Electrophoretic fabrication and pseudocapacitive properties of graphene/manganese oxide/carbon nanotube nanocomposites

Hybrid nanocomposites provided a synergistic improvement on electrochemical performance and stability for pseudocapacitor. Designed graphene/carbon nanotubes (CNTs)/MnO₂ nanocomposites with CNTs electrode (in short, GMC + C) with highly nanoporous framework surface structure are fabricated by a modified electrophoretic deposition (EPD) method. Scanning electron microscopy and transmission electron microscopy analysis demonstrate that the flake-like MnO₂ thickness (about less than 10 nm) and uniformly distributed on the porous graphene/CNTs framework. X-ray diffraction shows the formation of birnessite-type MnO₂. Pseudocapacitances of the GMC + C electrode calculated by cyclic voltammetry having different scan rates of 5, 20, 50, 100, and 300 mV s^-1 exhibit high specific capacitances of 481, 436, 413, 398, and 372 F g^-1, respectively. Sodium ion diffusion coefficients of the GMC + C electrode show a higher intercalation value of 3.647 × 10^-8 cm² s^-1 and deintercalation value of 2.899 × 10^-8 cm² s^-1 using chronoamperometry. Moreover, the GMC + C electrode maintains a high specific capacitance of 346 F g^-1, and is about 83.3% of the initial capacitance after 15,000 charge/discharge cycles. The designed hybrid GMC + C nanocomposites pseudocapacitor electrode using EPD route with the high specific capacitance, fast reaction rate, and high stability, exhibits high potential for practical applications.