Generation of OH radicals and oxidation mechanism in photocatalysis of WO3 and BiVO4 powders

• OH radicals were detected in WO3 and BiVO4 aqueous suspension photocatalytic systems.
• Cu2+ deposition increased the OH yield for BiVO4 but not for WO3 on 470 nm irradiation.
• Effects of Fe3+ and Ag+ in solution on the OH formation were different for WO3 and BiVO4.
• OH formation process for WO3 is different from that for BiVO4.
• Formation process of O2 may be different from that of OH for BiVO4.

WO3 and BiVO4 attract widely research interests for their ability to oxidize water and generate O2 by visible light. In order to clarify the photocatalytic oxidation mechanism, OH radical (OH) generation in the photocatalytic reactions was investigated by a fluorescence probe method under 470 nm LED irradiation using coumarin and coumarin-3-carboxylic acid as fluorescence probes. The generation yield of OH for WO3 was found to be comparable to that for anatase TiO2, while that for BiVO4 was much smaller. On Cu2+ deposition, the OH generation rate was increased for BiVO4, but not for WO3. On the addition of H2O2, the yield of OH was increased for all the photocatalysts used. On the basis of the results the difference in the oxidation mechanism in WO3 and BiVO4 photocatalysis was discussed.

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