Surface determination and electrochemical behavior of IrO2-RuO2-SiO2 ternary oxide coatings in oxygen evolution reaction application

Ti/IrO2-RuO2-SiO2 anodes were prepared using a sol-gel route, followed by thermal decomposition. X-ray diffraction (XRD), field emission-scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM) analysis and voltammetric charges calculation were performed to explore the surface properties of the coating. The electrochemical behavior of the anodes were investigated by cyclic voltammetry (CV), linear sweep voltammogram (LSV), Tafel lines and electrochemical impedance spectroscopy (EIS) measurements. The long-term stability of the anodes were evaluated using accelerated life test (ALT). It indicated that the compositions of the coating are rutile-type IrO2, RuO2 and IrO2-RuO2 solid solution. SiO2 existed in an amorphous state in the ternary oxide coating. The IrO2-RuO2-SiO2 ternary oxide coatings with compact structure and a large amount of acerose crystals of the IrO2-RuO2 solid solution dispersing were detected by FESEM analysis. The generation of the acerose crystals significantly increased the surface area that increased the electrocatalytic activity of the coating. The active surface area of the coating was “outer” active surface dominated. The rate-determining step of the coating for oxygen evolution reaction in sulphuric acid solution can be regarded as the rearrangement of the intermediate. An increase of Ru content can improve the electrocatalytic activity, however, decrease the service lifetime of the anodes. The anode with a molar ratio of Ir:Ru:Si = 9:21:70 is most suitable for OER due to its high electrocatalytic activity, a certain lifetime and low cost.