Crystallinity swayed phase transformation and oxygen vacancy formation in TiO₂ aerogel photocatalysts

The lack of crystallinity of the aerogel materials has limited their significance which otherwise have found huge potential in wide variety of applications. In current work, we have developed TiO₂ aerogels by solid-state gelation method using commercially available P25 and ST-01 (commercial Ishihara TiO₂ Powder). The lack of crystallinity in the aerogel framework was resolved via utilizing crystalline TiO₂ nanoparticles and the phase transformation was assessed as a function of phase composition. Via controlled solid-state gelation, surface area retention of 88.7% was achieved whereas the rutile-to-anatase weight fraction (W_R) was considerably enhanced to 0.50. Interestingly, the phase transformation occurred only in P25, which suggests the mixed phase (anatase + rutile) composition as prerequisite for successful phase transformation. Favorably, TiO₂ aerogels imbibe high degree of oxygen vacancies (Vo) responsible for photocatalytic applications. Interestingly, Vo induction is higher for the TiO₂ with anatase phase composition (ST-01) followed by the sample with mixed phase composition (P25). The developed TiO₂ aerogel photocatalysts were employed to dye degradation of Rhodamine B (RhB) and Methylene Blue (MB). The samples attained 94.8% and 96.8% degradation efficiency within 15 min for RhB and MB with nearly 2-fold improvement in the photocatalytic efficiency compared to parent P25 TiO₂ respectively.