Synergy of structural engineering and dual-heteroatoms co-doping engineering boosting porous carbon toward efficient capacitive deionization

Abstract

Carbon materials have drawn increasing attention as promising electrode materials for capacitive deionization (CDI) on account of their excellent conductivity and high specific surface area. Nevertheless, the practical application of conventional carbon materials has been significantly impacted by the limited desalination capacity and the slow desalination rates. Herein, a series of hierarchical porous nitrogen and sulfur co-doped carbons (PNSC-X, X = 2.5, 5, and 7.5) were successfully prepared by combining the salt template method with the dual-heteroatoms co-doping method. Benefiting from the suitable degree of graphitization, the unique hierarchical porous structure (micropores-mesopores-macropores) and the synergistic effect between the nitrogen/sulfur (N/S) dual-dopant, the optimized electrode (PNSC-5) demonstrates an abundance of active sites and rapid reaction kinetics, which are conducive to remarkably improving the CDI performance. In consequence, as a promising electrode material for CDI, the PNSC-5 exhibits excellent desalination performance (39 mg g−1 under 1.2 V), outstanding salt adsorption rate (3.23 mg g−1 min−1) and eminent stability. The CDI device with PNSC-5 as electrode shows low energy consumption and high charging efficiency during the cycle test. Furthermore, the corresponding desalination mechanism is systematically expounded by various characterization methods. This work provides a new inspiration for exploiting high-performance carbon materials for efficient electrochemical desalination.