Efficient photocatalytic hydrogen production over titanate/titania nanostructures modified with nickel

Abstract

Nickel-modified titanate/TiO2 catalysts were prepared by deposition of nickel ions onto hydrothermally prepared titanate supports, followed by hydrogen temperature-programmed reduction. Two different nickel precursors (hydroxide and carbonate) were used to tune reducibility and to vary the crystal phase structure of the final catalysts. The precursor reducibility and functional properties of the final catalysts were investigated systematically using various characterisation techniques. The results revealed a more facile reduction of the hydroxide precursor compared to its carbonate counterpart. Moreover, it was found that the formation of the anatase phase was favoured by the use of the hydroxide precipitation agent. The photocatalytic activity towards hydrogen production of the prepared catalysts was evaluated in the presence of 2-propanol under simulated solar light irradiation. A thorough study of the photocatalytic performance of the synthesised catalysts was conducted as a function of the precipitation agent used and the reduction temperature applied. The catalyst with dominant anatase crystal phase displayed the highest photocatalytic activity with a maximum H2 production rate of 1040 μmol h−1 g−1, this being more than four times higher than that of its carbonate counterpart. The catalysts with titanate structure showed similar activity, independent of the precipitation method used. The nanotubular structure was found to be the dominant factor in the stability of photocatalysts under long-run working conditions.