Self-cleaning applications of TiO2 by photo-induced hydrophilicity and photocatalysis

• Published in: Applied catalysis. B, Environmental Environmental, 2015-10, Vol.176-177, p.396-428
• Main Authors: Banerjee, Swagata, Dionysiou, Dionysios D., Pillai, Suresh C.
• Format: Article
• Language: English
• Subjects: Anti-microbial; Doped titania; Energy and environmental; Fluoroalkylsilane; Graphene heterojunctions; Hydrophobic; Reduced graphene oxide (rGO); Synthesis; Tunable wettability; Water contact angle (WCA)
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2015.03.058

[Display omitted] •Various examples of self-cleaning materials have been reviewed.•Strategies to improve the efficiency of self-cleaning property have been discussed.•Wenzel, Cassie-Baxter and Miwa-Hashimoto models are discussed.•Examples of various commercial products have also been provided. Self-cleaning materials have gained considerable attention for both their unique properties and practical applications in energy and environmental areas. Recent examples of many TiO2-derived materials have been illustrated to understand the fundamental principles of self-cleaning hydrophilic and hydrophobic surfaces. Various models including those proposed by Wenzel, Cassie-Baxter and Miwa-Hashimoto are discussed to explain the mechanism of self-cleaning. Examples of semiconductor surfaces exhibiting the simultaneous occurrence of superhydrophilic and superhydrophobic domains on the same surface are illustrated, which can have various advanced applications in microfluidics, printing, photovoltaic, biomedical devices, anti-bacterial surfaces and water purification. Several strategies to improve the efficiency of photocatalytic self-cleaning property have been discussed including doping with metals and non-metals, formation of hetero-junctions between TiO2 and other low bandgap semiconductors, and fabrication of graphene based semiconductor nano-composites. Different mechanisms such as band-gap narrowing, formation of localized energy levels within the bandgap and formation of intrinsic defects such as oxygen vacancies have been suggested to account for the improved activity of doped TiO2 photocatalysts. Various preparation routes for developing efficient superhydrophilic–superhydrophobic patterns have been reviewed. In addition, reversible photo-controlled surfaces with tuneable hydrophilic/hydrophobic properties and its technological applications are discussed. Examples of antireflective surfaces exhibiting self-cleaning properties for the applications in solar cells and flat panel displays have also been provided. Discussion is provided on TiO2 based self-cleaning materials exhibiting hydrophilic and underwater superoleophobic properties and their utilities in water management, antifouling applications and separation of oil in water emulsions are discussed. In addition, ISO testing methods (ISO 27448: 2009, ISO 10678: 2010 and ISO 27447: 2009) for analysing self-cleaning activity and antibacterial action have also been discussed. Rapid photocatalytic self-cleaning t