The Superiority of MMO Coated Titanium Anode over Graphite Anodes in Chlor-alkali Industry

The Superiority of MMO Coated Titanium Anode over Graphite Anodes in Chlor-alkali Industry

MMO coated titanium anodes are composed of conducting titanium substrate coated with an activated oxide layer which can catalyze a particular electrochemical reaction. The catalysts are mainly made up of platinum group metal oxides (such as RuO2 and IrO2) mixed with other nonprecious metal components, such as additives likeTiO2 and Ta5O5.  

MMO coated titanium anodes have been used in the electrochemical industry like chlorine and oxygen evolution reactions. For Chlor-alkali production, coated titanium electrodes have demonstrated lifetimes of over 20 years, while graphite anodes of improved quality have a life span of at most 2 years. MMO coated titanium anodes allow for lower cell voltages, longer lifetimes, and improved product quality. This is largely due to the dimensional tolerance of the titanium substrate and the stability of the coating in the harsh chlorine-alkali electrolytic environment.

The graphite electrode has the same overpotential for anode chlorine evolution as MMO coated titanium anodes. Graphite was consumed during the anodic reactions by the O2 present in Cl2. The consumption of the graphite widened the electrode gap thus increasing the ohmic drop between the electrodes. Consequently,  energy consumption and the associated costs for the graphite anodes were high due to their consumption and instability.

MMO coated titanium anodes may operate under different conditions, varying from mild conditions (acid-water electrolysis, metal electrowinning, cathodic protection, electro-organic synthesis, etc.) to very severe conditions, such as fast electroplating processes operating at high current densities.