Abstract
We developed a simple and mild one-step chemical method to produce novel and highly efficient alpha-Fe2O3/polypyrrole (PPy) photocatalysts. The formation of alpha-Fe2O3/PPy nanocomposites proceeds via a simultaneous gelation and polymerization process. The XRD results revealed that all the diffraction peaks can be perfectly indexed to the rhombohedral structure of alpha-Fe2O3 and the polymerization of Py did not change the crystalline phase of alpha-Fe2O3. TEM images show that Fe2O3 nanoparticles are quite uniform in shape and size and their particle sizes are decreased from 20 to 5 nm by increasing Py content from 5 to 25%. The lattice fringes (3.7 angstrom) are distinctly visible and revealed structurally uniform crystals of alpha-Fe2O3 without dislocation. Compared to pure Fe2O3, the newly developed nanocatalyst demonstrated a remarkable activity toward the photocatalytic degradation of methylene blue (MB) under UV irradiation, at ambient temperature. Complete degradation of MB was achieved after only 20 min in the presence of the optimum photocatalyst containing 10% Py. The effective photocatalytic performance is associated with the mesoporous structure and crystalline nature of the prepared nanocomposites. Additionally, such enhanced photocatalytic behavior was rationalized in terms of a synergetic effect for light absorption between alpha-Fe2O3 and PPy that eventually led to better charge separation and suppression of charge recombination. The photocatalyst could be removed from the reaction mixture and its recyclability remains effective after five cyclic runs. Proposed mechanism for the degradation of MB with the alpha-Fe2O3/PPy nanocatalyst under UV irradiation is also presented and thoroughly discussed. (C) 2014 Elsevier B.V. All rights reserved.