Superior Electrochemical Properties of Nanofibers Composed of Hollow CoFe₂O₄ Nanospheres Covered with Onion‐Like Graphitic Carbon

Abstract

Nanofibers composed of hollow CoFe2 O4 nanospheres covered with onion-like carbon are prepared by applying nanoscale Kirkendall diffusion to the electrospinning process. Amorphous carbon nanofibers embedded with CoFe2 @onion-like carbon nanospheres are prepared by reduction of the electrospun nanofibers. Oxidation of the CoFe2 -C nanofibers at 300 °C under a normal atmosphere produces porous nanofibers composed of hollow CoFe2 O4 nanospheres covered with onion-like carbon. CoFe2 nanocrystals are transformed into the hollow CoFe2 O4 nanospheres during oxidation through a well-known nanoscale Kirkendall diffusion process. The discharge capacities of the carbon-free CoFe2 O4 nanofibers composed of hollow nanospheres and the nanofibers composed of hollow CoFe2 O4 nanospheres covered with onion-like carbon are 340 and 930 mA h g(-1) , respectively, for the 1000th cycle at a current density of 1 A g(-1) . The nanofibers composed of hollow CoFe2 O4 nanospheres covered with onion-like carbon exhibit an excellent rate performance even in the absence of conductive materials.

Red Bean Pod Derived Heterostructure Carbon Decorated with Hollow Mixed Transition Metals as a Bifunctional Catalyst in Zn‐Air Batteries

“…Thus, such heterostructure of carbon is desirable to provide catalytically active, stable, and conductive support for the FeCo nanoparticles. Additionally, the formation of a hollow structure seen in TEM/STEM agrees with the prior observation on the oxidation‐driven nanoscale Kirkendall effect, where interfacial diffusion or mass transport occurs due to the differences in respective diffusion rates of the atomic species [26,38,39] . After nucleating on the N−C‐Red Bean carbon support (likely due to high surface energy associated with defects), [40] the nanoparticles phase separate into Fe‐oxide and Co‐oxide.…”

Intricate Hollow Structures: Controlled Synthesis and Applications in Energy Storage and Conversion

“…This simple synthetic strategy can be generally applied to the fabrication of bubble‐within‐fiber‐structured metal oxide nanofibers and metal‐oxide–carbon composite nanofibers. For example, bubble‐within‐bubble‐structured nanofibers composed of Sn@void@SnO/SnO 2 yolk–shell nanospheres, hollow SnO/SnO 2 nanospheres, hollow SnO 2 nanospheres, hollow NiO nanospheres, and hollow CoFe 2 O 4 @onion‐like graphitic carbon nanospheres have been prepared by using a similar approach.…”

Superior Electrochemical Properties of Composite Microspheres Consisting of Hollow Fe2O3 Nanospheres and Graphitic Carbon

“…Hong et al synthesized CoFe 2 O 4 -GC composite nanofibers showing excellent performances for LIBs. 16 The metallic nanocrystal intermediate acted as a nanocatalyst for transformation of AC into GC. The graphitic carbon survived during the oxidation process at 300 °C to form CoFe 2 O 4 -GC composite nanofibers.…”

“…Metal oxide–GC composite materials formed by an in situ graphitization process have also been studied. Hong et al synthesized CoFe 2 O 4 -GC composite nanofibers showing excellent performances for LIBs . The metallic nanocrystal intermediate acted as a nanocatalyst for transformation of AC into GC.…”