Fabrication of TiO2 nanoflowers with bronze (TiO2(B))/anatase heterophase junctions for efficient photocatalytic hydrogen production

Abstract

Light harvesting and charge separation are both significant in the photocatalysis, but it is challenging to synchronously realize both in a single-component material. The novel porous TiO2 nanoflowers (NFs) photocatalysts with stable bronze (TiO2(B))/anatase heterophase junctions and large pore sizes are prepared via a hydrothermal/annealing method. The presence of porous nanoflower structure enhances the light absorption through reflection/refraction of light. The stable TiO2(B)/anatase heterophase junctions can efficiently promote the separation of photoinduced electrons and holes pairs and therefore suppress the charge recombination. The large pore sizes provide multi-level channels for the absorption and diffusion of reactants. With the increase of annealing temperatures from 350 to 550 °C, the H2 evolution activity is promoted. However, overhigh annealing temperature (650 °C) cause the broken of nanoflower structure and TiO2(B)/anatase heterophase junctions, thus inducing even decrease of H2 evolution activity. As a consequence, the obtained TiO2 NFs exhibit an enhanced photocatalytic H2 evolution activity at the optimal annealing temperature (550 °C) with Pt as co-catalysts (5.013 mmol h−1g−1), exceeding that of TiO2 NFs without annealing (0 mmol h−1g−1) and pure anatase TiO2 NFs (TiO2 NFs-650 °C, 4.722 mmol h−1g−1), respectively. Interestingly, TiO2 NFs-550 °C still show a high hydrogen evolution rate of 4.317 mmol h−1g−1 in the absence of co-catalysts.