Lignin-assisted construction of well-defined 3D graphene aerogel/PEG form-stable phase change composites towards efficient solar thermal energy storage

To counter the underutilization and pollution relative to lignin, a novel strategy was adopted, where lignin was introduced as a modifier to enhance graphene aerogel (GA), resulting in the lignin-modified graphene aerogel (LGA) with an ultralow density (2.80 g/cm 3 ). With the help of lignin, a well-defined 3D porous structure was successfully constructed in LGA with homogenous distribution of lignin, which was beneficial for supporting and extending GA skeleton that originally displayed significant shrinkage. The LGA skeleton achieved an extraordinarily high absorption of PEG (~99.0 wt%), which was higher than that of GA-based form-stable phase change materials whose absorption rate was already topped. Meantime, PEG@LGA exhibited not only reinforced light absorption in the whole light range from NIR to UV light benefitting to solar-to-thermal conversion, but also improved thermal stability and reusability as well as high latent heat efficiency (96.71%) and relative latent heat efficiency (98.41%). The material shows great potentials in energy storage and thermal management whose fabrication method at the same time paves a facile way for lignin utilization and valorization.