Reduced graphene oxide/polyaniline/vanadium pentoxide/stannic oxide quaternary nanocomposite, its high energy supercapacitance and green electrolyte

Challenge 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%:V₂O₅ 33.33%:SnO₂ 11.11% (GPVS). The GPVS exhibited different extents of energy storage in the presence of 1 M sulphuric acid (H₂SO₄) 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. H₂SO₄. The energy storage obtained in the presence of ASL is 38% higher than the energy storage obtained in the presence of H₂SO₄. The GPVS exhibited a remarkable feature of amelioration of energy storage with increase in CV cycles in the presence of H₂SO₄. The GPVS exhibited an extraordinary cyclic stability up to 41,300 cycles. The energy storage parameters achieved in the presence of H₂SO₄ after 33,800 cycles are, a specific capacitance (C_s) 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_s 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.