Diameter‐Controlled Synthesis and Capacitive Performance of Mesoporous Dual‐Layer MnO₂ Nanotubes

Abstract Mesoporous dual‐layer MnO₂ nanotubes assembled from well‐aligned MnO₂ 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 KMnO₄ solution to coat the carbon nanofiber (CNF) template with MnO₂ nanosheets until the CNFs are consumed. The synthesized dual‐layer MnO₂ nanotubes are composed of an inner shell of packed MnO₂, and an outer shell of mesoporous sheet‐like MnO₂. Importantly, the dimensions of the MnO₂ nanotubes can be easily controlled by tuning parameters including CNF diameter and redox reaction temperature. The MnO₂ 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 MnO₂ nanostructures as promising electrode materials.