Synthesis of MnNb2O6 with hierarchical structure as a novel electrode material for high-performance supercapacitors

Columbite compound MnNb2O6, consisted the layers with slightly distorted hexagonal-closed-packed oxygen sublattice, has abundant reaction sites whereby the interlayered ions can occur faradic reaction to enhance the charge storage capability. Here, we first report three-dimensional nanostructure of MnNb2O6 as electrode materials for electrochemical pseudocapacitor synthesized through hydrothermal method. The crystal morphologies of MnNb2O6 show an evolution with the hydrothermal time, from primary spindle-like particles grown for 12 h and undergrown star-like crystals for 18 h, to hierarchical star-like crystals for 1 day and overgrown crystals for 3 days. MNO-1d sample synthesized for 1 day possesses ordered six-leaf nanostructure composed of hierarchical nano-sheets (thickness-30 nm). To explore its potential applications for supercapacitor, MnNb2O6 sample as electrode material is characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge measurements. MNO-1d demonstrates an outstanding specific capacitance of 350 F g(-1) and rate capability with a high capacitance retention of-90% of its initial capacitance after 10000 cycles at a high current density of 10 A g(-1). (C) 2018 Elsevier B.V. All rights reserved.