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

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 concen-tration 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.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This paper presents a new method to introduce surface and bulk defects in SrTiO3 nanocrystals. The reducing agent, melamine, was carbonized under a nitrogen atmosphere to generate reductive NH3 and C, which reduced the SrTiO3 nanocrystals. The relative concentration ratio of bulk defects to surface defects in SrTiO3 nanocrystals could be tuned by this reduction treatment. The effects of surface and bulk defects on the band structures of SrTiO3 were studied, and it was found that the surface oxygen defects shifted the band structure to a higher energy level, while the bulk oxygen defects restored the energy levels of the band structure. Therefore, by adjusting the relative concentration ratio of bulk defects to surface defects in SrTiO3, the photocatalytic water splitting activity can be significantly improved.