A novel mechanism for deactivation of Pt/Nb anodes in chlorate oxidation process at different electrolyte temperatures

Platinum-plated niobium anodes are commonly used in the electrochemical oxidation of chlorate-containing solutions. In this research, a novel mechanism has been presented for the deactivation of Pt/Nb anodes in this process and the effect of the electrolyte temperature has been investigated in this mechanism. The samples were exposed to the accelerated life test (ALT) in the chlorate-containing electrolyte at temperatures of 35, 50, and 65 degrees C at a current density of 1200 mA cm(-2) for 3, 10, 40, and 70 h. The electrochemical behavior of the samples was studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods at each time interval. The morphology of the samples was also observed using scanning electron microscopy (SEM), before and after the ALT. The results showed that the highest corrosion resistance is obtained in the electrolyte with a temperature of 35 degrees C; the temperature at which the anode has the most increased electrocatalytic activity. However, at 65 degrees C, the anode is deactivated after 60 h of ALT, through the dissolution of platinum coating and subsequently the substrate passivation. Generally, passivation of niobium substrate is the progressive mechanism in the electrolyte at low temperatures, while, at high temperatures, deactivation starts from platinum coating dissolution and proceeds by substrate passivation.

Automated summary

A novel mechanism for the deactivation of Pt/Nb anodes in the electrochemical oxidation of chlorate-containing solutions has been presented in this research. The effect of electrolyte temperature on this mechanism has also been investigated. The samples were exposed to the accelerated life test at different temperatures, and their electrochemical behavior and morphology changes were studied. The results showed that the highest corrosion resistance and electrocatalytic activity of the anode were achieved at 35°C, while deactivation occurred at 65°C due to the dissolution of the platinum coating and subsequent substrate passivation.