Mesopore Dominated Capacitive Deionization of N-Doped Hierarchically Porous Carbon for Water Purification

Under the global shortage of freshwater resources, capacitive deionization (CDI) has attracted widespread attention as an efficient and energy-saving water purification technology. Herein, N-doped hierarchically porous carbons (NPCs) with excellent specific capacitance (194.75 F g-1), large specific surface area (1556.9 m2 g-1), high mesoporous content (51.27%), and fast ion transport capability were prepared by the pyrolysis of polyacrylonitrile using nano-silica and ZnCl2 as pore-making agents. As CDI electrode materials for desalination and heavy metal adsorption, the optimized NPC-0.75 electrode delivered a maximum electrosorption capacity of 21.14 mg g-1 at the optimum operating parameters (1.2 V, 10 mL min-1, 500 mg L-1 NaCl) and an excellent regeneration performance after continuous electrosorption-desorption cycles. The structure-activity relationship analysis indicated that the mesopore dominates the CDI performance of NPCs in water. In addition, NPC-0.75 electrode showed a high electrosorption capacity for Cu2+ (36.3 mg g-1), Cd2+ (30.02 mg g-1) and Pb2+ (21.5 mg g-1) in water. This study provides new insight into the design of high-efficiency porous carbons toward the CDI from water