Exploring redox-active electrolytes to boost energy density of carbon-based supercapacitors

To boost supercapacitor (SC) energy density, we introduced redox-active molecules into an aqueous H₂SO₄ electrolyte. Using retrosynthetic analysis, we identified aminoquinones, specifically triaminochlorobenzoquinone (TACBQ), as promising candidates. Characterization via elemental analysis, Fourier Transform Infrared Spectrometer (FT-IR), nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS) confirmed structure of TACBQ. We incorporated varying TACBQ concentrations into 1 M H₂SO₄, finding that 2 mg mL^-1 optimized SC performance. Compared to 1 M H₂SO₄ alone, the 2 mg mL^-1 TACBQ system showed marked improvements: in a three-electrode setup, specific capacitance increased from 141 F g^-1 to 358 F g^-1 at 1 A g^-1. In a two-electrode quasi-solid-state device, capacitance rose from 27 F g^-1 to 35 F g^-1 at 1 A g^-1, the voltage window expanded from 1 V to 1.6 V, and energy density improved from 3.75 Wh kg^-1 to 12.43 Wh kg^-1 at 1000 W kg^-1. After 10,000 cycles at 10 A g^-1, the device retained 84 % capacity.