Soft Synthesis of Yellow TiO2 Anatase Nano-Photocatalyst

Over the past decades, semiconductor photocatalysts have long been studied due to their potential application in a wide range of fields such as removal of toxic pollutants and photocatalytic water splitting. In this sense,... [ view full abstract ]

Over the past decades, semiconductor photocatalysts have long been studied due to their potential application in a wide range of fields such as removal of toxic pollutants and photocatalytic water splitting. In this sense, current research endeavors in the field of semiconductor photocatalysts are widely focused on the sustainable production of TiO₂ nanomaterials for environmental purification, hydrogen generation and/or solar energy conversion. Among the three common polymorphs of TiO₂ it is generally accepted that anatase is the most active photocatalyst. The properties influencing the photoactivity of anatase particles  include surface area, crystallinity, crystallite size, crystal structure; and the morphology of the particles. Among the key parameters boosting the photocatalytic efficiency of anatase nanoparticles, an increased light absorption to extend the optical response to the visible, together with an improved charge separation of the electrons and holes generated upon photoexcitation, shall be enumerated.

In this work, yellow anatase nanoparticles with sizes around 5-90 nm have been obtained through a facile solvothermal reaction and subsequent thermal treatment, in which urea plays a key role to promote the formation of defective TiO₂. These nanoparticles present a reduce band gap (< 3.0 eV), increasing the light absorption range and improved photocatalytic performance in the phenol degradation. The results point out that this is due to the presence of intrinsic V_Ti and Ti_i defects in the yellowish materials. In this context, it is confirmed that urea and reaction time play a key role to promote the formation of defective TiO₂, obtaining the best photocatalytic performance when reaction time is equal or over 24 h and a ratio of 1:4 Ti:Urea is used. As a result, the yellowish TiO₂ samples with the highest percentage of defects are able to photodegrade the phenol in contrast with the lack of photocatalytic activity which exhibits the commercial photocatalyst.