Flux syntheses of La-doped NaTaO3 and its photocatalytic activity

The La-doped (2%) NaTaO₃ perovskite-type solid was synthesized in high purity and homogeneity within a molten Na₂SO₄/K₂SO₄ (1:1 molar ratio) flux in much shortened reaction times, 0.5-1.0 h, compared to conventional solid-state techniques. The particle morphologies were investigated by scanning electron microscopy and were irregular block-shaped with dimensions of 500-100 nm and smaller surface features. The bulk particle sizes were found to decrease with increasing amounts of flux used in the synthesis, from 1:1 (NaTaO₃:flux), 1:2 to 1:3 for a reaction duration of 1 h. Photocatalytic activities of the NaTaO₃ products were measured in an aqueous methanol solution to be 535-1115 μmol H₂ h⁻¹ g⁻¹, and which increased with increasing particle sizes and decreasing amounts of flux used in the synthesis. These rates were up to ×2 greater than that measured for a conventionally prepared La-doped (2%) NaTaO₃ sample, which is currently one of the most efficient UV-photocatalysts known.