Covalent Ag-holey MXene link at interface boosting electrochemical dechlorination

Incorporating Ag species into conductive matrices can mitigate volumetric expansion and stabilize electrode structures in capacitive deionization (CDI). Yet, this approach may suffer from severe charge transfer resistance at their heterogeneous interface featuring physical contact or weak intermolecular link. To tackle this challenge, we linked Ag single atoms and nanoparticles covalently to holey MXene (HMX) via an in situ etching-and-reduction strategy, in which atomically dispersed Ag in covalent bond with HMX is generated and serves as pivots to guide growth of Ag nanoparticles. The elaborate covalent link promotes Ag-to-HMX electron transfer and creates electron-deficiency on Ag that facilitates faradaic dechlorination. Meanwhile, the perforated HMX nanosheets with rich in-plane nanopores assemble into thin films possessing a spatially interconnected porous matrix, enabling fast cross-film transfer of both electrons and ions. Consequently, the as-made hybrid electrodes exhibit enhanced dechlorination capacity (156.63 ± 2.6 mg g^-1), charge efficiency (91.2 ± 4.5%), and cyclic stability (>90% retention in 50 cycles) compared to the control samples. This synthetic strategy integrates Ag-mediated covalent interfacial bridging with pore-engineered MXene, providing a paradigm for designing CDI dechlorination electrodes.