ARTICLEa basic function to increase the strength of the interaction photocatalyst-pollutant. On the basis of the discussed theoretical considerations, the origin of the high acidity of Bi 2 WO 6 was attributed to the presence of specific sites located onto the lateral faces of platelets. Future work has to focus to control the morphology of platelets to increase the proportion of lateral faces.' ASSOCIATED CONTENT b S Supporting Information. For more details about MU-SIC calculations, the affinity constants and charge of surface groups for planes (100), ( 001), (101), and (10-1) are exposed here. This material is available free of charge via the Internet at http://pubs.acs.org.

Bismuth tungstate has attractive photocatalytic properties under visible light. A better understanding of the origin of that good activity should allow its control and its optimization. An improved photocatalytic activity to different pollutants was obtained using bismuth-based oxide obtained by microwave-assisted synthesis combined with the addition of sodium dodecylsulfate as a size tailoring agent. It is shown using electron paramagnetic resonance that bismuth tungstate is able to generate hydroxyl radicals in aqueous aerated solution, but no superoxide radical anions are formed. The catalytic efficiency relative to TiO 2 could be associated to differences in the number of excitons generated, to their lifetimes as holes and electrons in the semiconductor, and to valence and conduction band positions.

Bismuth vanadate has attractive photocatalytic properties under visible light. The influence of structure and morphology of BiVO 4 nanomaterials on its photocatalytic properties in the UV and the visible domain was investigated. The selection of different sets of synthetic parameters in aqueous solutionpH or the use of organic additivesallowed the formation of tetragonal zircon, tetragonal scheelite, and monoclinic scheelite structure and different morphologies of that last phase. First, the tetragonal zircon was found to be the only inactive structure. Then, the best material for photocatalytic degradation of rhodamine B in solution and stearic acid deposited directly on the photocatalyst is the core−shell tetragonal zircon−monoclinic scheelite system prepared in the presence of sodium dodecyl sulfate. The enhanced properties are explained by the presence of strong surface acidic sites corresponding to the presence of surface sulfate residues rather than to the specific morphology of the material. Additionally, an EPR study on the ability of BiVO 4 to generate active surface radical showed that hydroxyl radicals are not generated and that superoxide ion concentration under irradiation is close to the detection threshold. Depending on the selected irradiation wavelength, bismuth vanadate may present a better photocatalytic activity than titanium oxide. It is shown to be equivalent to bismuth tungstate under blue light.

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