A biodegradable nanocellulose based piezoelectric energy conversion device strengthened by designing PVA-cellulose dual-network structure for green in-situ synthesis of ZnO

The study systematically explored the effects of the combination of CNF and PVA on PVA-CMZ composite films. • PVA-CNF dual-network structure possesses high specific surface and abundant active sites. • The abundant binding of ZnO is promoted by the active sites on the above structure. • The interface interaction formed by the oxygen-containing groups of CNF and PVA makes the overall bonding tighter, where tensile strength of composite films reaches 72.50 ± 7.39 MPa. • V OC and I SC of PENG reaches 10.11 V and 698 nA under pressure of 100 kPa respectively. High-performance and environmentally friendly piezoelectric films based on biomass have received extensive attention recently. Among them, wooden cellulose nanofiber (CNF) has become a research hotspot for its low cost, high flexibility and good biocompatibility. In this work, the interwoven PVA-CNF dual-network structure with abundant active sites for its high specific surface was constructed by adding CNF and polyvinyl alcohol (PVA) with abundant oxygen-containing groups, in which MXene was also added as filler, as well as that ZnO was synthesized in the MXene and dual-network substrate via an efficient two-step hydrothermal process to obtain PVA-CNF/MXene@ZnO (PVA-CMZ) composite film. The abundant active sites on the surface of the dual-network structure promote the in-situ synthesis and binding of a large amount of ZnO, further enhancing the overall piezoelectric performance. Moreover, a strong interface interaction is formed by the abundant oxygen-containing groups of CNF and PVA in the assembly process, by which the tight bonding interface among the fillers is practically conducive to the charge and stress transfer, thereby enhancing the overall piezoelectric and mechanical performance. Therefore, the longitudinal piezoelectric constant and tensile strength of the composite film can reach as high as 16.05 ± 0.63 pC·N −1 and 72.50 ± 7.39 MPa respectively, along with the open-circuit voltage and short-circuit current of 10.11 V and 698 nA under a pressure of 100 kPa. Furthermore, it can charge commercial capacitors of specification efficiently, which can still generate stable output under the periodic cyclic force of 5000 s.