Multiscale MXene Engineering for Enhanced Capacitive Deionization via Adaptive Surface Charge Tailoring

Capacitive deionization (CDI), renowned for its eco-friendly and low-energy approach to water treatment, encounters challenges in achieving optimal deionization efficiency and cycle stability despite recent advancements. In this study, the CDI electrodes were crafted with multilevel pore structures using modified cellulose (MCNF) and porous activated MXene (PAMX), aiming to the impact of surface modification on adsorption efficiency, stability, and overall performance. The experimental results demonstrated the superiority of the electrode, specifically the formulation integrating sulfonic acid-treated cellulose and PAMX (SCNF@PAMX). This configuration exhibited remarkably a higher desalination rate (3.91 mg·g–1·min–1) and enhanced desalination capacity (31.24 mg·g–1), with cycling performance exceeding 90%. Density functional theory calculations underscored the formidable adsorption energy of SCNF for Na+ (2.15 eV), surpassing that of other modified electrodes. The enhancement of deionization performance and efficiency through surface charge modification, altering Na+ electrostatic adsorption, lays a solid foundation for advancing more efficient and durable seawater desalination technologies.