IrOx(OH)y Nanoparticles for Visible Light Water Oxidation

very stable IrOx(OH)y colloidal solutions were synthesized by the hydrolysis of aqueous IrCl6 2 ‐ at various temperatures and times without any stabilizer or template. The synthesized IrOx(OH)y nanoparticles in the colloidal solution have about 2 nm of diameter regardless of the synthetic temperatures of 60, 90 and 200 oC. The isolated IrOx(OH)y nanoparticles by the acidification were all almost amorphous and the XPS data of the nanoparticles showed that the oxidation states of Ir in the nanoparticles were somehow different depending on the synthetic temperature. The nanoparticles were crystalized to the tetragonal structure of IrO2 when they were annealed above ca. 400 oC. The crystallization temperature increased interestingly as the synthetic temperature decreased. The catalytic activities of the synthesized colloidal solutions for photochemical oxygen evolution in Ru(bpy)3 2+ persulfate system were strongly dependent on the synthetic temperature and time. The highest catalytic‐ activity was obtained with the colloidal solution that was prepared at the lowest temperature and shortest time. In the optimized condition, the initial oxygen evolving rate was as high as 300 mol/h and the turnover number forμ Rucomplex reached 400, which is the best ever reported in this Ru(bpy) ‐