Preparation and electrochemical properties of Fe/Fe 3 O 4 @r-GO composite nanocage with 3D hollow structure

Fe/Fe 3 O 4 @r-GO composite nanocages with a hollow porous heterostructure, which look like “flower cluster,” are prepared by a mild, simple, and flexible method, followed by a thermal treatment. Metal-organic framework Prussian blue (PB), used as a precursor of Fe 3 O 4 , possesses a special hollow porous morphology, which is able to shorten transmission path and relives the mechanical stress during charge/discharge cycles. Verified by SEM and TEM characterizations, the Fe/Fe 3 O 4 nanocage coated with uniform graphene sheets is achieved. Furthermore, XRD and XPS analysis combined with TEM results also prove that the composite is mainly composed of Fe, Fe 3 O 4 , and C. A series of electrochemical tests show that Fe/Fe 3 O 4 @r-GO composite electrodes exhibit a superior reversible capacity, rate capability, and cycling stability. The composite delivers a high reversible capability of 1200 mAh g −1 after 160 cycles at a current density of 100 mA g −1 . Especially, when the current density is increased to 1000 mA g −1 , the composite delivers a capacity of 455 mAh g −1 . Even at a current density of 2000 mA g −1 , a capacity of 355 mAh g −1 is retained. The outstanding electrochemical performances are mainly attributed to the integrity of hollow porous nanocube structure and doping of moderate graphene, which enables to promote the conductivity of electrode and build a continue network between Fe/Fe 3 O 4 nanocubes to further accelerate ion/electron migration rate and relieve mechanical stress during cycles.