3D-ordered honeycomb-like nitrogen-doped micro–mesoporous carbon for brackish water desalination using capacitive deionization

Abstract

Capacitive deionization (CDI) is currently one of the most popular methods in the field of desalination and its performance highly depends on the electrode materials. It is vital to reasonably design the structure of the electrode material to obtain high CDI salt adsorption capacity. In this work, an ordered porous structure was constructed from ZIF-8 by a novel sacrifice template method to obtain 3D-ordered honeycomb-like nitrogen-doped micro–mesoporous carbon materials (3D HPC). Its unique double continuous wall and hole structure facilitated the penetration and transport of ions and also improved the specific surface area utilization to provide active sites. Moreover, in situ nitrogen-doped 3D HPC improved the electrosorption of salt ions through the increased conductivity of 3D HPC. The electrochemical behavior of 3D HPC electrodes was analyzed through a series of electrochemical tests such as cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. The results show that 3D HPC has the advantages of low internal resistance, high reversibility and good stability. Through batch electrosorption experiments, the desalination ability of 3D HPC in NaCl aqueous solution was evaluated. The 3D HPC-based CDI electrodes displayed a maximum salt adsorption capacity of 21.45 mg g⁻¹ in 500 mg L⁻¹ NaCl solution at 1.2 V. The outstanding desalination performance and cycle stability proved its bright prospects for application in CDI.