Freestanding N-doped graphene membrane electrode with interconnected porous architecture for efficient capacitive deionization

Abstract

Freestanding electrodes without the influences of additives have been considered as a kind of ideal electrode structure in the field of capacitive deionization (CDI). However, subjected to conductivity, available surface areas, hydrophilicity and etc., effectively construction of freestanding CDI electrodes with high water desalination performance still face great challenges. Herein, we will demonstrate a unique N-doped graphene freestanding porous membrane electrode with excellent water desalination performance. The preparation process mainly includes the assembly of core-shell composites with incomplete graphene oxide shells into bulk membranes using compression molding method and the heat-treatment under NH3 atmosphere. These reserved spherical shells with loopholes and N-doping make up the freestanding membrane electrodes with network porous architecture. The interconnected sphere shells efficiently improve the availability of surface and pores in the monolithic assembly, while the doping of nitrogen element further enhances the accessibility of graphene-based surface by the electrolyte. As a result, such graphene carbonaceous freestanding electrodes exhibit excellent water desalination performance with a high CDI capacity of about 21.8 mg/g in NaCl solution. Moreover, such freestanding membrane electrodes also possess good desalination abilities towards some other salts such as KCl, CaCl2 and MgCl2, suggesting their potential applications in complex brine solution.