Intrinsic Manipulation of Interfacial Water in Titanium Carbide MXene via Carbon Vacancy Engineering for Superior Pseudocapacitive Storage

ABSTRACT The electrochemical performance of Ti ₃ C ₂ T _x MXene arises from chemical and electrostatic interactions between its surface terminations and interlayer molecules. Moving beyond the conventional paradigm of relying on the intercalation of external guest species to modulate this network, this study addresses a more fundamental question: can the interaction environment be intrinsically engineered from within the MXene lattice? Here, carbon (C) vacancies are introduced as a precise strategy to polarize the surface electronic structure, specifically enhancing the electronegativity of oxygen terminations. This polarization strengthens the hydrogen bonding (H‐bonding) interactions with confined water, leading to the formation of a thermally stable, “active and fixed” interlayer architecture. This optimized structure results in a significant increase in intrinsic capacitance, with the Ti ₃ C _1.7 electrode achieving 348 F g ⁻¹ at 5 mV s ⁻¹ , a 47% enhancement over the near‐stoichiometric Ti ₃ C _2.0 . Subsequent anodic oxidation alleviated ion diffusion limitations at high rates, synergistically improving rate capability. The co‐engineered electrode achieved a high capacitance of 382 F g ⁻¹ while retaining 45% capacitance at an ultra‐high scan rate of 5000 mV s ⁻¹ . This work establishes the rational design of interfacial H‐bonding networks as a core principle for advanced MXene electrodes, offering a pathway to high energy and power densities.