ZIF-8 modified PVDF-HFP nanofiber-based triboelectric nanogenerator for mechanical energy harvesting and self-powered ethanol detection

Abstract

The integration of multisensory functionalities into flexible and wearable platforms is essential and remains challenging for intelligent human–machine interfaces. Herein, we report a multifunctional composite based on electrospun ZIF-8/PVDF-HFP nanofibers that enables mechanical energy harvesting, human motion sensing, and self-powered ethanol detection. A ZIF-8 metal–organic framework (MOF) was synthesized by a one-pot solvothermal approach and subsequently incorporated into a PVDF-HFP matrix through electrospinning. The incorporation of ZIF-8 MOF promoted an increment in the electroactive β-phase and interfacial polarization of PVDF-HFP, leading to an improvement in the dielectric constant and markedly improved triboelectric nanogenerator (TENG) performance. The optimized 5 wt% ZIF-8/PVDF-HFP composite-based TENG achieved a peak-to-peak voltage of 1600 V, a current density of 1.16 µA cm⁻², and a power density of 735 µW cm⁻², while retaining excellent mechanical durability over 32 000 operating cycles with minimal humidity interference. In parallel, the increased surface area and abundant active sites endowed by ZIF-8 markedly improved ethanol sensing performance. To investigate the local atomic structure and coordination environment of the synthesized ZIF-8 filler, X-ray absorption spectroscopy (XAS) analysis was conducted on the pristine samples. The extended X-ray absorption fine structure (EXAFS) results confirm the presence of a well-defined Zn–N tetrahedral coordination geometry around the Zn metallic centers. This analysis reveals a high degree of local atomic ordering and structural integrity within the porous framework, indicating that the crystalline configuration of the MOF remains intact. Furthermore, an IoT-enabled self-powered ethanol sensor based on the same ZIF-8/PVDF-HFP composite is demonstrated for the first time. The self-powered sensing device exhibits a high response value of 11.02, alongside fast response and recovery times of 23.47/24.13 s, respectively, under exposure to 100 ppm ethanol. In comparison, when evaluated in the chemiresistive mode at a low concentration of 1 ppm, the Z5PV sensor displays response and recovery times of 20.70 and 23.91 s, respectively. In contrast, remarkable repeatability, long-term stability, and high selectivity are observed in different interfering volatile organic compound (VOC) environments. Integration with a smartphone-based IoT platform enables real-time ethanol monitoring and automated alert generation, highlighting the strong potential of this multifunctional system for wearable sensing and intelligent safety applications.