Dual-salt assisted one-step pyrolysis of bamboo toward hierarchical N-doped porous carbon for high-performance anti-fouling capacitive deionization in complex water matrices

Xinxi Teng a, Huakun Pan a, Guisong Zhang a, Yang Fan a, Junjie Chen a, Haodong Zhang a, Haiou Song b, Meiling Liu a, Shupeng Zhang a

Abstract

The global shortage of freshwater resources is becoming increasingly severe. Capacitive deionization (CDI), as a low-energy and environmentally friendly electrochemical desalination technology, holds great promise for brackish water desalination and treatment of complex water bodies. However, conventional carbon electrodes are often limited by insufficient pore structures, susceptibility to organic fouling, and poor selectivity toward multivalent/heavy metal ions. Herein, we propose a one-step dual-molten-salt-assisted pyrolysis approach to synergistically integrate physical pore formation, chemical etching, and nitrogen doping using a KCl/KHCO3 dual-salt system combined with melamine as the nitrogen source. As a result, a low-cost and sustainable bamboo-derived hierarchical porous nitrogen-doped carbon electrode material, denoted as NKPC, is successfully fabricated. The obtained NKPC exhibits an interconnected three-dimensional spongy hierarchical pore network with abundant micropores and mesopores, delivering a high specific surface area of 3402.74 m2/g and a pore volume of 1.96 cm3/g. Pyridinic N, pyrrolic N, and other active sites are uniformly embedded into the carbon framework. At a current density of 0.1 A/g, NKPC achieves a specific capacitance of 192.19 F/g and a low charge-transfer resistance of 0.846 Ω, along with excellent rate stability. In a 50 mg/L NaCl solution at 1.2 V, the salt adsorption capacity (SAC) reaches 19.11 mg/g, which increases to 30.78 mg/g at 500 mg/L. Cycling stability tests show that the retention of SAC still exceeds 70% after 83 cycles. Moreover, NKPC exhibits high adsorption capacities toward K+, Li+, Mg2+, Ca2+, and heavy metals Pb2+ and Cd2+. In complex water matrices containing humic acid, metronidazole, and bisphenol A, the SAC retention remains above 80%. This study provides a facile and efficient new strategy for the green modification of biomass-derived carbon electrodes, demonstrating significant application potential for CDI desalination and water resource regeneration in complex real-world water bodies.

原文链接：https://www.sciencedirect.com/science/article/pii/S0011916426009550

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