MOF-derived porous hollow α-Fe2O3 microboxes modified by silver nanoclusters for enhanced pseudocapacitive storage

Porous hollow α-Fe₂O₃ microboxes with high surface area are prepared by using metal-organic framework as precursor and self-template. To improve the conductivity of the derived α-Fe₂O₃ microboxes and thus enhance their capacitive storage and rate capability as effective electrode material, especially as anode material for supercapacitors, Ag nanoclusters are uniformly deposited on the surface of the α-Fe₂O₃ microboxes (α-Fe₂O₃@Ag microboxes) through a facile solution method. As pseudocapacitive material, the α-Fe₂O₃@Ag microbox electrode displays a high specific capacitance of 701 F g⁻¹ at a current density of 0.1 A g⁻¹, and remains 191 F g⁻¹ at a high current density of 10 A g⁻¹. Furthermore, the material shows 80% specific capacitance retention after 2000 charge-discharge cycles, and 72% retention after 10,000 cycles at a current density of 10 A g⁻¹. In addition, asymmetric supercapacitors are assembled with the α-Fe₂O₃@Ag as negative electrodes and commercial activated carbon as positive electrodes. A maximum specific capacitance of 123 F g⁻¹ and an energy density of 41.8 W h kg⁻¹ are demonstrated within a cell voltage of 1.6 V for the device.