Manufacturing of Photoactive β-Bismuth Oxide by Flame Spray Oxidation

Photoactive tetragonal bismuth oxide powder with different semiconducting characteristics was synthesized from Bi-pellets by flame spray oxidation. The effect of feedstock particle size and standoff distance (SOD) on the physical properties of beta-Bi2O3 keeping constant the fuel/oxygen ratio is here reported. The flame spray oxidized powder was collected either from evaporated or in-flight particles quenched in water. The combination of flame spray processing parameters led to different beta-Bi2O3 phase contents, oxidation characteristics, size distribution (nanometric and micrometric sized), morphology, and optical properties of the sprayed powder. The highest micrometric beta-Bi2O3 content quenched in water was obtained at a SOD of 30 cm using a particle size distribution of 12-60 mu m of Bi-feedstock. The obtained powder from in-flight particles collected in water allowed us to analyze the oxidation characteristics of bismuth. Micrometric powder shows the synthesis of snowman-like Bi/beta-Bi2O3 Janus particles. The nanometric sized Bi2O3 powder was continuously obtained by spray oxidation, where its collection efficiency depends on processing parameters and showed spherical morphology and a highly pure tetragonal phase with narrow visible light absorbance (E-g = 2.26 eV). These optical characteristics indicate that the obtained beta-Bi2O3 powder is suitable for high-performance visible-light photocatalyst.

Automated summary

In this study, photoactive tetragonal bismuth oxide powder with different semiconducting characteristics was synthesized from Bi-pellets by flame spray oxidation, where the physical properties of beta-Bi2O3 were affected by feedstock particle size and standoff distance. The results showed that varying processing parameters led to differences in phase contents, oxidation characteristics, size distribution, morphology, and optical properties of the sprayed powder, indicating its potential as a high-performance visible-light photocatalyst.