Graphene/Azobenzene Photothermal Material Based on Zinc Coordination

Azobenzene has two configurations which are trans-configuration and cis-configuration. As a photo-isomerization molecule, azobenzene can transfer from trans-configuration in low energy state to cis-configuration in a high energy state under the irradiation of ultraviolet light (UV), which is the process of photo-isomerization. Herein, azobenzene and its derivatives are used in different industries and fields. However, due to their low energy density compared with other molecular solar thermal energy storage (MOST) like anthracene and norbornadiene, their applications in energy storage are influenced severely. The purpose of this paper is to find a method to solve the problem above. In this paper, 4-nitro-4'- aminoazobenzene (Azo) was grafted onto reduced graphene oxide (rGO) by the coupling reaction and then interacted with ZnCl₂ to get the azobenzene graphene composite with zinc ion interaction (AGO/Zn). There are two mechanisms of energy storage/release in this method, photoisomerization of azobenzene onto graphene template, and ion interaction formation/destruction, which is a unique attempt to improve energy density through multiple mechanisms of heat release. It has been proved that the nanoscale templates have a significant effect on improving the energy density of azobenzene derivatives. FT-IR spectroscopy show that AGO/Zn is successfully prepared by this method. Moreover, the maximum energy density of that is up to 504.2 J/g under the irradiation of UV (365 nm) for 4 h, which is about 1.69 times of the azobenzene graphene composite (AGO) without ion interaction. Results show that the introduction of zinc and graphene templates greatly improves the energy density of azobenzene, which provides a reference for the development and application of azobenzene composites with multiple mechanisms of energy storage in the future.