| Summary: | Hierarchical porous birnessite-MnO<sub>2</sub>-based nanostructure composite materials were prepared on a nickel foam substrate by a successive ionic layer adsorption and reaction method (SILAR). Following composition with reduced graphene oxide (rGO) and multiwall carbon nanotubes (MWCNTs), the as-obtained MnO<sub>2</sub>, MnO<sub>2</sub>/rGO and MnO<sub>2</sub>/rGO-MWCNT materials exhibited pore size distributions of 2–8 nm, 5–15 nm and 2–75 nm, respectively. For the MnO<sub>2</sub>/rGO-MWCNT material in particular, the addition of MWCNT and rGO enhanced the superb distribution of micropores, mesopores and macropores and greatly improved the electrochemical performance. The as-obtained MnO<sub>2</sub>/rGO-MWCNT/NF electrode showed a specific capacitance that reached as high as 416 F·g<sup>−1</sup> at 1 A·g<sup>−1</sup> in 1 M Na<sub>2</sub>SO<sub>4</sub> aqueous electrolyte and also an excellent rate capability and high cycling stability, with a capacitance retention of 85.6% after 10,000 cycles. Electrochemical impedance spectroscopy (EIS) analyses showed a low resistance charge transfer resistance for the as-prepared MnO<sub>2</sub>/rGO-MWCNT/NF nanostructures. Therefore, MnO<sub>2</sub>/rGO-MWCNT/NF composites were successfully synthesized and displayed enhanced electrochemical performance as potential electrode materials for supercapacitors.
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