Removing Cr (VI) in water via visible-light photocatalytic reduction over Cr-doped SrTiO₃ nanoplates

It is crucial to develop a high-efficiency visible-light responsive photocatalyst for settling the increasing contamination stemmed from toxic heavy metal ions in wastewater. In this study, Cr-doped SrTiO₃ (CrSTO) nanoplates were synthesized by a facile one-pot solvothermal method with ethylene glycol as both the solvent and morphology controller. The resultant CrSTO nanoplates are about 100 nm in size and 20 nm in thickness, which are composed of SrTiO₃ nanocrystals about 19 nm in diameter. Furthermore, they possess the mesopore 3.0 nm in size, endowing their much higher specific surface area than the commercial SrTiO₃ particles. The Cr element is doped into the crystal lattice of SrTiO₃ by the substitution of Cr³⁺ for Sr²⁺, which enables the absorption edge redshift to the visible light region, thus elevating the visible-light absorption capability. In addition, the CrSTO-0.9 nanoplate with 0.9% Cr element content exhibits the highest photocatalytic performance for the Cr(VI) reduction under visible light irradiation, which can reduce nearly all Cr(VI) within 3.5 h and preserve the excellent stability after six recycles. This kind of CrSTO nanoplates may serve as a potential and promising photocatalyst for efficient Cr(VI) removal in wastewater.