▎ 摘　　要

Birnessite-type manganese dioxide (delta-MnO2) with hierarchical micro-/mesoporosity was synthesized via sacrificial graphene template approach under mild hydrothermal conditions for the first time. Graphene template was obtained by a surfactant (cetyltrimethylammonium bromide, CTAB) assisted liquid phase exfoliation (LPE) in water. A thin PEDOT:PSS (poly (3,4-ethylene dioxythiophene): poly (styrene sulfonate)) layer was applied to improve electrical conductivity and rate capability of MnO2. The MnO2 (535 F g(-1) at 1 A g(-1) and 45 F g(-1) at 10 A g(-1) ) and MnO2/PEDOT:PSS nanocomposite (550 F at 1 A g(-1) and 141 F g(-1) at 10 A g(-1) ) delivered electrochemical performances superior to their previously reported counterparts. An asymmetric supercapacitor, composed of MnO2 /PEDOT:PSS (positive) and Fe3O4/Carbon (negative) electrodes, provided a maximum specific energy of 18 Wh kg(-1) and a maximum specific power of 4.5 kW kg(-1) (Delta V= 2 V, 1M Na2SO4) with 85% capacitance retention after 1000 cycles. The graphene-templated MnO2 /PEDOT:PSS nanocomposite obtained by a simple and green approach promises for future energy storage applications with its remarkable capacitance, rate performance and cycling stability.