A Review of the Single-Step Flame Synthesis of Defective and Heterostructured TiO2 Nanoparticles for Photocatalytic Applications

Titanium dioxide (TiO2) is an excellent UV-photocatalytic material that is widely used in various applications, including clean energy production, environmental remediation, and chemical production. However, the use of TiO2 is limited in the field of visible light photocatalysis due to its large bandgap and fast recombination rate between electron and hole pairs, which generally results in a low photocatalytic reaction. Defect/bandgap engineering by doping and the introduction of heterojunctions has been successfully employed to improve the photocatalytic activities of TiO2 over a wide wavelength. To apply the unconventional structured TiO2 with high photocatalytic performance to industries, the development of efficient methods for large-scale production is of high importance. Flame synthesis is a very promising method for the rapid production of nanoparticles. In this article, we summarize the latest reports on the synthesis of defective and heterostructured TiO2 using the single-step method of flame synthesis. Fundamental understandings of reactor configurations, synthesis conditions, precursor preparation and their physicochemical properties are intensively discussed.