Bimetallic ions modified 2-methylimidazolium functionalized polypyrrole/graphene oxide for the improved supercapacitor

Thin films with two-dimensional (2D) nanostructures possess good environmental stability, thinner thickness and large surface area, which are widely used as a promising modified electrode material in the field of energy storage, supercapacitors, electrochemical sensors and biosensors. Herein, unique bimetallic ions modified polypyrrole/graphene oxide (PPy/GO) nanosheets, including Co²⁺-Zr⁴⁺/(2-MeIm)_x@PPy/GO and Co²⁺-Ruⁿ⁺/(2-MeIm)_x@PPy/GO (n = 0, 4), are prepared by using 2-methylimidazolium (2-MeIm) as the linkers between PPy/GO and metal ions. The obtained electrodes constructed by Co²⁺-Ruⁿ⁺/(2-MeIm)_x@PPy/GO (n = 0, 4) and Co²⁺-Zr⁴⁺/(2-MeIm)_x@PPy/GO exhibit improved capacitor electrochemical properties due to the reversible redox reaction, the large specific surface area and the high theoretical specific capacitance value of the metal ions compared to the unmodified PPy/GO. Especially, the specific capacitance value of Co²⁺-Ruⁿ⁺/(2-MeIm)_x@PPy/GO (n = 0, 4) electrode reaches 321.78 F g⁻¹ at a current density of 1 A g⁻¹ and the capacitance retention rate is achieved to 100% in the long cycle charge/discharge test after 10 000 cycles (10 A g⁻¹). It will provide a practical experience for the design and preparation of supercapacitors based on bimetallic ions modified PPy/GO.