Goethite hierarchical nanostructures: Glucose-assisted synthesis, chemical conversion into hematite with excellent photocatalytic properties

This paper describes an original and facile method for preparing goethite (α-FeOOH) hierarchical nanostructures (HNSs), as well as chemically converting into hematite (α-Fe2O3) under the preservation of α-FeOOH complex morphology. This method was based on a forced hydrolysis–oxidation of iron (II) salts in the presence of d-(+)-glucose as structure-directing agents, where control over the concentration and feeding way of d-(+)-glucose can considerably modulate the morphologies of the α-FeOOH HNSs from 1D unique architecture composed of arrayed nanoplates to 3D sea urchin-like superstructures. Moreover, using the sea urchin-like α-FeOOH nanostructures as precursors, the α-Fe2O3 HNSs with the same morphology but tailored crystallization and texture characteristics are robustly achieved only by adjusting annealing temperature. The formation mechanism of the α-FeOOH HNSs is proposed to be the synergistic effects of polar interaction and magnetic interaction between the building blocks of the nanoparticles. Due to the high BET specific surface area and favorable crystallization, the α-Fe2O3 HNSs obtained at 300 °C show excellent photocatalytic efficiency. Taking advantages of environmental benign biocompatibility, chemical stability and potential for mass generation, the α-Fe2O3 HNSs described in this work are believed to have a wide range of applications including catalysis, gas sensing.