Photodeposition of uranium oxides onto TiO2 from aqueous uranyl solutions

The photoreduction of uranyl solutions on illuminated TiO2 suspensions and electrodes has been investigated. The photoreduction leads to the formation, on TiO2, of an uranium oxide having a stoichiometry close to U3O8. Adsorption of uranyl species in the dark was examined. It was found that the degree of adsorption depended on pH and on the formation of uranyl complexes in solution. Initial rates of photoreduction are given for the cases when propan-2-ol, sodium acetate or sodium formate are used as scavengers of the photogenerated holes. With the use of microelectrode theory, it was possible to calculate the photoreduction rates from photoelectrochemical data obtained with TiO2 electrodes. The reduction rates calculated in this way were from 3.5 to 4 times lower with the electrode than with the suspension, in agreement with the larger area available in the latter case.