The design of nitrogen-doped core–shell-structured mesopore-dominant hierarchical porous carbon nanospheres for high-performance capacitive deionization

Abstract

Capacitive deionization has been extensively regarded as a promising technology for the desalination of brackish water. So far, the main bottleneck hindering CDI from large-scale applications is the low desalination capacity, which is closely associated with the unprogressive electrode material. Exploring advanced electrode materials is, therefore, the top priority of research efforts. In this work, through structural optimization and a polarization enhancement strategy, we have designed nitrogen-doped, core–shell-structured, mesopore-dominant hierarchical porous carbon nanospheres (N-CS-MD-HPCS) that deliver a superior electrosorption capacity of 28.10 mg g⁻¹ in 1000 mg L⁻¹ NaCl solution with a voltage of 1.2 V and is repeatable in desalination testing. The considerable significance of nitrogen-doping is revealed via multiple material measurements, which contribute to the improvement of physicochemical properties such as conductivity and wettability, the amelioration of pore structure and the morphological transformation from the yolk–shell to the core–shell structure. The boost in the capacitance behavior is partly attributed to the increment of the electrical-double-layer capacitance and partly associated with the generation of pseudopotential capacitance by introducing nitrogen according to the electrochemical measurements. Consequently, all results demonstrate that the acquired N-CS-MD-HPCS would be a remarkable material for realizing high desalination performance in CDI systems.