Biosourced quinones for high-performance environmentally benign electrochemical capacitors via interface engineering

Biosourced and biodegradable organic electrode materials respond to the need for sustainable storage of renewable energy. Here, we report on electrochemical capacitors based on electrodes made up of quinones, such as Sepia melanin and catechin/tannic acid (Ctn/TA), solution-deposited on carbon paper engineered to create high-performance interfaces. Sepia melanin and Ctn/TA on TCP electrodes exhibit a capacitance as high as 1355 mF cm⁻² (452 F g⁻¹) and 898 mF cm⁻² (300 F g⁻¹), respectively. Sepia melanin and Ctn/TA symmetric electrochemical capacitors operating in aqueous electrolytes exhibit up to 100% capacitance retention and 100% coulombic efficiency over 50,000 and 10,000 cycles at 150 mA cm⁻² (10 A g⁻¹), respectively. Maximum power densities as high as 1274 mW cm⁻² (46 kW kg⁻¹) and 727 mW cm⁻² (26 kW kg⁻¹) with maximum energy densities of 0.56 mWh cm⁻² (20 Wh kg⁻¹) and 0.65 mWh cm⁻² (23 Wh kg⁻¹) are obtained for Sepia melanin and Ctn/TA.