Carbon-Encapsulated Iron Oxide Nanoparticles in Self-Supporting Carbon Nanofiber for High-Performance Supercapacitor in Acid Electrolyte with Superior Stability
Wei Shi, Bin Hu, Hexuan Zhang, Jingjing Li, Jianmao Yang, Jianyun Liu
Abstract
Most of the iron oxides based electrode materials are unstable during long-term running, especially in an acid environment. Herein, a simple method was rationally designed to prepare an acid-resistant self-supporting iron oxide decorated carbon nanofiber (CNF). By one-pot electrospinning β-cyclodextrin (β-CD), iron acetylacetonate (Fe-ac), and polyacrylonitrile (PAN) solution, followed by carbonization, the carbon-encapsulated iron oxide composite carbon nanofiber (FeOx@C–CNF) was successfully synthesized with good flexibility and high stability in an acid solution. A uniform carbon protecting layer (about 3.5 nm) was formed around iron oxide particles during the pyrolysis of β-CD and Fe-ac. The obtained FeOx@C–CNFs exhibited a high specific capacitance of 341.3 F·g–1 at 0.5 A·g–1 in a 1 M H2SO4 electrolyte, much higher than that in KOH and Na2SO4 electrolyte solutions. The FeOx@C–CNF-based supercapacitor cell achieved a high energy density of 45.2 Wh·kg–1 at a power density of 0.71 kW·kg–1 and superior cycle stability (99.8% retention after 80 000 cycles). This carbon protecting layer around iron oxides endows FeOx@C–CNF superb stability in acidic solution. This strategy renders the carbon-protected FeOx as an electrode material for supercapacitor and other electrochemical devices in an acidic medium desirable and applicable.