Construction of SrTiO3/TiO2 heterojunction by in-situ ion exchange method to enhance photochemical performance

Construction of heterojunctions has been shown to be one of the most promising methods for the preparation of highly efficient catalysts, because it is feasible and effective for the separation of electron-hole pairs, prolonging the lifetime of photogenerated electrons. In this study, TiO2 was grown on fluorine-doped tin oxide glass (FTO), and then a strontium source was added to obtain heterojunctions between SrTiO3 and TiO2 using in-situ ion exchange hydrothermal method. The in-situ grown SrTiO3/TiO2 (TST) composite has a better absorption performance, a narrower band gap, and a lower carrier recombination rate compared to the pure TiO2 sample, which improves the photoelectrochemical performance. The photocurrent density of TST-10 (hydrothermally treated for 10 h) has the largest value of 0.06 mA·cm−2, which is about three times higher than that of pure TiO2. Then, the first-principles density functional theory (DFT) calculation was used to further explore the photocatalytic mechanism of TST. The exchange correlation energy was based on the Generalised Gradient Approximation (GGA) with Perdew–Burke–Ernzerhof (PBE) functional calculation method to study the electronic and optical properties of SrTiO3/TiO2 heterostructures. The results show that the carrier transfer rate and the optical absorption coefficient of the material increase significantly after the establishment of the in-situ heterojunction. This study offers insight into the heterostructures' interface significance on photocatalytic activity.