ZnO nanostructures and nanocomposites as promising photocatalysts for the remediation of wastewater pollution

Abstract

Recently, hierarchical 3D nanostructures have attracted attention due to their multiple advantages, such as large surface area, porous structures, as well as enhanced light harvesting ability. Zinc oxide is a promising photocatalyst alternative to TiO2 used for environmental remediation of wastewater pollutants due to its high photosensitivity, non-toxic nature, low cost, and environmental friendliness. ZnO can be crystallized in three forms under different conditions i.e., wurtzite, zinc-blende, and rock-salt structures. ZnO exhibits a higher quantum efficiency and has a similar bandgap as TiO2 as it has a larger number of inherent active defect sites on the surface, which makes it capable of absorbing a larger fraction of the solar spectrum. Various approaches have been used to efficiently utilize the solar radiation and to enhance the efficiency of zinc oxide photocatalyst. These techniques enhance the photocatalytic performance ZnO under visible light by shifting the bandgap energy, suppressing the recombination rate of electron-hole pairs, increasing charge separation efficiency. In future there is a need of developing green, scalable, low-cost and highly efficient hierarchically ZnO nanostructures and nanocomposites photocatayst for remediation of wastewater pollution. In this chapter the emphasis has been on the advantages, fabrication methods, and photocatalytic applications of hierarchical ZnO nanostructures for the degradation of organic contaminants present in wastewater.