Capacitive deionization of saline water using graphene nanosphere decorated N-doped layered mesoporous carbon frameworks

Abstract

Capacitive deionization (CDI) is an alternative water purification technology. Electrode materials are crucial for the deionization performance. However, the commonly used carbon electrode materials suffer from such issues as unsuitable porous structures, low conductivity and poor wettability, which limit their practical applications. Herein, we developed a cost-effective strategy to fabricate graphene nanosphere decorated N-doped layered mesoporous carbon frameworks as highly-efficient electrode materials for CDI applications. The effects of unique morphology, chemical composition and N-doping were clarified by conducting controlled experiments. The obtained materials exhibit a layered porous sheet-like structure decorated with graphene nanospheres, large surface area, regular micro and mesopores channels and high-level N-doping (up to 10.56 at%). The obtained CDI electrode delivers high specific capacitance, fine wettability, fast ion diffusion and excellent charge transfer ability. A high salt removal capacity (23.42 mg g⁻¹) with a high removal rate has been demonstrated at 1.2 V in a 500 mg L⁻¹ NaCl solution, indicating the synergistic effect of N-doping and special morphological structures on the improvement of CDI performance. Besides, the obtained CDI electrode also presents good deionization stability over multi-regeneration cycles and the desalination efficiency is up to 90%. The results presented in this work open a new avenue for the development of highly efficient desalination of saline water.