Probing host-dopant interactions in conducting polymers for improved performance of electrochemical deionization

The escalating global scarcity of water resources has amplified the need to develop efficient desalination methods. Electrochemical deionization (ECDI) has emerged as a promising method to solve this pressing issue. Among various ECDI systems, conducting polymers have showcased remarkable potential for electrode materials due to their facile large-scale synthesis and precise control over the removal of anions and cations. We scrutinized the impact of diverse dopant sizes on the intrinsic properties of polypyrrole (PPy) chains, leading to the development of a high-performance ECDI system. Incorporation of para-substituted groups featuring elongated carbon chains, such as dodecylbenzene sulfonate (DBS), the PPy-DBS-1//PPy-ClO4 configuration attained a salt-adsorption capacity (SAC) of 61.7 mg g-1 in NaCl solution (10 mM) and sustained low energy consumption (0.22 kW h/kg-NaCl). Our findings suggest that the size and type of dopant have key roles in enhancing the ion transport and mobility of charge carriers within the conducting-polymer framework. Moreover, fine-tuning the doping ratio enhanced the cation-capture ability of electrodes and sustained their cycling stability. Overall, these insights into the symbiotic relationship between dopants and PPy framework within an ECDI system provide guidance framework for augmenting the electrode performance of conducting polymers with dopants, and expanding the potential applications of conducting polymers in ECDI. A synergistic interaction between dopants and polypyrrole enhanced ion-transport capabilities and charge-carrier mobility, thereby contributing to high-performance ECDI systems.