Improved electrochemical properties of polypyrrole with cucurbit[6]uril via supramolecular interactions

Abstract

A supramolecular polymer was developed through the encapsulation of polypyrrole by cucurbit[6]uril (PPy@Q[6]), which was employed as the electrode material to improve the capacitor ability of conductive polypyrrole. In the optimized ratio of 2 : 1 (C_PPy : C_Q[6]), the capacitor properties of the supramolecular material were evaluated, and a high specific capacitance of 414 F g⁻¹ at 10 mV s⁻¹ was obtained, which was 3.1 times higher than that of pure polypyrrole (132 F g⁻¹). A comprehensive analysis suggested that the capacitance performances should be relevant to the component, surface area, and pore volume of the materials. The addition of 0.4 M Fe₂(SO₄)₃ into the electrolyte provided a surprising specific capacitance of 3530 F g⁻¹ on the cucurbituril-encapsulated polypyrrole electrode material, with a high energy density of 707 W h kg⁻¹ at a power density of 32 000 W kg⁻¹ and a current density of 8 A g⁻¹. The 81.6% capacitance retention maintained after 1000 cycles revealed the acceptable cycling capacity of the proposed supramolecular supercapacitor system, which demonstrated good performance even at a low temperature of −20 °C.