A High Energy Density Azobenzene/Graphene Oxide Hybrid with Weak Nonbonding Interactions for Solar Thermal Storage.

Incorporating photochromic chromophores into polymer composites provides the possibility of a reversible photoswitch of the intrinsic properties of these materials. In this paper we report a route to attach azobenzene (AZO) moiety covalently to graphene oxide (GO) to create chromophore/graphene oxide (AZO-GO) hybrid, in which GO is both part of the chromophore and the template. Due to the high grafting density of AZO moiety and the low mass of the novel structure, the hybrid is a potential solar thermal storage material with high energy density of about 240 Wh·kg. It is found that C-H···π interaction between the cis-AZO chromophores and the aromatic rings of the substrate induces collective electronic modifications of GO at critical percentage of cis-isomers and reduce the thermal barrier of π-π* transition of the chromophores directly, which results in two sections of first-order reactions during the photoisomerization of trans- to cis-hybrid and also thermally stabilizes the cis-hybrid. Our findings demonstrate that high-performance AZO-GO hybrid can be manipulated by optimizing intermolecular nonbonding interactions.