Synthesis of La-doped Ag1.4K0.6Ta4O11 nanocomposites as efficient photocatalysts for hydrogen production and organic pollutants degradation

A new silver tantalate material has been synthezied by heating a mixture of AgNO3, Ta2O5 and KCl at 850 degrees C for 20 h. XRD, EDX, XPS, SEM, TEM and HRTEM show that the material consists of Ag1.4K0.6Ta4O11 nanoplates, with Ag nanoparticles present on the surface, which is consistent with enhanced absorption of the material in the visible region. Addition of 0.5-5 mol% of La2O3 in the preparation of Ag1.4K0.6Ta4O11 results in significant change in the morphology from nanoplates to nanoplates/nanowire composites. The photocatalytic activities of Ag1.4K0.6Ta4O11 and La-Ag1.4K0.6Ta4O11 have been evaluated by degradation of the organic pollutants rhodamine B (RhB) and pentachlorophenol (PCP) in water under visible light (lambda >420 nm), as well as by photocatalytic reduction of water to H-2 at lambda >390 nm. The photocatalytic activity of Ag1.4K0.6Ta4O11 is significantly enhanced by La-doping; the optimal La content is 1 mol% for degradation of organic substrates and 5 mol% for H-2 evolution, with photocatalytic activity significantly higher than that of P25 TiO2. The enhancement of photocatalytic activity upon La doping is attributed to trapping of excited electrons by La3+, and the formation of nanowires which further promote charge separation. (C) 2013 Elsevier B.V. All rights reserved.