Anchoring mesoporous Fe3O4 nanospheres onto N-doped carbon nanotubes toward high-performance composite electrodes for supercapacitors

Fe-based oxide electrodes for practical applications in supercapacitors (SCs) suffer from low conductivity and poor structural stability. To settle these issues, we report on the design and synthesis of Fe3O4/carbon nanocomposites via firmly anchoring mesoporous Fe3O4 nanospheres onto N-doped carbon nanotubes (N-CNTs) via C–O–Fe bonds. Mesoporous Fe3O4 nanospheres are featured by rich electroactive sites and short ion diffusion pathways. The N-CNTs, on the other hand, serve as the scaffolds, which not only provide conductive networks but also suppress the accumulation between mesoporous Fe3O4 nanospheres as well as alleviate volume changes during charge/discharge cycles. Accordingly, the constructed Fe3O4/N-CNTs nanocomposite electrode demonstrates improved specific capacity values of up to 314 C g−1 at 1 A g−1, with 92% retention of the initial capacity after 5000 cycles at 10 A g−1. In addition, the assembled Fe3O4/N-CNTs//active carbon (AC) asymmetric supercapacitor (ASC) device possesses an energy density of 25.3 Wh kg−1, suggesting that the prepared Fe3O4/N-CNTs nanocomposites are promising electrode materials for use in SCs.