Green and all-carbon asymmetric supercapacitor based on polyaniline nanotubes and anthraquinone functionalized porous nitrogen-doped carbon nanotubes with high energy storage performance

Abstract

Aqueous electrolyte-based asymmetric supercapacitors (ASCs) are one of the hot topics in the field of energy storage due to their high ionic conductivity, their environmental friendliness and lower cost. However, most research work on ASCs has involved non-renewable metal oxides (or hydroxides). Herein, an all-carbon and high-energy asymmetric supercapacitor (ASC) is constructed using polyaniline nanotubes (PNTs) as the positive electrode and anthraquinone-functionalized porous nitrogen-doped carbon nanotubes (AQ@PNCNTs) as the negative electrode. The PNTs are prepared by a facile chemical self-assembly method, and further carbonization/activation of the PNT precursor results in the formation of the porous nitrogen-doped carbon nanotubes (PNCNTs). Under solvothermal conditions, PNCNTs serve as a conductive substrate to adsorb anthraquinone (AQ) molecules, which can contribute additional electrochemical capacitance to the overall capacitance of the electrode. The as-assembled AQ@PNCNTs//PNTs ASC exhibits excellent supercapacitive performances in 1 M H₂SO₄ aqueous electrolyte. In particular, the device can deliver an energy density as high as 32.7 W h kg⁻¹ at a power density of 700 W kg⁻¹. Even at the power density of 14.0 kW kg⁻¹, the energy density still remains at 20.2 W h kg⁻¹. This strategy provides a feasible way to construct green supercapacitors with high power density and energy density.