Why IrO2-Ta2O5 Titanium Anode is the Best Anode for Oxygen Evolution Reactions

Why IrO2-Ta2O5 Titanium Anode is the Best Anode for Oxygen Evolution Reactions (OER)?
  
Dimensionally stable anode (DSA) made of IrO2 and Ta2O5 or other mixed metal oxides  as a catalytically active layer coated on a titanium substrate have been successfully used for oxygen evolution reactions (OER). Thermally prepared IrO2-based coatings deposited on titanium metal supports are the most promising anodes for electrometallurgy. Cheaper cost materials such as lead alloys are environmentally undesired materials and have been dismissed, even though they have application in the OER such as electroplating, electrowinning, electro-floatation, electrosynthesis, cathodic protection, and wastewater treatment.  

It is well known that the traditional DSA has a very limited service life in the OER due to the serious corrosion of RuO2 which is an active component in the oxide mixture. Iridium dioxide (IrO2) has become an indispensable active component for high-performance anodes owing to its good activity of OER and better corrosion resistance compared to other precious metal oxides. The stability of IrO2 can be further improved by the addition of inert components such as TiO2, SnO2, Ta2O5, or Nb2O5 in order to form mixed metal oxides. It was reported that the mixed metal oxide anode with a composition of IrO2-Ta2O5 (Ir/Ta being in 7:3 in mole ratio concentration) is the best anode for OER.

Some researchers have reported on the degradation mechanism of an IrO2-Ta2O5 coated titanium oxide anode in different media. They observed that the process with a very little amount of initial oxide loading leads to significant changes of the electrochemical parameters, especially above the critical loading for OER. In the case of a thick layer (often used for commercial application), the degradation mechanism seems difficult to establish because of the long time scale during practical use in electrochemical processes, resulting from slow deterioration.