Diameter‐Controlled Synthesis and Capacitive Performance of Mesoporous Dual‐Layer MnO 2 Nanotubes

Mesoporous dual‐layer MnO 2 nanotubes assembled from well‐aligned MnO 2 nanosheets are synthesized via a facile and efficient sacrificial template method. To begin with, the self‐standing carbon nanofibrous membranes are prepared via electrospinning and high‐temperature carbonization, followed by an in situ redox reaction in KMnO 4 solution to coat the carbon nanofiber (CNF) template with MnO 2 nanosheets until the CNFs are consumed. The synthesized dual‐layer MnO 2 nanotubes are composed of an inner shell of packed MnO 2 , and an outer shell of mesoporous sheet‐like MnO 2 . Importantly, the dimensions of the MnO 2 nanotubes can be easily controlled by tuning parameters including CNF diameter and redox reaction temperature. The MnO 2 nanotube electrode thus prepared manifests excellent cycling stability with a specific capacitance of 231 F g −1 and an areal capacitance of 309 mF cm −2 for supercapacitors. This approach opens up a new way for designing MnO 2 nanostructures as promising electrode materials.