Synthesis of hexagonal-symmetry α-iron oxyhydroxide crystals using reduced graphene oxide as a surfactant and their Li storage properties

Microcrystalline α-iron oxyhydroxide/reduced graphene oxide (α-FeOOH/rGO) samples have been successfully synthesized by a facile hydrothermal process. The α-FeOOH/rGO samples are either hexagonal disks with a diameter of ∼1 μm and a thickness of 300 nm or hexapods with a diameter of ∼2 μm and a thickness of 700 nm, while only bulk and aggregated FeOOH is observed without the addition of graphene oxide sheets. The size and shape of the α-FeOOH depend on the reaction time, concentration of Fe³⁺, and the addition of graphene oxide. The growth of the hexagonal disks and hexapods is mainly due to a series of phase and structural transformations. The α-FeOOH/rGO displays superior anode performance with a high reversible specific capacity of 569 mA h g^-1 at the 50 ^th cycle.