Abstract: Activated carbons have been widely employed as electrode materials of aqueous supercapacitors but the use of hazardous and corrosive activating agents challenges conventional activation procedures. Here, using a unique molten salt assisted self-activation technique, we have devised an eco-friendly and simple method to synthesize oxygen-rich hierarchical porous carbon with controllable architecture. Mixture of sodium carboxymethylcellulose and NaCl was pyrolyzed in one step, creating in-situ produced Na₂CO₃-NaCl molten salt that carried out the activation work. Na₂CO₃ acts as the activating agent in the reaction media of NaCl during the self-activation process. The obtained carbon exhibited a remarkable specific capacitance of 278 F g^-1 at 0.5 A g^-1 and retained 76% capacitance at 50 A g^-1 in a three-electrode cell. The fabricated aqueous coin cell achieved 81% capacitance retention at 50 A g^-1 and the highest specific energy density of 12.8 Wh kg^-1 at 214.6 W kg^-1, which are superior compared to the commercial activated carbon (64% at 50 A g^-1 and 8.4 Wh kg^-1 at 194.8 W kg^-1). Moreover, capacitance fading was not observed after 10000 cycles at 5 A g^-1. Considering the species diversity and low cost of self-salt polymers on the market, this strategy will expect to become a scalable approach for synthesizing high-performance capacitive carbons.

Key words: Molten salt, Self-template, Porous carbon, Controllable architecture, Aqueous supercapacitors