Fast Scalable Synthetic Methodology to Prepare Nanoflower‐Shaped Bi/BiOClxBr1−x Heterojunction for Efficient Immobilized Photocatalytic Reactors under Visible Light Irradiation

The metal/photocatalyst heterojunction has demonstrated an excellent capability for pollutant degradation under visible light irradiation. In this study, for the first time, highly stable colloidal dispersions of Bi/BiOClxBr1−x heterojunction with an exposed (001) facet are successfully prepared from inorganic simple salts using low‐frequency ultrasound irradiation (LFUI) at ambient conditions without further post‐treatment. The colloidal dispersion series of Bi/BiOClxBr1−x heterojunction (x = 0, 0.2, 0.5, 0.8 and 1) is simply obtained by adding stoichiometric aqueous solutions of NaCl and NaBr, into an acidic aqueous solution of Bi(NO)3.5H2O in a typical ultrasonication bath at room temperature within ≈5 min. Bi/BiOClxBr1−x heterojunction films are also fabricated using a simple drop‐casting technique and tested as immobilized photocatalytic reactors. Compared to its counterparts, the Bi/BiOCl0.8Br0.2 film possesses a 3D flower‐like morphology with a highly exposed (001) facet showing the highest electron‐hole generation and separation efficiencies. In addition, the Bi/BiOCl0.8Br0.2 film demonstrates the highest photocatalytic degradation rate of the rhodamine RhB aqueous solutions (≈5 ppm), achieving ≈99% in 60 min under the visible light component of the solar spectrum. This study demonstrates the potential of LFUI as a rapid scalable synthetic strategy for cost‐effective and energy‐efficient practical production of highly active immobilized photocatalytic reactors.