Synthesis of Bi2O3/Cu2O nanoflowers by hydrothermal method and its photocatalytic activity enhancement under simulated sunlight

Bi2O3/Cu2O nanoflower composites are successfully synthesized via simple hydrothermal method at low temperature. The effect of calcination on their properties has been explored as well. The prepared samples have been characterized by X-ray diffraction, scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy. The photocatalytic activity is tested by rhodamine-B degradation under simulated sunlight and the mechanism for the activity enhancement compared with pure Bi2O3 is investigated in detail. The results show that the prepared samples are monoclinic and have high crystallinity. After annealing, delta-Bi2O3 phase is converted to Bi2O3 and Bi2O3/Cu2O composite is formed. Additionally, the band gap of the prepared samples decreases from 3.55 to 2.71 eV. The photocatalytic activities of the flower-like samples are in the order of Bi2O3/Cu2O > delta-Bi2O3 > Bi2O3. The synergistic effect of the crystal and electronic structures on the photocatalytic activity of Bi2O3/Cu2O composite is proposed. The higher photocatalytic activity of the samples can be closely related to their smaller band gap, higher crystallinity and unique tunnel structure. Substantially, the activity enhancement is also attributed to the special electron structure of the composite, which leads to the important role of photogenerated electron transfer. (C) 2013 Elsevier B.V. All rights reserved.