Synthesis of spherical macroporous WO3 particles and their high photocatalytic performance

Tungsten trioxide (WO3) materials have excellent performance in transferring visible light energy and are widely used in photocatalysis, solar cells, and hydrogen generation. However. WO3 is expensive and in short supply. It is therefore important to develop efficient materials that use smaller amounts of WO3. One strategy is to produce porous materials so that the entire area of the WO3 material can be used and activated effectively. In this study, we synthesized macroporous WO3 particles using a spray-pyrolysis method with colloidal templating. Ammonium tungsten pentahydrate (ATP) was used to produce WO3 without impurities, and polystyrene (PS) spheres were used to promote spherical macropore formation. The synthesized particles were characterized using thermogravimetric analysis, X-ray diffraction, nitrogen adsorption, scanning electron microscopy, and transmission electron microscopy (TEM). Several process parameters (i.e. initial precursor concentration and mass ratio between host and template) were investigated to get highly ordered porous particles with controllable porous structure and particle outer diameter. Photocatalytic analysis results showed that the amount of PS that provided the optimum photocatalytic enhancement. Our results showed that a PS/ATP mass ratio of 0.60 provided WO3 particles with a photocatalytic rate 2.5 Limes that of dense WO3. TEM analysis showed that highly ordered macropores were produced, enabling better penetration and interaction of molecules and light in the deepest part of the active catalyst, resulting in enhancement of the photocatalytic rate. This method will be useful for large-scale synthesis of small amounts of WO3 with high photocatalytic performance. (C) 2013 Elsevier Ltd. All rights reserved.