Mesoporous Monoclinic BiVO4 for Efficient Visible Light Driven Photocatalytic Degradation of Dyes

Abstract

The protection of environment and creation of the new and efficient energy resources are two exceptionally hot problems round the world. The environment friendly visible-light-driven photocatalysis process can be employed for the resolution of both of these alarming issues. The requirement of the development of new energy resources can be addressed by green-energy hydrogen production by the splitting of water molecule using photocatalyst whereas the protection of environment can be accomplished by the cost-effective removal of organic contaminants using the efficient technique of photocatalysis. Therefore, the green technology of photocatalysis is one the most favorable approaches for addressing the issue of new energy source development as well as environment protection. Several traditional wastewater treatment processes, including adsorption using activated carbon, flocculation and different biological treatments are employed to encounter the issue but these technologies are unable to produce remarkable results. This study will present my efforts for addressing the environmental problem. This study was performed in three steps. In first step, mesoporous visible-light-driven photocatalysts are synthesized, in second step the synthesized catalysts are analyzed by several characterization techniques and the last step is to measure their photocatalytic performance. A novel ultrasonic assisted hydrothermal calcination process is used for the development of mesoporous BiVO4 using mesoporous silica (KIT-6). BiVO4 particles are grown inside the pores and on the surface of KIT-6. The hybrid material of BiVO4 and KIT-6 is formed and NaOH based template etching process is employed to remove the mesoporous silica (KIT-6) which result in the development of extraordinary surface area and monoclinic mesoporous BiVO4 with visible light driven photocatalysis. The as-synthesized photocatalysts are then characterized by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Ultravoilet-visible Diffused Reflectance Spectroscopy (UV-vis DRS), Energy Dispersive X-ray Spectroscopy (EDS) and Brunauer–Emmett–Teller (BET). XRD confirms the synthesis of as-prepared photocatalysts. SEM tells the morphology. UV-vis DRS aids in the calculation of band gap. BET gives information about pore volume and surface area and EDS gives the percent elemental composition. The activity of as-synthesized catalysts is analyzed by the photocatalytic de-colorization efficiency for Methyl Blue (MB). The MB product samples are analyzed by UV-vis Spectroscopy. The photocatalytic efficiency of BiVO4 / KIT-6 nanocomposite and monoclinic mesoporous BiVO4 is much better than that of conventional BiVO4 semiconductor material. The huge surface area, reduced particle size and huge pore volume is responsible for absorbing comparatively more amount of light and providing more active sites resulting in excessive production of electron and hole pairs leading to the generation of hydroxyl and oxygen radicals. These radicals are more efficiently migrated due to larger surface area of both as-synthesized catalysts resulting in more efficient photocatalytic degradation of the model solution by de-colorizing it in about one hour. Moreover, monoclinic mesoporous BiVO4 is also verified for its industrial application by photocatalytic degradation ability of industrial effluent by de-colorizing the effluent in about 3 hours.