Highly efficient SrTiO3/Ag2O n-p heterojunction photocatalysts: improved charge carrier separation and enhanced visible-light harvesting

Abstract

Strontium titanate (SrTiO3) with perovskite structure has recently received significant attention in t he area of photocatalysis. However, challenges remain relating to its industrial applications; the high charge carrier recombination rate and low light-harvesting efficiency being the main two. Herein, a novel strategy based on fabrication of a typical n-p heterojunction has been proposed and the typical narrow-bandgap p-type semiconductor Ag2O was chosen to be coupled with SrTiO3 using a facile chemical precipitation method. The phase compositions, microstructures and optical properties of the prepared SrTiO3/Ag2O heterostructured photocatalysts have been systematically investigated with an x-ray diffractometer, scanning electron microscope, high resolution transmission electron microscope, x-ray photoelectron spectroscope and UV–vis spectrophotometer. The photocatalytic properties were evaluated through photodegradation of a common organic dye Rhodamine B (RhB). The results demonstrated that the heterostructured photocatalyst SrTiO3/Ag2O-0.15 outperformed pristine SrTiO3 and Ag2O. Specifically, the reaction rate of SrTiO3/Ag2O-0.15 is about 69 times and 4 times that of bare SrTiO3 and Ag2O respectively in photodegradation of RhB. The excellent photocatalytic performance was attributed to the synergetic effect between the improved visible-light harvesting efficiency and inhibited electron–hole recombination rate arising from the built-in electric field in a p-n heterojunction, as evidenced by the transient photocurrent and photoluminescence spectrum investigation. Furthermore, the excellent recyclability of the heterostructured photocatalyst was confirmed and holes were verified to be the major active species contributing to the overall degradation. Our findings demonstrate construction of p-n heterojunctions with narrow-bandgap semiconductors as a feasible avenue to promote overall photocatalytic efficiency, through simultaneously boosting charge-carrier separation and expanding photon-absorption range.