Unveiling Confined Proton Desolvation Dynamics in Interlayer-Engineered MXenes

The rational design of proton-based energy storage systems requires a fundamental understanding of proton behavior under nanoscale confinement. Herein, we elucidate the desolvation dynamics and charge-transfer mechanisms of confined protons within interlayer-engineered Ti 3 C 2 T x MXenes through a combined theoretical and experimental approach. Density functional theory (DFT) calculations reveal that proton transport strongly depends on the interlayer spacing: when the gallery distance exceeds 0.6 nm, hydrated protons (H 5 O 2 + ) undergo efficient desolvation and interfacial charge transfer, whereas narrower spacing traps protons in a suspended, fully solvated state, thereby impeding charge transport. Guided by these insights, Mo-doped MXenes (Mo-MXene) with tunable interlayer spacing were synthesized, exhibiting enlarged galleries and enhanced surface charge density. The optimized Mo-MXene-based hybrid supercapacitors deliver a high volumetric energy density of 94.2 Wh L −1 at a power density of 398.9 W L −1 , and more importantly, maintain an impressive energy density of 74.0 Wh L −1 even at an ultrahigh power density of 156.7 kW L −1 . This study establishes interlayer spacing as a decisive structural parameter governing proton desolvation and electron-transfer coupling, providing a universal design strategy for high-rate, high-capacitance proton-based electrochemical energy storage systems.