Electroactive ultra-thin rgo-enriched FeMoO₄ nanotubes and MnO₂ nanorods as electrodes for high-performance all-solid-state asymmetric supercapacitors

A flexible asymmetric supercapacitor (ASC) with high electrochemical performance was constructed using reduced graphene oxide (rGO)-wrapped redox-active metal oxide-based negative and positive electrodes. Thin layered rGO functionality on the positive and the negative electrode surfaces has promoted the feasible surface-active sites and enhances the electrochemical response with a wide operating voltage window. Herein we report the controlled growth of rGO-wrapped tubular FeMoO₄ nanofibers (NFs) via electrospinning followed by surface functionalization as a negative electrode. The tubular structure offers the ultrathin-layer decoration of rGO inside and outside of the tubular walls with uniform wrapping. The rGO-wrapped tubular FeMoO₄ NF electrode exhibited a high specific capacitance of 135.2 F g⁻¹ in Na₂SO₄ neutral electrolyte with an excellent rate capability and cycling stability (96.45% in 5000 cycles) at high current density. Meanwhile, the hydrothermally synthesized binder-free rGO/MnO₂ nanorods on carbon cloth (rGO-MnO₂@CC) were selected as cathode materials due to their high capacitance and high conductivity. Moreover, the ASC device was fabricated using rGO-wrapped FeMoO₄ on carbon cloth (rGO-FeMoO₄@CC) as the negative electrode and rGO-MnO₂@CC as the positive electrode (rGO-FeMoO₄@CC/rGO-MnO₂@CC). The rationally designed ASC device delivered an excellent energy density of 38.8 W h kg⁻¹ with a wide operating voltage window of 0.0–1.8 V. The hybrid ASC showed excellent cycling stability of 93.37% capacitance retention for 5000 cycles. Thus, the developed rGO-wrapped FeMoO₄ nanotubes and MnO₂ nanorods are promising hybrid electrode materials for the development of wide-potential ASCs with high energy and power density.