Highly efficient 3-D hierarchical Bi2WO6 catalyst for environmental remediation

Bi2WO6 is a layered semiconductor material which has a moderate band gap (similar to 2.7 eV). Owing to its partial activity in visible light, Bi2WO6 has been widely investigated for photocatalytic application. It is well established that the photocatalytic activity of a material depends on its structure, morphology, size, etc. Depending on the method of synthesis, diverse morphologies can be obtained for Bi2WO6 like nanosheets, nanoflakes, nanorods, nanospheres, nanoparticles, nanocages, nanoplates, etc. Apart from the method of synthesis, there are other factors which influence it's structure and morphology. In this work, the effect of pH on structure and morphology of Bi2WO6 has been investigated. Structural analysis reveals formation of orthorhombic structure of the material in all samples. High pH samples showed formation of pure Bi2WO6, without any impurities. Morphological analyses were performed using FESEM and HRTEM which revealed the formation of Bi2WO6 nanosheets. The thickness of nanosheets decreases with increase in pH from 4 to 10. XPS analysis confirms the presence of Bi 4f, W 4f and O 1s states in the composition. Photocatalytic activity was tested using Methylene Blue (MB) as the model pollutant. Bi2WO6 sample with pH 10 showed the highest efficiency by degrading 99.8% of the dye in 160 min. Furthermore, the effect of various photocatalytic reaction parameters such as pH, dye concentration, and dosage of the photocatalyst on photodegradation of MB was investigated to determine the maximum degradation efficiency.