Oxygen vacancies enhancing capacitive properties of MnO2 nanorods for wearable asymmetric supercapacitors

In this work, we demonstrate an effective strategy to intrinsically improve the conductivity and capacitive performance of MnO2 by inducing oxygen vacancies. Oxygen-deficient MnO2 (denoted as MnO2-x) nanorods (NRs) prepared by a simple hydrogenation treatment deliver significantly improved electrochemical performance than the untreated MnO2 electrode, and yield a large areal capacitance of 0.22 F cm(-2) (449 F g(-1)) with excellent rate capability and cycling stability. Our results have shown that the concentration of oxygen vacancies has great influence on the capacitive performance of MnO2, and the moderate concentration of oxygen vacancies is necessary to achieve the optimized electrochemical activity. Moreover, a wearable asymmetric supercapacitor (ASC) based on the as-prepared MnO2-x NRs as cathode and reduced graphene oxide (denoted as RGO) as anode was fabricated and achieved a remarkable energy density of 0.25 mWh cm(-3). These findings may further broaden the application of MnO2-based materials and provide new insight into the oxygen nonstoichiometry in material electrochemistry. (C) 2014 Elsevier Ltd. All rights reserved.