Interfacial Thermodynamics of Ti₃C₂T _x MXene-PVDF-PTFE Triple Interface Systems for Hierarchical Membrane...

This work establishes a comprehensive thermodynamic framework for vapor transport in hierarchical titanium carbide (Ti₃C₂T _x ) MXene-poly-(vinylidene fluoride) (PVDF) coated polytetrafluoroethylene (PTFE) composite membranes through integrated physics-based analysis and experimental validation. The composite architecture leverages PTFE's exceptional hydrophobicity of 135° with PVDF's processability, creating triple interfaces governed by Gibbs excess surface thermodynamics. Controlled spinodal decomposition during nonsolvent-induced phase separation yielded β-phase-rich PVDF matrices with uniformly dispersed Ti₃C₂T _x MXene nanosheets forming angstrom-precision transport channels. Vapor flux governed by Maxwell-Stefan multicomponent diffusion theory, coupled with molecular kinetic models for two-dimensional material interlayers, resulted in experimental vapor fluxes of 42 ± 3.1 kg·m^-2·h^-1 representing 80% enhancement over pristine PVDF membranes. The Ti₃C₂T _x MXene-based nanochannels created thermodynamic selectivity barriers enabling >99.6% salt rejection over 36 h operation. The composite membranes exhibited substantially reduced NaCl crystallization/deposition compared to pristine PVDF, attributed to modified surface energetics and hierarchical pore architectures that disrupt salt nucleation. Thermal analysis revealed a compounding energy benefit: higher membrane porosity reduced the effective thermal conductivity and conductive heat loss while the enhanced vapor flux increased the evaporative heat flux, raising thermal efficiency from 49% for pristine PVDF to 68% for the optimized MXene-PVDF composite and demonstrating that flux enhancement and energy efficiency can be improved simultaneously rather than traded off against each other.