Post-Regulation of Nitrogen Configurations in Nitrogen-Doped Carbon Electrodes for Enhanced Capacitive Deionization

Nitrogen doping is widely used to enhance the electrochemical performance of carbon materials, yet its effectiveness is often limited by electrochemically inactive or inaccessible nitrogen configurations. Here, we develop a coupling-agent-mediated amidation strategy to postregulate nitrogen-doped carbon, selectively enriching amino nitrogen while tailoring the distribution of pyridinic, pyrrolic, and graphitic nitrogen. The introduced -NH2 groups elevate the surface charge density, which is favorable for ion adsorption and diffusion. Density functional theory calculations, together with electrochemical kinetic analyses, reveal that edge-type nitrogen, particularly the lone electron pairs on amino nitrogen, can strongly interact with salt ions, resulting in effective electrical-double-layer compression and shortened ion diffusion distance. Consequently, the optimized electrode achieves a specific adsorption capacity of 70.3 mgNaCl g-1 and a time-averaged adsorption rate of 2.3 mgNaCl g-1 min-1 in 1000 mg L-1 NaCl solution at a cell voltage of 1.6 V. Its electrosorption behavior toward monovalent and divalent cations is also systematically evaluated in synthetic brines and actual industrial recirculating cooling water. This study provides a facile, powerful strategy to rationally design carbon electrodes for high-performance electrochemical ion storage and separation applications.