Binder-free MoSe/MMSe composite and onion-derived activated carbon electrode materials for high-performance hybrid supercapacitors

Strategies and preparation of innovative novel electrode materials are essential for the supercapacitor (SC) industry to enhance their electrochemical performance and cycling stability. Recently, binary transition metal selenides have attracted considerable interest for SC applications owing to their significant theoretical capacitance, easily tunable nanostructures, low cost, environmental friendliness, and high electrical conductivity. In this report, we synthesized molybdenum selenide (Mo₁₈Se₂₄) and magnesium molybdenum selenide (Mg₃Mo₁₈Se₂₄) (MoSe/MMSe) composite electrode materials on Ni foam (NF) via a facile hydrothermal technique. The MoSe/MMSe composite electrode exhibited superior areal capacity/specific capacity values of 1154.4 μA h cm⁻²/250.9 mA h g⁻¹ compared to individual electrodes. In addition, the effects of the single metal selenides MoSe and MgSe on the electrochemical properties were analyzed. Meanwhile, onion-derived activated carbon-coated NF (OAC/NF) was used as the negative electrode and exhibited high specific capacitance. Finally, a MoSe/MMSe/NF (positive (+))//OAC/NF (negative (−)) hybrid SC (HSC) cell was assembled. The HSC cell delivered maximum energy density of 28.5 W h kg⁻¹, maximum power density of 2353.8 W kg⁻¹, and long-term cycling stability of 74.3% after 45 000 cycles. Furthermore, the real-time practical applications of the HSC cell were tested by powering various electronic components.