be supplied, the magnesium-air cell is considered a fuel cell.
In this cell, magnesium is oxidized at the anode, the electrons migrate towards the cathode, drive an electrical load and finally react with oxygen. Overall magnesium hydroxide is formed under the release of electrical energy.