Interface-engineered composite nanofibers for boosting piezoelectric outputs of polymeric nanogenerators

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Polymeric piezoelectric nanogenerators (PENGs) hold great promise for flexible energy harvesters and self-powered sensors. However, achieving high piezoelectricity in inherently piezoelectric polymers while maintaining their flexibility remains a challenge. Herein, we propose a simple yet effective approach to fabricate flexible and cost-effective PENGs based on interface-engineered composite nanofibers of poly(vinylidene fluoride) (PVDF)/carbon nanotubes (CNTs) using electrospinning. Our strategy involves the incorporation of a tailor-made interfacial coupling agent, maleic anhydride grafted PVDF (PVDF-g-MA), onto PVDF/CNTs interfaces. This mild interface-engineering strategy not only promotes interfacial interactions within composites but also stabilizes electrospinning flow jets, yielding defect-free nanofibers. More importantly, the interfacial anchoring of PVDF-g-MA molecules promotes the preferential crystallization of electroactive β-phase within PVDF matrix. By incorporating a small quantity of PVDF-g-MA (up to 1.0 wt%), our approach significantly enhances piezoelectric outputs while preserving flexibility. This eliminates the need for excessive nanofiller usage that can sacrifice the flexibility associated with conventional methods. Remarkably, the resulting composite nanofiber-based PENGs exhibit excellent piezoelectric performance, generating high output voltages (10.6 V) and remarkable power density (3.15 µW/cm2) under tiny force stimuli. Our findings open new avenues for efficient and scalable fabrication of polymeric piezoelectric nanogenerators for flexible and wearable energy harvesting and self-powered sensing applications.