Precious metal compounds are often used for electrode coatings – especially for mixed metal oxide (MMO) electrodes. Electrodes are used in electrochemical processes – for example to produce chemicals via electrolysis or to prevent corrosion.

To produce these MMO electrodes – which are usually dimensionally stable anodes (DSA) – a substrate (e.g. titanium plate or mesh) is coated with a thin layer of precious metals (usually ruthenium and iridium) to provide enhanced properties to the anodes.

Key Benefits of MMO Electrodes

One of the key benefits of MMO electrodes is a lower overpotential compared to other electrodes (e.g. graphite) for electrochemical reactions – especially regarding evolution of hydrogen, oxygen or chlorine. A good example is the chlor-alkali process which uses electrolysis of a brine solution to produce chlorine and caustic soda. MMO electrodes are used as anode for chlorine evolution. Due to the lower overpotential at the MMO electrode, the required energy that needs to be applied for the electrochemical reaction is lower as well. As a result, precious metal coatings help to reduce energy costs for industrial processes and have a positive impact on the environment as less energy is needed to run the process.

On top, precious metals coatings are inert (non-reactive) and resistant against corrosive environments. An example is the chlor-alkali process which leads to an extended lifetime of the MMO electrodes compared to other electrodes. Especially the integration of iridium to the coating provides an enhanced stability and lifetime of the electrode. Thus, the process can run smoothly without disruptions (e.g. exchange of electrodes) for a long time.

Major Applications of MMO Electrodes and Other Precious Metal-Based Electrodes:

Chlor Alkali Electrodes
Water Treatment Electrodes
Ballast Water Treatment Electrodes
Cathodic Protection Electrodes (ICCP)
Electrodes for Copper foil production

Dihydrogen hexachloroiridate(IV)