Nanocomposites of GaBr3 and BiBr3 Nanocrystals on BiOBr for the Photocatalytic Degradation of Dyes and Tetracycline

In recent past decades, semiconductor-based photocatalysts have been studied worldwide as a promising technique for the degradation of organic dyes in wastewater. In this study, a nanoplate-like Bi-based heterojunction (BGB-1, -2, and -3) has been prepared for the first time through the in situ formation of BiBr3 and GaBr3 nanocrystals on the surface of BiOBr via a facile water bath method, followed by the hydrothermal process with a change in the composition. Multiple physiochemical processes such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared are analyzed to reveal the structural properties. The Brunauer–Emmett–Teller, UV–vis diffuse-reflectance, and photoluminescence spectra have been utilized for detailed analysis of the surface area, grain boundary, lattice imperfections, and light absorption properties. The photocatalytic activity and quantum efficiency of the as-synthesized nanocomposites have been evaluated by the photodegradation of Rhodamine B (RhB), methylene blue, methyl orange, Congo red, phenolic compounds, and colorless antibiotic tetracycline with visible-light illumination. Compared to pure BiOBr or the precursor materials, Bi-based nano/photocatalysts exhibit a significantly enhanced photocatalytic activity. Moreover, it is seen that the nanocomposite with a composition of 0.1 mol of Ga(NO3)3·xH2O and 2.9 mol of Bi(NO3)3·5H2O (BGB-1 nanocomposite) shows the highest photocatalytic activity against RhB degradation (∼100% within 20 min) and tetracycline antibiotic (∼92% within 20 min). The significantly improved photoreactivity has been ascribed to the effective separation of photogenerated electron–hole pairs and superoxide radical anions (•O2–). The hole (h+) also greatly impacts the degradation mechanism. Bi-based nanocomposites are found to kill Gram-positive and Gram-negative bacteria. These nanocomposites have been designed as efficient visible-light-driven heterojunction photocatalytic materials with significant antibacterial activity for wastewater purification.