Fe₂O₃/Porous Carbon Composite Derived from Oily Sludge Waste as an Advanced Anode Material for Supercapacitor...

It is urgent to improve the electrochemical performance of anode for supercapacitors. Herein, we successfully prepare Fe₂O₃/porous carbon composite materials (FPC) through hydrothermal strategies by using oily sludge waste. The hierarchical porous carbon (HPC) substrate and fine loading of Fe₂O₃ nanorods are all important for the electrochemical performance. The HPC substrate could not only promote the surface capacitance effect but also improve the utilization efficiency of Fe₂O₃ to enhance the pseudo-capacitance. The smaller and uniform Fe₂O₃ loading is also beneficial to optimize the pore structure of the electrode and enlarge the interface for faradaic reactions. The as-prepared FPC shows a high specific capacitance of 465 F g^-1 at 0.5 A g^-1, good rate capability of 66.5% retention at 20 A g^-1, and long cycling stability of 88.4% retention at 5 A g^-1 after 4000 cycles. In addition, an asymmetric supercapacitor device (ASC) constructed with FPC as the anode and MnO₂/porous carbon composite (MPC) as the cathode shows an excellent power density of 72.3 W h kg^-1 at the corresponding power density of 500 W kg^-1 with long-term cycling stability. Owing to the outstanding electrochemical characteristics and cycling performance, the associated materials' design concept from oily sludge waste has large potential in energy storage applications and environmental protection.