A hierarchical porous MnO2-based electrode for electrochemical capacitor

A hierarchical porous MnO₂-based electrode was prepared and its electrochemical performance for electrochemical capacitors was investigated. In this work, porous MnO₂ film with pore size of 2?C3?nm in diameter was deposited on a three-dimensional porous current collector by cathodic electrodeposition associated with subsequent controlled heat treatment at 200°C for 2?h. Transmission electron microscopy and X-ray photoelectron spectroscopy showed that the heat treatment has a great effect on the formation of the porous structure of MnO₂ layer, and the disordered porous structure was caused by dehydration during the heat treatment. Cyclic voltammetry and galvanostatic charge?Cdischarge tests showed that both energy and power densities are enhanced due to the unique hierarchical porous structure. The electrode delivers a high specific capacitance of 385?F?g^?1 at a high current density of 5?A?g^?1 within a potential window of ?0.05????0.85?V, and also exhibits excellent rate capability and electrochemical stability.