Hierarchical N-Doped porous 3D network electrode with enhanced capacitive deionization performance

Abstract

Capacitive deionization (CDI) has emerged as a promising method of desalination owing to its outstanding regeneration efficiency, low energy consumption, and without secondary contamination. The electrosorption capacity is largely determined by the electrode material. Nevertheless, the bottlenecks of present carbon-based CDI electrode materials are their limited desalination capability and single pore channel, which are unfavorable for salt ion diffusion and access to the internal space. Herein, we synthesized nitrogen-doped porous carbon (NPC) and performed a facile activation to obtain hierarchical porous carbon (KNPC) for CDI desalination. The optimized KNPC showed a remarkable desalination performance of 28.40 mg/g in 500 mg/L NaCl solution, with an exceptional regeneration performance of 94.44% after 15 consecutive cycles. The enhanced CDI performance could be attributed to the following aspects: (1) KNPC was introduced plenty of microporous and mesoporous structures, which provides convenient transport channels and accelerated salt ion transport. (2) The enlarged specific surface area and pore volume provide sufficient adsorption sites for salt ions. (3) The modified KNPC exhibited excellent electrochemical properties and wettability, consisting of higher specific capacitance, decreased internal resistance, and ultra-high hydrophilicity. (4) KOH activation promoted the capacitive contribution of the KNPC electrode, thus improving its CDI performance.