Photocatalytic hydrogen production over Au/SrTiO3

Abstract

In this work, a well stirred continuous system with top irradiation was designed for photocatalytic water splitting with the integration of online mass spectroscopy to evaluate hydrogen production quantitatively. As a preliminary work, different metals (Al, Cr, Ni, Mg) were doped to SrTiO3 via solid state reaction to improve the band gap of the perovskite, then the semiconductors obtained were loaded with Au as the co-catalyst, and tested for photocatalytic water splitting reaction under visible light conditions. The results showed that Al doped SrTiO3, which was prepared via solid state reaction and Au loading via homogeneous deposition precipitation method in the presence of urea gave much better results for photocatalytic hydrogen production under visible light irradiation. Therefore, in the remaining part of thesis, different Al doped and Au loaded SrTiO3 was prepared and tested with 10, 20, 30 % aqueous solutions of various sacrificial agents such as methanol, ethanol, isopropyl alcohol. The band gap energy of prepared photocatalysts was determined by diffuse reflectance UV-visible spectroscopy. Al-doping increased band gap energy of SrTiO3 from 3.3 eV to around 3.4 eV. Besides, samples were characterized by scanning electron microscope (SEM), X-ray diffraction technique (XRD) and X-ray photoelectron spectroscopy (XPS). SEM results were not conclusive since effective dispersion of Au in some samples were not observed. XRD analysis showed that Al may have been incorporated to SrTiO3, resulting in change of the crystal structure of the perovskite. The results of XPS exhibited that Al might be incorporated into both Sr and Ti sites SrTiO3 leading to shifts in Sr and Ti binding energy peaks. The optimum condition was achieved with 1 % Al doped, 0.25 % Au loaded SrTiO3 in the presence of 30 % isopropyl alcohol, yielding 347 µmol/h. gcat H2 evolution rate under 5 hour visible light irradiation.