Passivation of defect states in anatase TiO2 hollow spheres with Mg doping: Realizing efficient photocatalytic overall water splitting

•Mg doped anatase TiO2 hollow spheres are synthesized successfully.•Mg dopants could suppress the intrinsic defect states in anatase TiO2 hollow spheres.•The Mg doped anatase TiO2 hollow spheres could direct split water as H2 and O2 under sunlight.•The Mg doped anatase TiO2 hollow spheres Exhibit 19.4% quantum efficiency in 350 nm light driven overall water splitting.

Since tremendous numbers of defect are distributed in anatase TiO2 materials, the photocatalytic overall water splitting (POWS) can not be occurred on anatase TiO2 nanostructures under normal sunlight. Meanwhile, it is still lacking of effective method to suppress the intrinsic defect states in anatase TiO2. In the present work, it has been found that the defect induced light absorption in anatase TiO2 hollow spheres could be reduced by Mg doping. In-depth detecting of the defect states evolution is investigated by the transient infrared absorption-excitation energy scanning spectroscopic measurement (TRIRA-EESS), indicating that the Mg doping could eliminate the intrinsic deep defect states and weaken the shallow defect states in TiO2. The efficient and stable sunlight-driven POWS is firstly realized on anatase TiO2 hollow spheres only after doping of Mg rather than Ni, Cr. The H2 and O2 evolution rates can be as high as 850 and 425 μmol g−1 h−1, respectively. First principle calculations reveal that the weakening of defect states in Mg doped anatase TiO2 is mainly caused by the unique electronic structure of Mg dopant.

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