Synthesis of Disk-Shaped Tungsten(VI) Oxide Particles with Various Physical Properties for Mineralization of Acetic Acid in Water Under Irradiation of Visible Light

Disk-shaped tungsten(VI) oxide (D-WO3) particles were synthesized according to a previously reported method consisting of pyrolysis, precipitation, and calcination, and the calcination temperature was changed (200-600 degrees C). The samples were characterized by field-emission scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, the Brunauer-Emmett-Teller single-point method, and diffuse reflectance spectroscopy. In addition, to evaluate the photocatalytic activities of the samples, the mineralization of acetic acid to carbon dioxide (CO2) was measured by loading Pt particles onto the surface of the samples by photodeposition and irradiating them in an aqueous suspension with a blue light-emitting diode. Increasing the calcination temperature was associated with several changes: the crystallites grew larger, increasing the crystallinity; the specific surface area decreased, decreasing the adsorption capacity; and the rate of the photocatalytic CO2 evolution reaction increased. Pt-loaded (0.1 wt%) D-WO3 calcined at 600 degrees C showed the highest activity with a CO2 evolution rate of 5.9 mu mol h(-1). These results indicated that improving the crystallinity of the D-WO3 samples was effective in increasing their photocatalytic activities.