Viswanathan, A.Nityananda Shetty, A.N.2026-02-032024Bulletin of Materials Science, 2024, 47, 4, pp. -2504707https://doi.org/10.1007/s12034-024-03303-3https://idr.nitk.ac.in/handle/123456789/20801Challenge of achieving high energy density (E) comparable with Li-ion batteries in supercapacitors, with low potential window offering aqueous electrolytes (1.2 V) has been overcome by using the electrode material composed of rGO 3.70%:PANI 51.86%:V<inf>2</inf>O<inf>5</inf> 33.33%:SnO<inf>2</inf> 11.11% (GPVS). The GPVS exhibited different extents of energy storage in the presence of 1 M sulphuric acid (H<inf>2</inf>SO<inf>4</inf>) and acidified supernatant liquid (ASL), a green electrolyte. Here, the ASL is the by-product, which is obtained as supernatant liquid after the synthesis of GPVS composites in an in situ synthetic method, and acidified using conc. H<inf>2</inf>SO<inf>4</inf>. The energy storage obtained in the presence of ASL is 38% higher than the energy storage obtained in the presence of H<inf>2</inf>SO<inf>4</inf>. The GPVS exhibited a remarkable feature of amelioration of energy storage with increase in CV cycles in the presence of H<inf>2</inf>SO<inf>4</inf>. The GPVS exhibited an extraordinary cyclic stability up to 41,300 cycles. The energy storage parameters achieved in the presence of H<inf>2</inf>SO<inf>4</inf> after 33,800 cycles are, a specific capacitance (C<inf>s</inf>) of 694.44 F g?1, an E of 138.88 W h kg?1 (comparable with E of Li-ion batteries) and a power density (P) of 2.1020 kW kg?1 at 1 A g?1. The energy storage parameters achieved in the presence of ASL are, a C<inf>s</inf> of 212.31 F g?1, an E of 42.46 W h kg?1 (comparable with E of Ni–Cd batteries) and a P of 3.1583 kW kg?1 at 2 A g?1. It is satisfying that all these high energy characters are achieved with the real two electrodes–supercapacitor cell step up. The green supercapacitors are made by using the by-product, which is obtained as supernatant liquid after the synthesis of GPVS as its electrolytes. © Indian Academy of Sciences 2024.Aluminum compoundsCapacitor storageCrystallitesGallium compoundsGraphene oxideIndium compoundsLead acid batteriesNickel cadmium batteriesPhosphatesPhotodissociationReduced Graphene OxideSolid electrolytesBy-product electrolyteEnergyEnergy densityEnergy storage parametersGreen electrolyteIon batteriesQuaternary nanocompositeReduced graphene oxidesSupercapacitanceSupernatant liquidsGermanium compounds