Facile synthesis of bismuth oxide nanostructures derived from solvent-mediated oxalates and their visible-light-driven photocatalytic removal of organic pollutants

Stacked plate type beta-Bi2O3 microstructures with a substantial specific surface area and excellent visible-light-driven photocatalytic activity were successfully prepared using a simple precipitation-calcination method. By varying ethanol/water ratio, the solvent-mediated competition between oxalate coordination and bismuth ammonium citrate hydrolysis resulted in the formation of mixture of bismuth oxalate and bismuth hydroxide. A series of micro-structured precursors with various sizes and morphologies were synthesized through adjustment of solvents that allowed the formation of tetragonal beta-Bi2O3 upon further calcination. The optimal catalyst [beta-Bi2O3 (S6)] with exceptional photocatalytic activity due to its enhanced specific surface area (62.7 m(2) g(-1)) and narrower bandgap (2.20 eV), was highly dependent on ethanol-to-water ratio during precursor preparation. The as-prepared catalyst (S6) degraded rhodamine B, methyl orange, methylene blue and ciprofloxacin up to 99%, 98.8%, 71% and 70%, respectively in 180 min under visible-light. Moreover, effects of initial catalyst loading, dye concentration, and solution pH on photocatalytic behavior over S6 were studied. The optimized catalyst degraded 69% of the simulated dye-bath solution in 180 min. Photo-generated holes (h(+)) were identified as dominant active species in photodegradation. The increased surface area and stacked structure facilitated separation and transfer of photo-generated charges and favored active site exposure, resulting in improved photocatalytic activity.

Automated summary

Stacked plate type beta-Bi2O3 microstructures with substantial specific surface area and excellent photocatalytic activity were successfully prepared. The optimal catalyst exhibited enhanced specific surface area and narrower bandgap, resulting in highly efficient degradation of various dyes under visible-light.