Estimation of the Redox Potential of Photoexcited Uranyl Ion

Spectrophotometric monitoring of the photolysis of 1–3 mM uranyl solutions containing 0.4 mM terbium(III) perchlorate or 0.1 mM silver(I) perchlorate and 1 mM unsaturated phosphotungstate K10P2W17O61 at pH 2 and below has not revealed the formation of terbium(IV) and silver(II). Because the TbIVL2/TbIIIL (L is unsaturated phosphotungstate anion) and Ag(II)/Ag(I) oxidation potentials are about 2 V, it follows from the experimental data that the *UO22+/UO2+ potential is lower than 2 V. The water oxidation to the ОН radical has not been confirmed. However, it is known from the published data that the photolysis yields Н2О2. Therefore, it can be stated that the potential of the excited uranyl ion is higher than the potential of the Н2О2, Н+/Н2О system, i.e., higher than Е0(H2O2, Н+/H2O (liq.) = 1.763 V.