A review of hierarchical nanostructures of TiO2: Advances and applications

In the past few decades, extensive studies have been carried out on TiO2 nanostructures having hierarchical morphologies and their applications in diverse fields. By controlling the size and composition of the different TiO2 morphologies, new and improved properties have been realized, leading to significant advancements in materials chemistry, in the broad areas of energy and environment. The improved efficiency and wide applications of these materials are attributed to their physicochemical properties such as stability, efficient electronic and ionic charge transfer, higher specific surface area, etc. In this review, we discuss the different morphologies of hierarchical TiO2 nanoparticles and the properties that have been influenced by these morphologies, enabling their diverse applications. Several composites using the different TiO2 hierarchical forms have been synthesized which too find wide applications. The excellent physical properties of zero, one, two, and three-dimensional TiO2 nanostructures, the relationship between the morphologies of TiO2 nanostructures, and their activities in energy and environment applications have been discussed.