Photo-Isomerization Energy Storage Using Azobenzene and Nanoscale Templates: A Topical Review

Azobenzene (AZO) has attached tremendous attention in the field of photo-isomerization energy storage due to its advantages of absorbing light in ultraviolet-visible range and reversible isomerization. However, the issues of low energy density and short half-lifetime restrict the further development of AZO. Therefore, a method, by preparing hybrid photo-isomerization energy storage materials using nanoscale templates, was proposed to handle the above two issues. In this paper, a summary of hybrid photo-isomerization energy storage materials with AZO and nanoscale templates is conducted from the aspects of templates, preparation methods, derivatives and applications. The performances of template candidates, i.e. carbon nanotubes (CNTs) and graphene (GO) are reviewed and compared based on the analysis of grafting density, energy density, and half-lifetime of hybrid materials. Then, two major preparation methods of AZO hybrid materials including non-covalent and covalent functionalizations are discussed. Furthermore, the studies on AZO derivatives functionalized on nanoscale templates are summarized to further point to the direction of derivatization towards high performance AZO-functionalized materials. Finally, due to the superiority of AZO hybrid solid-state films in large-scale utilization, their current applications are reviewed to find out some promising applications.