Morphological and structural evolution from akaganeite to hematite of nanorods monitored by ex situ synchrotron X-ray powder diffraction

Author(s)

Xavier, Allan Moreira ^[1] ; Ferreira, Fabio Furlan ^[1] ; Souza, Flavio Leandro ^[1]

Affiliation

^[1] Univ Fed ABC UFABC, Ctr Ciencias Nat & Humanas, BR-09210580 Santo Andre, SP - Brazil

• Document type: Journal article
• Source: RSC ADVANCES; v. 4, n. 34, p. 17753-17759, 2014.
• Web of Science Citations: 21

Abstract

Hematite (alpha-Fe2O3) is one of the most abundant minerals in nature and a thermodynamically-stable phase of iron oxide. One-dimensional (1D) hematite nanostructures have attracted, due to their fundamental characteristics such as excellent chemical stability in aqueous environments and low cost, considerable interest for a series of technical applications (as sensors, catalysis, lithium ion batteries and solar energy production and storage). Our study describes the phase evolution of iron oxide nanorods, from beta-FeOOH to alpha-Fe2O3, with increasing temperatures of thermal treatment monitored by ex situ synchrotron X-ray powder diffraction data. These data used in conjunction with the Rietveld method allowed us to infer the phase concentration, elucidate the influence of temperature on the unit cell parameters and preferred growth orientation of the nanorods. Only the use of synchrotron radiation allowed us to precisely identify and quantify the presence of a minor Fe2O3 phase, which has never before been reported for those systems. Moreover, the formation of one-dimensional nanorods was accompanied by using scanning and transmission electron microscopies (SEM and TEM). At the highest temperatures of thermal treatments the hematite nanorods exhibited changes that varied from a quasi-perfect crystal up to polycrystalline rods (> 500 degrees C). These findings were used for discussing and explaining recent results using this kind of nanostructure synthesized under hydrothermal conditions. Changes in the preferred orientation of the crystal faces of the rods could be responsible for a low photocatalytic performance reported by this strategy. (AU)

• FAPESP's process: 08/10537-3 - Study of crystalline pharmaceuticals polymorphs by X-ray powder diffraction and the Rietveld method
• Grantee: Fabio Furlan Ferreira
• Support type: Research Grants - Young Investigators Grants
• FAPESP's process: 11/19924-2 - Study and development of advanced novel materials: electronic, magnetic and nanostructured: an interdisciplinary approach
• Grantee: Carlos Rettori
• Support type: Research Projects - Thematic Grants
• FAPESP's process: 12/19926-8 - Metal oxide nanostructures applied in photoelectrochemical devices
• Grantee: Flavio Leandro de Souza
• Support type: Regular Research Grants