Enhancement of Zn-N-C charge-directed rearrangement for high-performance selectivity of heavy metal ions in capacitive deionization

The construction of heteroatom active sites in carbon materials is particularly important yet challenging for capacitive deionization (CDI). Nitrogen-doped carbon with ZnN moieties as adsorption sites were created using Zn-polytriazine by an in-situ pyrolysis process. The optimized carbon material exhibits selective ability toward Mn2+ ions, with an electrosorption capacity of ∼280 mg/g. Experimental results show that the dispersed ZnN species acted as effective active sites that maximized the electrosorption capacity through coordination, and in turn, enhanced the CDI process. Density functional theory simulations confirm that ZnN moieties are efficient adsorption sites that can significantly increase charge density and increase the binding energy of adsorbed ions, thus boosting the CDI process. This paper expands the theoretical basis for CDI-based heavy metal ion recovery.