TiO2-based photocatalysts for controllable hydrogen evolution from ammonia borane

Abstract

Results on the photocatalytic hydrolysis and hydrothermolysis of NH3BH3 in the presence of the titania-based photocatalysts (TiO2 Hombifine N, samples obtained by its hydrothermal treatment in KOH and after modification by colloidal silver) are presented. It was shown that in the hydrolysis of 0.3 M solution of NH3BH3 at 40 °C under UV irradiation (λ = 365 nm) the highest activity has been achieved with the photocatalyst synthesized at 120 °C in 10 M КOH solution. In this sample, the nanodispersed particles of the unreacted anatase get in contact with titanate nanorods. Modification of the titania-based photocatalysts by colloidal silver allowed the quantum efficiency under UV irradiation to be increased and the hydrogen formation became possible under visible light (λ = 450 nm). It was established that the use of low concentration of the supported silver (0.06 wt.%) makes possible to control the H2 generation by the use of irradiation. Photocatalytic hydrothermolysis of NH3BH3 under heating (90 °C) and UV irradiation of the reaction mixture (NH3BH3+H2O + Ag/TiO2) with the molar ratio H2O/NH3BH3 = 1.24 has been carried out for the first time. High values of the rate of generation and the yield of hydrogen have been achieved.