Self-powered graphene quantum dot/poly(vinylidene fluoride) composites with remarkably enhanced mechanical-to-electrical conversion

Abstract

We report a facile fabrication approach of a self-powered piezoelectric polymer matrix composite which can efficiently convert mechanical, vibrational and hydraulic energy into electricity without any treatment of electrical poling. The hybrid composite, based on poly(vinylidene fluoride) (PVDF) with a luminescent graphene quantum dot (GQD), finalized its self-polarization process by high pressure crystallization. The size-distributed GQD aggregates in situ catalyzed the self-assembly of PVDF molecules into crystalline beta form 1D nanowires and 3D micro/nanowire architectures concurrently at high pressure. Based on these, we have developed some simple piezoelectric generators. The corresponding open-circuit voltage and short-circuit current generally increased with the increase of GQD loadings. Among them, the GQD/PVDF (3/97, wt/wt) composite revealed more than four times larger electrical output if compared to the pure PVDF. Therefore, these unique self-assembled structures evidently enabled a remarkably improved electrical output during the composite deformation. Furthermore, by modulating GQD concentration together with chemical etching, controllable wettability was observed on the surfaces of the pressure-crystallized GQD/PVDF composites, due to the competition effect between enhanced surface roughening and exposed micro/nanoscale polar crystalline hierarchical structures. The study presented here may open a new avenue for the design and mass production of novel self-powered multifunctional polymer matrix composites with self-reinforcement.