The effects of cotton cellulose on both energy band gap of g-C₃N₄–TiO₂ nanoparticles and enhanced photocatalytic properties of cotton-g-C₃N₄–TiO₂ composites

To recycle powdered photocatalysts and make full use of their active sites, one efficient way is to load these particles on the supporting materials. It is demonstrated that the supports are beneficial because they adsorb organic pollutants to be degraded. However, the effect of the supports on the energy band structure of the generated composite photocatalysts remains unclear. In this study, a heterojunction composed of graphitic carbon nitride (g-C₃N₄) and TiO₂ (g-C₃N₄–TiO₂) was constructed and simultaneously immobilized on the surface of cotton fibers in a one-step hydrothermal process. The structural characteristics and photocatalytic performance of the g-C₃N₄–TiO₂ modified cotton fibers (C–g-C₃N₄–TiO₂) were systematically examined. It was found that g-C₃N₄ nanosheets were combined with as-synthesized TiO₂ nanoparticles during the hydrothermal reaction to form an intimate heterojunction, which was chemically grafted onto cotton fibers via C/O–Ti⁴⁺/Ti³⁺ bonds. Meanwhile, TiO₂ nanoparticles were introduced into the swollen cotton fibers. Most notably, the cellulosic cotton substrates could increase the energy band gap of g-C₃N₄–TiO₂ nanocomposites, as demonstrated by the density functional theory (DFT) calculations. The reaction order of radical species (·O₂⁻ > ¹O₂ > ·OH > h⁺) did not change during MO photodegradation no matter whether the g-C₃N₄–TiO₂ was loaded on cotton fibers. The self-cleaning experiments showed that g-C₃N₄–TiO₂ modified cotton fabrics could be repeatedly used to remove organic contaminants.