Paraffin based form-stable phase change composite with chitosan@polypyrrole aerogel as skeleton carrier for low temperature thermal energy storage and efficient photothermal conversion

This work focuses on the development of a paraffin-based shape stabilization phase change composite containing chitosan@polypyrrole aerogel as a skeleton carrier for low temperature thermal energy storage and efficient photothermal conversion. Such a composite is fabricated by incorporating the three-dimensional network aerogel, that synthesized through the deposition of polypyrrole on the pores of chitosan using the in situ oxidation and polymerization processes. Characterization results indicate that polypyrrole and chitosan are bonded via hydrogen bridges, forming a rigid and open-celled network structure that is able to accommodate the liquid paraffin with a mass ratio as high as 93.25%. At such a composition, the composite achieves a melting temperature of 36.86 °C and a latent heat of 194.95 J/g. The doping of polypyrrole largely improves the composite thermal stability and thermal conductivity. In comparison with the pure paraffin, the thermal decomposition temperature and thermal conductivity of the composite containing 9.66 wt% chitosan@polypyrrole aerogel are respectively enhanced by 33.7% and 3.26 times. Splendid thermal cycling performance is also achieved in the composite. After 300 repeated heat-cold cycles, the paraffin concentration is only decreased by 4.35%, and no apparent leakage or deformation is observed in the composite. Photothermal conversion tests reveal that polypyrrole endows the composite with highly efficient broadband light absorption capabilities. Under simulated sunlight irradiation of 100 mW/cm 2 , the heating rate of the composite can reach 33.74 °C/h, and the photothermal conversion efficiency is up to 73.22%.