Samarium and Nitrogen Co-Doped Bi2WO6 Photocatalysts: Synergistic Effect of Sm3+/Sm2+ Redox Centers and N-Doped Level for Enhancing Visible-Light Photocatalytic Activity

Samarium and nitrogen co-doped Bi2WO6 nanosheets were successfully synthesized by using a hydrothermal method. The crystal structures, morphology, elemental compositions, and optical properties of the prepared samples were investigated. The incorporation of samarium and nitrogen ions into Bi2WO6 was proved by X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. UV/Vis diffuse reflectance spectroscopy indicated that the samarium and nitrogen co-doped Bi2WO6 possessed strong visible-light absorption. Remarkably, the samarium and nitrogen co-doped Bi2WO6 exhibited higher photocatalytic activity than single-doped and pure Bi2WO6 under visible-light irradiation. Radical trapping experiments indicated that holes (h(+)) and superoxide radicals (O-center dot(2)-) were the main active species. The results of photoluminescence spectroscopy and photocurrent measurements demonstrated that the recombination rate of the photogenerated electrons and holes pairs was greatly depressed. The enhanced activity was attributed to the synergistic effect of the in-built Sm3+/Sm2+ redox pair centers and the N-doped level. The mechanism of the excellent photocatalytic activity of Sm-N-Bi2WO6 is also discussed.