Constructing bulk defective perovskite SrTiO₃ nanocubes for high performance photocatalysts

Defects (Ti³⁺ or oxygen vacancies) have been demonstrated to promote the charge separation process in TiO₂ based photocatalysts. Particularly, the bulk defects within a certain concentration can give a great enhancement for both light absorption and charge separation efficiency. In this report, we explored a one-step molten salts route to synthesize SrTiO₃ nanocubes with bulk defects (Ti³⁺ doped) by using SrCO₃ as a Sr source, and TiO₂ and Ti powder as Ti sources. The amount of defects can be tuned by changing the molar ratio of Ti/TiO₂. The corresponding bandgap of SrTiO₃ can be changed from 3.29 to 2.73 eV with the increase of defects. X-ray diffraction and electron microscopy disclose that SrTiO₃ is highly crystalline and has a cubic morphology. X-ray photoelectron spectroscopy and electron paramagnetic resonance indicate that the as-prepared SrTiO₃ is close to the Ti³⁺ doped SrTiO₃. Surface photovoltage spectroscopy (SPS) and field-induced SPS confirm that Ti³⁺ doping in the SrTiO₃ turns it from an n-type semiconductor to p-type. The SrTiO₃ with an optimal amount of defects exhibits highly enhanced photocatalytic performance. An excess amount of defects results in a weak SPS response and photocatalytic performance.