Sodium-ion-mediated pore size regulation in Pluronic F127-fructose-derived hydrothermal carbons for enhanced capacitive deionization performance

Hierarchically porous carbons (HPCs) were synthesized using a sodium ion (Na⁺)–Pluronic F127 coordination complex as a template for application in capacitive deionization (CDI). By incorporating NaCl into the Pluronic F127–glucose aqueous solution during hydrothermal carbonization, the HPC-8/12 exhibited the largest specific surface area (267.30 m²/g) and mesopore volume (85.7 %). Compared to HPC-0/12, HPC-8/12 demonstrated a specific capacitance of 94.22F/g in a 1 M NaCl aqueous electrolyte. The HPC-8/12 was subsequently mixed with graphene oxide and processed into non-woven fabrics via wet-spinning. These fabrics were then thermally annealed in an inert gas at 800 ℃ to produce CDI electrodes. The resulting HPC-8/12–graphene composite fibers achieved salt adsorption capacities (SAC) of 13.34 mg/g for KCl, 18.78 mg/g for NaCl, and 12.53 mg/g for LiCl at a working voltage of 1.2 V. The Na⁺–Pluronic F127 coordination complexes completely degrade during thermal annealing, resulting in enlarged mesopore sizes that reduce ion transport resistance. Additionally, they introduce specific adsorption sites for Na⁺. This study demonstrates the potential for selectively adsorbing Na⁺ using CDI technology.