Fabrication of van der Waals Heterostructured FePSe₃/Carbon Hybrid Nanosheets for Sodium Storage with High Performance

Abstract

Iron phosphorus triselenide (FePSe₃) is attractive for energy applications owing to its interesting layered geometry, electronic structure, and physiochemical property, while it is limited in actual application because of a very long fabrication time of over 7 days. Herein, we report a new synthetic route to a high-quality sheetlike hybrid of iron phosphorus triselenide nanocrystals coated with graphitic carbon (FePSe₃/C) as an alternative kind of van der Waals heterostructures for the first time via a pyrolytic process at 600 °C from the precursors of ferrocene, red phosphorus, and selenium in a quartz tube with a significantly shortened reaction time of 24 h and even down to 30 min. Investigations demonstrated that the component phase of FePSe₃ in the layered FePSe₃/C hybrid nanosheets is the rhombohedral phase, and the hybrid nanosheets other than bulk crystals are about 15 nm in thickness. Acting as a cathode in fabricating half-cell sodium-ion batteries, the layered FePSe₃/C hybrid nanosheets exhibited remarkable performance. Typically, when current density was set as 50 mA g^-1, the hybrid nanosheet-assembled battery exhibited a capacity of 182.7 mA h g^-1 after performing over 50 cycles, and the nanosheet battery exhibited a capacity of 142 mA h g^-1 after performing for 200 cycling trials at 1 A g^-1 in the 0.8-2.2 V voltage window. Meanwhile, the layered FePSe₃/C hybrid nanosheets also exhibited very high rate capabilities at a relatively large current density in the present study, that is, 172 and 95 mA h g^-1 under typical performing conditions at 0.5 and 5 A g^-1, respectively.