IrO2–SiO2 binary oxide films: Preparation, physiochemical characterization and their electrochemical properties

Mixed IrO2–SiO2 oxide films were prepared on titanium substrate by the thermo-decomposition of hexachloroiridate (H2IrCl6) and tetraethoxysilane (TEOS) mixed precursors in organic solvents. The solution chemistry and thermal decomposition kinetics of the mixed precursors were investigated by ultra violet/visible (UV/vis) spectroscopy and thermogravimetry (TGA) and differential thermal analysis (DTA), respectively. The physiochemical characterization of the resulting materials was conducted by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurements. It is shown from the UV/vis spectra that the electronic absorption intensity of IrCl62− complexes in the precursors decreases in the presence of TEOS, indicating the interaction between these two components. Thermal analysis shows the decomposition reaction of H2IrCl6 is inhibited by TEOS in the low temperature range, but the further oxidation reaction at high temperatures of formed intermediates is independent of the presence of silane component. Physical measurements show a restriction effect of silica on the crystallization and crystal growth processes of IrO2, leading to the formation of finer oxide particles and the porous morphology of the binary oxide films. The porous composite films exhibit high apparent electrocatalytic activity toward the oxygen evolution reaction. In addition, the long-term stability of Ti-supported IrO2 electrodes is found to apparently improve with appropriate amount of SiO2 incorporation, as tested under galvanostatic electrolysis.