Comparison of electrodes for high-performance electrochemical capacitors: Multi-layer MnO₂/Pt and composite MnO₂/Pt on carbon nanofibres

Four different types of electrodes for high-performance electrochemical capacitors were prepared using electrospinning method and/or impregnation methods: (1) conventional carbon nanofibres (CNF) supports, and CNFs decorated with (2) MnO₂ nanophases, (3) multi-layer MnO₂/Pt nanophases, and (4) composite MnO₂ and Pt nanophases. Their morphological, structural, chemical, and electrochemical properties were characterized using field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and galvanostatic charge/discharge measurements. Composite MnO₂ and Pt nanophases decorated on the CNFs exhibited superior capacitance (∼252.3 F/g at 10 mV/s), excellent capacitance retention (∼93.5% after 300 cycles), and high energy densities (13.53-18.06 Wh/kg). The enhanced electrochemical performances can be explained by the composite structure, presenting well-dispersed MnO₂ nanophases leading to high capacitance, and well-dispersed Pt nanophases leading to improved electrical conductivity.