Shape-controlled fabrication of TiO2 hollow shells toward photocatalytic application

This paper introduces a droplet-based microfluidic approach, followed by several post-treatments, for the fabrication of TiO2 hollow shells with novel morphology and perfectly uniform size distribution, which were further decorated with platinum nanostructures to improve their photocatalytic activity and their ability to remove organic pollutants. In particular, a single-emulsion technique was used to emulsify an oil phase containing a titanium dioxide precursor, titanium n-butoxide (TBT), and a UV-curable polymer resin, trimethylolpropane triacrylate (ETPTA), into an aqueous phase. These emulsion droplets then readily underwent phase separation and sol-gel reaction at the emulsion interface, forming a TiO2 shell that would eventually rupture, release the ETPTA core, and form an anatase TiO2 hollow shell after UV, isopropanol, and thermal post-treatments. Compared with TiO2 hollow spheres reported in the literature, the TiO2 hollow shells produced here have a well-defined inner cavity that significantly improves their photocatalytic activity and allows for the selective introduction of advanced functions by the addition of metal co-catalysts like platinum. This new approach, by offering the ability to uniformly control the shape of the TiO2 photocatalyst and the ability to selectively introduce co-catalysts, offers an alternative platform for the design and fabrication of high-performance photocatalysts for efficient water purification.