Enhancement of photocatalytic performance in degradation of aqueous trichloroethylene and methylene blue by using TiO₂ thin film fabricated by cellulose nanocrystals templating and Nb doping

This paper methodically reported the photocatalytic properties of TiO₂ thin films with high transparency and a mesoporous structure, which were synthesized by manipulating templating with cellulose nanocrystals (CNC) and doping with Nb. The TiO₂ precursors containing CNC and Nb chloride were synthesized through the sol–gel route, followed by spin coating on an indium tin oxide substrate with subsequent calcination for 1 h at 400 °C. The porous structure, phase composition, optical and morphological properties, and photocatalytic degradation activity of prepared materials were evaluated. The templated CNC played a major role in generating rod-like porous channels in TiO₂ film, providing a mesoporous structure, as well as enhancing the heterogeneous nucleation rate of anatase phase with an average crystallite size of 9.95 nm. The anatase phase was stabilized and the surface area of TiO₂ with 76.7 m²/g increased up to 127.3 m²/g with the aid of CNC templating and Nb doping into the TiO₂. The light absorption capacity of the CNC templated TiO₂ film doped with 5 at% Nb was significantly higher in the visible region than that of the TiO₂ films templated with and without CNC. The CNC templated TiO₂ film doped with 5 at% Nb presented a drastic enhancement of the photocatalytic degradation rate of trichloroethylene, which was completely decomposed in 30 min, twice faster compared with the TiO₂ film templated without CNC. In the case of methylene blue, the complete decomposition with the CNC templated TiO₂ film doped with 5 at% Nb occurred in 120 min, exhibiting the highest photodegradation activity. The photocatalytic performance was influenced by major factors, such as the larger active adsorption sites, strong visible light absorption, and efficient charge transfer, induced by templating with CNC and doping with Nb in TiO₂ film.