What Cause the Destruction of MMO Anodes?

What Cause the Destruction of MMO Anodes?

The lifetime of MMO anodes is affected by the electrocatalytic layer, which is conductive. It is corrosion resistance against the electrolyte like fluorides, bromides, cyanates, and nitrites. The roughness of this active coating layer affects the current density and kinetics of electrochemical reactions that in turn determine the operating potential of the electrode surface and the stability of the coating.

Per MMO anode for oxygen evolution in acid solutions, the destruction of platinum, ruthenium oxide is caused by oxidization and dissolution of the active component. The destruction reason of the anode is the activity loss of the active layer, which causes an increase of anode potential. And the base material starts to dissolve, the active layer will drop and becomes passive or the active layer has been dissolved or worn out.  

There are three different mechanisms for the destruction of anode: dissolution of coating, corrosion of base material causing breaking away of coating, and oxidation of base material surface isolating with an active oxide layer. Coating breaking away, dissolution, and mechanical wear are direct causes of anode destruction. Organic substances, oxidation of ruthenium to soluble or evaporable compounds can result in coating dissolution. Short circuits, current reversals can lead to mechanical wear.

The factors that affect the anode lifetime are wear of the active layer, decline of catalytical qualities on the active layer.