Pb²⁺—N Bonding Chemistry: Recycling of Polyaniline–Pb Nanocrystals Waste for Generating High-Performance Supercapacitor Electrodes

Abstract

Understanding of Pb—N bonding chemistry is not only fundamentally important in the view of relativistic inert-pair effect but also is important for therapeutic as well as environmental applications. In the present study, an unusual reactivity of N-containing π-conjugated polyaniline emeraldine base (EB) toward aqueous Pb 2+ ions has been identified. In the course of sequestering Pb 2+ ions by EB, cuboid-shaped nanocrystals were isolated. Synchrotron-based X-ray absorption near-edge structure and extended X-ray absorption fine structure techniques were employed to understand Pb–N bonding chemistry in EB-Pb nanocrystals. The adopted methodology of slow exposure of HCl vapor to EB-Pb nanomaterial facilitated the isolation of polyaniline emeraldine-salt (ES) with unique morphological patterns, porosity and electrical conductivity. The electrochemical device based on recycled ES showed high-capacitance value (∼606 F/g @1 A/g and ∼663 F/g @10 mV/s), high-energy density (∼14.8 Wh/kg at power density of ∼663 W/kg) and excellent-cycling stability (only ∼15% degradation after 1100 continued cycles at current density of 5 A/g). Notably, ES materials prepared directly from EB and upon exposing HNO 3 vapor exhibited greatly inferior device performance.