Hydrogen production from the photocatalytic hydrolysis of sodium borohydride in the presence of In–, Sn–, and Sb–TiO2s

To enhance the evolution of hydrogen from the photocatalytic hydrolysis of sodium borohydride solution, three photocatalysts; 0.5 mol% In, Sn, and Sb, incorporated into TiO2, were prepared using a hydrothermal method. The particle sizes of well-developed anatase were about 5.0 nm, except those for Sb–TiO2, which were above 5.0 nm, with closed to cubic form shapes, except for pure TiO2 that was spherical. In the X-ray photoelectron spectra (XPS) for Ti2p3/2, a band at 460.34 eV, attributed to partial MTiO3, was seen in Sn–TiO2. Additionally, two bands of Sn3d5/2 at 484.5 and 486.8 eV, assigned to the Sn and SnO or SnO2, respectively, appeared over Sn–TiO2, with the ratios of metal–OH/metal–O in the O1s bands, imply a hydrophilic property, also increased in this compared with the other catalysts. The hydrogen evolution from sodium borohydride (NaBH4) hydrolysis was enhanced in the Sn–TiO2 photocatalytic system compared to those for the other catalysts; hydrogen was evolved at 140 ml/g h over Sn–TiO2, which was different from the 100 ml/g h for the hydrolysis of pure NaBH4, and increased to 1350 ml/g after 5 h. In particular, the evolved hydrogen increased with increasing amounts of Sn–TiO2, and the production continued for 150 h.