Tailorable Dual-Redox Polymer with Molecular Flexibility for Enhanced Electrochemical Desalination and Water Purification
Jun Yang, Yueheng Tao, Cuijiao Zhao, Yu Cai, Peng Xiao, Minjie Shi
Abstract
The global water crisis demands sustainable desalination innovations, with capacitive deionization (CDI) emerging as an energy-efficient electrochemical alternative. While organic materials demonstrate pseudocapacitive ion capture through ion coordination for CDI electrodes, their effectiveness remains constrained by molecular chain packing and deficient redox-active sites. This work introduces a novel biocompatible dual-redox polymer (PNDBI) with high molecular flexibility to address these limitations. In-situ characterization and theoretical analyses unveil that the concerted interaction between C═O and C═N bifunctional groups enhances Na + capture. Concurrently, the polymer’s pliable backbone and narrow HOMO–LUMO gap ensure active site accessibility and facilitate electron mobility, which endow the PNDBI polymer with substantial pseudocapacitive capacitance and remarkable stability for 4Na + capture. The CDI device employing the PNDBI electrode demonstrates outstanding desalination performance, achieving a remarkable salt removal capacity of 112.1 mg g –1 and a rapid removal rate of 3.7 mg g –1 min –1 . Impressively, the CDI device exhibits excellent electrochemical regeneration stability, retaining 92.0% efficiency over 200 cycles, placing it among the state-of-the-art CDI devices reported. Beyond desalination, the PNDBI-based CDI device showcases significant multifunctionality, enabling efficient water purification through the removal of hard water ions and cationic dyes, thereby offering a versatile and sustainable solution for environmental remediation.