Bioinspired polydopamine supported on oxygen-functionalized carbon cloth as a high-performance 1.2 V aqueous symmetric metal-free supercapacitor

Abstract

The ongoing surge in demand for sustainable energy technologies with little to no environmental impacts calls for the exploration of advanced energy storage materials. Inspiration from nature is undoubtedly a promising approach to comply with environmental legislations. Herein, we describe a facile and green electrosynthesis approach to fabricate a polydopamine (PDA) nanofilm supported on oxygen-functionalized carbon cloth (FCC). The surface functionalization of carbon cloth facilitates the PDA nanofilm adhesion and endows the as-prepared PDA-FCC electrode with excellent flexibility, good electrical conductance (22.6 mS), and outstanding wettability to the aqueous electrolyte. Owing to these merits, the PDA-FCC electrode delivers a favorable capacitance of 626 F g⁻¹ at 1.0 A g⁻¹ (617 mF cm⁻² at 2.2 mA cm⁻², and 1296 mF cm⁻³ at 5.3 mA cm⁻³), in which the catechol, amine, and imine moieties of PDA are responsible for its excellent pseudocapacitive behavior. The symmetric all-solid-state flexible PDA-FCC||PDA-FCC device covers almost the entire thermodynamic stability window of aqueous electrolytes (1.2 V), delivers a high specific energy of 11.7 W h kg⁻¹, superb specific power of up to 6.4 kW kg⁻¹, and excellent flexibility along with outstanding cycling stability (81% retention of the initial capacitance after 10 000 cycles). These performance characteristics are in part due to the binder-free PDA biopolymer film that adopts the inherent texture of the carbon cloth, enabling the pores to play the role of temporary ion-buffering reservoirs that facilitate effective mass transport. This new approach to fabricate electrodes from green sources is considered an important step toward environmentally-benign energy storage technologies.