Nitrogen-doped graphene composites as efficient electrodes with enhanced capacitive deionization performance

Abstract

The desalination of seawater and brackish water is a desirable technique to address water scarcity today and in the uncertain future. Three-dimensional reduced graphene oxide–melamine formaldehyde composites (3D RGO–MF) were prepared by the carbonization of GO–MF composites, which were prepared through the electrostatic attraction between GO and MF nanoparticles. The obtained composites exhibited a hierarchical porous structure, with a specific surface area of 352 m² g⁻¹ and high degree of nitrogen doping of 10.86%. Thus, they had an enhanced specific capacity of 76.8 F g⁻¹, which is much larger than that of a pristine RGO electrode (23 F g⁻¹). With their enhanced electrochemical capacity, the as-prepared nitrogen-doped graphene composites were successfully employed as high performance electrodes for capacitive deionization. Their excellent electrochemical capacity with low inner resistance and high reversibility endows the 3D RGO–MF electrodes with an outstanding specific electrosorptive capacity of 21.93 mg g⁻¹ at a direct voltage of 2.0 V in NaCl aqueous solution. It was confirmed that the 3D RGO–MF electrode is quite appropriate for high-performance capacitive deionization.