IrO_2-SiO_2 binary oxide films: Preparation, physiochemical characterization and their electrochemical properties

摘要

Mixed IrO_2-SiO_2 oxide films were prepared on titanium substrate by the thermo-decomposition of hexachloroiridate (H_2IrCl_6) 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 Ir(Cl_6)~(2-) complexes in the precursors decreases in the presence of TEOS, indicating the interaction between these two components. Thermal analysis shows the decomposition reaction of H_2IrCl_6 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 IrO_2, 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 IrO_2 electrodes is found to apparently improve with appropriate amount of SiO_2 incorporation, as tested under galvanostatic electrolysis.