Ammonium decavanadate nanodots/reduced graphene oxide nanoribbon as “inorganic-organic” hybrid electrode for high potential aqueous symmetric supercapacitors

Abstract

The issue of relatively low operating potential window in aqueous supercapacitors is usually conquered by fabrication of asymmetric devices. To achieve the same in symmetric cells, electrodes with high electrochemical activity and wide working potential are needed. Herein, we report a strategy to extend the operating potential by utilizing ammonium decavanadate-holey reduced graphene oxide nanoribbons (rGONR-ADV) as hybrid electrode for supercapacitors. Besides high charge storage, use of redox-active ADV in hybrid provides a large overpotential towards water reduction, enabling wide potential window. The nano hybrids are synthesized at three different temperatures (140 °C, 160 °C, 180 °C) where rGONR-ADV 160 shows unsurpassed performance (1186 F g−1 @ 1 A g−1) owing to the optimized synergistic effect, highly electroactive surface area and improved ionic diffusion. The rGONR-ADV 160‖rGONR-ADV 160 cell displays high specific capacitance (406 F g−1 @ 0.5 A g−1), decent cycling stability (83% after 5000 cycles) with high energy/power density (120.2 Wh kg−1 and 1624.14 W kg−1). Interestingly, this device works well up to 1.5 V in 1 M H2SO4 i.e. well beyond thermodynamic limit of water decomposition. Present study illustrates the performance of polyoxometalates based hybrid electrode for high potential aqueous supercapacitors and energy density for practical applications.