Effect of pH on the phase transformation of strontium titanium materials and their photocatalytic property

Strontium titanium (Sr/Ti) system materials with different morphologies (like nanospheres, sheet-like, nanocubes) were synthesized via hydrothermal method by adjusting the solution pH. The main purpose was to study the effect of pH value on phase and morphologies of Sr/Ti system materials. Four different phases of catalysts (Ti₄O₇/SrF₂/TiO₂, TiO₂/SrF₂, TiO₂, SrTiO₃) were prepared when pH value of the reactant solution was 1.5, 3, 6, 14, respectively. The photocatalytic performance of the as-obtained catalysts with different phase has been investigated in rhodamine B (RhB) solution. The results show that four products exhibit great difference in photocatalytic RhB performance. Furthermore, the photodegradation efficiency and kinetic results show: Ti₄O₇/SrF₂/TiO₂ > TiO₂ > SrF₂/TiO₂ > SrTiO₃. The probable influence factors have been explored. The photocatalysts were characterized by X-ray diffraction, ultraviolet visible diffuse reflectance spectroscopy, scanning electron microscope and Mott–Schottky (M–S) curves. The results show that phases transformation, crystalline size, and morphologies may affect the photocatalytic properties a lot.