<p>Efficient seawater desalination is vital for addressing the global freshwater crisis. Membrane capacitive deionization (MCDI) has emerged as a promising next-generation desalination technology, offering environmental sustainability, energy efficiency, cost-effectiveness, and facile electrode regeneration. However, the desalination performance of conventional carbon-based electrodes remains limited. Carbon nanofibers (CNFs) are attractive candidates for MCDI due to their extensive surface area, feasible access, chemical stability, and structural robustness, yet their inherently low electrical conductivity—caused by the porous microstructure of polyacrylonitrile-derived CNFs—restricts desalination efficiency. In this study, multi-walled carbon nanotubes (MWCNTs) were incorporated into electrospun CNFs to enhance their conductivity. A series of self-supporting electrodes (CNF, CNF@MWCNT1, CNF@MWCNT5, CNF@MWCNT10, and CNF@MWCNT20) were fabricated via sequential electrospinning, pre-oxidation, and carbonization. The morphology, composition, and structure were examined by SEM, XPS, Raman spectroscopy, and other techniques, while conductivity and electrochemical performance were assessed using four-point probe measurements, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge–discharge (GCD) testing. Among the tested materials, CNF@MWCNT10 achieved the highest desalination performance, with a capacity of 44.85&#xa0;mg&#xa0;g⁻¹ and a time-averaged rate of 0.19&#xa0;mg&#xa0;g⁻¹&#xa0;s⁻¹, representing approximately fourfold and 2.5-fold improvements over pristine CNFs, respectively. Moreover, CNF@MWCNT10 maintained excellent cycling durability, retaining ~ 112% of its initial capacity after 250 cycles. These findings highlight the promise of CNF@MWCNT composites as advanced electrodes for MCDI, providing a foundation for future research toward highly efficient and durable desalination systems.</p> Graphical abstract <p></p>