Preparation of the cactus-like porous manganese oxide assisted with surfactant sodium dodecyl sulfate for supercapacitors

Highlights: • The cactus-like porous MnO₂ was synthesized by hydrothermal method assisted with SDS. • The MnO₂ exhibits a max specific capacitance of 187.8 F g⁻¹ (0.2 A g⁻¹, 1 M Na₂SO₄). • Excellent cycling stability: 92.9% capacitance retention after 1000 cycles. - Abstract: The cactus-like porous manganese dioxide (MnO₂) was synthesized by a simple hydrothermal method assisted with the surfactant sodium dodecyl sulfate (SDS). The morphology, composition, property of the prepared materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, Brunauer–Emmett–Teller (BET), Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM) measurements. It was found that the sample without surfactant was composed of nanoflakes which piling up together, whereas in the presence of the surfactant, the MnO₂ samples with the max specific surface of 321.9 m² g⁻¹ showed a porous cactus-like microstructure, consisted of uniform nanowires and porous nanoflakes. The electrochemical performances of the MnO₂ with and without surfactant were analyzed using Cyclic Voltammetry (CV), Electrochemical Impedance Spectrometry (EIS) and Galvanostatic Charge–Discharge (GCD) tests. The results showed that the MnO₂ assisted with 1 wt.% SDS displayed a higher specific capacitance of 187.8 F g⁻¹ at the current density of 0.2 A g⁻¹ compared with the MnO₂ without surfactant (134.8 F g⁻¹). And such MnO₂ samples with higher specific capacitance also afford an excellent cyclic stability with the capacity retention of approximately 92.9% after 1000 cycles in 1 M Na₂SO₄ solution at a current density of 1 A g⁻¹. The superior capacitive performance of the as-prepared materials could be attributed to its unique cactus-like porous structure, which provided good electronic conductivity, large specific surface area as well as fast electron and ion transport