Amorphous TiO2 nanostructures: synthesis, fundamental properties and photocatalytic applications

Abstract

Titanium dioxide (TiO₂) nanostructures have been extensively investigated in the field of photocatalysis, and many previous review articles have summarized the progress made in the design and synthesis of crystalline TiO₂ with tailored nanostructures. However, the physical and chemical properties of TiO₂, including light absorption, surface adsorption, and charge carrier separation, are related to the disordered arrangement of intrinsic atoms. Therefore, amorphous TiO₂ (am-TiO₂) with long-range atomic disorder plays an important role in the photocatalytic performances. Unfortunately, at present we still know less about amorphous TiO₂-based materials than crystalline ones from a scientific viewpoint, and a comprehensive review on am-TiO₂ is lacking and highly desirable to further advance the development of novel function-oriented TiO₂-based nanostructures. In this review, we comprehensively summarize the structural characteristics, optical properties, synthesis principles and current morphologies of am-TiO₂ nanostructures. In particular, photocatalytic applications with regard to am-TiO₂-based nanostructures are highlighted. Additionally, we briefly propose several perspectives on the challenges and new direction for future investigation. This review will act as a useful guideline for researchers who are currently concentrating on TiO₂ materials to fabricate novel amorphous-based nanomaterials for photochemical applications.