Sol–gel hydrothermal synthesis of visible-light-driven Cr-doped SrTiO3 for efficient hydrogen production

Abstract

Using a sol–gel hydrothermal method, we have synthesized Cr-doped SrTiO₃ with a high specific surface area (19.3–65.4 m² g⁻¹, depending on the hydrothermal temperature). X-ray diffraction (XRD), UV-Vis diffuse reflectance spectra, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the Cr-doped SrTiO₃. XRD analysis showed that Cr-doped SrTiO₃ exhibited good crystallinity and the crystalline size calculated using Scherrer equation is about 20–30 nm. UV-Vis diffuse reflectance spectra showed that Cr doping can extend the absorption edge of SrTiO₃ into visible region (540 nm). TEM images of Cr-doped SrTiO₃ showed that the high temperature during the hydrothermal reaction will prompt the aggregation of primary particles into porous spheres. The porous structure was further certified by nitrogen physisorption results. By loading Pt (0.6 wt.%) nanoparticles as a cocatalyst, the as-prepared Cr-doped SrTiO₃ photocatalyst exhibited high H₂ evolution rate (82.6 μmol h⁻¹) from 20% methanol solution under visible light irradiation, which is 3 times higher than that of the sample synthesized by solid state reaction. The high activity of the as-prepared Cr-doped SrTiO₃ can be attributed to the high specific surface area and good crystallinity.