Flux synthesis of AgNbO3: Effect of particle surfaces and sizes on photocatalytic activity

The molten-salt flux synthesis of AgNbO3 particles was performed in a Na2SO4 flux using 1:1, 2:1 and 3:1 Flux-to-reactant molar ratios and heating to 900 degrees C for reaction times of 1-10 h. Rectangular-shaped particles are obtained in high purity and with homogeneous microstructures that range in size from similar to 100 to 5000 nm and with total surface areas from 0.16 to 0.65 m(2) g(-1). The smallest particle-size distributions and highest surface areas were obtained for the largest amounts of Flux (3:1 ratio) and the shortest reaction time (1 h). Measured optical bandgap sizes of the AgNbO3 products were in the range of similar to 2.8 eV. The photocatalytic activities of the AgNbO3 particles for H-2 formation were measured in visible light (lambda > 420 nm) in an aqueous methanol solution and varied from similar to 1.7 to 5.9 mu mol g(-1) h(-1). The surface microstructures of the particles were evaluated using field-emission SEM, and the highest photocatalytic rates of the AgNbO3 particles were correlated with the formation of high densities of similar to 20-50 nm terraced surfaces. By comparison, the solid-state sample showed no well-defined morphology or microstructure. Thus, the results presented herein demonstrate the utility of Flux-synthetic methods in targeting new particles sizes and surface microstructures for the enhancement and understanding of photocatalytic reactivity over metal-oxide particles. (C) 2010 Elsevier B.V. All rights reserved.