Achieving high-performance energy harvesting and self-powered sensing in a flexible cellulose nanofibril/MoS2/BaTiO3 composite piezoelectric nanogenerator

Abstract

As good alternatives to conventional rigid piezoelectric materials, environment-friendly biomass-based piezoelectric nanocomposites comprising piezoelectric ceramic fillers and a natural polymer matrix are highly desirable for flexible piezoelectric nanogenerators (PENGs) with high output performance. In this work, composite piezoelectric films were successfully prepared through uniform assembly of MoS₂ nanosheets and tetragonal BaTiO₃ nanoparticles in a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibril (TOCN) matrix using a facile, cost-effective and scalable method. The TOCN/MoS₂/BaTiO₃ ternary composite film demonstrated excellent mechanical properties with the highest tensile strength of 335 MPa and outstanding piezoelectric properties with the maximum longitudinal piezoelectric constant (d₃₃) of 45 pC N⁻¹ much higher than that of other cellulose-based piezoelectric materials. Benefiting from the prominent performance of the flexible cellulose-based nanocomposite, the resulting flexible TOCN/MoS₂/BaTiO₃ composite film-based PENG exhibited very high and stable output piezoelectric signals: namely, a maximum open-circuit voltage of 8.2 V and a maximum short-circuit current of 0.48 μA. Furthermore, the electricity generated by the PENG illuminated a LED directly or charged a 10 μF capacitor up to 3.1 V at 110 s. With high flexibility and sensitivity, the innovative device can work not only as a self-powered motion sensor to detect tiny forces in the environment and in human motion, but also as an electronic skin with good pyroelectric properties to monitor the temperature. Thus, this research provides new insights into the design and preparation of lightweight and simple-structure PENGs with high flexibility and remarkable piezoelectric performance, presenting great potential in the development of efficient mechanical energy harvesters, active sensor networks and wearable electronics.