Highly thermally conductive phase change composites with anisotropic graphene/cellulose nanofiber hybrid aerogels for efficient temperature regulation and solar-thermal-electric energy conversion applications

With the increasing concerns about the shortage of fossil fuels and the environmental pollution, it is imperative to utilize clean and renewable solar energy. Although organic phase change materials have great potentials in storing and releasing thermal energy, the poor solar light absorption and low thermal conductivity limit their efficiencies in absorbing solar energy and converting it to thermal and electrical energies. Herein, highly thermally conductive phase change composites with enhanced thermal energy storage capabilities are prepared by constructing vertically aligned graphene/cellulose nanofiber aerogels (GCAs) followed by vacuum-assisted impregnation of paraffin for efficient temperature regulation and solar-thermal-electric energy conversion applications. An optimal GCA/paraffin phase change composite exhibits an exceptional thermal conductivity of 15.9 W m−1 K−1 at the low graphene loading of 3.35 wt%, a high latent heat retention of 98%, and a greatly enhanced shape stability. Furthermore, the phase change composite is efficient in the temperature regulation of a greenhouse and the solar-thermal-electric energy conversion. A high output voltage of 823.2 mV is achieved under the solar light irradiation of 5 kW m−2. This work demonstrates a promising strategy for efficiently absorbing and converting solar energy, and storing and utilizing thermal energy for applications in energy-related devices and systems.