Temperature driven high-performance pseudocapacitor of carbon nano-onions supported urchin like structures of α-MnO2 nanorods

The promising pseudocapacitive charge storage insists the strategic design of three-dimensional architecture of nanostructures with extra-active redox sites on and/or near surface with high capacity of ionic insertion into the porous network of electrodes. Herein, we report the urchin like structure of alpha-MnO2 nanorods grown on carbon nano-onion (CNO) support via simple, cost-effective wet chemical method. The highly crystalline alpha-MnO2 nanorods with larger spinel sizes of 0.46 nm and 0.18 nm are characterized by SEM, TEM, XRD and Raman spectra. These spinel structures of alpha-MnO2 nanorods offers large cavity for ions insertion, which further improved by increasing temperature due to fast ionic mobility. The temperature driven increment of specific capacity from 202 Cg(-1) to 363 Cg(-1) at current density 0.3 Ag-1 is accomplished owing to the improved ionic conductivity, surface area and fast charge transfer. Further the 78% capacitance retention after 1000 cycles at 70 degrees C is realized, which is just 17% lower that the cyclic stability at 4 degrees C. It emphasizes an importance of three-dimensional design/architecture of electrode materials for the high-temperature pseudocapacitor applications. (C) 2020 Elsevier Ltd. All rights reserved.