Hydrothermal synthesis and formation mechanism of photocatalytically active SrTiO3 nanocrystals using anatase TiO2 with different facets as a precursor

Abstract

Strontium titanate (SrTiO₃) nanocrystals have been synthesized by a hydrothermal reaction route using anatase TiO₂ nanosheets with dominant {001} facets and commercial anatase TiO₂ nanoparticles as precursors. Time-resolved quenching experiments showed that the speed of hydrothermal formation of SrTiO₃ was relatively fast (in minutes). The initial particle morphology and exposed crystal facets of anatase TiO₂ precursor cannot be retained in the final SrTiO₃ products. SrTiO₃ nuclei are formed by the reaction between Ti(OH)_x^4−x and Sr ions at the TiO₂ solid/liquid interface. As surface adsorbed F⁻ is necessary to stabilize the {001} facets of anatase TiO₂, the hydrothermal crystallization of SrTiO₃ from TiO₂ with {001} facets not only exhibits a slower reaction rate but also a higher activation energy. Moreover, the photoelectrochemical and photocatalytic activity studies indicated that the SrTiO₃ products obtained from TiO₂ with {001} facets showed enhanced photocurrent density and photocatalytic hydrogen production activity. The present study sheds some light on the understanding of the crystal facets of the precursor on the hydrothermal formation process as well as the photocatalytic activities of the corresponding products.