Photo-assisted activation of H2O2 over Nb2O5 - The role of active oxygen species on niobia surface in photocatalytic discoloration of Rhodamine B

The influence of hydrogen peroxide on the efficiency of Rhodamine B (RhB) photomddation over Nb2O5, which exhibits unique ability to generate strongly oxidative species both upon irradiation with UV light and upon treatment with hydrogen peroxide, was investigated. According to the results, niobia displays low activity in RhB discoloration by photocatalytic and Fenton-like processes, but the efficiency of the reaction is greatly improved when both advanced oxidation processes are combined. The tests with the use of various reactive oxygen species scavengers revealed that the crucial species responsible for the improved efficiency of RhB discoloration in the hybrid process were superoxide radical anions (O-2(center dot-)) and singlet oxygen (O-1(2)). It was documented that the former species exhibited low activity in RhB discoloration, but they were the precursors of the latter species, which played the key role in the dye discoloration.