Facile synthesis of urchin-like hierarchical Nb2O5 nanospheres with enhanced visible light photocatalytic activity

Urchin-like Nb2O5 nanospheres having an overall diameter of 300-500 nm and containing well-ordered independent nanorods with a diameter of 5-10 nm and a length of about 100 nm were synthesized using a facile and template-free method. X-ray diffraction (XRD) and field emission scanning electron microscopy results showed that the morphology of Nb2O5 can be regulated by adjusting the ratio of water/ethanol in the starting solution. High-resolution transmission electron microscopy images indicated that the nanorods grew along the [001] zone direction. Then, the formation mechanism of the urchin-like Nb2O5 was investigated through XRD and transmission electron microscopy. The urchin-like Nb2O5-1-1 nanospheres obtained at a water/ethanol ratio of 1/1 exhibited the highest photocatalytic activity for the degradation of Rhodamine B (RhB) under visible light, showing about 4.4 times of the activity of Nb2O5-1-4 and about 4.1 times of that of TiO2 (P25). The degradation mechanism of RhB on the urchin-like Nb2O5 nanospheres was demonstrated by terephthalic acid photoluminescence technique and photoelectrochemical measurements. The results revealed that the dye-sensitized photodegradation process was the main mechanism of RhB degradation under visible light irradiation.