Porous TiO₂ thin film-based photocatalytic windows for an enhanced operation of optofluidic microreactors in CO₂...

Using a photocatalytic window can simplify the design of an optofluidic microreactor, providing also a more straightforward operation. Therefore, the development of TiO₂ coatings on glass substrates seems appealing, although a priori they would imply a reduced accessible area compared with supported nanoparticle systems. Considering this potential drawback, we have developed an endurable photocatalytic window consisting on an inner protective SiO₂ layer and an outer mesoporous anatase layer with enhanced surface area and nanoscopic crystallite size (9-16 nm) supported on a glass substrate. The designed photocatalytic windows are active in the CO₂-to-methanol photocatalytic transformation, with maximum methanol yield (0.52 μmol·h^-1·cm^-2) for greatest porosity values and minimum crystallite size. Compared with benchmark supported nanoparticle systems, the nanoscopic thickness of the coatings allowed to save photoactive material using only 11-22 μg·cm^-2, while its robustness prevented the leaching of active material, thus avoiding the decay of performance at long working periods.