A novel strategy to promote photo-oxidative and reductive abilities via the construction of a bipolar Bi2WO6/N-SrTiO3 material

Focusing on holistically promoting both photo-oxidative and reductive abilities, we constructed a novel Bi2WO6/N-SrTiO3 composite, which was expected to have excellent properties for the removal of complicated contaminants from solution environments under visible light irradiation. The prepared Bi2WO6/N-SrTiO3 was assembled from massive N-SrTiO3 nanoballs segmented via 2D interlaced nanosheets of Bi2WO6. N-SrTiO3 on its own has good reductive ability and can easily reduce Cr(VI) ions, while Bi2WO6 has been demonstrated to have good oxidative ability to oxidize tetracycline under visible light irradiation. Importantly, mixed contaminants (TC and Cr6+ ions) could be completely removed under visible light by the assembled Bi2WO6/N-SrTiO3 material. It is proposed that the holes lying at the valence band of N-SrTiO3 are the main active species for the oxidation of tetracycline, while the electrons located at the conduction band of Bi2WO6 are mainly responsible for the reduction of Cr(VI) ions. The matched band structures of Bi2WO6 and N-SrTiO3 were beneficial for inhibiting the recombination of electron-hole pairs and maintaining the redox capacity through a Z-type n-n heterojunction. Such a bipolar design of photo-oxidative and photo-reductive semiconductor nanomaterials is concluded to be highly effective in remediating complicated toxic residual constituents of both unfixed pharmaceuticals and heavy metals in aquatic environments.