Preparation of PVDF/graphene ferroelectric composite films by in situ reduction with hydrobromic acids and their properties

A new two-step process was developed to prepare PVDF/reduced graphene oxide (PVDF/rGO) composite films: the synthesis of PVDF/GO composite films and immersion of such films in hydrobromic acids for reduction. This method avoided the agglomeration of rGO during reduction in PVDF/GO solutions and efficiently improved the dispersion effect of rGO in the PVDF matrix. Meanwhile, it simplified the preparation process due to no modification of GO being required, and opened a feasible way to scale up the production of PVDF/rGO composites. Experiments showed that PVDF with nearly all beta phase was obtained when the content of rGO was 0.1 wt% (PrGO-0.1), and the dielectric constant increased from 10 for the neat PVDF to 41 for PrGO-0.1 at 1 kHz. The ferroelectric, piezoelectric, and dynamic mechanical properties of the PVDF/rGO composites were also comprehensively studied. As the content of the b phase was nearly 100%, the piezoelectric constant and remnant polarization of the PrGO-0.1 film increased by 78.6% and 69.3%, respectively, compared with those of the neat PVDF, and therefore became the highest among all composite films. The rGO also, to a great extent, helped to enhance the mechanical properties of the PVDF composites. As a result, the improved piezoelectric and ferroelectric properties made the PVDF/rGO composite films with 0.1 wt% rGO content much better piezoelectric energy transfer and ferroelectric storage materials than the neat PVDF.