Surface Hydrophilicity Governs the Potential of Zero Charge and Capacitive Performance of MXenes

Interfacial properties at the electrode/electrolyte boundary dictate electrochemical energy storage efficiency. We employ grand-canonical DFT and hybrid solvation models to investigate the Ti 3 C 2 -based MXene/water interface, demonstrating that termination-dependent MXene-water interactions govern the potential of zero charge (PZC) and double-layer capacitance (C dl ). Oxygen (−O) terminations form a more hydrophilic, directional, and strongly coupled MXene-water interfacial structure, resulting in a high PZC of 1.03 ± 0.15 V vs SHE and an enhanced solvent-mediated capacitance response near the PZC due to potential-induced water reorientation. Conversely, fluorine (-F) terminations induce comparatively weaker and more field-sensitive MXene-water interactions, resulting in a lower PZC of 0.01 ± 0.00 V vs SHE and a more conventional capacitive response. The termination-dependent PZC trend is close to the work-function-based Vasenin relationship, identifying electronic structure and interfacial water organization as coupled descriptors. These insights provide a predictive molecular roadmap for tailoring MXene surface chemistry, directly advancing the development of high-performance double-layer supercapacitors and related capacitive energy storage systems.