Abstract
Uniquely structured FeSex-reduced graphene oxide (rGO) composite powders, in which hollow FeSex nanoparticles are uniformly distributed throughout the rGO matrix, were prepared by spray pyrolysis applying the nanoscale Kirkendall diffusion process. Iron oxide-rGO composite powders were transformed into FeSex-rGO composite powders by a two-step post-treatment process. Metallic Fe nanocrystals formed during the first-step post-treatment process were transformed into hollow FeSex nanoparticles during the selenization process. The FeSex-rGO composite powders had mixed crystal structures of FeSe and FeSe2 phases. A rGO content of 33% was estimated from the TG analysis of the FeSex-rGO composite powders. The FeSex-rGO composite powders had superior sodium-ion storage properties compared to those of the Fe2O3-rGO composite powders with similar morphological characteristics. The discharge capacities of the FeSex- and Fe2O3-rGO composite powders for the 200th cycle at a constant current density of 0.3 A g−1 were 434 and 174 mA h g−1, respectively. The FeSex-rGO composite powders had a high discharge capacity of 311 mA h g−1 for the 1000th cycle at a high current density of 1 A g−1.
Highlights
Nanostructured materials of metal selenides, such as MoSex, NiSex, FeSex, SnSex, CuSex, and GeSex, prepared mainly by a liquid solution process, have been studied to improve their sodium-ion storage properties by improving the structural stability during repeated sodium charge and discharge processes[19,20,21,22,23]
Iron oxide-reduced graphene oxide (rGO) composite powders were transformed into FeSex-rGO composite powders, in which hollow FeSex nanoparticles were uniformly distributed throughout the rGO matrix, by a two-step post-treatment process
Metallic Fe nanocrystals were transformed into hollow FeSex nanoparticles during the selenization process by the well-known nanoscale Kirkendall diffusion process
Summary
Nanostructured materials of metal selenides, such as MoSex, NiSex, FeSex, SnSex, CuSex, and GeSex, prepared mainly by a liquid solution process, have been studied to improve their sodium-ion storage properties by improving the structural stability during repeated sodium charge and discharge processes[19,20,21,22,23]. Uniquely structured FeSex-rGO composite powders were prepared by spray pyrolysis and subsequent selenization. Iron oxide-rGO composite powders prepared by spray pyrolysis were transformed into FeSex-rGO composite powders, in which FeSex hollow nanoparticles were uniformly distributed throughout the rGO matrix. Structured metallic iron nanopowders were transformed into hollow FeSex nanoparticles by the well-known nanoscale Kirkendall diffusion process during the selenization process by applying H2Se gas. The electrochemical properties and Na-ion storage of the uniquely structured FeSex-rGO composite powders were compared with Fe2O3-rGO composite powders with similar morphological characteristics
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