Solvent-polarity-induced hematite (alpha-Fe2O3) nanostructures for lithium-ion battery and photoelectrochemical applications

Abstract

A range of morphology-controlled hematite superstructures, including two-dimensional sheet assembly, microspheres with a vein-like network, hollow urchin with tapered nanorods, and flowers with porous branch-like structures, were obtained from different solvents via the solvothermal approach. The results showed that the variation of the solvent from protic to aprotic facilitated morphological modifications, with the solvent playing a key role in determining the overall architecture of the oxide particles under different polar conditions. A porous microsphere grown from water solvent delivered a reversible capacity of 880 mAh g(-1) over 60 cycles at 200 mA g(-1) with good rate stability. Here, the bicontinuous nanoporous structure, with well-developed mesoporosity in the microsphere, reduced the severity of volume changes during the cycling process and stabilized passivation layer growth. The hematite nanostructure grown from water/dimethylformamide solvent exhibited the highest photocurrent density of 190 mA/cm(-2) vs. Ag/AgCl, which was attributed to the rapid transport of charge carriers in the porous nanostructure. Thus, solvent-mediated synthesis can be used to prepare a range of hematite porous nanostructures for use as an anode in lithium-ion batteries and as a photoanode in photoelectrochemical cells, as well as for water splitting, gas sensors, and catalytic applications. (C) 2017 Elsevier Ltd. All rights reserved.