Trisbipyridyl Ruthenium Complex 유도체와 IrOx(OH)y촉매에 의한 물의 가시광 산화에 관한 연구

Abstract

The photochemical water oxidation system, which is composed of a photosensitizer Ru(bpy)32+, an oxidation catalyst IrO2 and a sacrificial electron acceptor, is one of well-studied half-cycle system for visible-light water splitting. Very stable IrO2 colloidal solutions were prepared without any stabilizer or template by simple basic hydrolysis of IrCl62- at three different temperatures of 60, 90, 200°C. The particle size of prepared IrO2 slightly increased as the synthetic temperature increased from 1.3 to 2.3 nm. The catalytic activities of the prepared IrO2 colloidal solutions were seriously different in the photochemical water oxidation system of Ru(bpy)32+/IrO2/S2O82- in NaHCO3 buffer. The colloid prepared at 60°C gave the highest activity among them while the prepared at 200°C gave the lowest one. More interestingly, the intermediate species Ir(OH)4 or Ir(OH)62-, that was not clearly identified, forming during the hydrolysis of IrCl62- to IrO2 gave even much better activity than any other prepared IrO2 in the photochemical water oxidation. The characteristics of IrOx(OH)ys that denote all Ir species isolated from prepared colloidal solutions were studied by XRD, XPS and thermal analysis. When the iridium hydroxide prepared at 60°C was used, the turnover number of the photosensitizer for the oxygen evolution reached 400 at the optimized concentration of the buffer and the electron acceptor. The several derivatives of Ru(bpy)32+, of which the ligands have functional group such as phosphonic acid and amino group were also tested with the iridium hydroxide in this photochemical water oxidation system.