Space-mediated confinement engineering of NaTi2(PO4)3 inside hollow carbon nanofibers via coaxial electrospinning: Enabling ultra-robust and highly-efficient faradic capacitive deionization

Abstract

NASICON-structured NaTi₂(PO₄)₃ (NTP) has emerged as a promising cathode material for faradaic capacitive deionization (FDI) in desalination, owing to its high theoretical sodium storage capacity. However, its practical application is limited by poor conductivity and significant volume expansion, leading to slow desalination rates and rapid performance degradation. Previous efforts to anchor NTP onto carbon substrates have improved conductivity, but at the expense of reducing the availability of electrochemically active sites and causing irreversible damage to the carbon matrix during Na-ion intercalation and de-intercalation. To address these issues, we propose a space-mediated confinement strategy, incorporating NTP into hollow core–shell carbon nanofibers (ch-NTP@CNFs). This approach combines a buffered protective scaffold with a continuous electron-conductive network, mitigating structural degradation and conductivity limitations. The resulting ch-NTP@CNFs-based FDI system demonstrates significantly enhanced desalination kinetics (0.652 mg g⁻¹ s⁻¹) and outstanding long-term stability, with only a 6.2 % capacity reduction over 200 cycles. These findings surpass the performance of most CDI systems reported to date. This study underscores the potential of space-mediated confinement and hollow core–shell designs in improving desalination kinetics and durability, advancing FDI anode development for sustainable water desalination technologies.