What Factors Affect the IrO2-Ta2O5/Titanium Anode Electrocatalytic Efficiency?

What Factors Affect the IrO2-Ta2O5/Titanium Anode Electrocatalytic Efficiency?

It is clear that the electrocatalytic properties of the anode depend significantly on the microstructure of the catalyst, such as surface morphology and phase composition. A larger electrochemically active surface area (ECSA) will also provide more sites for oxygen evolution and thus lead to a lower operating voltage. It is researched that the anodes with 50–70 mol% IrO2 have not only the largest ECSA but also the highest electrochemical activity. Also, the 70 mol% IrO2 with 30 mol% Ta2O5 was the best with respect to anode stability.

Normally the prepared IrO2-Ta2O5 has a heterogeneous “mud-crack” surface morphology, which is surrounded by a flat area with dispersed IrO2 and IrO2 aggregates. The boundaries of IrO2 crystallites are modified by amorphous Ta2O5. The fine IrO2 particles (around 30–100 nm) on the flat area in the coating surface dominate as a catalyst for OER while the others such as the larger IrO2 aggregates and the IrO2 particles embedded in the cracks show little influence. Even smaller IrO2 particles of 10 nm or less, which are uniformly dispersed on the “flat area” of the coating, have very good catalytic activity for OER. 

Lifetime is another issue for anodes in industrial applications. The deactivation mechanisms of IrO2-Ta2O5/Ti anode can generally be attributed to the consumption of the active component in the coating layer and/or the passivation of the substrate beneath the coating layer, which mainly depends on the coating microstructure. Furthermore, it has been proposed that the deactivation process of the anode is as follows: (1) the dissolution of coated oxides as the dominating stage, (2) dissolution and anodic oxidation of the Ti substrate, which then leads to coating detachment and failure of the anode.The lifetime of an oxide anode under OER will always be limited. Consequently, enhancing the stability of the coating layer to impede the dissolution process is as important as improving the electrocatalytic activity toward OER through modification of the coating microstructure.