Feeling the power: robust supercapacitors from nanostructured conductive polymers fostered with Mn2+ and carbon dots

Abstract

Polyaniline (PANI) is considered one of the most preferred electrically conductive polymers (CPs), which is widely studied as an electrode material in designing next-generation energy storage devices due to their chemical stability, fast redox reactions between the polymer and the electrolytes, high electrical conductivity, excellent electrochemical performance, and low cost. However, the inferior stability of PANI limits its application. In this work, the benefit of carbon dots (CDots) as light-weight and spherical carbon-based electrodes and fillers that allow the maintenance of the nanostructure of PANI while easing the ionic transport was studied together with the effect of manganese(II) (Mn²⁺) doping on the overall capacitive properties of PANI. The integration of N-doped spherical, nanosized carbon dots (N-CDots) in the copolymerization of nanostructured PANI in the presence of varying concentrations of Mn²⁺ as a dopant synergistically improved the overall conductivity and specific surface area of the PANI-based electrode and showed surface double layer ion exchange. Pseudocapacitance mechanisms were observed when the dopant concentration was kept at a molar percentage of Mn²⁺ to aniline of 1, which displayed exceptionally high specific capacitances of up to 595 F g⁻¹. The asymmetric supercapacitor devices made with N-CDot and nanostructured hybrid electrodes could reveal the great potential in the development of cheap yet efficient battery-sized supercapacitor devices. In addition to extensive electrochemical performance, advanced EPR spectroscopy revealed detailed information regarding the defect structures of electrode materials in terms of understanding the conduction behavior of defect centers.