Polyaminoanthraquinone with Modulated Iminium Electron Delocalization for Efficient Electrochemical Ammonium Removal

Abstract

The development of organic electrode materials for capacitive deionization (CDI) is hindered by limited redox-active sites and sluggish ion kinetics. Herein, a proton-acid-mediated interfacial polymerization strategy is proposed to fabricate nanoscale protonated polyaminoanthraquinone (PAAQ), mitigating these limitations. The protonated imine groups (-NH-) on the PAAQ chains to form -NH2+- polarons, induces extensive π-electron delocalization along the polymer backbone, which activates the latent redox sites and significantly boosts the electrochemical performance. In addition, leveraging the intrinsically low crystallinity of PAAQ, interfacial polymerization was coupled with agitation to disperse the aqueous oxidant template, yielding nanoparticles whose increased specific surface area increases the accessible active adsorption sites. The optimized PAAQ material delivers an exceptional NH4+ removal capacity of 120.43 mg g-1 and a high rate of 9.22 mg g-1 min-1, surpassing most reported organic electrodes. The material also shows outstanding cycling performance, maintaining 84.1 % of its original capacity after 50 CDI cycles. This work proposes a protonation-activated strategy that unlocks the latent redox sites of conjugated polymers and amplifies their electrochemical performance, providing valuable insights for the development of high-performance organic electrodes in CDI and related energy storage applications.