Molecular Solar Thermal Storage Enhanced by Hyperbranched Structures

Molecular solar thermal fuels have received more and more attention recently to meet the ever-increasing global energy demands. However, molecular solar fuels are still impeded by low storage energy and short half-life. Herein, novel molecular solar fuels are prepared from azobenzenes grafted on graphene with layer-by-layer dendritic hyperbranched structures. The storage performances of photoactive molecular fuels can be increased significantly via layer-by-layer dendritic amplification. The energy density of three-layer hyperbranched fuels can reach up to 104 W h kg(-1) (374 J g(-1)), which is more than three times that of pristine azobenzenes (32 W h kg(-1) or 115 J g(-1)). Moreover, the storage half life of three-layer hyperbranched fuels can reach 80 h, which is much longer than that of pristine azobenzenes (2.5 h). This strategy of fabricating the azobenzene-graphene hybrids with hyperbranched structures paves a new way for the development of high-performance molecular solar thermal fuels.