Enhanced photocatalytic overall water splitting by tuning the relative concentration ratio of bulk defects to surface defects in SrTiO3

Abstract

Defects such as oxygen vacancies play an important role in the photoactivation processes. However, the roles of surface and bulk defects in photocatalytic water splitting are still ambiguous. This paper would report a new method to introduce surface and bulk defects in SrTiO3 nanocrystals. Melamine was used as a reducing agent which would be carbonized under the N2 atmosphere. During thermal decomposition of melamine, reductive NH3 and C would generate in succession to reduce the SrTiO3 nanocrystals. The relative concentration ratio of bulk defects to surface defects in SrTiO3 nanocrystals would be tuned from 0.78 to 2.55 after reduction treatment. Furthermore, the band structures of surface and bulk defects in SrTiO3 were studied by DFT. The surface oxygen defects would make the band structure shift to a high energy level, while the bulk oxygen defects of SrTiO3 would restore the energy levels of the band structure. Thus, photocatalytic overall water splitting activity would improve significantly by rational relative concentration ratio of bulk defects to surface defects in SrTiO3.