Elucidating the Piezoelectric, Ferroelectric, and Dielectric Performance of Lead-Free KNN/PVDF and Its Copolymer-Based Flexible Composite Films

Ecofriendly, reliable, and high-performance piezoelectric materials are drawing huge interest in resolving the environmental problems arising due to consumption of fossil fuel energy. Among the lead-free ferroelectrics, potassium sodium niobate (KNN, (K,Na)NbO3) is one of the most promising piezoelectric ceramics that can replace Pb(Zr,Ti)O3. In the present work, the piezoelectric performance of KNN incorporated in poly(vinylidene fluoride) (PVDF) and its copolymers, polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) and poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), has been compared. The films were fabricated by a solution casting method and were further polarized by a corona poling technique. The results confirmed that the nanocomposite film with 8 wt % KNN filler in PVDF-TrFE (PTK8) exhibited the highest F(β) value, maximum remnant polarization, and dielectric constant value than other nanocomposites. The relative β-phase contents in PTK8, PHK8, and PK8 composite films reached 85, 76, and 75.8%, respectively, indicating that KNN acts as the most suitable nucleating agent in PVDF-TrFE. Also, the piezoelectric voltage output of the PTK8-based nanogenerator was found to be remarkably higher (∼20 V) as compared to other nanocomposite-based piezoelectric nanogenerators. It also exhibited a maximum power density of 0.54 μW/cm2 that was significantly improved in comparison to other composites. This nanogenerator was found to be a promising power generation device promoting miniaturization of self-powered systems

Piezoelectric-Driven Self-Charging Supercapacitor Power Cell

In this work, we have fabricated a piezoelectric-driven self-charging supercapacitor power cell (SCSPC) using MnO₂ nanowires as positive and negative electrodes and a polyvinylidene difluoride (PVDF)–ZnO film as a separator (as well as a piezoelectric), which directly converts mechanical energy into electrochemical energy. Such a SCSPC consists of a nanogenerator, a supercapacitor, and a power-management system, which can be directly used as a power source. The self-charging capability of SCSPC was demonstrated by mechanical deformation under human palm impact. The SCSPC can be charged to 110 mV (aluminum foil) in 300 s under palm impact. In addition, the green light-emitting diode glowed using serially connected SCSPC as the power source. This finding opens up the possibility of making self-powered flexible hybrid electronic devices

Graphdiyne–ZnO Nanohybrids as an Advanced Photocatalytic Material

The utility of carbonaceous materials for hybrid semiconductor photocatalysts has been rapidly increasing in recent years due to the synergetic effect via interfacial charge transfer reactions. In this study, we prepared a novel graphdiyne–ZnO nanohybrid by the hydrothermal method and examined its photocatalytic properties on the degradation of two azo dyes (methylene blue and rhodamine B). Interestingly, the graphdiyne–ZnO nanohybrids showed superior photocatalytic properties than that of the bare ZnO nanoparticles as evidenced by the absorption spectra and total organic carbon analyses. Moreover, the rate constant of graphdiyne–ZnO nanohybrids is nearly 2-fold higher compared to that of the bare ZnO nanoparticles on the photodegradation of both azo dyes. Further, a plausible mechanism for the enhanced photocatalytic properties of the graphdiyne–ZnO nanohybrids has been discussed. This work on the development of graphdiyne-based semiconductor photocatalysis can provide new insights into the design of novel hybrid photocatalysts for potential applications in the environmental remediation sectors