Highly photoactive TiO2 microspheres for photocatalytic production of hydrogen

In this study, the photocatalytic activity in hydrogen production of a TiO2 catalyst with hierarchical structure and microsphere morphology was tested. This catalyst was synthesised by hydrolysis and condensation processes from a Ti(OBut)4 precursor and calcined at 150 °C, 400 °C and 630 °C. Hydrogen production of the subsequent photocatalysts rose by two and three orders of magnitude after the incorporation of Au or Pt particles by photodeposition. The microspheres with and without metal modification were characterised by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), Raman, Brunauer–Emmett–Teller (BET) surface area, Fourier transform infrared spectroscopy (FTIR) and diffuse reflectance measurements. The highest production rates were obtained for the metal-modified photocatalysts calcined at 400 °C. Hydrogen production increased with Au loading, attaining a rate of 1118 μmol·h−1 for the 1.5 wt% Au photocatalyst. However, the highest production rate in the case of Pt was attained with just 0.27 wt% and was almost twice as high as that obtained with Au, 2125 μmol·h−1. When compared with previous studies by our team under the same conditions, this high production rate, obtained with a very low Pt loading, was only exceeded by the reference Aeroxide P25 TiO2 catalyst with a Pt loading greater than 1.5 wt%.