Capacitive deionization of saline water using sandwich-like nitrogen-doped graphene composites via a self-assembling strategy

Capacitive deionization (CDI) is a promising water treatment technology that is proposed to solve water scarcity. In this study, sandwich-like nitrogen-doped graphene composites were designed and produced as high-performance CDI electrodes via a self-assembling strategy. Nitrogen-doped mesoporous carbon was directly created and assembled onto the graphene surface using dopamine hydrochloride as a carbon and nitrogen source and nano-silica as a hard template. This unique sandwich architecture provides a large accessible surface area and lower electronic resistivity, resulting from creating a plane-to-porous plane conducting network for increased adsorption sites and rapid electron transportation pathways. The specific surface area (918 m(2) g(-1)) and excellent wettability of sandwich-like nitrogen-doped graphene were further improved by incorporating nitrogen in surface texture and chemistry. The material was tested for the CDI application in NaCl aqueous solution. The sandwich-like nitrogen-doped graphene electrodes demonstrated a high salt adsorption capacity of up to 18.4 mg g(-1) in a 500 mg L-1 NaCl aqueous solution with a larger charge efficiency and an ideal recycling performance. These enhanced capacitive deionization performances of the sandwich-like nitrogen-doped graphene electrodes are attributed to the unique plane-to-porous plane internetworked architecture. This study offers a promising solution to develop high-performance electrode materials for removal of ions from saline water.