Templated synthesis of hierarchically porous manganese oxide with a crystalline nanorod framework and its high electrochemical performance

Abstract

A simple approach has been developed to synthesize hierarchically porous MnO₂ with a crystalline nanorod framework using mesoporous silica SBA-15 as a template, combined with in situ ion-exchange and surfactant-extraction processes without calcination. XRD, nitrogen adsorption analysis, FE-SEM, TEM, XPS and FT-IR techniques are used for the structural characterization. Such MnO₂ materials show a macro–mesoporous hierarchical nanostructure containing large pores of several hundreds of nanometres and mesopores of 3.76 nm with a high surface area of 142 m² g⁻¹. The mesoporous framework of this material is composed of aligned single crystalline MnO₂ nanorods of ca. 5–6 nm in diameter and ca. 20–25 nm in length. The electrochemical properties of the prepared MnO₂ material were studied using cyclic voltammetry in a mild aqueous electrolyte, which shows that such a MnO₂ nanostructure has a very high specific capacitance of 258 F g⁻¹ and a good reversibility due to its favorable phase and hierarchically porous structure as well as high surface area.