Zipping assembly of an Fe₃O₄/carbon nanosheet composite as a high-performance supercapacitor electrode material

Reasonable structure design and component selection are crucial to electrochemical performance of supercapacitor electrode materials. Sodium alginate (SA), with a novel structure which can immobilize multivalent metal cations, was used to coordinate with Fe³⁺ to fabricate a carbon and Fe₃O₄ composite by an easy sol-gel method. Due to the chelation effect between SA and Fe³⁺, the carbon composite was constructed into a two-dimensional sheet-like structure, and the Fe₃O₄ particles were nanosize and homogenously distributed on the surface of the carbon nanosheet. As an electrode material for supercapacitors, the composite electrode showed a high specific capacitance of 550 F g^-1 at 1 A g^-1 in the potential range from -1.1 to 0 V, and excellent cycling stability of 89% retention after 2000 cycles. The enhanced electrochemical performance could be attributed to the abundant exposed active sites, producing high pseudocapacitance, to the two-dimensional nanosheet structure, facilitating electrolyte transport and to the strong attachment strength, improving cycle life. This environmentally-friendly design can provide an alternative to existing methods, resulting in the development of a two-dimensional carbon/metal oxide composite for energy storage devices.