Facile preparation of black Nb4+ self-doped K4Nb6O17 microspheres with high solar absorption and enhanced photocatalytic activity.

Black Nb(4+) self-doped K4Nb6O17 microspheres were prepared for the first time through a facile UV light photoreduction method. By the introduction of Nb(4+), the defective K4Nb6O17 can harvest the full spectrum of visible light as well as near-infrared light. The black K4Nb6O17 microspheres showed improved visible-light-driven photocatalytic H2 production activity. Importantly, the present synthetic approach is also applicable to the preparation of other Nb(4+) self-doped niobates.