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.