Physico-chemical and electrochemical characterization of Ti/RhOx–IrO2 electrodes using sol–gel technology

Sol–gel technology has been successfully used for the incorporation of RhOx–IrO2 on a Ti substrate. RhOx–IrO2 was prepared from chloride precursors of Rh and Ir, for surface studies. These metal oxides were then immobilised on solid Ti substrates via dip withdrawal coating methods to form thin films. The Ti/RhOx–IrO2 thin films were extensively characterized in terms of surface characterization and chemical composition and used in the oxidation of phenol. Thermo-gravimetric analysis (TGA) determined the calcination temperature at 700 °C where no further structural changes occurred due to mass loss. The rhodium oxide showed two-phase formations, RhO2 and Rh2O3, which were attributed to high calcinated temperatures compare to one phase IrO2 which was stable at lower temperatures. The scanning electron microscopy (SEM) showed that the morphology of the film was found to be rough with a grain-like appearance in the 150-nm range. The phase composition of these metal oxides was determined by X-ray diffraction (XRD) technique and found to have crystalline structures. The results obtained from Rutherford backscattering spectrometry (RBS) revealed information regarding the chemical composition of the metal oxides and confirmed the diffusion of Rh and Ir into the Ti substrate. Electrochemical characterization of the Ti/RhOx–IrO2 electrode, via cyclic voltammetry (CV), showed distinctive redox peaks: anodic and cathodic peaks associated with the oxidation and reduction of the ferricyanide–ferrocyanide couple was seen at 250 and 100 mV respectively; the peak observed at 1000 mV was associated with oxygen evolution and a broad reductive wave at −600 mV can be ascribed to the Ti/RuOx–IrO2 reduction, which proved that the Ti/RhOx–IrO2 electrode were electroactive and exhibit fast electrochemistry.