Vanadomanganate as a synergistic component in high-performance symmetric supercapacitor

Abstract

Supercapacitor devices fabricated from capacitive and battery-type hybrid electrodes have been projected as a promising energy storage system because of their ability to produce high specific power and energy simultaneously. In this work, we have demonstrated a facile method of impregnation of faradaic type manganese (III) polyoxovanadate, [MnV<inf>14</inf>O<inf>40</inf>]−6 on the high surface area substrate of activated carbon (AC) as well as graphene oxide (GO). Materials and electrochemical characterizations data confirm the successful incorporation of capacitive and faradaic type manganese (III) polyoxovanadate into the nanohybrid electrode material. Furthermore, the synergic effect between the carbonaceous nanostructures (AC/GO) and redox-active oxometalate (MnV<inf>14</inf>) provides a better pathway for ion transport to the interface resulting in enhancement of the conductivity, diffusion ability of the nanohybrid. Moreover, the battery-type MnV<inf>14</inf> clusters disperse in the micro/mesopores of AC, whereas the oxygen-containing functional groups in GO act as active sites for anchoring of MnV<inf>14</inf> clusters. Thus, the surface modification with MnV<inf>14</inf> clusters enhances the specific capacitance of nanohybrid with remarkable electrical and mechanical stability. The AC/MnV<inf>14</inf> nanohybrid exhibits an enhanced specific capacitance of 547 F g−1 with specific energy and power of 76 Wh kg−1 and 1600 W kg−1, respectively, at 0.8 A g−1 current density. Additionally, GO/MnV<inf>14</inf> shows a specific capacitance of 330 F g−1 with improved specific energy and power of 30 Wh kg−1 and 1276 W kg−1, respectively, at the same current density. Moreover, both the nanohybrids possess excellent cycle stability by retaining 92% (AC/MnV<inf>14</inf>) and 90.6% (GO/MnV<inf>14</inf>) of initial capacitance even after 5000 sweeping cycles. © 2021 Elsevier B.V.