Directional Electron Transfer in Island‐Sea Structured Contact‐Electro‐Catalysis Enables Cascade Defluorination of PFAS

The exceptional stability of C─F bonds in per- and polyfluoroalkyl substances (PFAS) impedes their activation and degradation through conventional redox processes. Contact-Electro-Catalysis (CEC) offers an oxidant-free alternative but suffers from uncontrolled electronic structures and non-directional electron transfer. Here, we design an "island-sea" structured CEC system by embedding atomically dispersed Cu─N₄ islands within a polyvinylidene fluoride (PVDF) matrix. The Cu─N₄ domains trigger interfacial electron transfer that induces β-phase crystallization of PVDF. The aligned dipoles amplify piezoelectric polarization and strengthen interfacial electric fields (IEFs). This configuration enables efficient electron harvesting from interfacial water and field-emission-driven injection into Cu─N₄ sites. The electron-enriched Cu sites activate O₂ to form ^•O₂ ^- for nucleophilic defluorination while simultaneously populating the C─F σ* orbitals to facilitate bond cleavage. In parallel, ^•OH and ¹O₂ promote oxidative mineralization of low-fluorinated intermediates, establishing a cascade redox pathway. This cooperative mechanism achieves 95% degradation and 94.4% defluorination of perfluorooctanoic acid with excellent stability. This study defines β-phase-mediated IEF engineering in polymer/single-atom hybrids as a general concept for directing interfacial electron dynamics in catalytic systems.