Rapid photodegradation mechanism enabled by broad-spectrum absorbing black anatase and reduced graphene oxide nanocomposites

• Black TiO 2 can utilize abundant visible–NIR for photocatalysis. • Reduced graphene oxide (RGO) enhances charge separation and photo-efficiency. • Black TiO 2 /RGO is kinetically superior for broad spectrum photocatalysis. • Superoxide radicals are the primary ROS in black TiO 2 /RGO catalysis. Black titanium dioxide (bTiO 2 ) is a new narrow bandgap photocatalyst that exploits the full solar spectrum with applications in sustainable environmental remediation and energy harvesting. Composition of bTiO 2 with 5 wt% of reduced graphene oxide (RGO) increases the Rhodamine B photodegradation rate by 3.2 and 12.2-fold relative to bTiO 2 alone and anatase, respectively, under simulated sunlight. Broad spectrum utilization and charge carrier separation enabled by bTiO 2 and RGO, respectively, resulted in rapid generation of superoxide radial anions that, though less energetic than hydroxyl radicals generated by UV-excited anatase, are sufficient for degrading all but the most recalcitrant contaminants. The kinetic advantages of RGO/bTiO 2 composites enable highly efficient removal of organic pollutants by exploiting the less energetic, but abundant, Vis-NIR spectrum.