Mechanism on durability enhancement of Ta/IrO2–Ta2O5 anodes

Using FIB-TEM and other characterization techniques, this study systematically investigated the structural evolution of the coating-substrate interface in Ta/IrO2-Ta2O5 electrodes during accelerated lifetime testing. Comparative analysis with the Ti/IrO2-Ta2O5 electrode revealed that the Ta/IrO2-Ta2O5 exhibited a service life 5 times longer. It originates from the distinct characteristics of the passive films formed after substrate passivation following coating detachment: Compared to titanium-based electrodes, tantalum-based electrodes generate significantly lower internal stress during electrolysis. This is primarily attributed to the slower growth rate of the tantalum oxide film and its lower dielectric constant, which consequently leads to reduced electrostrictive stress. Furthermore, the passive film formed on Ta/IrO2-Ta2O5 electrode demonstrates a higher critical stress for fracture. The synergistic effect of these two factors endows the tantalum oxide film with significantly superior resistance to mechanical breakdown compared to the titanium oxide film, thereby substantially reducing the rate of cell voltage increase in the Ta/IrO2-Ta2O5 electrode during electrolysis. These findings elucidate the crucial role of tantalum substrate in determining electrode durability.