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Piezoelectric nanogenerators (PENGs) that can harvest mechanical energy from ambient environment have broad prospects for multi-functional applications. Here, multi-layered piezoelectric composites with a porous structure based on highly oriented Pb(Zr0.52Ti0.48)O3/PVDF (PZT/PVDF) electrospinning fibers are prepared via a laminating method to construct high-performance PENGs. PZT particles as piezoelectric reinforcing phases are embedded in PVDF fibers and facilitate the formation of polar β phase in PVDF. The multi-layered, porous structure effectively promotes the overall polarization and surface bound charge density, resulting in a highly efficient electromechanical conversion. The PENG based on 10 wt% PZT/PVDF composite fibers with a 220 µm film thickness outputs an optimal voltage of 62.0 V and a power of 136.9 µW, which are 3.4 and 6.5 times those of 10 wt% PZT/PVDF casting film-based PENG, respectively. Importantly, the PENG shows a high sensitivity of 12.4 V·N−1, presenting a significant advantage in comparison to PENGs with other porous structures. In addition, the composites show excellent flexibility with a Young’s modulus of 227.2 MPa and an elongation of 262.3%. This study shows a great potential application of piezoelectric fiber composites in flexible energy harvesting devices.

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A combination of a triboelectric nanogenerator (TENG) and natural wood presents a sustainable approach toward a smart home due to the wood’s biodegradability, low cost, and abundant resource. Major challenges for achieving a cellulose-based TENG are the brittleness, low crystallinity, and low surface charge density. We demonstrated a facile method to process and modify natural wood to satisfy application requirements. The treated wood has both good flexibility and tensile mechanical properties. After pressing, its crystallinity also saw a big increase, with the figure almost tripled. A further surface modification was inspired by dyeing technology. The cellulose on the surface of wood was cationically modified by 3-chloro-2-hydroxypropyl trimethylammonium chloride (CHPTAC) via the solution-immersion method. After modification, the surface potential increased two times compared to that of the unmodified one. Density functional theory was used to calculate the absorption energy between cellulose molecules and CHPTAC to further verify the feasibility of the chemical modification. Larger differences between the two tribo-layers in terms of the energy level produce a high electrostatic charge flow. The modified pressed wood-based TENG can generate a peak current of 9.74 μA, a voltage of 335 V, and a transferred charge density of 71.45 μC/m2 through contact electrification. A concept of a self-powered and sensing smart floor integrated with this modified cellulose-based TENG was further developed to provide real-time motion monitoring for a smart home. This work not only removes the wood brittleness but also puts forward a novel method to improve the wood surface charge density from an interdisciplinary perspective, which is crucial to facilitate the application of natural wood in the nanogenerator area.

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