Bioinspired Intelligent Solar-Responsive Thermally Conductive Pyramidal Phase Change Composites with Radially Oriented Layered Structures toward Efficient Solar-Thermal-Electric Energy Conversion

To remedy the drawbacks of weak solar-thermal conversion capability, low thermal conductivity, and poor structural stability of phase change materials, pyramidal graphitized chitosan/graphene aerogels (G-CGAs) with numerous radially oriented layers are constructed, in which the long-range radial alignment of graphene sheets is achieved by a novel directional-freezing strategy. A G-CGA/polyethylene glycol phase change composite exhibits a thermal conductivity of 2.90 W m(-1) K-1 with a latent heat of 178.8 J g(-1), and achieves a superior solar-thermal energy conversion and storage efficiency of 90.4% and an attractive maximum temperature of 99.7 degrees C under a light intensity of 200 mW cm(-2). Inspired by waterlilies, solar-responsive phase change composites (SPCCs) are designed for the first time by assembling the G-CGA/polyethylene glycol phase change composites with solar-driven bilayer films, which bloom by day and close by night. The heat preservation effect of the solar-driven films leads to a higher temperature of SPCC for a longer period at night. The SPCC-based solar-thermal-electric generator achieves output voltages of 499.2 and 1034.9 mV under light intensities of 200 and 500 mW cm(-2), respectively. Even after stopping the solar irradiation, the voltage output still occurs because of the latent heat release and the heat preservation of the films.