Effects of hydrothermal treatment of cellulose nanocrystal templated TiO₂ films on their photodegradation activity of methylene blue, methyl orange, and rhodamine B

Transparent mesoporous TiO₂ films with enhanced photocatalytic degradation efficiency were systematically synthesized. The films were prepared using a mixed sol containing a cellulose nanocrystal (CNC) template that was spin-coated onto an ITO substrate, followed by calcination at 400 °C for 1 h. Subsequently, the fabricated films were subjected to hydrothermal treatment in a pure aqueous medium for various periods of time (1, 2, and 4 h) and at different temperatures (150 and 250 °C). The surface area and crystallite size of the prepared TiO₂ film were increased and decreased from 76.7 m²/g and 12.78 nm (without the template) to 127.3 m²/g and 9.95 nm (with the template), and then to 233.4 m²/g and 4.43 nm (1 h and 150 °C) with hydrothermal treatment, respectively. Hydrothermal treatment plays an important role in enlarging the surface area, and decreasing the crystallite size. Furthermore, the optimized TiO₂ film exhibits exceptional photodegradation activity towards organic dyes with performance nearly equal to that of the standard photocatalyst. Because of the exceptional properties of the prepared optimized TiO₂ film, the adsorption of organic dyes on its surface increases, which promotes the photocatalytic degradation efficiency during light irradiation.