RHTC/HO-BNNS structure collaboratively improves thermal conductivity and photothermal conversion properties of phase change materials

The application of phase change materials (PCMs) to improve the efficiency of solar energy has been widely studied. However, most composite PCMs can only maintain high photothermal conversion performance in solid phase environment. To expand the application range of PCM in solar energy field, a flexible composite film which can stably exist in both solid and aqueous environments was prepared. Polyethylene glycol (PEG) as the temperature control core, hydroxyl boron nitride nanosheets (HO-BNNS) and carboxy-rich carbon (RHTC) as the thermally conductive filler and high photothermal converter, respectively, and polyvinylidene fluoride (PVDF) as the flexible supporting material. RHTC/HO-BNNS, as a key bridge, forms a thermal conductivity and photothermal conversion network in the composite film, making its photothermal conversion storage efficiency up to 92.1%, and its thermal conductivity 4 times higher than that of pure PEG. Together with the excellent mechanical strength (2.35 MPa), composite film can be operate at night solar evaporators. It can both improve the effective utilization of solar energy and accelerate the progress of seawater desalination, providing a new idea for expanding the application of PCM. •VRBP composites has excellent light absorption ability in both solid and aqueous phase environments.•The mechanical strength of VRBP composites can reach 2.35 MPa.•VRBP composites can be used to all-weather interfacial solar steam generators.