Changes in the redox state of iridium oxide clusters and their relation to catalytic water oxidation: radiolytic and electrochemical studies

摘要: Radiolytically prepared iridium oxide (IrO{sub x}{center dot}nH{sub 2}O) clusters have been shown to catalyze the photochemical oxidation of water. These catalysts oxidized by radiolytic or electrochemical methods and changes in their optical absorptions redox states studied. The contain four five Ir atoms a mixture Ir{sup III} IV} states, formally described as 3.2+}. Time-resolved pulse-radiolytic studies revealed three processes subsecond time scale. first step produces short-lived intermediate ({lambda}{sub max} {approximately} 360 nm), possibly an OH adduct, that is transformed more stable species 340 580 nm). In third step, there rise 580-nm absorption. same were observed {gamma}-radiolysis spectroelectrochemical experiments. Cyclic voltammetric coulometric measurements suggest initial IrO{sub x} cluster two stages, from 3.2+} 3.8+} then 4+}. Further leads water O{sub 2}.