Graphene Doping to Enhance the Electrocaloric Properties of a Hydrogenated Poly(Vinylidene Fluoride-Trifluoroethylene-Chlorotrifluoroethylene)-Based Composite

The electrocaloric effect (ECE) in ferroelectric materials is considered a candidate for solid-state refrigeration technology due to its merits of environmental friendliness, high integration, and low energy consumption. Herein, a series of poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) terpolymers are synthesized by using the hydrogenation method and are then compounded with the conductive filler graphene nanosheets (GR) to obtain GR/P(VDF-TrFE-CTFE) composites. Benefiting from the large specific surface area of GR, the interfacial polarization of GR/P(VDF-TrFE-CTFE) composite is significantly improved, contributing to a high maximum polarization (~2.35 μC/cm 2 ). As such, a maximum adiabatic temperature change (Δ T ) of ~4.22 K (at 320.6 K) is realized in GR/P(VDF-TrFE-CTFE) composite with 0.05 wt% GR at a low electric field of 50 MV/m, which is an improvement of 51.8% compared to the pure P(VDF-TrFE-CTFE) (Δ T is ~0.08 K at 320.5 K). This result indicates the latent capacity of GR fillers in increasing the ECE of ferroelectric polymer materials, providing a new approach for designing the optimal filler/polymer combination suitable for solid-state refrigeration.