Mixed metal oxide (MMO) electrodes are devices with useful properties for chemical electrolysis. The term refers to electrodes in which the surface contains two kinds of metal oxides. One kind, usually RuO2, IrO2, or PtO0.12, conducts electricity and catalyzes the desired reaction such as production of chlorine gas. The other metal oxide is typically titanium dioxide which does not conduct or catalyze the reaction, but is cheaper and prevents corrosion of the interior. The interior of the electrode is typically made of titanium. The amount of precious metal (that is, other than the titanium) can be around 10 to 12 grams per square metre.[1]
Applications include electrolytic cells for producing free chlorine from saltwater in swimming pools, and anodes for cathodic protection of buried or submerged structures.