Weiquan Zhan

Selective recovery of dilute rare earth elements (REEs) from complex aqueous streams remains challenging because conventional carbon electrodes rely predominantly on nonspecific electrical double-layer (EDL) accumulation and lack sufficient chemical affinity toward REEs. Here, we demonstrate a coupled electrosorption strategy that integrates electric-field-induced interfacial enrichment with site-specific coordination using ZIF-8-derived nitrogen-doped porous carbon (NPC) electrodes. By tuning the pyrolysis temperature, the pore structure, nitrogen configuration, and electrochemical properties of NPC were systematically regulated, enabling identification of the physicochemical characteristics governing REE capture. The optimized NPC-1000 electrode achieved a La(III) electrosorption capacity of 102.2 mg·g−1 at an initial concentration of 50 mg·L−1, while exhibiting preferential uptake over abundant competing Na+ and Ca2+ ions, stronger affinity toward heavier REEs, and effective regeneration. Mechanistic analysis combining electrochemical characterization, X-ray photoelectron spectroscopy, and density functional theory calculations reveals complementary roles of different nitrogen configurations: pyridinic- and pyrrolic-N provide favorable coordination sites for La(III), whereas graphitic-N contributes primarily to the electronic properties of the carbon framework. Under an applied electric field, EDL enrichment increases the local availability of La3+ at the electrode–solution interface, where coordination with chemically active nitrogen sites stabilizes the accumulated ions. These findings establish the coupling of interfacial ion enrichment and site-specific coordination as a materials-design principle for efficient and selective electrosorption of dilute REEs.

Electrosorption is a promising strategy for the recovery of low-concentration rare earth elements (REEs) from aqueous solutions; however, conventional carbon electrodes such as activated carbon (AC) often suffer from limited adsorption capacity and poor selectivity. Herein, ZIF-8-derived nitrogen-doped porous carbon (NPC) materials were synthesized via pyrolysis at different temperatures (800–1100 °C) and employed as cathodes for the recovery of La(III) through a chemisorption and electrosorption coupling process. Compared with conventional AC, nitrogen doping not only improved the electrochemical properties of the carbon electrode by increasing the specific capacitance and reducing the charge-transfer resistance, but also introduced nitrogen-containing active sites that enhanced the chemisorption interaction between La(III) and the carbon surface. Among the prepared materials, NPC-1000 achieved the maximum electrosorption capacity of 102.2 mg·g-1 for La(III) at an initial concentration of 50 mg·L-1 under 1.2 V and pH = 5.0. In addition, the NPC electrode demonstrated excellent selectivity toward La(III) over competing ions such as Na+ and Ca2+, while showing relatively stronger affinity for heavier REEs. Mechanistic analysis revealed that pyridinic-N and pyrrolic-N species served as the dominant nitrogen-containing active sites, which coordinated with La(III) to form La–N coordination structures. The enhancement in REEs recovery was attributed to the synergistic coupling of the electrical double-layer (EDL) effect and nitrogen-induced chemisorption. This work demonstrates that the MOF pyrolysis-derived strategy for fabricating nitrogen-doped porous carbon materials represents a promising approach for the efficient recovery of rare earth elements from aqueous systems.

Solar‐driven evaporation enables scalable, energy‐efficient lithium recovery from saline water, but it is challenged by slow kinetics, low selectivity, and ionic interference. Here, we present a bilayer Mo‐Layered Double Hydroxide@Sponge composite that integrates photothermal evaporation with hydration‐controlled adsorption for selective lithium extraction. A dynamic two‐stage behavior emerges, where photothermal energy initially enhances both ion transport and interfacial water evaporation, followed by hydration‐induced suppression of further adsorption. This transition reflects a shift in the dominant transport regime, where thermal stimulation initially accelerates mobility, but prolonged exposure alters the hydration structure. Elevated temperatures promote the formation of more compact hydration shells around Li ⁺ , which in turn hinder diffusion by increasing viscosity and enhancing ion‐solvent interactions, highlighting a hydration‐controlled adsorption mechanism. Meanwhile, high salt concentrations contribute to reduced interfacial cohesion, which further facilitates evaporation and reinforces concentration‐driven Li ⁺ transport, complementing the hydration‐governed adsorption dynamics. The composite exhibits strong Li ⁺ selectivity, structural robustness, and stable solar performance, providing a mechanistic basis for scalable lithium recovery.