Template-free synthesis of highly ordered 3D-hollow hierarchical Nb2O5 superstructures as an asymmetric supercapacitor by using inorganic electrolyte

Nb2O5 appeared as a promising candidate for a large number of applications. In the present work novel, 3D-hollow hierarchical Nb2O5 superstructures are prepared by self-organization of mesorods. The work emphasizes on the synthesis and detailed investigation of 3D-hollow hierarchical Nb2O5 superstructures, which are attained by two-step, template-free hydrothermal synthesis route. The obtained orthorhombic (T)-Nb2O5 superstructures have shown a high crystallinity, with a wide band gap of 3.1 eV. Among semiconductor oxides Nb2O5 with different morphologies are less explored due to complicated synthesis, growth and nucleation process. Thus, in general, factors involved for self-organized superstructures are not studied in detail. In this context, assembly of T-Nb2O5 superstructures is investigated in depth by applying SEM, TEM and UV/Vis absorption measurements. Based on the realized results a formation mechanism is proposed, which is further strengthened by the time and precursor dependent experiments. In addition, asymmetric supercapacitor properties of T-Nb2O5 superstructures are studied for the first time by using an inorganic electrolyte. The devised T-Nb2O5 superstructures have demonstrated excellent supercapacitor performance. The supercapacitor is operated at a wide potential window of 2.5 V in Na2SO4 electrolyte and exhibited high power density (650 W/Kg), energy density (86 Wh/Kg) with good cycling capability. (C) 2016 Elsevier Ltd. All rights reserved.