Cobalt‑iron layered double hydroxide coated fungal mycelial biochar surface as a capacitive deionization anode for...

Layered double hydroxides (LDHs) have emerged as a promising class of two-dimensional Faradaic materials for capacitive deionization (CDI), benefiting from their tunable interlayer spacing, high anion-exchange capacity, and highly reversible ion intercalation/deintercalation characteristics. However, their practical application in CDI is hindered by nanosheet self-aggregation and low intrinsic electrical conductivity, which collectively impair desalination performance. To address these limitations, a three-dimensional CoFe-LDH/fungal hyphae-derived biochar composite (FBC/CoFe-LDH) was synthesized via a facile hydrothermal approach and employed as a Faradaic CDI anode. The FBC/CoFe-LDH composite possesses a unique three-dimensional fiber structure with abundant pores. This structure effectively inhibits the self-stacking of LDH sheets and facilitates ion transport. In addition, the introduced mycelial biochar can act as a conductive network, enhancing the conductivity of the composite. When evaluated in a 1000 mg L^-1 NaCl solution, the FBC/CoFe-LDH₂ anode delivered an exceptional salt adsorption capacity (SAC, 89.6 mg g^-1) and rapid salt adsorption rate (SAR, 15.4 mg g^-1 min^-1), outperforming conventional LDH-based electrodes. The composite also demonstrated remarkable resistance to ionic interference and long-term cycling stability (>50 times). The mechanism of Chloride ions (Cl^-) embedded pseudo-capacitance reaction of FBC/CoFe-LDH₂ was revealed by electrochemical kinetic analysis and X-ray photoelectron spectroscopy (XPS) characterization. This research provides a novel guiding method for the removal of Cl^- in high-salt wastewater.