Facile crystal-structure-controlled synthesis of iron oxides for adsorbents and anode materials of lithium batteries

Abstract

Iron oxides exhibit excellent physicochemical properties as functional materials because of the diversity of crystal structure. Nano-sized iron oxides, including akaganite (β-FeOOH), maghemite (γ-Fe2O3), ferrihydrite (Fe5HO8∙4H2O) and hematite (α-Fe2O3), were prepared by a facile reflux treatment of iron powder in NaClO solution at 50 °C for 12 h. The crystal structures were controlled by adjusting the pH values of reaction systems. Akaganite, maghemite, ferrihydrite, and hematite were formed when pHs were adjusted to 2–4, 6, 8, and 10, respectively. They showed excellent adsorption performance for As(III), and the adsorption capacity was affected by crystal structure as well as specific surface area. The maximum adsorption capacity for akaganite, maghemite, ferrihydrite, and hematite reached 89.8, 79.1, 78.4, and 63.4 mg g−1, respectively. Hematite showed lithium storage capacity of 2043 mAh g−1 for the first cycle and then kept stable after twenty cycles at a current density of 100 mA g−1. The discharge specific capacity stabilized at 639 mAh g−1 after 100 cycles. The as-prepared iron oxides might be applied as potential adsorbents and anode materials for rechargeable lithium-ion battery.