An electron-delocalized sp²-N hybridized organic electrode enables sustainable and high-efficiency electrochemical ammonium removal

Water scarcity emerges as a critical global challenge, with the purity of aquatic ecosystems intimately linked to ammonium concentrations. The removal of ammonium ions (NH₄ ⁺) is vital for mitigating ammonium contamination and promoting the sustainability of nitrogenous resources. Capacitive deionization (CDI) utilizing organic electrodes offers a promising electrochemical solution through a unique "ion coordination" mechanism; however, its efficacy is hindered by the presence of electrochemically inert units within the molecular framework for ion capture. Here, we introduce a rod-shaped DHPZ organic compound designed as a CDI electrode, distinguished by four imine rings and lone pair electrons in sp² orbitals. This configuration establishes a hybridized sp²-N framework that exhibits significant electron delocalization and an exceptionally low HOMO-LUMO gap of 1.18 eV, enhancing its affinity for fast, stable, and efficient NH₄ ⁺ capture. The DHPZ-based CDI device achieves an impressive NH₄ ⁺ removal capacity of 136.6 mg g^-1 at 1.2 V, a swift removal rate of 4.55 mg g^-1 min^-1, and outstanding regeneration (95.76% retention after 200 cycles), positioning it among the leading technologies in current CDI devices for NH₄ ⁺ adsorption. Furthermore, we have developed interconnected CDI devices for targeting NH₄ ⁺ removal from real wastewater, highlighting a sustainable and innovative approach to water remediation.