Photocatalyst ZnO-doped Bi₂O₃ powder prepared by spray pyrolysis

In the present study, nanocrystalline photocatalyst Bi₂O₃ powders with various ZnO additions were synthesized by spray pyrolysis at 600 (SP600) and 700°C (SP700). The Bi₂O₃ powder converted from a monoclinic α phase to a tetragonal β phase at pyrolysis temperatures ≥600°C. The crystallinity of the SP powder increased with the increase in pyrolysis temperature. The morphology of the SP powders was observed to reveal a porous structure. The photocatalytic activity of the Bi₂O₃-based powder strongly depends on its specific surface area. Based on a constant specific surface area, 5mol% ZnO addition can significantly increase the photocatalytic efficiency of SP700 Bi₂O₃ powder from 46% to 86% under visible irradiation for 6h. Intrinsically, the photocatalytic performance of the SP powder is affected by the crystallite size. Furthermore, the photocatalytic activity of the resulting powders was compared with that of the P25 powder (a commercialized TiO₂ powder). The mechanisms for the formations of the porous powders are also delineated.