Electron‐Delocalized Benzimidazole‐Linked Organic Electrode with Enhanced Redox Availability for High‐Performance Ammonium Capture via Capacitive Deionization

Abstract Capacitive deionization (CDI) employing pseudocapacitive electrodes is emerging as a promising electrochemical technology for contaminant removal and water purification. While organic materials hold significant potential as pseudocapacitive electrodes, their applications in CDI devices are hindered by inadequate redox availability and sluggish adsorption kinetics. Addressing these limitations, an innovative electron‐delocalized organic molecule, designated as NDDQ is developed, which incorporates a π‐conjugated benzimidazole‐linked framework with extensive electron delocalization and a reduced HOMO‐LUMO gap. This molecular architecture enables a high 81.8% utilization efficiency of its available C═O and C═N active sites, augmenting NH 4 + electrosorption capacity, as validated by in situ analyses and theoretical calculations. When implemented into a CDI device, the NDDQ electrode delivers a high NH 4 + adsorption capacity of 232 mg g −1 and an impressive rate of 7.66 mg g −1 min −1 , outperforming all existing CDI technologies (typically <150 mg g −1 ) while maintaining regeneration stability over 100 cycles. The CDI‐based electrochemical system can rapidly reduce NH 4 + concentration from an initial 500 to 7.8 mg L −1 within a mere 90‐min operation period, achieving a consistent volumetric treatment capacity in the range of 6.126–8.052 L m −2 h −1 , which offers an efficient, rapid, and sustainable solution for water treatment applications.