Preparation and Phase Transition of FeOOH Nanorods: Strain Effects on Catalytic Water Oxidation

Gisang Park,§,a Yong-Il Kim,§,b Young Heon Kim,§,b Mira Park,c Kyu Yeon Jang,a Hyunjoon Songc, and Ki Min Nam, 2017
strained FeOOH nanorods
Image courtesy of Nanoscale

Abstract

The evolution of the phase and morphology of FeOOH nanorods prepared by a hydrothermal method is studied via X-ray diffraction (XRD) and in situ transmission electron microscopy. The FeOOH nanorod with a tetragonal structure (β-FeOOH) is gradually converted into a rhombohedral Fe2O3 nanorod by a simple thermal treatment. The existence of an intermediate FeOOH structure with high lattice strains during the phase transition is identified by Rietveld analysis using XRD. The electrochemical properties of the nanorods are investigated based on the crystal phases to elucidate their relative catalytic activities. The strained-FeOOH nanorods exhibited enhanced catalytic water oxidation activity and stability. Typically, the strained-FeOOH nanorods showed high electrochemical stability under neutral conditions, while tetragonal FeOOH nanorods under the same conditions showed rapid deactivation for water oxidation reaction.

Impact Statement

Evolution of β-FeOOH to Fe2O3 nanorods was investigated via in situ TEM and verified with ex-situ results. Additionally, catalytic properties were correlated to structural changes.