Pyrochlore-like K2Ta2O6 synthesized from different methods as efficient photocatalysts for water splitting

Abstract

Pyrochlore-type K₂Ta₂O₆ with a high dielectric constant, which may lead to facile charge separation, is a prospective medium for photocatalytic water splitting. We synthesized K₂Ta₂O₆ catalyst powders using sol–gel (SG) and hydrothermal (HT) methods. The Rietveld refinement simulation of the X-ray diffraction data shows that the SG catalyst has a lower density of ionic vacancy states and a more flattened Ta–O–Ta bond angle than the HT catalyst. Photoluminescence analysis indicates that the flattened Ta–O–Ta bond angle of the SG catalyst facilitates charge separation to suppress intrinsic recombination emission, and the lower vacancy density leads to a suppressed extrinsic defect emission. The SG catalyst has a higher photocatalytic water splitting activity, which is more than twice that of the HT catalyst under mercury lamp irradiation. The higher charge separation efficiency and lower electron-trapping vacancy density are responsible for the higher photocatalytic activity. The K₂Ta₂O₆ SG catalyst shows an apparent photocatalysis quantum yield which is superior to that of the well-documented NaTaO₃ catalysts. Our results suggest that K₂Ta₂O₆ is a promising catalyst for use in photon energy conversion in various applications.