Electrochemical behavior and corrosion mechanism of Ti/IrO2-RuO2 anodes in sulphuric acid solution

Abstract

Ti/IrO2-RuO2 anodes calcined at different temperatures were prepared using thermal decomposition method. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy dispersive spectrosmeter (EDS) analysis were performed to explore the composition and microstructure of the IrO2-RuO2 binary oxide coatings. To explore the electrochemical behavior of the anodes in sulphuric acid solution, anodic polarization and cyclic voltammetry (CV) experiments were performed. The rate-determining step of the anodes for oxygen evolution reaction (OER) was determined by the calculated Tafel slope values. The corrosion mechanism of the anodes in sulphuric acid solution was investigated by EIS measurements, FESEM and EDS analysis before and after accelerated life test (ALT). It was found that the surface morphology (e.g., cracks, crystallinity degree and crystallite size) is influenced by the calcination temperature. The active surface area of the anodes decreases with increasing calcination temperature. The active surface area for the anodes calcined at 350–450°C is dominated by the “inner” active surface, while the anodes calcined at 500–600°C is dominated by the “outer” active surface. Increasing calcination temperature decreases the electrocatalytic activity, while increases the stability of the anode for OER. Considering the electrocatalytic activity and stability, the moderate temperature of 450–500°C is suitable for the preparation of the Ti/IrO2-RuO2 anode.