Electronic Delocalization‐Confinement Coupling in Edge‐Coordinated CQDs@MXene Enables Hydrogen‐Bond Modulation for Ultrafast Proton Transport

Abstract

ABSTRACT Efficient proton transport in 2D confined electrodes critically depends on the flexibility of interfacial hydrogen‐bond networks. However, the interfacial issue becomes more pronounced in the 2D confined space. The strong hydrogen bonds between confined water molecules and surface ─O terminations of MXenes immobilize protons and hinder charge storage kinetics. Here, we introduce an edge‐coordination strategy to achieve precise electronic delocalization modulation in Ti 3 C 2 T x MXene by anchoring carboxyl‐functionalized carbon quantum dots (CQDs) at positively charged edges. The CQDs induce substantial electron delocalization on surface ─O sites, which simultaneously weakens rigid hydrogen bonds and facilitates interfacial charge transfer. This regulation establishes a dynamic hydrogen‐bond network that supports continuous Grotthuss‐type proton migration within the confined channels. Consequently, the optimized CQDs@MXene electrode delivers a volumetric capacitance of 2507.2 F cm −3 , retains 65.8% at 1000 mV s −1 , and maintains nearly 100% stability over 10 000 cycles. In situ vibrational spectroscopy and density functional theory reveal that the electron delocalization drives the weak hydrogen‐bond interface and charge transfer coupling governs proton transport kinetics. This work establishes electronic delocalization as an effective paradigm for manipulating hydrogen‐bond dynamics and interfacial charge transport for ultrafast ion transport in confined electrochemical systems.