Mechanistic insight into the enhanced photodegradation by black titanium dioxide nanofiber-graphene quantum dot composites.

[Display omitted] • Graphene quantum dots enhance the photocatalytic activity of black TiO 2 nanofibers. • Graphene quantum dots enhance charge carrier separation and photodegradation. • Increased surface adsorption has negligible contribution to photodegradation. • Superoxide radical anions are the main reactive oxygen species generated. The photocatalytic activity of black titanium dioxide nanofibers (bTiO 2 NFs) can be enhanced through composition with carbon nanomaterials. However, it is unclear whether enhanced charge separation or increased surface adsorption of organic pollutants to the nanocomposite surfaces is the dominant contributor. This knowledge gap was filled when we sought to enhance the surface contact of carbon with the bTiO 2 NFs by using graphene quantum dots (GQDs) hypothesizing that this would further enhance photocatalytic activity. The results showed a similar Rhodamine B (RhB) photodegradation rate between the optimal loadings of GQDs and RGO we reported previously. This allowed for further elucidation of the enhancement mechanism, where charge carrier separation enhancement at the photocatalyst surface is the dominant effect, whereas RhB adsorption does not make significant contribution. This significant insight enhances our understanding towards engineering highly efficient composite photocatalysts for organic pollutant removal in water. [ABSTRACT FROM AUTHOR]