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

Black titanium dioxide (bTiO2) is a new narrow bandgap photocatalyst that exploits the full solar spectrum with applications in sustainable environmental remediation and energy harvesting. Composition of bTiO2 with 5 wt% of reduced graphene oxide (RGO) increases the Rhodamine B photodegradation rate by 3.2 and 12.2-fold relative to bTiO2 alone and anatase, respectively, under simulated sunlight. Broad spectrum utilization and charge carrier separation enabled by bTiO2 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/bTiO2 composites enable highly efficient removal of organic pollutants by exploiting the less energetic, but abundant, Vis-NIR spectrum.