Highly stable 3D cellulose micro-rolls support TiO for efficient photocatalysis degradation experiment under weak light conditions.

Immobilization of nanometer-scale photocatalysts on a 3D polymeric substrate could play several complementary roles in photocatalysis, such as providing mechanical stability, facilitating easy recycling after usage, enhancing adsorption capability, and improving light harvesting properties through multiple reflections. To achieve stable and efficient photocatalysis under weak light conditions, 3D cellulose micro-rolls were introduced into the photocatalytic composites. Here, the formation of micro-rolls is attributed to the presence of titania nanoparticles, which generate uneven shrinkage stress in cellulose during the freeze-drying process, thereby inducing the cellulose to curl up. The dramatic structural transformation of the 3D micro-rolls increased the Brunauer-Emmett-Teller (BET) surface area of the sample. The 3D micro-roll structure is more favorable for photocatalysis due to its efficient mass transfer and exposed reactive sites, laying the foundation for enhanced adsorption capacity and photocatalytic reactions. The adsorption experiments suggested that the inner space of the micro-rolls provides a sufficient reaction zone, enabling fast mass transfer of molecules and easy access to the active sites. The samples could stand a high strain of 80 % and retain 96 % of the original maximum stress after 200 cyclic compressions, indicating excellent long-term stability. In addition, the photocatalytic tests show that with the help of micro-rolls, TiO can convert and utilize weak light that would otherwise be unused, and the catalysate exhibits almost no toxicity towards Escherichia coli.