Removal of hexavalent chromium from water by Z-scheme photocatalysis using TiO2(rutile)nanorods loaded with Au core-Cu20 shell particles

All-solid-state Z-scheme photocatalysts,containing Cu2O,TiO2(rutile),and Au as the elec-tron mediator,were prepared and applied to the reduction of Cr(Ⅵ)in aqueous solutions.The Cu2O-Au-TiO2 composites were prepared by loading Au core-Cu2O shell hemisphere particles on TiO2(rutile)nanorods using a two-step photocatalytic deposition process.Un-der ultraviolet-visible(UV-vis)light illumination,the Cu2O-Au-TiO2 composites exhibited higher photocatalytic Cr(Ⅵ)reduction activities than those exhibited by single TiO2(rutile)and Cu2O.In this reaction,a precipitate containing Cr,which was considered to be Cr(OH)3,was deposited site-selectively on the Au core-Cu2O shell particles of the composites,indi-cating that the reduction site of the composite was Cu2O,and the reaction proceeded accord-ing to the Z-scheme.The Cu2O-Au-TiO2 composites also exhibited photocatalytic activity under visible light illumination.The oxidation state of Cu in the Cu2O-Au-TiO2 composite gradually changed from Cu(Ⅰ)to Cu(Ⅱ)during the photocatalytic Cr(Ⅵ)reduction.However the composite maintained its high photocatalytic performance even after oxidation.The role of Au in the Cu2O-Au-TiO2 composite was examined by comparing the properties of the Cu2O-Au-TiO2 composite with those of the Cu2O-TiO2 composite prepared via direct Cu2O deposition on TiO2.