Abstract
A novel process for the preparation of aggregate-free metal oxide nanopowders with spherical (0D) and non-spherical (1D) hollow nanostructures was introduced. Carbon nanofibers embedded with iron selenide (FeSe) nanopowders with various nanostructures are prepared via the selenization of electrospun nanofibers. Ostwald ripening occurs during the selenization process, resulting in the formation of a FeSe-C composite nanofiber exhibiting a hierarchical structure. These nanofibers transform into aggregate-free hollow Fe2O3 powders via the complete oxidation of FeSe and combustion of carbon. Indeed, the zero- (0D) and one-dimensional (1D) FeSe nanocrystals transform into the hollow-structured Fe2O3 nanopowders via a nanoscale Kirkendall diffusion process, thus conserving their overall morphology. The discharge capacities for the 1000th cycle of the hollow-structured Fe2O3 nanopowders obtained from the FeSe-C composite nanofibers prepared at selenization temperatures of 500, 800, and 1000 °C at a current density of 1 A g−1 are 932, 767, and 544 mA h g−1, respectively; and their capacity retentions from the second cycle are 88, 92, and 78%, respectively. The high structural stabilities of these hollow Fe2O3 nanopowders during repeated lithium insertion/desertion processes result in superior lithium-ion storage performances.
Highlights
Nanoscale Kirkendall diffusion and Ostwald ripening processes, in which filled structures are transformed into hollow structures during heat treatment, have been applied in the preparation of hollow nanospheres (0D) in the absence of templates[21,22,23,24,25]
The hollow Fe2O3 nanopowders obtained from the FeSe-C composite nanofibers prepared at 500, 800, and 1000 °C are referred to as “Sel.500-Oxi.600,” “Sel.800-Oxi.600,” and “Sel.1000-Oxi.600,” respectively
The hollow Fe2O3 nanopowders prepared in this study showed superior lithium-ion storage performances compared to those of the other Fe2O3 materials prepared from various processes even at a high current density of 1.0 A g−1 during 1000 cycles
Summary
Nanoscale Kirkendall diffusion and Ostwald ripening processes, in which filled structures are transformed into hollow structures during heat treatment, have been applied in the preparation of hollow nanospheres (0D) in the absence of templates[21,22,23,24,25]. Metal nanospheres embedded within amorphous carbon and reduced graphene oxide were transformed into their corresponding oxide and selenide hollow nanospheres during the heat treatment stage of the nanoscale Kirkendall diffusion process[26,27,28,29]. We investigate the nanoscale Kirkendall diffusion process for the preparation of metal oxide nanopowders with hollow nanostructures of equal compositions but different dimensions (i.e., 0D and 1D). Carbon nanofibers embedded with metal selenide nanopowders exhibiting nanostructures of different dimensions were prepared via selenization of the electrospun nanofibers. A subsequent oxidation process under air produced the desired aggregate-free metal oxide nanopowders via the nanoscale Kirkendall diffusion process. The morphological and electrochemical properties of the iron oxide (Fe2O3) nanopowders, which were selected as the initial target material, were systematically studied
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
