Visible Light Induced Photocatalytic Degradation Rhodamine B on One-Dimensional Iron Oxide Particles

Visible light (lambda > 420 nm) induced photocatalytic degradation of rhodamine B (RhB) in the presence of H2O2 by one-dimensional (1D) nanorods of goethite (alpha-FeOOH) and hematite (alpha-Fe2O3) has been investigated, and results were compared to those of micrometer-sized rods. alpha-FeOOH nanorods were self-assembled by oriented attachment of alpha-FeOOH primary nanoparticles, while porous alpha-Fe2O3 rods were prepared by thermal dehydration of respective alpha-FeOOH precursors via a topotactic transformation. The as-prepared samples were characterized by powder X-ray diffraction, micro-Raman spectroscopy, diffuse reflectance UV-visible spectroscopy, X-ray photoelectron spectroscopy, nitrogen adsorption-desorption, high-angle annular dark-field scanning transmission electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. Nanosized alpha-FeOOH and alpha-Fe2O3 particles appeared to be more active than microsized ones in terms of surface area normalized reaction rate, suggesting intrinsic photocatalytic properties of nanorods as compared to microrods in both alpha-FeOOH and alpha-Fe2O3. In addition, alpha-Fe2O3 nanorods exhibited the greatest activity among the as-prepared samples. The observed photocatalytic performance by iron oxide particles was attributed to the synergetic effects of the particle composition, size. porosity, and the variations of local structure. The results from current study will be potentially applicable to a range of naturally abundant semiconducting minerals and compounds (e.g., metal oxyhydroxides and metal oxides).