A comprehensive study on two types of supercapacitor composite electrodes comprising MnO₂ and activated carbon nanofibers: Self-supporting membrane and ground powder

Manganese dioxide (MnO₂)@carbon composites have been attractively considered as electrode materials for supercapacitors (SCs) due to synergistic effects. This work systematically investigated the structure of MnO₂@carbon nanofiber (CNF) composite electrodes with the different forms of CNFs and the corresponding electrochemical performance of SCs. In brief, novel activated carbon nanofibers were first fabricated by electrospinning the hydroxyl-containing poly(amic acid) solution, and then the preferred CNF material was decorated by MnO₂ crystals in the form of self-supporting membrane and ground powders, respectively. The synthesis parameters were investigated and optimized based on the electrochemical performance of SCs. The results reveal that the powdered composite electrode exhibits a higher specific surface area of 501 m² g⁻¹ compared to the self-supporting membrane composite electrode under the same conditions, resulting in a promising specific capacity of 214.1 mAh g⁻¹ (770.8 F g⁻¹) in 6 M KOH solution at 0.5 A g⁻¹. In addition, the capacitance of the symmetrical SC device assembled by G-HMC-1:3–80 reaches 179.8 F g⁻¹, coupled with an energy density of 24.86 Wh kg⁻¹ at 230 W kg⁻¹ power density. This work provides valuable hints for designing SC composite electrode materials with outstanding performance.