Hydrophilic surface modification of TiO2 to produce a highly sustainable photocatalyst for outdoor air purification

Recently, TiO2 photocatalysts have been applied in various ways for outdoor air purification. The main challenge with these applications is the stability of the photocatalysts, as the surface of TiO2 can be easily deactivated by contaminants found in outdoor environments. For example, it is difficult to remove oily contaminants with water once they are exposed to the photocatalyst surface since the hydrophilicity of TiO2 is not sufficiently high to allow for self-cleaning. In the present work, we modified the surface of commercial TiO2 nanoparticles to be more hydrophilic; this was done by coating them with a thin polydimethylsiloxane (PDMS) layer and applying a subsequent heat treatment under vacuum. The surface-modified TiO2 showed outstanding ability to repel oily contaminants deposited on its surface upon exposure to water droplets due to its superhydrophilic properties. Then, we evaluated the UV-light-driven photocatalytic activity of the surface-modified TiO2 for the decomposition of acetaldehyde. The surface-modified TiO2 showed photocatalytic activity for the decomposition of acetaldehyde that was comparable to that of bare TiO2. We show that our hydrophilic-surface-modified TiO2 has high potential for applications in outdoor air purification for an extended time period.